The Nervous System

1. Chapter 12
Nervous System

2. Overview
The nervous system is coordinates and
controls body function. It receives sensory
input, makes decisions, and then orders body
responses. The nervous system can be
subdivided into the central nervous system
(CNS) and the peripheral nervous system
(PNS).

3. The Central Nervous System
The CNS consists of the brain and the spinal cord; it is able to
receive impulses from all over the body, process this information,
and then respond with an action.
Sensory information comes into the central nervous system, where
it is processed. Motor messages then exit the CNS carrying
commands to the muscles and glands.
Consist of gray and white matter
gray matter: comprised of unsheathed or uncovered cell bodies
and dendrites
white matter: myelinated nerve fibers
Encased and protected by 3 membranes known as meninges

4. Brain
One of the largest organs in the body and
coordinates most body activities.
Center for all thought, memory, judgement,
and emotion
Each part of the brain is responsible for
controlling different body functions, such as
temperature regulation, blood pressure, and
breathing

5. Brain (cont.)
4 sections:
cerebrum: largest section that processes thoughts,
judgement, memory problem solving, and language
Subdivided into left and right cerebral hemispheres and
each hemisphere has 4 lobes-- frontal, parietal,
occipital, and temporal lobes
cerebellum: 2nd largest portion located beneath the
posterior part of the cerebrum; aids in coordinating
voluntary body movements and maintaining balance and
equilibrium.

6. Brain (cont.)
diencephalon: located below the cerebrum and consist if the
thalamus and hypothalamus
thalamus: composed of gray matter and acts as center for
relaying impulses from eyes, ears, and skin to the
cerebrum; pain receptors
hypothalamus: controls body temperature, appetite, sleep,
sexual desire, and emotions; also controlling the autonomic
nervous system, digestive system, release of hormones from
pituitary gland.
brain stem: 3 components
midbrain: pathway for impulses to be conducted between
brain and spinal cord
pons: connects cerebellum to the rest of the brain
medulla oblongata: most inferior positioned of the brain
connects brain to the spinal cord; center that controls
heart rate, respiration, and blood pressure

7. Spinal Cord
The function of the spinal cord is to provide
a pathway for impulses traveling to and from
the brain.
Column of nervous tissue that extends from
the medulla oblongata to the brain down the
2nd lumbar vertebra within the vertebral
column
33 vertebrae of the backbone form a
continuous canal for the spinal cord called
the spinal cavity or vertebral canal

8. Spinal Cord (cont.)
Protected by cerebrospinal fluid
Inner core of spinal cord consists of cell
bodies and dendrites of peripheral nerves
and is gray matter
Out portion of spinal cord is myelinated
white matter
ascending tracts: carrying sensory
information to brain
descending tracts: carrying motor
commands down from the brain to the
peripheral nerve

9. Peripheral Nervous Sytem
The PNS includes both 12 cranial nerves and 31 pairs of spinal
nerves
Cranial nerves arise from the brain, mainly the medulla
oblongata
Spinal nerves split off from the spinal cord, and 1 pair (right
and left) exit between each pair of vertebrae
The nerves of the PNS are subdivided into 2 divisions
autonomic nervous system (ANS): Involved with the control of
involuntary or unconscious bodily functions
2 branches- sympathetic and parasympathetic branches
somatic nerves: The skin and skeletal muscles are mainly
involved with the conscious and voluntary activities of the
body. These nerves carry motor commands to skeletal muscles