AMA 175 - Anatomy &
Physiology/Medical
Terminology/Pathology 6
Nervous System
Nervous System


Function: One of the most complex systems in the
body. Contains more than 100 billion nerve cells.
Coordinates all the activities of the human body both
voluntarily or consciously and involuntarily or
unconsciously. (Sight, taste, hearing, touch, speaking,
moving muscles, thinking, breathing and the heart
pumping blood and more).
Nervous impulses (the release of electrical energy),
travel all over the body from external receptors
(sense organs) to the brain, where they are
interpreted, and are then sent back to the
appropriate parts of the body.
Structure of the Nervous
System
2 major divisions: Central and Peripheral
Central Nervous System:
 Brain: controls body activities; cerebrum controls
thought; medulla oblongata in the brain stem controls
involuntary such as respiratory, cardiac and
vasomotor

Spinal Cord: column of nervous tissue extending
from the medulla oblongata to the lumbar area of the
spinal cord (nerves go from here to all parts of the
body)
Structure of the Nervous
System continued:
2 major divisions: Central and Peripheral
Peripheral Nervous System:
 Cranial Nerves: carry impulses between the brain and
the head and neck (exception is the vagus nerve which
carries messages to and from the neck, chest and
abdomen); mainly voluntary

Spinal Nerves: carry messages between the spinal cord
and the chest, abdomen and extremities; mainly
voluntary

Plexus: large networks of nerves in the peripheral
nervous system
Structure of the Nervous
System continued:

Autonomous Nervous System: included in the peripheral nervous
system, function involuntarily to control breathing, cardiovascular,
digestion etc…

Sensory (afferent) nerves carry messages toward the spinal cord
and brain

Motor (efferent) nerves carry messages from the spinal cord and
brain to muscles telling them how to respond

Sympathetic Nerves: stimulate the body in times of stress and
crisis by increasing heart rate, relax airways for more oxygen,
stimulates adrenal gland to secrete adrenaline, inhibits digestion

Parasympathetic Nerves: act as a balance to sympathetic and
restore homeostasis after crisis is over