A psychological presentation on 'Neural basis of Human Behaviour'

1. Neural
Basis of
Human
behavior

2. The Central Nervous System
 Composed of the Brain and the Spinal cord.
 The CNS relays messages from the brain to
the Peripheral Nervous System, and vice
versa.
 A series of neurons that connect organs and
muscles to the CNS.
 The PNS receives messages from the brain
sends messages to it from the senses.
THE PERIPHERAL NERVOUS SYSTEM

3. SPECIALIZATION INTEGRATION
Individual parts perform
one or more functions
for the body
The brain coordinates
many parts to fully
accomplish a task

4. There are about 100 billion neurons in the brain.
These neurons carry out certain functions, store
information, can change functions and make
connections with other neurons.

5. NEURONS
These are the billions of cells in the CNS and PNS that relay the messages throughout the body.
Sensory Neurons
Send signals from the
senses to the brain
Motor Neurons
Sent signals from the
brain to parts of the body

6. Neuron Structure
SOMA: the neuron’s cell body
DENDRITES: branches from the cell body that receive incoming signals
AXON: extension that carries signals from the soma (outgoing)

7. Classification of neurons
Functional classification of neurons :Sensory and Motor
Classification as per neurotransmitter release: Cholinergic, dopaminergic, serotonergic
Classification on basis of axonal length

8. Nerves and Tracts
Collection of nerves outside CNS is nerves and inside CNS is called tracts.

9. Each cell has a cell membrane, which surrounds the cell and protects the inner
components. These internal components include a nucleus (a central structure that
holds your genetic information),ribosomes (tiny structures that make proteins)
and organelles (little organs that perform various functions). All cells also
have cytoplasm, which is a clear, jelly-like fluid that fills the inside of the cell and
surrounds all of the internal structures.
Mitochondria : An organelle that break down nutrients such as glucose and provide
the cell with energy to perform its functions. It produce a chemical called
Adenosine Triphospate (ATP) : an energy-bearing molecule found in all living cells.
Formation of nucleic acids, transmission of nerve impulses, muscle contraction, and
many other energy-consuming reactions of metabolism are made possible by the
energy in ATP molecules. The energy in ATP is obtained from the breakdown of
foods.

10. The nucleus includes many important structures, and perhaps most important are
the chromosomes, which are made up of strands of deoxyribonucleic acid (DNA),
which are made up of genes. These genes contain "programs" or "blue prints" for
the direction of protein synthesis, which is the creation of structures that carry out
the cell's work.

11. Speed of Nerve Impulses
Impulses travel very rapidly along
neurons. The presence of a myelin
sheath greatly increases the velocity at
which impulses are conducted along the
axon of a neuron. In unmyelinated
fibres, the entire axon membrane is
exposed and impulse conduction is
slower.

12. Supporting Cells of the Nervous
System
There are several types of supporting cells that occur in both the CNS and the PNS.
None of them conduct impulses, instead they “assist” neurons.
As a group they are called neuroglia or “glia” cells, (means “nerve glue”) found in between neurons.
Different cells do different jobs.
In the CNS the cell is called the oligodendrocyte
In the PNS the cell is the Schwann cell.

13. Blood Brain Barrier
Over one hundred years ago, Paul Ehrlich discovered that if a blue dye is injected
into an animal’s bloodstream, all tissues except the brain and spinal cord will be
tinted blue. However, if the same dye is injected into the fluid-filled ventricles of
the brain, the blue color will spread throughout the CNS (Bradbury, 1979). This
experiment demonstrates that a barrier exists between the blood and the fluid
that surrounds the cells of the brain: the blood–brain barrier.

14. selectively permeable (per, “through”;meare, “to pass”)
The blood–brain barrier is not uniform throughout the nervous system.
area postrema (poss tree ma) A region of the medulla where the blood–brain barrier
barrier is weak; poisons can be detected there and can initiate vomiting.

16. Neural Communication

18. Membrane Potential
Cell membranes in general, and membranes of nerve cells in particular, maintain a small voltage or
"potential" across the membrane in its normal or resting state. In the rest state, the inside of the
nerve cell membrane is negative with respect to the outside (typically about -70 millivolts).
there is an electrical potential difference between the inside of the cell and the surrounding
extracellular fluid
changes in their membrane potentials are used to code and transmit information
When a nerve or muscle cell is at "rest", its membrane potential is called the resting membrane
potential. In a typical neuron, this is about –70 millivolts (mV). The minus sign indicates that the
of the cell is negative with respect to the surrounding extracellular fluid.

19. Properties of the Neuron
Neurons contain many ions and are charged
A- are large protein ions that always
stay inside the cell
K+ is potassium. At rest it is mostly
inside the cell
Cl- is chloride. It exists both inside
and outside the cell
Na+ is sodium. It exists primarily
outside the cell

21. Resting Potential
When a neuron is not sending a signal, it is "at rest." When a neuron is at rest, the inside of the
neuron is negative relative to the outside. Although the concentrations of the different ions attempt
to balance out on both sides of the membrane, they cannot because the cell membrane allows only
some ions to pass through channels (ion channels). At rest, potassium ions (K+) can cross through the
membrane easily. Also at rest, chloride ions (Cl-)and sodium ions (Na+) have a more difficult time
crossing. The negatively charged protein molecules (A-) inside the neuron cannot cross the
membrane.

24. The fluid within cells (intracellular fluid) and the fluid surrounding them
(extracellular fluid) contain different ions.
The action potential is an explosion of electrical activity that is created by
a depolarizing current. This means that some event (a stimulus) causes the resting
potential to move toward 0 mV. When the depolarization reaches about -55 mV a
neuron will fire an action potential. This is the threshold. If the neuron does not
reach this critical threshold level, then no action potential will fire. Also, when the
threshold level is reached, an action potential of a fixed sized will always fire...for
any given neuron, the size of the action potential is always the same

26. As an action potential travels down the axon, there is a change in polarity across the membrane. The
Na+ and K+ gated ion channels open and close as the membrane reaches the threshold potential, in
response to a signal from another neuron. At the beginning of the action potential, the Na+ channels
open and Na+ moves into the axon, causing depolarization. Repolarization occurs when the K+
channels open and K+ moves out of the axon. This creates a change in polarity between the outside
of the cell and the inside. The impulse travels down the axon in one direction only, to the axon
terminal where it signals other neurons.

28. An ion is an atom or group of atoms in which the number of electron s is different
from the number of proton s. If the number of electrons is less than the number
of protons, the particle is a positive ion, also called a cation.
Anions have negative charge
There are several important ions in these fluids.
Four of them here: organic anions (symbolized by A-), chloride ions (Cl-), sodium
ions (Na+), and potassium ions (K+).

29. Nerve Conduction
Within the Neuron
Depolarization- An electrical process
-70 mill volts
When the neuron is resting, not
conducting nerve impulses, it is
polarized.
The cell is invaded by Na ions and
the expulsion of K ions. The electric
charge is gone. Depolarization occurs!
Between Neurons
A chemical process
When depolarization reaches the
terminal buttons, neurotransmitters
are released into the synapse.
Either excite or inhibit the following
neuron!
Sending neuron-presynaptic neuron
Receiving neuron- postsynaptic
neuron.

30. Delivering the Message
1. Impulse is received through the dendrites from another neuron or a sense.
2. Soma fires; an impulse is sent down the axon to the next neuron.

31. Myelin sheaths a layer of proteins that are wrapped around the axon, protects the axon,
and speeds up transmission of signal.
Myelin sheaths can send several waves of impulses down longer axons at once.
Breakdown of myelination connected to development of Multiple Sclerosis (an
autoimmune disorder in which the myelin is destroyed - fatigue, pain, motor disorders,
cognitive disorders, etc.)
Axons are millimeter long up to one meter (base of spinal cord to foot)
Difference between Axon and Dendrites: Axon takes information away from cell body
whereas dendrites receive information from other neurons. One neuron simultaneously
receive information from 10,000 neurons.

32. Impulse Conduction
Unmyelinated fibers conduct impulses over their entire membrane surface. Without myelin, neural
transmission is inefficient
Myelinated fibers conduct impulses from node of Ranvier to node of Ranvier, a phenomenon called
saltatory conduction.
Saltatory conduction is many times faster than conduction on unmyelinated neurons.
Myelination in PNS is through Schwann cells and mylienal cells in CNS is through OLigodend

33. All-or-None Response
If a nerve fiber responds at all to a stimulus, it responds completely by conducting an impulse (all-or-
none response).
Greater intensity of stimulation triggers more impulses per second, not stronger impulses.

35. Neurons communicate in two ways
Electrical signal: within a neuron
Chemical signal: between neurons
Electrical signal is sent from one part of the neuron to the other: The signal travels
the dendrite through the cell body to the axon
◦Dendrites receive the signal from another neuron
◦Axons send the signal to other neurons
Chemical signal is sent from the axon of one neuron to the dendrite of another neuron

36. When the sum of the potentials reaches the base
of the axon, a sufficient charge may be present to
cause an action potential.

37. Removal of Neurotransmitter
After the NT is initially released, the
chemical must be removed
This is done in a couple of different ways
◦Biochemical breakdown of the NT
◦Reuptake: NT is pulled back into the
presynaptic button and packaged to be
released again

38. Neurotransmitters
Chemicals that are produced and
stored in the axon.
Neurotransmitters pass from one
neuron to the next to help relay
messages through the body.
Sending neuron
Receiving neuron
Neuro-
transmitters

39. Neurotransmitters enter the synaptic gap,
where most are absorbed by the receiving
neuron.
Excess neurotransmitters are reabsorbed
by the sending neuron; this is called
“reuptake.”
Synaptic Gap

40. Excitatory and Inhibitory
Messages
Excitatory message—increases the likelihood that the
postsynaptic neuron will activate
Inhibitory message—decreases the likelihood that the
postsynaptic neuron will activate

41. Types of Neurotransmitters
Excitatory
◦ Glutamate
◦ Acetylcholine
Inhibitory
◦ GABA
◦ Norepinephrine
Both
◦ Dopamine
◦ Serotonin

42. Different neurotransmitters carry out different functions. The role and effects of
malfunctioning of most common neurotransmitters are:
Acetylcholine (ACh) enables muscle action, learning and memory.
 linked to Alzheimer’s Disease
Neurons that produce ACh deteriorate later in life, reducing the levels of it in the brain
and disrupting memory and retention of new skills and occurrences (learning).

43. D O P A M I N E
LOW RANGE:
Body tremors
and decreased
mobility
NORMAL RANGE
HIGH RANGE:
hallucinations
= Parkinson’s
Disease symptoms = Schizophrenia
Dopamine influences movement, emotion and learning.

44. Chlorpromazine used to treat schizophrenia hallucinations. Too much led to Parkinson’s
like symptoms, connecting dopamine to the disease.
Serotonin affects mood, sleep and arousal.
 low levels linked to depression
Common use of Selective Serotonin Reuptake Inhibitors (SSRIs) to prevent reuptake of
serotonin.
This effectively increases the amount absorbed from the synaptic gap.
SSRI examples: Prozac, Zoloft, Paxil

45. Endorphins
Morphine and codeine work on endorphin receptors; involved in healing
effects of acupuncture
Runner’s high— feeling of pleasure after a long run is due to heavy endorphin
release

46. Different Neurotransmitter
Substances and their Effects on
Behavior
Neurotransmitter Effects on Behavior
1. Acetylcholine Found in neuromuscular
junctions
Involved in muscle movement
Facilitates learning and memory
Deficiency of ACH disrupts
learning and memory
2. Norepinephrine Arousal, depression & stress
Fight or flight response
Too little may lead to depression
Too much causes hyperactivity

47. Different Neurotransmitter Substances
and their Effects on Behavior
Neurotransmitter Effects on Behavior
3. Dopamine Involved in movement, attention &
learning
Over supply may lead to schizophrenic
reaction
Under supply causes Parkinson’s
Diseases (a neurological disorder
disrupting coordinated movement)
4. Serotonin Involved in sleep & depression
Lack of serotonin produces anemia
Prevents dreaming in the waking state
Considered as the “worry” chemical
in the brain

48. Different Neurotransmitter
Substances and their Effects on
Behavior
Neurotransmitter Effects on Behavior
5. GABA (gamma
aminobutyric acid)
Decreases the activity of
the neuron/brain activity
May decrease levels of
anxiety
6. Endorphins Control pain & pleasure
Released in response to
pain
Pain relieving effect; a
neuropeptide