2. GETTING STARTES
The Air Traffic Control (ATC) in an airport is the
authorized agency in charge of giving instructions to
pilots on how they will land their planes and of
organizing the traffic in the sky.
If there is no air traffic control, there will be
chaos in the landing ports. ATCs are like command
centers. The human body also has one.
Just like in the human body, if there is no
command center to control and manage the organs,
the body will not function properly.
3. NERVOUS SYSTEM
• The nervous system is the
organ system which
performs many functions in
the body, mostly for control
and regulation. (See Figure
13.1) It consists of the brain,
the spinal cord, and the
neurons.
• The nervous system is a
complex network of nerves
and cells that carry
messages to and from the
brain and spinal cord to
various parts of the body. Figure 13.1
GETTING INFORMED
4. BRAIN
The brain is the main organ in the nervous system which receives
impulses from the body, processes data, initiates appropriate
responses to stimuli, and regulates and maintains homeostasis in the
body. It is also where memory, speech, learning, and thought are
processed.
6. SPINAL CORD
The spinal cord is a cylindrical bundle of
nerve fibers that extends the medulla and
vertebral column. It is the main pathway of
impulses from the brain to the peripheral
nervous system of the body. It also serves as
the connector mechanism for the spinal
reflexes.
8. REFLEX
Reflex is an automatic response to a stimuli that does not need
thought or thinking like when you pull away your hand when
you touched a hot surface. The impulse does not need to go to
the brain, because the command will travel longer. Instead, the
impulse is transmitted to the spinal cord and retransmitted to
the motor neurons to perform the reflex action.
By reflex, Hall meant the automatic response of a muscle or
several muscles to a stimulus that excites an afferent nerve.
The term is now used to describe an action that is an inborn
central nervous system activity, not involving consciousness, in
which a particular stimulus, by exciting an afferent nerve,
produces a stereotyped, immediate response of muscle or
gland.
9. STIMULUS
A stimulus is anything in the internal or
external environment that triggers a
response to any part of the body.
10. HOMEOSTASIS
Homeostasis is dynamic process that
ensures ideal conditions are maintained
within living cells in spite of constant internal
and external changes. It has four
components, a change, a receptor, a control
center, and an effector.
11. 1. CHANGE
Cells of living systems constantly experience
changes in and around them. A change is anything
that requires a cell to react. Cells may react to a
change in temperature or to any pressure inside or
surrounding them.
Changes occur constantly in and around the cells of
living systems. A change is anything that requires a
cell to react, such as a change in temperature,
pressure or chemical composition inside or
surrounding the cell.
12. 2. RECEPTOR
When a change occurs, the receptor detects it and alerts the
proper control center to counteract it in order to return the cell
and the overall system into a balanced state.
Once a change occurs, it’s the receptors job to detect the
change and alert the proper control center to counteract it,
returning the cell and the overall system to a balanced state --
homeostasis. For example, your blood pressure has risen after
vigorous exercise. Receptors in certain arteries will detect the
pressure increase and send impulses to the body’s control
center for the cardiovascular system -- the medulla oblongata.
Receptors, or nerve endings, are located in every system and
tissue.
13. 3. CONTROL CENTER
control center is the one which receives impulses
from the receptors and sends command to the
effector to counteract the change in the environment.
As the control center receives impulses from its
remote receptors, it sends commands to the effector
to counteract the change in the environment. Using
the same example, the medulla oblongata
commands the effector -- the heart in this case -- to
slow its pulse. Control centers are located in the
brain.
14. 4. EFFECTOR
The effector acts on the impulses from its control
center that will counteract the change and return the
internal and external cell environment to a balanced
state.
The effector acts on the impulses from its specific
command center, counteracting the change and
returning the internal and external cell environment
to a balanced state. Effectors are the physical
change agents such as the heart, organs and fluids
of the body -- the workhorses of homeostasis.
15. NEURON
The neuron or the nerve cell is a major component of the brain and the spinal
cord of the central the nervous system. The neuron is responsible for
communicating information through electrical and chemical signals.
is a cell that carries electrical impulses. Neurons are the basic units of the
nervous system and its most important part is the brain.
Every neuron is made of a cell body (also called a soma), dendrites and an
axon. Dendrites and axons are nerve fibres. There are about 86 billion neurons
in the human brain, which comprises roughly 10% of all brain cells. The
neurons are supported by glial cells and astrocytes.
Neurons are connected to one another and tissues. They do not touch and
instead form tiny gaps called synapses. These gaps can be chemical synapses
or electrical synapses and pass the signal from one neuron to the next.
19. SENSORY
The sensory or afferent neuron receives stimuli from the
outside environment and sends them to the brain.
are pathways that carry sensory information from the body to
the central nervous system (the brain and spinal cord). These
neurons receive information from sensory stimuli and carry
impulses from receptors in muscles, organs, and glands to the
central nervous system where it is perceived by the brain. The
opposite of this are efferent neurons which are conducting cells
that carry information from the central nervous system to
muscles and organs throughout the body. They carry electrical
impulses that tell organs and muscles what to do.
20. INTERNEURON
The interneuron , which is found in the brain and
spiral cord, relays impulses from afferent to efferent
neurons.
is a broad class of neurons found in the human
body. Interneurons create neural circuits, enabling
communication between sensory or motor
neurons and the central nervous system (CNS).
They have been found to function in reflexes,
neurona oscillations, and neurogenesis in the adult
mammalian brain.
21. MOTOR
The motor or efferent neuron transmits impulses from the
brain or the spinal cord to the muscles or glands in the body.
are conducting cells that carry information from the central
nervous system (the brain and spinal cord) to muscles and
organs throughout the body. These neurons carry electrical
impulses that tell organs and muscles what to do. To move your
arm efferent neurons would carry the electrical impulse from
your brain, throughout the spinal cord and to your arm where
muscles receive the information to move. The opposite of
efferent neurons are afferent neurons which carry impulses
from receptors in muscles, organs, and glands to the central
nervous system.
22. The neuron is like a wire in a computer that
sends command and information to the
processing unit. And, like the computer it has
parts. Figure 13.6 shows that a typical
neuron consists of a cell body or soma,
dentrites, and an axon.
24. CELL BODY
The cell body or the soma that contains the nucleus of the cell.
It is responsible for the metabolic processes and the
maintenance of the cell. Inside the cell body are granular
structures called nissl bodies
is the factory of the neuron. It produces all the proteins for the
dendrites, axons and synaptic terminals and contains
specialized organelles such as the mitochondria, Golgi
apparatus, endoplasmic reticulum, secretory granules,
ribosomes and polysomes to provide energy and make the
parts, as well as a production line to assemble the parts into
completed products.
25. MITOCHONDRIA
are organelles, or parts of a eukaryote cell.
They are in the cytoplasm, not the nucleus.
They make most of the cell's supply of
adenosine triphosphate (ATP), a molecule
that cells use as a source of energy. Their
main job is to convert energy.
26. GOLGI APPARATUS
Is a membrane-bound structure that plays a
role in packaging peptides and proteins
(including neurotransmitters) into vesicles.
27. ENDOPLASMIC RETICULUM
is a type of organelle found in eukaryotic
cells that forms an interconnected network of
flattened, membrane-enclosed sacs or tube-
like structures known as cisternae. The
membranes of the ER are continuous with
the outer nuclear membrane. The
endoplasmic reticulum occurs in most types
of eukaryotic cells, but is absent from red
blood cells and spermatozoa.
28. SECRETORY GRANULES
are unique organelle in which neuropeptides
and/or hormones are packaged and stored
for secretion via the regulated secretory
pathway (RSP) upon stimulation in
neuroendocrine and endocrine cells.
29. RIBOSOMES
is a complex molecular machine, found within all
living cells, that serves as the site of biological
protein synthesis (translation). Ribosomes link amino
acids together in the order specified by messenger
RNA (mRNA) molecules. Ribosomes consist of two
major components: the small ribosomal subunits,
which read the RNA, and the large subunits, which
join amino acids to form a polypeptide chain.
30. POLYSOMES
is a complex of an mRNA molecule and two
or more ribosomes that act to translate
mRNA instructions into polypeptides.
31. NISSL BODIES
Groups of ribosomes used for protein synthesis.
A Nissl body, also known as Nissl substance
and Nissl material, is a large granular body found
in neurons. These granules are of rough
endoplasmic reticulum (RER) with rosettes of
free ribosomes, and are the site of protein synthesis.
It was named after Franz Nissl, a German
neuropathologist who invented the Nissl staining
method.
32. The axon in the neuron surrounded by an
insulating layer called as the myelin sheath
that is made up to Schwann cells.
There are periodic gaps in the myelinated
axons called nodes of Ranvier. These gaps
allow the impulses to jump in the myelinated
axon. This process is called saltatory
canduction.
33. MYELIN SHEATH
Myelin is an insulating layer, or sheath that
forms around nerves, including those in the
brain and spinal cord. It is made up of protein
and fatty substances. This myelin
sheath allows electrical impulses to transmit
quickly and efficiently along the nerve cells.
Ifmyelin is damaged, these impulses slow
down.
34. NODES OF RANVIER
is the 1-2 micrometre gap between the glial cells of
the myelin sheath. These glial cells are
called Schwann cells, and they help to electrically
insulate the neuron. The Nodes of Ranvier are only
present when the axon of a neuron is myelinated.
Myelination allows for an increased rate of action
potential transmission due to action potentials
"jumping" between Node of Ranvier, this is
called saltatory conduction.
35. SALTARORY CONDUCTION
is the propagation of action potentials along
myelinated axons from one node of Ranvier to the
next node, increasing the conduction velocity of
action potentials. The uninsulated nodes of Ranvier
are the only places along the axon where ions are
exchanged across the axon membrane, regenerating
the action potential between regions of the axon that
are insulated by myelin, unlike electrical conduction
in a simple circuit.
36. AXON
Is a long projection from the cell body which carries the
impulses in the nerves to the knob- like swellings at the end of
the axon that release neurotransmitters called axon terminals.
or nerve fiber, is a long, slender projection of a nerve cell,
or neuron, in vertebrates, that typically conducts electrical
impulses known as action potentials, away from the nerve cell
body. The function of the axon is to transmit information to
different neurons, muscles, and glands. In certain sensory
neurons (pseudounipolar neurons), such as those for touch and
warmth, the axons are called afferent nerve fibers and the
electrical impulse travels along these from the periphery to the
cell body, and from the cell body to the spinal cord along
another branch of the same axon.
37. AXON TERMINAL
are distal terminations of the telodendria (branches)
of an axon. An axon, also called a nerve fiber, is a
long, slender projection of a nerve cell, or neuron,
that conducts electrical impulses called action
potentials away from the neuron's cell body, or
soma, in order to transmit those impulses to other
neurons, muscle cells or glands.
When the axon terminals release neurotransmitters
to the synapse they will be received by the fibers that
project in the adjacent neuron called dendrites
AXON TERMINAL
38. In order for a message to be transferred, the
message should jump into the space in between
neurons called as synapse. And instead of
electricity, the neurons transport message from one
neuron to another with the use of certain chemical
called neurotransmitters. The neurotransmitters
are transported and released in the synapse with the
use of synaptic vesicles that are seen from the
axon terminal and it is received by the receptors of
the dendrites in the next neurons.
40. DIVISION OF THE NERVOUS SYSTEM
Figure 13.8 shows the two divisions of the
nervous system which are: the center
nervous system and the peripheral
nervous system.
42. Central Nervous System
The central nervous system is made up of the
brain and the spinal cord.
Figure 13.9
43. BRAIN
The brain is the central processing unit of the
nervous system. It made up of approximately 100
billion neurons that do not have the capacity to
regenerate when they are destroyed. The brain is
composed of three functional regions: the forebrain,
the midbrain and the hindbrain.
The brain is the control center of the body. It has a
wrinkled appearance due to bulges and depressions
known as gyri and sulci. One of these furrows, the
medial longitudinal fissure, divides the brain into left
and right hemispheres. Covering the brain is a
protective layer of connective tissue known as
the meninges.
45. HINDBRAIN
The hindbrain is the rear lower part of the brain,
comprising the cerebellum, pons, and medulla
oblongata.
The hindbrain extends from the spinal cord and
contains structures such as
the pons and cerebellum. These regions assist in
maintaining balance and equilibrium, movement
coordination, and the conduction of sensory
information. The hindbrain also contains the medulla
oblongata which is responsible for controlling such
autonomic functions as breathing, heart rate, and
digestion.
46. MEDULLA OBLONGATA
The medulla oblongata is the continuation of the spinal cord
within the skull and contains control centers for the heart and
lungs. It also controls a person’s sneezing, swallowing,
vomiting, and even coughing.
The medulla oblongata (or medulla) is located in the brainstem,
anterior and partially inferior to the cerebellum. It is a cone-
shaped neuronal mass responsible for autonomic (involuntary)
functions ranging from vomiting to sneezing. The medulla
contains the cardiac, respiratory, vomiting and vasomotor
centers and therefore deals with the autonomic functions of
breathing, heart rate and blood pressure.
MEDULLA OBLONGATA
47. PONS
The pons connect he upper and lower parts of the
brain. It is responsible for controlling breathing and
sleep cycles. It also serves as a message center
between several parts of the brain.
is a portion of the hindbrain that connects
the cerebral cortex with the medulla oblongata. It
also serves as a communications and coordination
center between the two hemispheres of the brain. As
a part of the brainstem, the pons helps in the
transferring of nervous system messages between
various parts of the brain and the spinal cord.
48. CEREBELLUM
Cerebellum, which is about the size of a plum and is found at
the back of the brain. It is the most neuron-densed region of the
brain. The cerebellum controls the body’s posture and the
coordination of voluntary movement.
is the area of the hindbrain that controls movement
coordination, balance, equilibrium and muscle tone. Like
the cerebral cortex, the cerebellum is comprised of white
matter and a thin, outer layer of densely folded gray matter. The
folded outer layer of the cerebellum (cerebellar cortex) has
smaller and more compact folds than those of the cerebral
cortex. The cerebellum contains hundreds of millions
of neurons for processing data. It relays information between
body muscles and areas of the cerebral cortex that are involved
in motor control.
49. MIDBRAIN
The midbrain is the smallest region in the human
brain. This region plays an important role in reward-
based learning and relays the sensory input from the
body to the forebrain.
The midbrain and the hindbrain together make up
the brainstem. The midbrain is the portion of the
brainstem that connects the hindbrain and the
forebrain. This region of the brain is involved in
auditory and visual responses as well as motor
function.
50. FOREBRAIN
The forebrain, contains the cerebrum, thalamus and hypothalamus.
The forebrain is responsible for a variety of functions including
receiving and processing sensory information, thinking, perceiving,
producing and understanding language, and controlling motor function.
The forebrain contains structures, such as
the thalamus and hypothalamus, which are responsible for such
functions as motor control, relaying sensory information, and
controlling autonomic functions. It also contains the largest part of the
brain, the cerebrum. Most of the actual information processing in the
brain takes place in the cerebral cortex. The cerebral cortex is the thin
layer of gray matter that covers the brain. It lies just beneath
the meninges and is divided into four cortex lobes: frontal
lobes, parietal lobes, occipital lobes, and temporal lobes. These lobes
are responsible for various functions in the body that include
everything from sensory perception to decision-making and problem-
solving. Below the cortex is the brain's white matter, which is
composed of nerve cell axons that extend from the neuron cell bodies
of gray matter. White matter nerve fiber tracts connect the cerebrum
with different areas of the brain and spinal cord.
51. CEREBRUM
The cerebrum is divided by the medial longitudinal
fissure into two hemispheres, the left and right . The
two hemispheres are connected by a thick band of
tissue called corpus callosum, which is also known
as the callosal commissure. Each hemisphere is
covered by an outer layer of gray matter called the
cerebral cortex.
The cerebrum is the most superior and anterior of
the brain’s major regions. It is the seat of reason,
planning, memory, and sensory integration. All
conscious thought originates in the cerebrum and
can influence the subconscious functions of the
lower regions of the brain.
52. CORPUS CALLOSUM
The corpus callosum also callosal commissure, is
a wide, thick, nerve tract consisting of a flat bundle
of commissural fibers, beneath the cerebral cortex in
the brain. The corpus callosum is only found
in placental mammals. It spans part of
the longitudinal fissure, connects the left and
right cerebral hemispheres, and enables
communication between the hemispheres. It is the
largest white matter structure in the human brain,
about ten centimeters in length and consisting of
200–300 million axonalprojections.
53. CEREBRAL CORTEX
The cerebral cortex is the largest region of the
cerebrum in the mammalian brain and plays a key
role in memory, attention, perception, cognition,
awareness, thought, language, and consciousness.
The cerebral cortex is the most anterior (rostral)
brain region and consists of an outer zone of neural
tissue called gray matter, which contains neuronal
cell bodies. It is also divided into left and right
cerebral hemispheres by the longitudinal fissure, but
the two hemispheres are joined at the midline by
the corpus callosum.
55. THALAMUS
The function of the thalamus is to sort and send most
of the sensory signals to and from the proper regions
of the cerebral cortex.
The thalamus is a small structure within the brain
located just above the brain stem between the
cerebral cortex and the midbrain and has extensive
nerve connections to both. The main function of the
thalamus is to relay motor and sensory signals to the
cerebral cortex. It also regulates sleep, alertness and
wakefulness.
56. HYPOTHALAMUS
The hypothalamus is the control center of the
homeostasis of the internal environment. It receives
signals of the state of the body and regulates body
temperature, thirst, and appetite.
It also controls the sexual drive of a person and it is
an endocrine gland that interacts with the adjacent
pituitary gland.
The hypothalamus is a portion of the brain that
contains a number of small nuclei with a variety of
functions. One of the most important functions of the
hypothalamus is to link the nervous system to
the endocrine system via the pituitary gland.
57. Reticulated Activating System
The reticulated activating system is a set of connected nuclei
in the brain that is responsible for regulating the information that
comes to the brain from the sense organs.
s a set of interconnected nuclei that are located throughout
the brainstem. The reticular formation is not anatomically well
defined because it includes neurons located in diverse parts of
the brain. The neurons of the reticular formation make up a
complex set of networks in the core of the brainstem that
stretch from the upper part of the midbrain to the lower part of
the medulla oblongata. The reticular formation includes
ascending pathways to the cortex in the ascending reticular
activating system (ARAS) and descending pathways to
the spinal cord via the reticulospinal tracts of the descending
reticular formation.
58. PITUITARY GLAND
The pituitary gland is protrusion off the bottom of the
hypothalamus at the base of the brain. The hormones of the
pituitary gland help regulated the growth, development, and
functioning of other endocrine glands. One of the functions of
the hypothalamus is to monitor the amount of hormones it will
release to the pituitary gland and commands it to release
hormones that will stimulate some endocrine glands that needs
to produce hormones for the proper body regulation.
The pituitary gland is a tiny organ, the size of a
pea, found at the base of the brain. As the
“master gland” of the body, it produces many
hormones that travel throughout the body, directing
certain processes or stimulating other glands to
produce other hormones.
60. MENINGES
The brain and the spinal cord are covered with three
layers of membranes called meninges.
The meninges contain cerebrospinal fluid that
cushions two structure. The brain is encased in skull
and the spinal cord is protected by the vertebral
column.
The meninges is a series of membranes that cover
the central nervous system. The meninges consist of
three layers: the dura mater, the arachnoid mater,
and the pia mater. These layers cover the brain and
spinal cord with the primary function of protecting and
nourishing the central nervous system. Read on to
learn more about the meninges, and the role it plays
in your body.
61. CEREBROSPINAL FLUID
Cerebrospinal fluid (CSF) is a clear, colorless body fluid found in
the brain and spinal cord. It is produced by the specialised ependymal
cells in the choroid plexuses of the ventricles of the brain, and
absorbed in the arachnoid granulations. There is about 125mL of CSF
at any one time, and about 500mL is generated every day. CSF acts
as a cushion or buffer for the brain, providing basic mechanical
and immunological protection to the brain inside the skull. CSF also
serves a vital function in cerebral autoregulation of cerebral blood flow.
CSF occupies the subarachnoid space (between the arachnoid
mater and the pia mater) and the ventricular system around and inside
the brain and spinal cord. It fills the ventricles of the brain, cisterns,
and sulci, as well as the central canal of the spinal cord. There is also
a connection from the subarachnoid space to the bony labyrinth of
the inner ear via the perilymphatic duct where the perilymph is
continuous with the cerebrospinal fluid.
62. PERIPHERAL NERVOUS SYSTEM
The peripheral nervous system or PNS refers to the
parts of the nervous system outside the brain and
spinal cord. The PNS is made up to the somatic
nervous system.
The peripheral nervous system (PNS) is the
division of the nervous system containing all the
nerves that lie outside of the central nervous system
(CNS). The primary role of the PNS is to connect the
CNS to the organs, limbs, and skin. These nerves
extend from the central nervous system to the
outermost areas of the body. The peripheral system
allows the brain and spinal cord to receive and send
information to other areas of the body, which allows
us to react to stimuli in our environment.
64. SOMATIC NERVOUS SYSTEM
Which is composed of the cranial nerves and spinal
nerves, and the autonomic nervous system.
The somatic nervous system is responsible for
movement of voluntary muscles and the process
known as a reflex arc. This system carries nerve
impulses back and forth between the central
nervous system, which is the brain and the spinal
cord, and the skeletal muscles, skin, and sensory
organs.
65. AUTONOMIC NERVOUS SYSTEM
Which controls the voluntary actions of the body
such as breathing, heartbeat, digestion and
urination.
The autonomic nervous system (ANS), formerly
the vegetative nervous system, is a division of
the peripheral nervous system that supplies smooth
muscle and glands, and thus influences the function
of internal organs. The autonomic nervous system is
a control system that acts largely unconsciously and
regulates bodily functions such as the heart rate,
digestion, respiratory rate, pupillary response,
urination, and sexual arousal
67. The autonomic nervous system governs mostly
the homeostatic mechanism of the body. This
mechanism has two parts: the first one is the
sympathetic mechanism and the second one
is parasympathetic mechanism
68. SYMPATHETIC MECHANISM
The sympathetic mechanism works when a person in a tough
situation. It initiates the fight-or-fight reaction by increasing your
heartbeat and breathing to have faster blood flow and increase
oxygen supply in the muscles in order to convert the sugar in
the muscle cells into energy or adenosine triphospate (ATP)
is one of the two main divisions of the autonomic nervous
system, the other being the parasympathetic nervous system.
(The enteric nervous system (ENS) is now usually referred to
as separate from the autonomic nervous system since it has its
own independent reflex activity.
69. PARASYMPATHETIC MECHANISM
is one of the two divisions of the autonomic nervous system (a
division of the peripheral nervous system (PNS)), the other
being the sympathetic nervous system. (The enteric nervous
system (ENS) is now usually referred to as separate from
the autonomic nervous system since it has its own independent
reflex activity.) The autonomic nervous system is responsible
for regulating the body's unconscious actions. The
parasympathetic system is responsible for stimulation of "rest-
and-digest" or "feed and breed" activities that occur when the
body is at rest, especially after eating, including sexual
arousal, salivation, lacrimation (tears), urination, digestion and
defecation. Its action is described as being complementary to
that of the sympathetic nervous system, which is responsible
for stimulating activities associated with the fight-or-flight
response.
