Transcript Chp.6 Nervous System

Nervous System
Responsible for coordinating the many
activities performed inside and outside
the body
Every square inch of the human body is
supplied with fine fibers known as
nerves; there are over 100 billion nerve
cells, known as neurons, in the body
Neurology
The study of the nervous system and its
disorders
The nervous system is one of the most
important systems of the body; controls
and coordinates the function of all other
systems, making them work
harmoniously and efficiently
Divisions of Nervous System
Principal parts are the brain, spinal
cord and nerves
Cerebrospinal System
Also known as the central nervous system
Consists of the brain, spinal cord, spinal
nerves & cranial nerves
It controls consciousness and all mental
activities, voluntary functions of the five
senses
Seeing, hearing, feeling, smelling & tasting
Controls voluntary muscle actions, including
all body movements and facial expressions
Peripheral Nervous System
Made up of sensory and motor nerve
fibers that connect the peripheral
(outer) parts of the body to the central
nervous system
It has both sensory and motor nerves
and carries messages to and from
central nervous system
Autonomic Nervous System
Controls the involuntary muscles
Regulates the action of the smooth
muscles, glands, blood vessels and
heart
Brain Spinal Cord
Brain is largest mass of tissue in the
body
Average weight is 44-48 ounces
Central power station of the body
Brain Spinal Cord
Contains 12 pairs of cranial nerves
All of which originate in the brain & reach
various parts of the head, face & neck
Spinal cord originates in the brain
Enclosed & protected by spinal column
31 pairs of spinal nerves
Extend from spinal cord to muscles & skin
of trunk & limbs
Nerve Cell Structure &
Function
Neuron or nerve cell
Primary structural unit of nervous system;
composed of cell body & nucleus
Dendrites
Tree-like branching of nerve fibers
extending from the nerve ell that receive
impulses from other neurons
Nerve Cell Structure &
Function
Axon & Axon terminal
Send impulses to other neurons, glands &
muscles
Nerves
Long, whitish cords made up of bundles of
fibers held together by connective tissue,
through which impulses are transmitted
Types of Nerves
Sensory nerves (afferent)
Carry impulses or messages from sense
organs to the brain, where sensations of
touch, cold, heat, sight, hearing, taste,
smell, pain & pressure are experienced
Motor (efferent) nerves
Carry impulses from brain to muscles; the
transmitted impulses produce movement
Types of Nerves
Mixed nerves
Contain both sensory and motor fibers and have
the ability to both send and receive messages
Reflex
Automatic response to a stimulus that involves
movement of an impulse from a sensory receptor
along an afferent nerve to the spinal cord, and a
responsive impulse along an efferent neuron to a
muscle causing a reaction
Example: the quick removal of a hand from a hot object
Reflexes do not have to be learned