Medical assisting Administrative and clinical procedures (5e) Chapter 30 The nervous system

The learning objectives for this chapter include: Explain the difference between the central nervous system and the peripheral nervous system, describe the functions of the nervous system, describe the structure of a neuron, describe the function of a nerve impulse and how a nerve impulse is created,...

The Nervous

System

Learning Outcomes (cont.)

30.1 Describe the general functions of the

nervous system

30.2 Summarize the structure of a neuron

30.3 Explain the function of nerve impulses and

the role of synapses in their transmission

30.4 Describe the structures and functions of the

central nervous system

Learning Outcomes (cont.)

30.5 Compare the structures and functions of the

somatic and autonomic nervous systems in the peripheral nervous system

30.6 Recognize common tests that are performed

to determine neurologic disorders

30.7 Describe the causes, signs and symptoms,

and treatments of various diseases and disorders of the nervous system

Introduction

• Highly complex system

• Controls and helps to

maintain balance in all

other organ systems

Disorders are numerous and often

difficult to diagnose and treat

General Functions of the Nervous System

movement or action

afferent and efferent nerves

Apply Your Knowledge

Match the following:

_ Somatic nervous system A Motor nerves

_ Autonomic nervous system B Governs skeletal or voluntary

muscles _ Afferent nerves C Governs respiratory and GI

systems

_ Efferent nerves D Go-betweens or interpreters

_ Interneurons E Sensory nerves

Neuron Structure (cont.)

• Neurons

– Cell body

• Nucleus and organelles

• Generates proteins and energy

– Nerve fibers ~ extend from cell body

Neuron Structure (cont.)

• Axons

– One per neuron – Send nerve impulses away from the cell body

• Dendrites

– One or more per neuron – Receive nerve impulses for the neuron

Neuron Structure (cont.)

• Schwann cells

– Wrap around axons

– Membranes contain myelin

• White matter – myelin sheath

• Gray matter – no myelin sheath

Apply Your Knowledge

True or False:

_ Effectors are neurons.

_ Neurons can reproduce.

_ Astrocytes anchor blood vessels to nerve cells.

_ Microglia act as phagocytes.

_ Oligodendrocytes are reproductive cells.

_ Repolarization is the return to the resting state.

They are the muscles or glands.

Neurons cannot reproduce.

They take part in myelin production.

GOOD JOB!

Nerve Impulse and Synapse

• Cell membrane potential - polarized

• Depolarized – sodium ions move into the cell

• Action potential is created

• Repolarization

– Positive ions move out

– Returns to polarized state

Nerve Impulse (cont.)

• Synaptic knob contains vesicles

– Produced in vesicles

– Released to allow impulse

transmission to post-synaptic structures– Functions

Apply Your Knowledge

What is the function of neurotransmitters?

ANSWER: Neurotransmitters cause muscles to

contract or relax, cause glands to secret products,

activate neurons to send nerve impulses, or inhibit

neurons from sending them.

Right!

Central Nervous System

• Brain and spinal cord

• Blood-brain barrier

– Protects layers of the

membranes of the CNS– Formed by tight capillaries

Central Nervous System (cont.)

cerebrospinal fluid (CSF)

Spinal Cord (cont.)

• Gray matter

– Neuron cell bodies

and their dendrites– Horns

Spinal Cord (cont.)

• Ascending tracts – sensory

• Descending tracts – motor

• Reflexes – predictable automatic responses

Stimulu s

Stimulu

s

Response

– Gyri– Longtidtudinal fissure

Brain

Brain (cont.)

– CSF

• Diencephalon

– Thalamus– Hypothalamus

– Fine muscle movements

Brain

Apply Your Knowledge

Match the following:

_ Meninges A Carry motor information from brain

_ Ascending tracts B Stores memories and creates emotions

_ Descending tracts C Grooves on the surface of the cerebrum

_ Cerebral cortex D Carry sensory information to the brain

_ Hypothalamus E Predictable, automatic response to stimuli

_ Sulci F Maintains homeostasis

_ Cerebellum G Coordinates skeletal muscle contractions

_ Reflexes H Protects the brain and spinal cord

Peripheral Nervous System

• Nerves that branch off

the CNS

– Cranial nerves

– Spinal nerves

Cranial Nerves (cont.)

VII Facial nerves

Spinal Nerves

• 31 pairs of spinal nerves

– 8 pairs of cervical nerves – 12 pairs of thoracic nerves – 5 pairs of lumbar nerves – 5 pairs of sacral nerves

– 1 pair of coccygeal nerves

Spinal Nerves

Spinal Nerves (cont.)

– Skin segment innervated by spinal nerve

– C1 is not associated with a dermatome

• Ventral root – axons of motor neurons

• Dorsal root

– Axons of sensory neurons

– Dorsal root ganglion ~ cell bodies of sensory

neurons

Spinal Nerves (cont.)

• Nerve plexuses

– Cervical ~ skin and neck

– Brachial ~ arms

– Lumbosacral ~ lower abdomen, external

genitalia, buttocks, thighs, legs, and feet– Coccygeal ~ anus and back of thighs

Spinal Nerves

Somatic and Autonomic Nervous System

• Somatic Nervous System

– Nerves that connect the CNS to skin and

skeletal muscle– “Voluntary” nervous system

– Controls skeletal muscles

(cont.)

• Autonomic Nervous System

– Connect the CNS to organs and other structures – “Involuntary” nervous system

Organs and blood vessels

Organs and blood vessels

– Controls constriction of blood vessels

(cont.)

– Prepares body for rest and digesting

– Controls most of the body’s organs

– Releases acetylcholine

• Sympathetic and parasympathetic

divisions are antagonistic

Apply Your Knowledge

What is the difference between the sympathetic

and parasympathetic nervous systems?

ANSWER: The sympathetic nervous system prepares

the body for stress It releases norepinephrine,

causing an increase in heart and respiratory rate,

slows down the GI system, and dilates pupils The

sympathetic system also controls constriction of

blood vessels.

The parasympathetic system prepares the body for

resting and digesting It releases acetylcholine, which

slows heart and respiratory rates, constricts pupils,

and stimulates the GI system It has no effect on most

blood vessels.

• Electroencephalogram (EEG)

• X-ray

Cranial Nerve Tests

• Olfactory nerve (I) –

have patient

smell various

substances

• Cranial nerves III, IV, and VI – have

patient visually track movement of finger

Cranial Nerve Tests (cont.)

• Cranial nerve V – have patient clench

teeth, feel jaw muscles

• Cranial nerve VII – check

patient’s facial expression

• Cranial nerve XII – have

patient extend and move

tongue

Apply Your Knowledge

Match the following:

_ State of consciousness A Determines the health of

peripheral nerves _ Reflex activity B Loss of balance,

abnormal posture _ Speech patterns C Stupor, delirium,

vegetative _ Motor patterns D Loss of ability to

Nervous System

• Brain and spinal cord injuries

– Causes

• Motor vehicle accidents

• Sports and recreational accidents

• Violence

– Children and teens at highest risk

– Most are preventable

Nervous System (cont.)

Nervous System (cont.)

Disease/Disorder Description

Bell’s palsy Weak or paralyzed facial

musclesBrain tumors and

cancers Abnormal growths Can be primary or secondary

tumors; most common – gliomas

Nervous System (cont.)

Disease/Disorder Description

Epilepsy and

seizures Occurs as a result of bursts of electrical signals that disrupt

normal brain functioning

Guillain-Barré

Syndrome Body’s immune system attacks the PNS; sudden and

unexpected onset

Nervous System (cont.)

attacks occur in groups

Nervous System (cont.)

Disease/Disorder Description

Meningitis Inflammation of meninges

Multiple sclerosis

(MS) Chronic disease of CNS; myelin is destroyed

Neuralgias Disorders causing nerve pain

Nervous System (cont.)

Apply Your Knowledge

_ Neuralgias are motor system disorders.

_ Stroke occurs when brain cells die because of inadequate

blood flow.

F

F

T

Due to a burst of electrical signals that disrupt brain function

They are group of disorders referred to as nerve pain.

T

In Summary

30.1 The central nervous system is composed of the

brain and spinal cord The peripheral nervous system consists of the peripheral nerves located

throughout the body

Three types of neurons carry out the functions of the nervous system: the afferent (sensory) nerves detect sensation or other stimuli from the body or

environment and bring it to the CNS for interpretation, the

efferent (motor) nerves produce movement or other

functions at the direction of the CNS, and the interpretive

interneurons act as “interpreters” between the afferent and

efferent nerves

In Summary (cont.)

30.2 All neurons are composed of a cell body, the

shorter and more numerous dendrites that receive information for the cell body, and the longer axons that function to bring impulses from the cell body to the dendrite of the next neuron

In Summary (cont.)

30.3 Nerve impulses send information either from the

CNS to the PNS or vice versa

A synapse is the space between the axon of one neuron and the dendrite of the next

At the end of each axon is the synaptic knob, which contains vesicles that produce neurotransmitters

These are released by the synaptic bulb to allow impulse transmission to continue to the next neuron.

In Summary (cont.)

30.4 The brain consists of the cerebrum, diencephalon,

brain stem, and cerebellum Other structures include the blood-brain barrier and the meninges.

The spinal cord consists of 31 spinal segments The basic function of the spinal cord is to carry sensory information to the brain and motor information to the muscles and glands of the body

Cerebrospinal fluid (CSF) is located within the subarachnoid space and the central canal of the

spinal cord It cushions the brain and spinal cord.

In Summary (cont.)

30.5 The somatic nervous system connects the CNS to

the skin and skeletal muscle (voluntary functions)

The autonomic nervous system connects the CNS to the internal organs (involuntary functions)

The autonomic nervous system is divided into the sympathetic system, which prepares the body for

“fight or flight” (stressful) situations, and the parasympathetic system, which is the body’s everyday

“resting” system for normal situations.

In Summary (cont.)

30.6 Tests commonly used to determine neurologic

disorders include tests of the reflexes and cranial

nerves, as well as diagnostic procedures such as

lumbar puncture, MRI, PET, cerebral angiography, CT

scan, EEG, and X-ray.

30.7 Many types of diseases and disorders are related to

the nervous system

The signs, symptoms, and treatments of these diseases are as varied as the diseases themselves

Many of the more common diseases are included in the pathophysiology section at the end of this

chapter

Activity of the nervous system improves the

capacity for activity, just

as exercising a muscle makes it stronger.”

~ Dr Ralph Gerard

End of Chapter 30