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NEUROPHYSIOLOGY
MISS TIFFY MARIAM JOHN
INTRODUCTION
 The field of neurophysiology provides insight into how the nervous
system works and how its dysfunction can lead to disease.
 Physiology is the study of how organisms and their parts function.
 Neurophysiology can be defined as the study of the functioning of the
nervous system, which includes the brain, the spinal cord, peripheral
nerves, and sensory organs.
 The nervous system is a complex
collection of nerves and specialized cells
known as neurons that transmit signals
between different parts of the body. It is
essentially the body's electrical wiring.
 Structurally, the nervous system has two
components: the central nervous system
and the peripheral nervous system.
 The central nervous system is made up
of the brain, spinal cord and nerves.
 The peripheral nervous system consists
of sensory neurons, ganglia (clusters of
neurons) and nerves that connect to one
another and to the central nervous system.
 Functionally, the nervous system has two
main subdivisions: the somatic, or voluntary,
component; and the autonomic, or
involuntary, component.
 The autonomic nervous system regulates
certain body processes, such as blood
pressure and the rate of breathing, that work
without conscious effort.
 The somatic system consists of nerves that
connect the brain and spinal cord with
muscles and sensory receptors in the skin.
 Neurons send signals to other cells through thin fibers
called axons, which cause chemicals known as
neurotransmitters to be released at junctions called
synapses.
 There are over 100 trillion neural connections in the
average human brain, though the number and location can
vary.
 A synapse gives a command to the cell and the entire
communication process typically takes only a fraction of a
millisecond.
 Sensory neurons react to physical stimuli such as light,
sound and touch and send feedback to the central nervous
system about the body's surrounding environment.
 Motor neurons, located in the central nervous system or in
peripheral ganglia, transmit signals to activate the muscles
or glands.
 Glial cells, derived from the Greek word for "glue," are
specialized cells that support, protect or nourish nerve
cells.
 The brain's connections and thinking ability grew over
thousands of years of evolution.
STRUCTURE OF NEURONS
 The neuron is the basic building block of the brain and
central nervous system.
 Neurons are specialized cells that transmit chemical and
electrical signals.
 The brain is made up entirely of neurons and glial cells,
which are non-neuronal cells that provide structure and
support for the neurons.
 Nearly 86 billion neurons work together within the nervous
system to communicate with the rest of the body.
 They are responsible for everything from consciousness
and thought to pain and hunger.
 Cell Body
 Like other cells, each neuron has a cell body (or
soma) that contains a nucleus, smooth and rough
endoplasmic reticulum, Golgi apparatus,
mitochondria, and other cellular components.
 Dendrite
 Dendrites are branch-like structures extending
away from the cell body, and their job is to receive
messages from other neurons and allow those
messages to travel to the cell body.
 Although some neurons do not have any
dendrites, other types of neurons have multiple
dendrites.
 Dendrites can have small protrusions called
dendritic spines, which further increase surface
area for possible connections with other neurons.
 Axon
 An axon, at its most basic, is a tube-like structure
that carries an electrical impulse from the cell body
(or from another cell’s dendrites) to the structures at
opposite end of the neuron—axon terminals, which
can then pass the impulse to another neuron.
 The cell body contains a specialized structure, the
axon hillock, which serves as a junction between the
cell body and the axon.
 Synapse
 The synapse is the chemical junction between the
axon terminals of one neuron and the dendrites of
the next.
 It is a gap where specialized chemical interactions
can occur, rather than an actual structure.
 Myelin Sheath
 Some axons are covered with myelin, a fatty
material that wraps around the axon to form the
myelin sheath.
 This external coating functions as insulation to
minimize dissipation of the electrical signal as it
travels down the axon.
 Myelin’s presence on the axon greatly increases
the speed of conduction of the electrical signal,
because the fat prevents any electricity from
leaking out.
 This insulation is important, as the axon from a
human motor neuron can be as long as a
meter—from the base of the spine to the toes.
 Periodic gaps in the myelin sheath are called
nodes of Ranvier.
 Glial Cells
 Myelin is produced by glial cells (or simply
glia, or “glue” in Greek), which are non-
neuronal cells that provide support for the
nervous system.
 Glial function to hold neurons in place
(hence their Greek name), supply them with
nutrients, provide insulation, and remove
pathogens and dead neurons.
 In the central nervous system, the glial cells
that form the myelin sheath are called
oligodendrocytes; in the peripheral nervous
system, they are called Schwann cells.
TYPES OF NEURON
 Two basic classes of neurons
 Based on structure –
1. Unipolar
2. Bipolar
3. Multipolar
4. Pseudounipolar
 Based on functions –
1. Sensory neurons
2. Motor neurons
Based on structure
 Neurons are broadly divided into four basic types:
unipolar, bipolar, multipolar, and pseudounipolar.
 Unipolar neurons have only one structure that
extends away from the soma. These neurons are
not found in vertebrates but are found in insects
where they stimulate muscles or glands.
 A bipolar neuron has one axon and one dendrite
extending from the soma. An example of a bipolar
neuron is a retinal bipolar cell, which receives
signals from photoreceptor cells that are sensitive
to light and transmits these signals to ganglion
cells that carry the signal to the brain.
 Multipolar neurons are the most common
type of neuron. Each multipolar neuron
contains one axon and multiple dendrites.
Multipolar neurons can be found in the
central nervous system (brain and spinal
cord). The Purkinje cell, a multipolar neuron
in the cerebellum, has many branching
dendrites, but only one axon.
 Pseudounipolar cells share characteristics
with both unipolar and bipolar cells.
 Most sensory neurons are pseudounipolar
and have an axon that branches into two
extensions: one connected to dendrites that
receives sensory information and another
that transmits this information to the spinal
cord.
 Sensory Neurons
 Sensory neurons are neurons responsible for
converting external stimuli from the environment
into corresponding internal stimuli.
 They are activated by sensory input and send
projections to other elements of the nervous
system, ultimately conveying sensory information to
the brain or spinal cord.
Based on function
 Sensory neurons are activated by physical
modalities (such as visible light, sound, heat,
physical contact, etc.) or by chemical signals
(such as smell and taste).
 Most sensory neurons are pseudounipolar,
meaning they have an axon that branches
into two extensions—one connected to
dendrites that receive sensory information
and another that transmits this information to
the spinal cord.
 Motor Neurons
 Motor neurons are neurons located in the
central nervous system, and they project their
axons outside of the CNS to directly or
indirectly control muscles.
 The interface between a motor neuron and
muscle fiber is a specialized synapse called
the neuromuscular junction.
 The structure of motor neurons is multipolar,
meaning each cell contains a single axon and
multiple dendrites.
 This is the most common type of neuron.
 Interneurons
 Interneurons are neither sensory nor
motor; rather, they act as the “middlemen”
that form connections between the other
two types.
 Located in the CNS, they operate locally,
meaning their axons connect only with
nearby sensory or motor neurons.
 Interneurons can save time and therefore
prevent injury by sending messages to the
spinal cord and back instead of all the way
to the brain.
 Like motor neurons, they are multipolar in
structure.
FUNCTIONS OF NEURON
1. Receive signals (or information).
2. Integrate incoming signals (to determine whether the information should be
passed along).
3. Communicate signals to target cells (other neurons or muscles or glands).
MYELINATED AND NON - MYELINATED
NERVE FIBRES
NERVE IMPLUSE PRODUCTION
 The central nervous system (CNS) goes through a three-step process when it functions: sensory input, neural
processing, and motor output.
 The sensory input stage is when the neurons (or excitable nerve cells) of the sensory organs are excited
electrically.
 Neural impulses from sensory receptors are sent to the brain and spinal cord for processing.
 After the brain has processed the information, neural impulses are then conducted from the brain and spinal
cord to muscles and glands, which is the resulting motor output.
 When a neuron is not actively transmitting a
nerve impulse, it is in a resting state, ready to
transmit a nerve impulse.
 During the resting state, the sodium-potassium
pump maintains a difference in charge across the
cell membrane of the neuron.
 The sodium-potassium pump is a mechanism of
active transport that moves sodium ions out of
cells and potassium ions into cells.
 The sodium-potassium pump moves both ions
from areas of lower to higher concentration,
using energy in ATP and carrier proteins in the
cell membrane.
 The figure below shows in greater detail how
the sodium-potassium pump works.
 Sodium is the principal ion in the fluid outside
of cells, and potassium is the principal ion in
the fluid inside of cells.
 These differences in concentration create an
electrical gradient across the cell membrane,
called resting potential. Tightly controlling
membrane resting potential is critical for the
transmission of nerve impulses.
 An action potential, also called a nerve impulse, is an electrical charge that travels along the
membrane of a neuron.
 It can be generated when a neuron’s membrane potential is changed by chemical signals from a
nearby cell.
 In an action potential, the cell membrane potential changes quickly from negative to positive as
sodium ions flow into the cell through ion channels, while potassium ions flow out of the cell.
 The action potential is a rapid change in
polarity that moves along the nerve fiber
from neuron to neuron. In order for a
neuron to move from resting potential to
action potential-the neuron must be
stimulated by pressure, electricity,
chemicals, or another form of stimuli.
 The level of stimulation that a neuron must
receive to reach action potential is known
as the threshold of excitation, and until it
reaches that threshold, nothing will
happen.
 Different neurons are sensitive to different
stimuli, although most can register pain.
 The change in membrane potential results in
the cell becoming depolarized.
 An action potential works on an all-or-nothing
basis. That is, the membrane potential has to
reach a certain level of depolarization, called
the threshold, otherwise, an action potential
will not start.
 This threshold potential varies but is
generally about 15 millivolts (mV) more
positive than the cell's resting membrane
potential.
 If a membrane depolarization does not reach
the threshold level, an action potential will not
happen. You can see in Figure below that two
depolarizations did not reach the threshold
level of -55mV.
 The first channels to open are the sodium ion channels, which allow sodium ions to enter the
cell.
 The resulting increase in positive charge inside the cell (up to about +40 mV) starts the action
potential. This is called the depolarization of the membrane.
 Potassium ion channels then open, allowing potassium ions to flow out of the cell, which ends
the action potential. The inside of the membrane becomes negative again. This is called
repolarization of the membrane.
 Both of the ion channels then close, and the sodium-potassium pump restores the resting
potential of -70 mV.
 The action potential will move down the axon toward the synapse like a wave would move
along the surface of the water.
 In myelinated neurons, ion flows occur only at the nodes of Ranvier.
 As a result, the action potential signal "jumps" along the axon membrane from node to
node rather than spreading smoothly along the membrane, as they do in axons that do
not have a myelin sheath.
 This is due to a clustering of Na+ and K+ ion channels at the Nodes of Ranvier.
 Unmyelinated axons do not have nodes of Ranvier, and ion channels in these axons are
spread over the entire membrane surface.
TRANSMITTING NERVE IMPULSES
 The place where an axon terminal meets another cell is called a synapse. This is where the
transmission of a nerve impulse to another cell occurs. The cell that sends the nerve impulse
is called the presynaptic cell, and the cell that receives the nerve impulse is called the
postsynaptic cell.
 Some synapses are purely electrical and make direct electrical connections between
neurons. However, most synapses are chemical synapses. Transmission of nerve impulses
across chemical synapses is more complex.
 At a chemical synapse, both the presynaptic and
postsynaptic areas of the cells are full of the
molecular machinery that is involved in the
transmission of nerve impulses.
 As shown in the diagram below, the presynaptic
area contains many tiny spherical vessels called
synaptic vesicles that are packed with chemicals
called neurotransmitters.
 When an action potential reaches the axon
terminal of the presynaptic cell, it opens channels
that allow calcium to enter the terminal.
 Calcium causes synaptic vesicles to fuse
with the membrane, releasing their contents
into the narrow space between the
presynaptic and postsynaptic membranes.
This area is called the synaptic cleft.
 The neurotransmitter molecules travel
across the synaptic cleft and bind
to receptors, which are proteins that are
embedded in the membrane of the
postsynaptic cell.
 Membrane potential – It is the difference in the total charge between the inside of
the cell and the outside of the cell.
 Resting membrane potential – It is the difference in voltage across the cell
membrane in a resting state. (A neuron is said to be at rest when it does not
any impulse. At this stage, the axonal membrane of the neuron is more permeable
the potassium ions and not permeable to the sodium ions.)
 Action potential – It is a short-term change in the electrical potential that travels
across the neuron cell.
 Resting potential: Before the action potential occurs, the neuron should be in a state of rest
(approx. –70 mV)
A typical action potential will last for roughly 3 – 5 milliseconds and contain 3 key stages:
 Depolarisation: A rising spike corresponds to the depolarisation of the membrane via
sodium influx (up to roughly +30 mV)
 occurs when ion channels open and cause a change in membrane potential
 Hence, depolarisation at one point of the axon triggers the opening of ion channels in the
segment of the axon
 This causes depolarisation to spread along the length of the axon as a unidirectional wave
 Repolarisation: A falling spike corresponds to repolarisation via potassium efflux
(undershoots to approx. –80 mV)
 Refractory period: The oscilloscope trace returns to the level of the resting potential (due
to the action of the Na+/K+ pump)
An action potential will only occur if the initial depolarisation exceeds a threshold potential of
approximately –55 mV
 Nerve impulses are action potentials that move along the length of an axon as a wave of
depolarisation
IMPULSE PROPAGATION
 Propagation of nerve impulses is the result of local currents that cause each successive part of
the axon to reach the threshold potential.
ALL OR NONE LAW
 Action potentials are generated within the axon according to the all-or-none principle
 An action potential of the same magnitude will always occur provided a minimum electrical
stimulus is generated
 This minimum stimulus – known as the threshold potential (–55 mV) – is the level
required to open voltage-gated ion channels
 If the threshold potential is not reached, an action potential cannot be generated and hence
the neuron will not fire
CONTINUOUS CONDUCTION AND SALTATORY
CONDUCTION
 Continuous conduction of an impulse - It propagates from one segment of a neurons
membrane to the next.
 Saltatory conduction - However, to accelerate this process, most nerve cells are enclosed by a
multilamellar membrane, the so called myelin sheath (consisting of Schwann cells).
 This sheath is not entirely enclosed around the axon but regularly leaves uncovered sectors called
“nodes of Ranvier“.
 The covered membrane regions do not posses ion channels and thus no connection to the
extracellular matrix. In this case these regions can not develop an action potential.
 Therefore the equalizing currents agitate between the nodes of Ranvier, from each node to the
successive one.
 As a result the impulses proceed about ten times faster along the axon as a lot less depolarization
need to happen.
 Also the energy required for the reestablishing of the resting potential is less, therefore the
process is also much more energy efficient.
SYNAPSE
 Synapse can be defined as functional junction between
parts of two different neurons.
 There is no anatomical continuity between two neurons
involved in the formation of synapse.
 At level of synapse, impulse gets conducted from one
neuron to another due to release of neurotransmitters,
like Acetyl Choline, noradrenaline, serotonin, etc.
 The synapses, which require release of some
chemical substance (neurotransmitter) during
synaptic transmission, are termed as chemical
synapses.
 In human body, almost all synapses are chemical
type, rarely also consists of electrical type.
 Presynaptic region is mostly contributed by axon and
postsynaptic region may be contributed by dendrite
or soma (cell body) or axon of another neuron.
Properties of Synapse:
1. One-way conduction (unidirectional conduction):
 In chemical synapse, since neurotransmitter is present only in presynaptic region, impulse
gets conducted from pre- to postsynaptic region only and not vice versa.
2. Synaptic delay is for neurotransmitter to:
 a. Get released from synaptic vesicles when action potential has reached presynaptic region.
 b. Pass through synaptic cleft.
 c. Act on postsynaptic region to bring about production of action potential in postsynaptic
region.
 For all the above events to be brought about, sometime is required. This is known as
synaptic delay, which is normally about 0.5 msec at every synapse.
3. Fatigability:
 When synapses are continuously stimulated, after some time, due to exhaustion of
neurotransmitter at presynaptic terminals, impulses fail to get conducted.
 This results in fatigue occurring at level of synapse.
 Fatigue is a temporary phenomenon. If some rest is given to neurons, resting facilitates
synthesis of neurotransmitter for further conduction of impulse across synapse.
4. Convergence and divergence:
 Impulses from one presynaptic nerve fiber may end on postsynaptic region of large
number neurons and this is called as divergence.
 When nerve fibers of different presynaptic neurons end on a common postsynaptic
neuron, this is known as convergence.
 In CNS, on an average about 10000 synapses are found on any one neuron.
5. Summation:
 When a stimulus of subthreshold strength is applied, no action potential will be passed to
post synaptic neuron.
 But if many subthreshold stimuli are applied at presynaptic region, effects of these stimuli
get added up and lead to action potential development in postsynaptic region. This is
as summation.
 There are two types of summation namely spatial and temporal.
6. Excitation or inhibition:
 The impulse conduction across a synapse may either stimulate or inhibit activity of
postsynaptic region.
 If there is stimulatory influence, then there will be production of action potential in
postsynaptic neuron
 if it has an inhibitory influence, then there is no action potential generation in postsynaptic
region.
TYPES OF SYNAPTIC CONNECTIONS
BASED ON FUNCTION
 CHEMICAL
 ELECTRICAL
BASED ON STRUCTURE
 AXODENDRITIC
 AXOSOMATIC
 AXOAXONIC
Chemical synapse
 A chemical synapse is a gap between two
neurons where information passes
chemically, in the form of neurotransmitter
molecules.
 chemical synapses are:
 slow
 active (require ligand-gated channels)
like Na- K channels
 unidirectional
Electrical synapse
 An electrical synapse is a gap which has channel proteins
connecting the two neurons.
 While electrical synapses are faster (electricity moves
quicker than molecules, and you don't need receptors).
 You often find electrical synapses in systems requiring quick
responses, like instincts and , are often found in all nervous
systems, including the human brain.
•very rapid (no synaptic delay)
•passive
•Bidirectional -"post"synaptic cell can actually send
messages to the "pre"synaptic cell
Axodendritic synapse
one between the axon of one neuron and the dendrites of another.
Axosomatic synapse
one between the axon of one neuron and the body of another.
Axoaxonic synapse
one between the axon of one neuron and the axon of another neuron.
SYNAPTIC TRANSMISSION
 Synapses are junctions between neurons and receptor or effector cells.
 Nerves transmit electrical impulses by changing the ionic distribution across the neuronal
membrane (membrane potential).
 Synapses are the physical gaps that separate neurons from other cells (other neurons and
receptor or effector cells).
 Neurons transmit information across synapses by converting the electrical signal into a chemical
signal
Mechanism of Synaptic Transmission:
 Arrival of impulse
 Depolarization of pre-synaptic region
 Influx of calcium ions from interstitial space (outside the neuron) into presynaptic region
 Release of neurotransmitter
 Passage of neurotransmitter through synaptic cleft
 Binding of neurotransmitter to receptors on postsynaptic region.
 Change in electrical activity of postsynaptic region.
 Generation of action potential in post synaptic neuron and thereby the transmission of signal
continues from neuron to neuron.
NEUROTRANSMITTERS
 Neurotransmitters are often referred to as the body’s chemical messengers. They are the
molecules used by the nervous system to transmit messages between neurons, or from
neurons to muscles.
 A neurotransmitter influences a neuron in one of three ways: excitatory, inhibitory or
modulatory.
 An excitatory transmitter promotes the generation of an electrical signal called an action
potential in the receiving neuron, while an inhibitory transmitter prevents it.
 Most neurotransmitters are either small amine molecules, amino acids, or neuropeptides.
Acetylcholine (ACh)
Type Excitatory in all cases except in the heart (inhibitory)
Released from Motor neurons, basal ganglia, preganglionic neurons of the autonomic
nervous system, postganglionic neurons of the parasympathetic nervous
system, and postganglionic neurons of the sympathetic nervous system
that innervate the sweat glands
Functions Regulates the sleep cycle, essential for muscle functioning
Norepinephrine (NE)
Type Excitatory
Released from Brainstem, hypothalamus, and adrenal glands
Functions Increases the level of alertness and wakefulness, stimulates various
processes of the body
Epinephrine (Epi)
Type Excitatory
Released from Chromaffin cells of the medulla of adrenal gland
Functions The fight-or-flight response (increased heart rate, blood pressure,
and glucose production)
Dopamine
Type Both excitatory and inhibitory
Released from Substantia nigra
Functions Inhibits unnecessary movements, inhibits the release of prolactin, and
stimulates the secretion of growth hormone
Gamma–Amino Butyric Acid (GABA)
Type Inhibitory
Released from Neurons of the spinal cord, cerebellum, basal ganglia, and
areas of the cerebral cortex
Functions Reduces neuronal excitability throughout the nervous system
Glutamate (Glu)
Type Excitatory
Released from Sensory neurons and cerebral cortex
Functions Regulates central nervous system excitability, learning process, memory
Serotonin (5-HT)
Type Inhibitory
Released from Neurons of the brainstem and gastrointestinal tract,
thrombocytes
Functions Regulates body temperature, perception of pain, emotions, and
sleep cycle
Histamine
Type Excitatory
Released from Hypothalamus, cells of the stomach mucosa, mast cells, and
basophils in the blood
Functions Regulates wakefulness, blood pressure, pain, and sexual
behaviour; increases the acidity of the stomach; mediates
inflammatory reactions
BRAIN WAVES
 At the root of all our thoughts, emotions and behaviours is the
communication between neurons within our brains. Brainwaves are produced by
synchronised electrical pulses from masses of neurons communicating with each
other.
 Brainwaves are detected using sensors placed on the scalp. They are divided into
bandwidths to describe their functions (below), but are best thought of as a
continuous spectrum of consciousness; from slow, loud and functional - to fast, subtle,
and complex.
 Our brainwaves change according to what we’re doing and feeling. When
slower brainwaves are dominant we can feel tired, slow, sluggish, or dreamy.
The higher frequencies are dominant when we feel wired, or hyper-alert.
 Brainwave speed is measured in Hertz (cycles per second) and they are divided
into bands delineating slow, moderate, and fast waves.
DELTA WAVES THETA WAVES ALPHA WAVES
BETA WAVES GAMMA WAVES
DELTA WAVES (.5 TO 3 HZ)
 Delta brainwaves are slow, loud brainwaves (low frequency
and deeply penetrating, like a drum beat).
 They are generated in deepest meditation and dreamless
sleep.
 Delta waves suspend external awareness and are the source
of empathy.
 Healing and regeneration are stimulated in this state, and that
is why deep restorative sleep is so essential to the healing
process.
THETA WAVES (3 TO 8 HZ)
 Theta brainwaves occur most often in sleep but are also
dominant in deep meditation.
 Theta is our gateway to learning, memory, and intuition. In
theta, our senses are withdrawn from the external world and
focused on signals originating from within.
 It is that twilight state which we normally only experience
fleetingly as we wake or drift off to sleep.
 In theta we are in a dream; vivid imagery, intuition and
information beyond our normal conscious awareness.
 It’s where we hold our ‘stuff’, our fears, troubled history, and
nightmares.
ALPHA WAVES (8 TO 12 HZ)
 Alpha brainwaves are dominant during quietly
flowing thoughts, and in some meditative states.
 Alpha is ‘the power of now’, being here, in the
present.
 Alpha is the resting state for the brain.
 Alpha waves aid overall mental coordination,
calmness, alertness, mind/body integration and
learning.
BETA WAVES (12 TO 38 HZ)
 Beta brainwaves dominate our normal waking state of
consciousness when attention is directed towards cognitive
tasks and the outside world.
 Beta is a ‘fast’ activity, present when we are alert, attentive,
engaged in problem solving, judgment, decision making, or
focused mental activity.
GAMMA WAVES (38 TO 42 HZ)
 Gamma brainwaves are the fastest of brain waves (high
frequency, like a flute), and relate to simultaneous
processing of information from different brain areas.
 Gamma brainwaves pass information rapidly and
quietly.
 The most subtle of the brainwave frequencies, the mind
has to be quiet to access gamma.
 It is highly active when in states of universal love,
altruism, and the ‘higher virtues’.
EEG (ELECTROENCEPHALOGRAM)
 An electroencephalogram (EEG) is a test used to evaluate the electrical activity in the
brain.
 Brain cells communicate with each other through electrical impulses.
 An EEG can be used to help detect potential problems associated with this activity.
 An EEG tracks and records brain wave patterns.
 Small flat metal discs called electrodes are attached to the scalp with wires.
 The electrodes analyse the electrical impulses in the brain and send signals to a
computer that records the results.
 The electrical impulses in an EEG recording look like wavy lines with peaks and valleys.
 These lines allow doctors to quickly assess whether there are abnormal patterns.
 Any irregularities may be a sign of seizures or other brain disorders.
WHY IS AN EEG PERFORMED?
 An EEG is used to detect problems in the electrical activity of the brain that may be associated with
certain brain disorders.
The measurements given by an EEG are used to confirm or rule out various conditions, including:
 seizure disorders (such as epilepsy)
 Head Injury
 Encephalitis (Inflammation Of The Brain), Encephalopathy (disease that causes brain dysfunction).
 Brain Tumour
 Memory Problems
 Sleep Disorders
 Stroke
 Dementia
 When someone is in a coma, an EEG may be performed to determine the level of brain activity.
 The test can also be used to monitor activity during brain surgery.
PREPARATIONS BEFORE THE EEG TEST
 Wash your hair the night before the EEG, and don’t put any products (like sprays or gels) in your
hair on the day of the test.
 Inform about the existing medications to the doctor.
 Avoid eating or drinking containing caffeine for at least eight hours before the test.
 Less sleep during previous night for proper sleep during the test or else the person will be given
sedatives to properly sleep during the test.
STEPS INVOLVED IN EEG TEST
Specialized technicians administer EEGs at hospitals, doctor’s offices, and laboratories. The test
usually takes 30 to 60 minutes to complete, and involves the following steps:
 You’ll lie down on your back in a reclining chair or on a bed.
 The technician will measure your head and mark where to place the electrodes. These spots
are scrubbed with a special cream that helps the electrodes get a high-quality reading.
 The technician will put a sticky gel adhesive on 16 to 25 electrodes, and attach them to spots
on your scalp.
 Once the test begins, the electrodes send electrical impulse data from your brain to the
recording machine. This machine converts the electrical impulses into visual patterns that appear
on a screen. A computer saves these patterns.
 The technician may instruct you to do certain things while the test is in progress. They may ask
you to lie still, close your eyes, breathe deeply, or look at stimuli (such as a flashing light or a
picture).
 After the test is complete, the technician will remove the electrodes from your scalp.
 During the test, very little electricity passes between the electrodes and your skin, so you’ll
feel very little to no discomfort.
 In some instances, a person may undergo a 24-hour EEG. These EEGs use video to capture
seizure activity. The EEG may show abnormalities even if the seizure does not occur during
the test. However, it does not always show past abnormalities related to seizure.
EEG TEST RESULTS - Normal results
 Electrical activity in the brain appears in an EEG as a pattern of waves.
 Different levels of consciousness, like sleeping and waking, have a specific range of frequencies
of waves per second that are considered normal.
 For example, the wave patterns move faster when you’re awake than when you’re asleep.
 The EEG will show if the frequency of waves or patterns are normal.
 Normal activity typically means you don’t have a brain disorder.
EEG TEST RESULTS - Abnormal results
 Epilepsy or another seizure disorder
 Abnormal bleeding or hemorrhage, Head injury
 Sleep disorder
 Encephalitis (swelling of the brain)
 Tumour
 Dead tissue due to a blockage of blood flow
 Migraines
 Alcohol or drug abuse
NEURAL DISORDERS
 Alzheimer's Disease (AD)
 Dementia
 Parkinson's Disease
 Epilepsy
 Schizophrenia
ALZHEIMER'S DISEASE (AD)
 Alzheimer's Disease (AD), also known as Alzheimer disease, or just Alzheimer’s.
 It is a chronic neurodegenerative disease that usually starts slowly and gets worse over time.
 The most common early symptom is difficulty in remembering recent events (short term
memory loss).
 As the disease advances, symptoms can include: problems with language, disorientation
(including easily getting lost), mood swings, loss of motivation, not managing self care, and
behavioural issues.
 The onset of Alzheimer's disease is usually very slow and gradual, seldom occurring before
age 65.
 Over time, however, it follows a progressively more serious course.
 Problems of memory, particularly recent or short-term memory, are common early in the course of
the disease.
 Mild personality changes, such as less spontaneity or a sense of apathy and a tendency to withdraw
from social interactions, may occur early in the illness.
 As the disease progresses, problems in abstract thinking or in intellectual functioning develop.
 The average course of the disease from the time it is recognized to death is about 6 to 8 years, but
it may range from under 2 years to over 20 years. Those who develop the disorder later in life may
die from other illnesses (such as heart disease) before Alzheimer's disease reaches its final and most
serious stage.
 The reaction of an individual to the illness and the way he or she copes with it also varies and may
depend on such factors as lifelong personality patterns and the nature and severity of the stress in
the immediate environment.
Warning Signs of Alzheimer's Disease
 Confusion with time or place
 Decreased or poor judgment
 Difficulty completing familiar tasks
 Changes in mood and personality
 Memory changes that disrupt daily life
 Withdrawal from work or social activities
 Challenges in planning or solving problems
 New problems with words in speaking or writing
 Misplacing things and losing the ability to retrace steps
 Trouble understanding visual images and spatial relationships
DEMENTIA
 Not a specific disease, dementia is a group of conditions characterized by impairment of at
least two brain functions, such as memory loss and judgement.
 Symptoms include forgetfulness, limited social skills and thinking abilities so impaired that it
interferes with daily functioning.
 A deficiency in a chemical (Acetylcholine) utilized by nervous tissues to transmit impulses
and communicate between each other.
 Many of the symptoms, notably the learning difficulties were explained by the lack of
Acetylcholine.
People may experience:
 Cognitive: mental decline, confusion in the evening hours, disorientation, inability to speak or
understand language, making things up, mental confusion, or inability to recognize common
things
 Behavioural: irritability, personality changes, restlessness, lack of restraint, or wandering and
getting lost
 Mood: anxiety, loneliness, mood swings, or nervousness
 Psychological: depression, hallucination, or paranoia
 Muscular: inability to combine muscle movements or unsteady walking
 Also common: memory loss, falling, jumbled speech, or sleep disorder
 Therapies
 Rehabilitation and Occupational Therapy
PARKINSONS DISEASE
 Nerve cell damage in the brain causes dopamine levels to drop, leading to the symptoms
of Parkinson's.
 Parkinson's often starts with a tremor in one hand. Other symptoms are slow movement,
stiffness and loss of balance.
 Medication can help control the symptoms of Parkinson’s.
Medications
 Dopamine promoter, Antidepressant, Cognition-enhancing medication and Anti-Tremor

People may experience:
 Tremor: can occur at rest, in the hands, limbs, or can be postural
 Muscular: stiff muscles, difficulty standing, difficulty walking, difficulty with bodily movements,
involuntary movements, muscle rigidity, problems with coordination, rhythmic muscle
contractions, slow bodily movement, or slow shuffling gait
 Sleep: early awakening, nightmares, restless sleep, or sleep disturbances
 Whole body: fatigue, dizziness, poor balance, or restlessness
 Cognitive: amnesia, confusion in the evening hours, dementia, or difficulty thinking and
understanding
 Speech: difficulty speaking, soft speech, or voice box spasms
 Nasal: distorted sense of smell or loss of smell
 Urinary: dribbling of urine or leaking of urine
 Mood: anxiety or apathy
 Facial: jaw stiffness or reduced facial expression
 Also common: blank stare, constipation, depression, difficulty swallowing, drooling, falling,
fear of falling, loss in contrast sensitivity, neck tightness, small handwriting, trembling,
unintentional writhing, or weight
EPILEPSY
 Epilepsy may occur as a result of a genetic disorder or an acquired brain injury, such as a trauma or
stroke.
 During a seizure, a person experiences abnormal behaviour, symptoms and sensations, sometimes
including loss of consciousness.
 Epilepsy is usually treated by medication and in some cases by surgery, devices or dietary changes.
 Anticonvulsant - Prevents or controls seizures, relieves pain and treats symptoms of certain
psychiatric disorders
 Sedative Causes drowsiness, calmness and dulled senses. Some types may become addictive.
 Nerve pain medication - Blocks pain caused by damaged nerves.

 Usually self-diagnosable
 During a seizure, a person experiences abnormal behaviour, symptoms and sensations,
sometimes including loss of consciousness. There are few symptoms between seizures.
 People may experience:
 Whole body: fainting or fatigue
 Muscular: rhythmic muscle contractions or muscle spasms
 Sensory: aura or pins and needles
 Also common: seizures, amnesia, anxiety, depression, or staring spells
SCHIZOPHRENIA
 The exact cause of schizophrenia isn't known, but a combination of genetics, environment and
altered brain chemistry and structure may play a role.
 Schizophrenia is characterized by thoughts or experiences that seem out of touch with reality,
disorganized speech or behaviour and decreased participation in daily activities. Difficulty with
concentration and memory may also be present.
 Treatment is usually lifelong and often involves a combination of medications, psychotherapy
and coordinated specialist care services.
 People may experience:
 Behavioural: social isolation, disorganized behaviour, aggression, agitation, compulsive
behaviour, excitability, hostility, repetitive movements, self-harm, or lack of restraint
 Cognitive: thought disorder, delusion, amnesia, belief that an ordinary event has special and
personal meaning, belief that thoughts aren't one's own, disorientation, mental confusion,
slowness in activity, or false belief of superiority
 Mood: anger, anxiety, apathy, feeling detached from self, general discontent, loss of interest or
pleasure in activities, elevated mood, or inappropriate emotional response
 Psychological: hallucination, paranoia, hearing voices, depression, fear, persecutory delusion,
religious delusion
 Speech: circumstantial speech, incoherent speech, rapid and frenzied speaking, or speech
disorder
 Also common: fatigue, impaired motor coordination, lack of emotional response, or memory loss
Medications
 Antipsychotic - Reduces or improves the symptoms of certain psychiatric conditions
 Anti-Tremor - Helps control tremor, shaking and unsteadiness.

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Neurophysiology

  • 2. INTRODUCTION  The field of neurophysiology provides insight into how the nervous system works and how its dysfunction can lead to disease.  Physiology is the study of how organisms and their parts function.  Neurophysiology can be defined as the study of the functioning of the nervous system, which includes the brain, the spinal cord, peripheral nerves, and sensory organs.
  • 3.  The nervous system is a complex collection of nerves and specialized cells known as neurons that transmit signals between different parts of the body. It is essentially the body's electrical wiring.  Structurally, the nervous system has two components: the central nervous system and the peripheral nervous system.  The central nervous system is made up of the brain, spinal cord and nerves.  The peripheral nervous system consists of sensory neurons, ganglia (clusters of neurons) and nerves that connect to one another and to the central nervous system.
  • 4.  Functionally, the nervous system has two main subdivisions: the somatic, or voluntary, component; and the autonomic, or involuntary, component.  The autonomic nervous system regulates certain body processes, such as blood pressure and the rate of breathing, that work without conscious effort.  The somatic system consists of nerves that connect the brain and spinal cord with muscles and sensory receptors in the skin.
  • 5.  Neurons send signals to other cells through thin fibers called axons, which cause chemicals known as neurotransmitters to be released at junctions called synapses.  There are over 100 trillion neural connections in the average human brain, though the number and location can vary.  A synapse gives a command to the cell and the entire communication process typically takes only a fraction of a millisecond.  Sensory neurons react to physical stimuli such as light, sound and touch and send feedback to the central nervous system about the body's surrounding environment.  Motor neurons, located in the central nervous system or in peripheral ganglia, transmit signals to activate the muscles or glands.  Glial cells, derived from the Greek word for "glue," are specialized cells that support, protect or nourish nerve cells.  The brain's connections and thinking ability grew over thousands of years of evolution.
  • 6. STRUCTURE OF NEURONS  The neuron is the basic building block of the brain and central nervous system.  Neurons are specialized cells that transmit chemical and electrical signals.  The brain is made up entirely of neurons and glial cells, which are non-neuronal cells that provide structure and support for the neurons.  Nearly 86 billion neurons work together within the nervous system to communicate with the rest of the body.  They are responsible for everything from consciousness and thought to pain and hunger.
  • 7.
  • 8.  Cell Body  Like other cells, each neuron has a cell body (or soma) that contains a nucleus, smooth and rough endoplasmic reticulum, Golgi apparatus, mitochondria, and other cellular components.  Dendrite  Dendrites are branch-like structures extending away from the cell body, and their job is to receive messages from other neurons and allow those messages to travel to the cell body.  Although some neurons do not have any dendrites, other types of neurons have multiple dendrites.  Dendrites can have small protrusions called dendritic spines, which further increase surface area for possible connections with other neurons.
  • 9.  Axon  An axon, at its most basic, is a tube-like structure that carries an electrical impulse from the cell body (or from another cell’s dendrites) to the structures at opposite end of the neuron—axon terminals, which can then pass the impulse to another neuron.  The cell body contains a specialized structure, the axon hillock, which serves as a junction between the cell body and the axon.  Synapse  The synapse is the chemical junction between the axon terminals of one neuron and the dendrites of the next.  It is a gap where specialized chemical interactions can occur, rather than an actual structure.
  • 10.  Myelin Sheath  Some axons are covered with myelin, a fatty material that wraps around the axon to form the myelin sheath.  This external coating functions as insulation to minimize dissipation of the electrical signal as it travels down the axon.  Myelin’s presence on the axon greatly increases the speed of conduction of the electrical signal, because the fat prevents any electricity from leaking out.  This insulation is important, as the axon from a human motor neuron can be as long as a meter—from the base of the spine to the toes.  Periodic gaps in the myelin sheath are called nodes of Ranvier.
  • 11.  Glial Cells  Myelin is produced by glial cells (or simply glia, or “glue” in Greek), which are non- neuronal cells that provide support for the nervous system.  Glial function to hold neurons in place (hence their Greek name), supply them with nutrients, provide insulation, and remove pathogens and dead neurons.  In the central nervous system, the glial cells that form the myelin sheath are called oligodendrocytes; in the peripheral nervous system, they are called Schwann cells.
  • 12. TYPES OF NEURON  Two basic classes of neurons  Based on structure – 1. Unipolar 2. Bipolar 3. Multipolar 4. Pseudounipolar  Based on functions – 1. Sensory neurons 2. Motor neurons
  • 13. Based on structure  Neurons are broadly divided into four basic types: unipolar, bipolar, multipolar, and pseudounipolar.  Unipolar neurons have only one structure that extends away from the soma. These neurons are not found in vertebrates but are found in insects where they stimulate muscles or glands.  A bipolar neuron has one axon and one dendrite extending from the soma. An example of a bipolar neuron is a retinal bipolar cell, which receives signals from photoreceptor cells that are sensitive to light and transmits these signals to ganglion cells that carry the signal to the brain.
  • 14.  Multipolar neurons are the most common type of neuron. Each multipolar neuron contains one axon and multiple dendrites. Multipolar neurons can be found in the central nervous system (brain and spinal cord). The Purkinje cell, a multipolar neuron in the cerebellum, has many branching dendrites, but only one axon.  Pseudounipolar cells share characteristics with both unipolar and bipolar cells.  Most sensory neurons are pseudounipolar and have an axon that branches into two extensions: one connected to dendrites that receives sensory information and another that transmits this information to the spinal cord.
  • 15.  Sensory Neurons  Sensory neurons are neurons responsible for converting external stimuli from the environment into corresponding internal stimuli.  They are activated by sensory input and send projections to other elements of the nervous system, ultimately conveying sensory information to the brain or spinal cord. Based on function
  • 16.  Sensory neurons are activated by physical modalities (such as visible light, sound, heat, physical contact, etc.) or by chemical signals (such as smell and taste).  Most sensory neurons are pseudounipolar, meaning they have an axon that branches into two extensions—one connected to dendrites that receive sensory information and another that transmits this information to the spinal cord.
  • 17.  Motor Neurons  Motor neurons are neurons located in the central nervous system, and they project their axons outside of the CNS to directly or indirectly control muscles.  The interface between a motor neuron and muscle fiber is a specialized synapse called the neuromuscular junction.  The structure of motor neurons is multipolar, meaning each cell contains a single axon and multiple dendrites.  This is the most common type of neuron.
  • 18.  Interneurons  Interneurons are neither sensory nor motor; rather, they act as the “middlemen” that form connections between the other two types.  Located in the CNS, they operate locally, meaning their axons connect only with nearby sensory or motor neurons.  Interneurons can save time and therefore prevent injury by sending messages to the spinal cord and back instead of all the way to the brain.  Like motor neurons, they are multipolar in structure.
  • 19. FUNCTIONS OF NEURON 1. Receive signals (or information). 2. Integrate incoming signals (to determine whether the information should be passed along). 3. Communicate signals to target cells (other neurons or muscles or glands).
  • 20. MYELINATED AND NON - MYELINATED NERVE FIBRES
  • 21.
  • 22.
  • 23. NERVE IMPLUSE PRODUCTION  The central nervous system (CNS) goes through a three-step process when it functions: sensory input, neural processing, and motor output.  The sensory input stage is when the neurons (or excitable nerve cells) of the sensory organs are excited electrically.  Neural impulses from sensory receptors are sent to the brain and spinal cord for processing.  After the brain has processed the information, neural impulses are then conducted from the brain and spinal cord to muscles and glands, which is the resulting motor output.
  • 24.  When a neuron is not actively transmitting a nerve impulse, it is in a resting state, ready to transmit a nerve impulse.  During the resting state, the sodium-potassium pump maintains a difference in charge across the cell membrane of the neuron.  The sodium-potassium pump is a mechanism of active transport that moves sodium ions out of cells and potassium ions into cells.  The sodium-potassium pump moves both ions from areas of lower to higher concentration, using energy in ATP and carrier proteins in the cell membrane.
  • 25.  The figure below shows in greater detail how the sodium-potassium pump works.  Sodium is the principal ion in the fluid outside of cells, and potassium is the principal ion in the fluid inside of cells.  These differences in concentration create an electrical gradient across the cell membrane, called resting potential. Tightly controlling membrane resting potential is critical for the transmission of nerve impulses.
  • 26.  An action potential, also called a nerve impulse, is an electrical charge that travels along the membrane of a neuron.  It can be generated when a neuron’s membrane potential is changed by chemical signals from a nearby cell.  In an action potential, the cell membrane potential changes quickly from negative to positive as sodium ions flow into the cell through ion channels, while potassium ions flow out of the cell.
  • 27.  The action potential is a rapid change in polarity that moves along the nerve fiber from neuron to neuron. In order for a neuron to move from resting potential to action potential-the neuron must be stimulated by pressure, electricity, chemicals, or another form of stimuli.  The level of stimulation that a neuron must receive to reach action potential is known as the threshold of excitation, and until it reaches that threshold, nothing will happen.  Different neurons are sensitive to different stimuli, although most can register pain.
  • 28.  The change in membrane potential results in the cell becoming depolarized.  An action potential works on an all-or-nothing basis. That is, the membrane potential has to reach a certain level of depolarization, called the threshold, otherwise, an action potential will not start.  This threshold potential varies but is generally about 15 millivolts (mV) more positive than the cell's resting membrane potential.  If a membrane depolarization does not reach the threshold level, an action potential will not happen. You can see in Figure below that two depolarizations did not reach the threshold level of -55mV.
  • 29.  The first channels to open are the sodium ion channels, which allow sodium ions to enter the cell.  The resulting increase in positive charge inside the cell (up to about +40 mV) starts the action potential. This is called the depolarization of the membrane.  Potassium ion channels then open, allowing potassium ions to flow out of the cell, which ends the action potential. The inside of the membrane becomes negative again. This is called repolarization of the membrane.  Both of the ion channels then close, and the sodium-potassium pump restores the resting potential of -70 mV.  The action potential will move down the axon toward the synapse like a wave would move along the surface of the water.
  • 30.  In myelinated neurons, ion flows occur only at the nodes of Ranvier.  As a result, the action potential signal "jumps" along the axon membrane from node to node rather than spreading smoothly along the membrane, as they do in axons that do not have a myelin sheath.  This is due to a clustering of Na+ and K+ ion channels at the Nodes of Ranvier.  Unmyelinated axons do not have nodes of Ranvier, and ion channels in these axons are spread over the entire membrane surface.
  • 31. TRANSMITTING NERVE IMPULSES  The place where an axon terminal meets another cell is called a synapse. This is where the transmission of a nerve impulse to another cell occurs. The cell that sends the nerve impulse is called the presynaptic cell, and the cell that receives the nerve impulse is called the postsynaptic cell.  Some synapses are purely electrical and make direct electrical connections between neurons. However, most synapses are chemical synapses. Transmission of nerve impulses across chemical synapses is more complex.
  • 32.  At a chemical synapse, both the presynaptic and postsynaptic areas of the cells are full of the molecular machinery that is involved in the transmission of nerve impulses.  As shown in the diagram below, the presynaptic area contains many tiny spherical vessels called synaptic vesicles that are packed with chemicals called neurotransmitters.  When an action potential reaches the axon terminal of the presynaptic cell, it opens channels that allow calcium to enter the terminal.
  • 33.  Calcium causes synaptic vesicles to fuse with the membrane, releasing their contents into the narrow space between the presynaptic and postsynaptic membranes. This area is called the synaptic cleft.  The neurotransmitter molecules travel across the synaptic cleft and bind to receptors, which are proteins that are embedded in the membrane of the postsynaptic cell.
  • 34.
  • 35.
  • 36.  Membrane potential – It is the difference in the total charge between the inside of the cell and the outside of the cell.  Resting membrane potential – It is the difference in voltage across the cell membrane in a resting state. (A neuron is said to be at rest when it does not any impulse. At this stage, the axonal membrane of the neuron is more permeable the potassium ions and not permeable to the sodium ions.)  Action potential – It is a short-term change in the electrical potential that travels across the neuron cell.
  • 37.  Resting potential: Before the action potential occurs, the neuron should be in a state of rest (approx. –70 mV) A typical action potential will last for roughly 3 – 5 milliseconds and contain 3 key stages:  Depolarisation: A rising spike corresponds to the depolarisation of the membrane via sodium influx (up to roughly +30 mV)  occurs when ion channels open and cause a change in membrane potential  Hence, depolarisation at one point of the axon triggers the opening of ion channels in the segment of the axon  This causes depolarisation to spread along the length of the axon as a unidirectional wave
  • 38.  Repolarisation: A falling spike corresponds to repolarisation via potassium efflux (undershoots to approx. –80 mV)  Refractory period: The oscilloscope trace returns to the level of the resting potential (due to the action of the Na+/K+ pump) An action potential will only occur if the initial depolarisation exceeds a threshold potential of approximately –55 mV  Nerve impulses are action potentials that move along the length of an axon as a wave of depolarisation
  • 39.
  • 40.
  • 41. IMPULSE PROPAGATION  Propagation of nerve impulses is the result of local currents that cause each successive part of the axon to reach the threshold potential.
  • 42. ALL OR NONE LAW  Action potentials are generated within the axon according to the all-or-none principle  An action potential of the same magnitude will always occur provided a minimum electrical stimulus is generated  This minimum stimulus – known as the threshold potential (–55 mV) – is the level required to open voltage-gated ion channels  If the threshold potential is not reached, an action potential cannot be generated and hence the neuron will not fire
  • 43. CONTINUOUS CONDUCTION AND SALTATORY CONDUCTION  Continuous conduction of an impulse - It propagates from one segment of a neurons membrane to the next.  Saltatory conduction - However, to accelerate this process, most nerve cells are enclosed by a multilamellar membrane, the so called myelin sheath (consisting of Schwann cells).  This sheath is not entirely enclosed around the axon but regularly leaves uncovered sectors called “nodes of Ranvier“.  The covered membrane regions do not posses ion channels and thus no connection to the extracellular matrix. In this case these regions can not develop an action potential.  Therefore the equalizing currents agitate between the nodes of Ranvier, from each node to the successive one.  As a result the impulses proceed about ten times faster along the axon as a lot less depolarization need to happen.  Also the energy required for the reestablishing of the resting potential is less, therefore the process is also much more energy efficient.
  • 44.
  • 45. SYNAPSE  Synapse can be defined as functional junction between parts of two different neurons.  There is no anatomical continuity between two neurons involved in the formation of synapse.  At level of synapse, impulse gets conducted from one neuron to another due to release of neurotransmitters, like Acetyl Choline, noradrenaline, serotonin, etc.
  • 46.  The synapses, which require release of some chemical substance (neurotransmitter) during synaptic transmission, are termed as chemical synapses.  In human body, almost all synapses are chemical type, rarely also consists of electrical type.  Presynaptic region is mostly contributed by axon and postsynaptic region may be contributed by dendrite or soma (cell body) or axon of another neuron.
  • 47. Properties of Synapse: 1. One-way conduction (unidirectional conduction):  In chemical synapse, since neurotransmitter is present only in presynaptic region, impulse gets conducted from pre- to postsynaptic region only and not vice versa. 2. Synaptic delay is for neurotransmitter to:  a. Get released from synaptic vesicles when action potential has reached presynaptic region.  b. Pass through synaptic cleft.  c. Act on postsynaptic region to bring about production of action potential in postsynaptic region.  For all the above events to be brought about, sometime is required. This is known as synaptic delay, which is normally about 0.5 msec at every synapse.
  • 48. 3. Fatigability:  When synapses are continuously stimulated, after some time, due to exhaustion of neurotransmitter at presynaptic terminals, impulses fail to get conducted.  This results in fatigue occurring at level of synapse.  Fatigue is a temporary phenomenon. If some rest is given to neurons, resting facilitates synthesis of neurotransmitter for further conduction of impulse across synapse. 4. Convergence and divergence:  Impulses from one presynaptic nerve fiber may end on postsynaptic region of large number neurons and this is called as divergence.  When nerve fibers of different presynaptic neurons end on a common postsynaptic neuron, this is known as convergence.  In CNS, on an average about 10000 synapses are found on any one neuron.
  • 49.
  • 50. 5. Summation:  When a stimulus of subthreshold strength is applied, no action potential will be passed to post synaptic neuron.  But if many subthreshold stimuli are applied at presynaptic region, effects of these stimuli get added up and lead to action potential development in postsynaptic region. This is as summation.  There are two types of summation namely spatial and temporal. 6. Excitation or inhibition:  The impulse conduction across a synapse may either stimulate or inhibit activity of postsynaptic region.  If there is stimulatory influence, then there will be production of action potential in postsynaptic neuron  if it has an inhibitory influence, then there is no action potential generation in postsynaptic region.
  • 51. TYPES OF SYNAPTIC CONNECTIONS BASED ON FUNCTION  CHEMICAL  ELECTRICAL BASED ON STRUCTURE  AXODENDRITIC  AXOSOMATIC  AXOAXONIC
  • 52.
  • 53. Chemical synapse  A chemical synapse is a gap between two neurons where information passes chemically, in the form of neurotransmitter molecules.  chemical synapses are:  slow  active (require ligand-gated channels) like Na- K channels  unidirectional
  • 54. Electrical synapse  An electrical synapse is a gap which has channel proteins connecting the two neurons.  While electrical synapses are faster (electricity moves quicker than molecules, and you don't need receptors).  You often find electrical synapses in systems requiring quick responses, like instincts and , are often found in all nervous systems, including the human brain. •very rapid (no synaptic delay) •passive •Bidirectional -"post"synaptic cell can actually send messages to the "pre"synaptic cell
  • 55. Axodendritic synapse one between the axon of one neuron and the dendrites of another.
  • 56. Axosomatic synapse one between the axon of one neuron and the body of another.
  • 57. Axoaxonic synapse one between the axon of one neuron and the axon of another neuron.
  • 58. SYNAPTIC TRANSMISSION  Synapses are junctions between neurons and receptor or effector cells.  Nerves transmit electrical impulses by changing the ionic distribution across the neuronal membrane (membrane potential).  Synapses are the physical gaps that separate neurons from other cells (other neurons and receptor or effector cells).  Neurons transmit information across synapses by converting the electrical signal into a chemical signal
  • 59. Mechanism of Synaptic Transmission:  Arrival of impulse  Depolarization of pre-synaptic region  Influx of calcium ions from interstitial space (outside the neuron) into presynaptic region  Release of neurotransmitter  Passage of neurotransmitter through synaptic cleft  Binding of neurotransmitter to receptors on postsynaptic region.  Change in electrical activity of postsynaptic region.  Generation of action potential in post synaptic neuron and thereby the transmission of signal continues from neuron to neuron.
  • 60.
  • 61. NEUROTRANSMITTERS  Neurotransmitters are often referred to as the body’s chemical messengers. They are the molecules used by the nervous system to transmit messages between neurons, or from neurons to muscles.  A neurotransmitter influences a neuron in one of three ways: excitatory, inhibitory or modulatory.  An excitatory transmitter promotes the generation of an electrical signal called an action potential in the receiving neuron, while an inhibitory transmitter prevents it.  Most neurotransmitters are either small amine molecules, amino acids, or neuropeptides.
  • 62. Acetylcholine (ACh) Type Excitatory in all cases except in the heart (inhibitory) Released from Motor neurons, basal ganglia, preganglionic neurons of the autonomic nervous system, postganglionic neurons of the parasympathetic nervous system, and postganglionic neurons of the sympathetic nervous system that innervate the sweat glands Functions Regulates the sleep cycle, essential for muscle functioning
  • 63. Norepinephrine (NE) Type Excitatory Released from Brainstem, hypothalamus, and adrenal glands Functions Increases the level of alertness and wakefulness, stimulates various processes of the body
  • 64. Epinephrine (Epi) Type Excitatory Released from Chromaffin cells of the medulla of adrenal gland Functions The fight-or-flight response (increased heart rate, blood pressure, and glucose production)
  • 65. Dopamine Type Both excitatory and inhibitory Released from Substantia nigra Functions Inhibits unnecessary movements, inhibits the release of prolactin, and stimulates the secretion of growth hormone
  • 66. Gamma–Amino Butyric Acid (GABA) Type Inhibitory Released from Neurons of the spinal cord, cerebellum, basal ganglia, and areas of the cerebral cortex Functions Reduces neuronal excitability throughout the nervous system
  • 67. Glutamate (Glu) Type Excitatory Released from Sensory neurons and cerebral cortex Functions Regulates central nervous system excitability, learning process, memory
  • 68. Serotonin (5-HT) Type Inhibitory Released from Neurons of the brainstem and gastrointestinal tract, thrombocytes Functions Regulates body temperature, perception of pain, emotions, and sleep cycle
  • 69. Histamine Type Excitatory Released from Hypothalamus, cells of the stomach mucosa, mast cells, and basophils in the blood Functions Regulates wakefulness, blood pressure, pain, and sexual behaviour; increases the acidity of the stomach; mediates inflammatory reactions
  • 70. BRAIN WAVES  At the root of all our thoughts, emotions and behaviours is the communication between neurons within our brains. Brainwaves are produced by synchronised electrical pulses from masses of neurons communicating with each other.  Brainwaves are detected using sensors placed on the scalp. They are divided into bandwidths to describe their functions (below), but are best thought of as a continuous spectrum of consciousness; from slow, loud and functional - to fast, subtle, and complex.
  • 71.  Our brainwaves change according to what we’re doing and feeling. When slower brainwaves are dominant we can feel tired, slow, sluggish, or dreamy. The higher frequencies are dominant when we feel wired, or hyper-alert.  Brainwave speed is measured in Hertz (cycles per second) and they are divided into bands delineating slow, moderate, and fast waves.
  • 72. DELTA WAVES THETA WAVES ALPHA WAVES BETA WAVES GAMMA WAVES
  • 73. DELTA WAVES (.5 TO 3 HZ)  Delta brainwaves are slow, loud brainwaves (low frequency and deeply penetrating, like a drum beat).  They are generated in deepest meditation and dreamless sleep.  Delta waves suspend external awareness and are the source of empathy.  Healing and regeneration are stimulated in this state, and that is why deep restorative sleep is so essential to the healing process.
  • 74. THETA WAVES (3 TO 8 HZ)  Theta brainwaves occur most often in sleep but are also dominant in deep meditation.  Theta is our gateway to learning, memory, and intuition. In theta, our senses are withdrawn from the external world and focused on signals originating from within.  It is that twilight state which we normally only experience fleetingly as we wake or drift off to sleep.  In theta we are in a dream; vivid imagery, intuition and information beyond our normal conscious awareness.  It’s where we hold our ‘stuff’, our fears, troubled history, and nightmares.
  • 75. ALPHA WAVES (8 TO 12 HZ)  Alpha brainwaves are dominant during quietly flowing thoughts, and in some meditative states.  Alpha is ‘the power of now’, being here, in the present.  Alpha is the resting state for the brain.  Alpha waves aid overall mental coordination, calmness, alertness, mind/body integration and learning.
  • 76. BETA WAVES (12 TO 38 HZ)  Beta brainwaves dominate our normal waking state of consciousness when attention is directed towards cognitive tasks and the outside world.  Beta is a ‘fast’ activity, present when we are alert, attentive, engaged in problem solving, judgment, decision making, or focused mental activity.
  • 77. GAMMA WAVES (38 TO 42 HZ)  Gamma brainwaves are the fastest of brain waves (high frequency, like a flute), and relate to simultaneous processing of information from different brain areas.  Gamma brainwaves pass information rapidly and quietly.  The most subtle of the brainwave frequencies, the mind has to be quiet to access gamma.  It is highly active when in states of universal love, altruism, and the ‘higher virtues’.
  • 78. EEG (ELECTROENCEPHALOGRAM)  An electroencephalogram (EEG) is a test used to evaluate the electrical activity in the brain.  Brain cells communicate with each other through electrical impulses.  An EEG can be used to help detect potential problems associated with this activity.  An EEG tracks and records brain wave patterns.
  • 79.  Small flat metal discs called electrodes are attached to the scalp with wires.  The electrodes analyse the electrical impulses in the brain and send signals to a computer that records the results.  The electrical impulses in an EEG recording look like wavy lines with peaks and valleys.  These lines allow doctors to quickly assess whether there are abnormal patterns.  Any irregularities may be a sign of seizures or other brain disorders.
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  • 84. WHY IS AN EEG PERFORMED?  An EEG is used to detect problems in the electrical activity of the brain that may be associated with certain brain disorders. The measurements given by an EEG are used to confirm or rule out various conditions, including:  seizure disorders (such as epilepsy)  Head Injury  Encephalitis (Inflammation Of The Brain), Encephalopathy (disease that causes brain dysfunction).
  • 85.  Brain Tumour  Memory Problems  Sleep Disorders  Stroke  Dementia  When someone is in a coma, an EEG may be performed to determine the level of brain activity.  The test can also be used to monitor activity during brain surgery.
  • 86. PREPARATIONS BEFORE THE EEG TEST  Wash your hair the night before the EEG, and don’t put any products (like sprays or gels) in your hair on the day of the test.  Inform about the existing medications to the doctor.  Avoid eating or drinking containing caffeine for at least eight hours before the test.  Less sleep during previous night for proper sleep during the test or else the person will be given sedatives to properly sleep during the test.
  • 87. STEPS INVOLVED IN EEG TEST Specialized technicians administer EEGs at hospitals, doctor’s offices, and laboratories. The test usually takes 30 to 60 minutes to complete, and involves the following steps:  You’ll lie down on your back in a reclining chair or on a bed.  The technician will measure your head and mark where to place the electrodes. These spots are scrubbed with a special cream that helps the electrodes get a high-quality reading.  The technician will put a sticky gel adhesive on 16 to 25 electrodes, and attach them to spots on your scalp.
  • 88.  Once the test begins, the electrodes send electrical impulse data from your brain to the recording machine. This machine converts the electrical impulses into visual patterns that appear on a screen. A computer saves these patterns.  The technician may instruct you to do certain things while the test is in progress. They may ask you to lie still, close your eyes, breathe deeply, or look at stimuli (such as a flashing light or a picture).  After the test is complete, the technician will remove the electrodes from your scalp.
  • 89.  During the test, very little electricity passes between the electrodes and your skin, so you’ll feel very little to no discomfort.  In some instances, a person may undergo a 24-hour EEG. These EEGs use video to capture seizure activity. The EEG may show abnormalities even if the seizure does not occur during the test. However, it does not always show past abnormalities related to seizure.
  • 90. EEG TEST RESULTS - Normal results  Electrical activity in the brain appears in an EEG as a pattern of waves.  Different levels of consciousness, like sleeping and waking, have a specific range of frequencies of waves per second that are considered normal.  For example, the wave patterns move faster when you’re awake than when you’re asleep.  The EEG will show if the frequency of waves or patterns are normal.  Normal activity typically means you don’t have a brain disorder.
  • 91. EEG TEST RESULTS - Abnormal results  Epilepsy or another seizure disorder  Abnormal bleeding or hemorrhage, Head injury  Sleep disorder  Encephalitis (swelling of the brain)  Tumour  Dead tissue due to a blockage of blood flow  Migraines  Alcohol or drug abuse
  • 92. NEURAL DISORDERS  Alzheimer's Disease (AD)  Dementia  Parkinson's Disease  Epilepsy  Schizophrenia
  • 93. ALZHEIMER'S DISEASE (AD)  Alzheimer's Disease (AD), also known as Alzheimer disease, or just Alzheimer’s.  It is a chronic neurodegenerative disease that usually starts slowly and gets worse over time.  The most common early symptom is difficulty in remembering recent events (short term memory loss).  As the disease advances, symptoms can include: problems with language, disorientation (including easily getting lost), mood swings, loss of motivation, not managing self care, and behavioural issues.  The onset of Alzheimer's disease is usually very slow and gradual, seldom occurring before age 65.  Over time, however, it follows a progressively more serious course.
  • 94.  Problems of memory, particularly recent or short-term memory, are common early in the course of the disease.  Mild personality changes, such as less spontaneity or a sense of apathy and a tendency to withdraw from social interactions, may occur early in the illness.  As the disease progresses, problems in abstract thinking or in intellectual functioning develop.  The average course of the disease from the time it is recognized to death is about 6 to 8 years, but it may range from under 2 years to over 20 years. Those who develop the disorder later in life may die from other illnesses (such as heart disease) before Alzheimer's disease reaches its final and most serious stage.  The reaction of an individual to the illness and the way he or she copes with it also varies and may depend on such factors as lifelong personality patterns and the nature and severity of the stress in the immediate environment.
  • 95. Warning Signs of Alzheimer's Disease  Confusion with time or place  Decreased or poor judgment  Difficulty completing familiar tasks  Changes in mood and personality  Memory changes that disrupt daily life  Withdrawal from work or social activities  Challenges in planning or solving problems  New problems with words in speaking or writing  Misplacing things and losing the ability to retrace steps  Trouble understanding visual images and spatial relationships
  • 96. DEMENTIA  Not a specific disease, dementia is a group of conditions characterized by impairment of at least two brain functions, such as memory loss and judgement.  Symptoms include forgetfulness, limited social skills and thinking abilities so impaired that it interferes with daily functioning.  A deficiency in a chemical (Acetylcholine) utilized by nervous tissues to transmit impulses and communicate between each other.  Many of the symptoms, notably the learning difficulties were explained by the lack of Acetylcholine.
  • 97. People may experience:  Cognitive: mental decline, confusion in the evening hours, disorientation, inability to speak or understand language, making things up, mental confusion, or inability to recognize common things  Behavioural: irritability, personality changes, restlessness, lack of restraint, or wandering and getting lost  Mood: anxiety, loneliness, mood swings, or nervousness  Psychological: depression, hallucination, or paranoia  Muscular: inability to combine muscle movements or unsteady walking  Also common: memory loss, falling, jumbled speech, or sleep disorder  Therapies  Rehabilitation and Occupational Therapy
  • 98. PARKINSONS DISEASE  Nerve cell damage in the brain causes dopamine levels to drop, leading to the symptoms of Parkinson's.  Parkinson's often starts with a tremor in one hand. Other symptoms are slow movement, stiffness and loss of balance.  Medication can help control the symptoms of Parkinson’s. Medications  Dopamine promoter, Antidepressant, Cognition-enhancing medication and Anti-Tremor 
  • 99. People may experience:  Tremor: can occur at rest, in the hands, limbs, or can be postural  Muscular: stiff muscles, difficulty standing, difficulty walking, difficulty with bodily movements, involuntary movements, muscle rigidity, problems with coordination, rhythmic muscle contractions, slow bodily movement, or slow shuffling gait  Sleep: early awakening, nightmares, restless sleep, or sleep disturbances  Whole body: fatigue, dizziness, poor balance, or restlessness  Cognitive: amnesia, confusion in the evening hours, dementia, or difficulty thinking and understanding
  • 100.  Speech: difficulty speaking, soft speech, or voice box spasms  Nasal: distorted sense of smell or loss of smell  Urinary: dribbling of urine or leaking of urine  Mood: anxiety or apathy  Facial: jaw stiffness or reduced facial expression  Also common: blank stare, constipation, depression, difficulty swallowing, drooling, falling, fear of falling, loss in contrast sensitivity, neck tightness, small handwriting, trembling, unintentional writhing, or weight
  • 101. EPILEPSY  Epilepsy may occur as a result of a genetic disorder or an acquired brain injury, such as a trauma or stroke.  During a seizure, a person experiences abnormal behaviour, symptoms and sensations, sometimes including loss of consciousness.  Epilepsy is usually treated by medication and in some cases by surgery, devices or dietary changes.  Anticonvulsant - Prevents or controls seizures, relieves pain and treats symptoms of certain psychiatric disorders  Sedative Causes drowsiness, calmness and dulled senses. Some types may become addictive.  Nerve pain medication - Blocks pain caused by damaged nerves. 
  • 102.  Usually self-diagnosable  During a seizure, a person experiences abnormal behaviour, symptoms and sensations, sometimes including loss of consciousness. There are few symptoms between seizures.  People may experience:  Whole body: fainting or fatigue  Muscular: rhythmic muscle contractions or muscle spasms  Sensory: aura or pins and needles  Also common: seizures, amnesia, anxiety, depression, or staring spells
  • 103. SCHIZOPHRENIA  The exact cause of schizophrenia isn't known, but a combination of genetics, environment and altered brain chemistry and structure may play a role.  Schizophrenia is characterized by thoughts or experiences that seem out of touch with reality, disorganized speech or behaviour and decreased participation in daily activities. Difficulty with concentration and memory may also be present.  Treatment is usually lifelong and often involves a combination of medications, psychotherapy and coordinated specialist care services.
  • 104.  People may experience:  Behavioural: social isolation, disorganized behaviour, aggression, agitation, compulsive behaviour, excitability, hostility, repetitive movements, self-harm, or lack of restraint  Cognitive: thought disorder, delusion, amnesia, belief that an ordinary event has special and personal meaning, belief that thoughts aren't one's own, disorientation, mental confusion, slowness in activity, or false belief of superiority  Mood: anger, anxiety, apathy, feeling detached from self, general discontent, loss of interest or pleasure in activities, elevated mood, or inappropriate emotional response  Psychological: hallucination, paranoia, hearing voices, depression, fear, persecutory delusion, religious delusion
  • 105.  Speech: circumstantial speech, incoherent speech, rapid and frenzied speaking, or speech disorder  Also common: fatigue, impaired motor coordination, lack of emotional response, or memory loss Medications  Antipsychotic - Reduces or improves the symptoms of certain psychiatric conditions  Anti-Tremor - Helps control tremor, shaking and unsteadiness.