PowerPoint® to accompany
Medical Assisting
Chapter 27
Second Edition
Ramutkowski Booth Pugh Thompson Whicker
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1
The Nervous System
Objectives:
271 Explain the difference between the central
nervous system and the peripheral nervous
system.
272 Describe the functions of the nervous system.
273 Describe the structure of a neuron.
274 Describe the function of a nerve impulse and
how a nerve impulse is created.
275 Describe the structure and function of a synapse.
276 Describe the function of the bloodbrain barrier.
2
The Nervous System
Objectives:
277 Describe the structure and functions of meninges.
278 Describe the structure and functions of the spinal
cord.
279 Define reflex and list the parts of a reflex arc.
2710 List the major divisions of the brain and give the
general functions of each.
2711 Describe the differences between the somatic
nervous system and autonomic nervous system.
3
The Nervous System
Objectives:
2712 Explain the two divisions of the autonomic
nervous system.
2713 Explain the functions of the cranial and spinal
nerves.
2714 Describe the location and function of
cerebrospinal fluid.
2715 Describe various disorders of the nervous system
and how they are diagnosed and treated.
4
Introduction
Nervous system is a
highly complex system
divided into two major
parts;
Controls all other organs
systems and is important
for maintaining balance
within those systems.
Central nervous system
(CNS)
Peripheral nervous
system.
Disorders of the nervous system are numerous and often very
Disorders of the nervous system are numerous and often very
difficult to diagnose and treat because of the complexity of
difficult to diagnose and treat because of the complexity of
this system.
this system.
5
General Functions of the
Nervous System
Detect and interpret
sensory information,
Make decisions about
the sensory
information that is
received,
Carry out motor
functions based on
the decisions made.
For example, if you feel
For example, if you feel
pain, your brain might
pain, your brain might
decide you need to move
decide you need to move
away from the painful
away from the painful
stimulus.
stimulus.
6
Neuron Structure
Transmit
electrochemical
messages called nerve
impulses to other
neurons and effectors
(muscles or glands)
Neurons lose their
ability to divide
When destroyed by
disease, they cannot be
replaced
7
Neuron Structure (cont.)
Neurons have cell
Neurons
Neurons have cell
Neurons
body processes called
body processes called
nerve fibers that
nerve fibers that
extend from the cell
extend from the cell
body.
body.
Dendrites short
Dendrites
function is to receive
information (nerve
impulses) for the neuron
Axons long function
Axons
is to send information
(nerve impulses) away
from the cell body.
8
Nerve Impulse
Nerve impulse is the flow of electric current along
the axon membrane
At rest, or in its polar state, more sodium (Na+) is on
the outside of the membrane, which makes the
outside positive and the inside negative.
When sodium moves into the cell, the membrane
depolarizes, which means that the inside becomes
more positive.
The membrane repolarizes when potassium (K+) and
later sodium move to the outside of the cell
membrane.
9
Synapse
Synaptic knobs contact dendrites, cell bodies and
the axons of other neurons
Synaptic knob is contacting is called a postsynaptic
structure.
Within synaptic knobs are vesicles or small sacs that
contain chemicals called neurotransmitters. When
the nerve impulse reaches the synaptic knobs, the
neurotransmitters are released onto postsynaptic
structures.
10
Neurotransmitters
Functions:
Causes muscles to contract or relax
Causes glands to secrete products
Activates neurons to send nerve impulses,
inhibiting neurons from sending nerve
impulses.
11
Apply Your Knowledge
What is the function of a dendrite?
12
Apply Your Knowledge Answer
What is the function of a dendrite?
Dendrite’s function is to receive information
(nerve impulses) for the neuron.
13
Central Nervous System
Includes the spinal cord and brain.
Includes the spinal cord and brain.
Has a bloodbrain barrier:
Has a bloodbrain barrier:
Barrier prevents certain substances from
Barrier prevents certain substances from
entering the tissues of the CNS
entering the tissues of the CNS
Tight capillaries form the bloodbrain
Tight capillaries form the bloodbrain
barrier.
barrier.
Meninges are membranes that protect the
Meninges are membranes that protect the
brain and spinal cord.
brain and spinal cord.
14
Cerebrospinal fluid
Location:
Between the arachnoid mater and
pia mater is an area called the
subarachnoid space
Function:
Cushions the CNS
15
Spinal Cord
Slender structure that is continuous with the
brain
Descends into the vertebral canal and ends
around the level of the first or second lumbar
vertebra.
31 spinal segments:
8 cervical segments
12 thoracic segments
5 lumbar segments
5 sacral segments
1 coccygeal segment
16
Spinal Cord (cont.)
Name the spinal
segments and tell how
many of each segment
are present on the spinal
cord.
8 cervical segments
12 thoracic segments
5 lumbar segments
5 sacral segments
1 coccygeal segment
17
Spinal Cord –
Gray and White Matter
Gray matter inner tissue with darker color
Gray matter inner tissue with darker color
contains neuron cell bodies and their dendrites
contains neuron cell bodies and their dendrites
divisions are called horns and the divisions of
divisions are called horns and the divisions of
the white matter are called columns (funiculi)
the white matter are called columns (funiculi)
columns contain groups of axons called nerve
columns contain groups of axons called nerve
tracts
tracts
central canal runs down the entire length of the
central canal runs down the entire length of the
spinal cord through the center of the gray
spinal cord through the center of the gray
matter
matter
White matter the outer tissue
White matter the outer tissue
18
contains myelinated axons
contains myelinated axons
Spinal Cord Ascending and
Descending Tracts
Function of the spinal cord
is to carry sensory
information to and from
the brain
Ascending tracts carry
sensory information up to
the brain
Descending tracts carry
motor information down
from the brain to muscles
and glands
19
Spinal Cord Reflexes
Function of the spinal cord is to participate in
reflexes
Reflex a predictable, automatic response to
stimuli
Receptor
Sensory Neurons
Interneurons
Effectors
Motor Neurons
20
Apply Your Knowledge
What are the descending tracts of the
spinal cord?
21
Apply Your Knowledge Answer
What do the descending tracts of the
spinal cord do?
Descending tracts carry motor
information down from the brain
to muscles and glands
22
The Brain
Four Parts:
Cerebrum
Diencephalons
Brain stem
Cerebellum
23
The Brain Cerebrum
Lobes
Largest part of the
brain
Frontal
Parietal
Two halves cerebral
Temporal
hemispheres
Occipital
Thick bundle of
Cortex
nerve fibers called
the corpus callosum Ventricles
connect the two
hemispheres
24
The Brain Diencephalons
Located between the cerebral hemispheres
Located between the cerebral hemispheres
and is superior to the brain stem
and is superior to the brain stem
Thalamus relay
station for
sensory
information that
heads to the
cerebral cortex
for interpretation
Hypothalamus
maintains balance
by regulating many
vital activities such
as heart rate, blood
pressure, and
breathing rate.
25