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6
The Nervous
System
Lesson 6.1: Overview of the Nervous System
Lesson 6.2: Transmission of Nerve Impulses
Lesson 6.3: Functional Anatomy of the Central
Nervous System
Lesson 6.4: Functional Anatomy of the Peripheral
Nervous System
Lesson 6.5: Injuries and Disorders of the
Nervous System
Chapter 6: The Nervous System
Lesson 6.1
Overview of the
Nervous System
Nervous System Overview
• organization of the nervous system
– two major divisions
– the efferent nerves
• nervous tissues
– neuroglia
– neurons
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Organization of the Nervous System
• two major divisions
– central nervous system (CNS)
– peripheral nervous system (PNS)
• sensory receptors
• afferent (sensory) nerves
• efferent (motor) nerves
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Two Major Divisions
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The Efferent Nerves
• somatic nervous system
– voluntary
• autonomic nervous system
– involuntary
– sympathetic
– parasympathetic
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Nervous Tissues
• neuroglia
– also known as glial cells
– support the neurons
– protect the neurons
• neurons
– transmit nerve impulses
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Neuroglia
• central nervous system
–
–
–
–
astrocytes
microglia
ependymal
oligodendrocytes
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Neuroglia
• peripheral nervous system
– Schwann cells
– satellite cells
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Neurons
• dendrites
– send information to cell body
• cell bodies
• axons
– send information away from cell body
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Neuron Types by Function
• sensory neurons
– send impulses toward CNS
• motor neurons
– send impulses away from CNS
• interneurons
– bridges between neurons
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Neuron Structures
• bipolar
– one axon
and one
dendrite
• unipolar
– one axon
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• multipolar
– one axon
and many
dendrites
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Review and Assessment
Match these words with 1–4 below: sympathetic
nervous system, myelin, synapse, axon.
1. high alert
2. transmits impulses away from cell body
3. fatty insulating material
4. gap between neurons
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Chapter 6: The Nervous System
Lesson 6.2
Transmission of
Nerve Impulses
Transmission of Nerve Impulses
• action potentials
– change in cell membrane charge
• impulse transmission
– charge change travels along axon
• reflexes
– involuntary response to stimulus
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Action Potentials
•
•
•
•
polarized
depolarized
repolarized
refractory period
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Impulse Transmission
• saltatory conduction
• transmission at synapses
–
–
–
–
gap junctions
neurotransmitter
excitatory effect
inhibitory effect
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Reflexes
• somatic
– stimulate skeletal muscles
• autonomic
– stimulate involuntary muscles
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Review and Assessment
Fill in the blanks with: reflexes, saltatory conduction,
neurotransmitter, or action potential.
1. A(n) _______________ is an all or none
response.
2. _______________ occurs only in myelinated
axons.
3. _______________ are rapid, involuntary
responses.
4. The axon terminal has tiny vesicles filled with
_______________.
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Chapter 6: The Nervous System
Lesson 6.3
Functional Anatomy of the
Central Nervous System
The Brain
– Cerebrum
– Diencephalon
– brain stem
– cerebellum
– meninges
– blood-brain barrier
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Cerebrum
– Cerebrum
• Associated with sensory (interpret impulses) and motor
functions (control muscular movement)
• Provides higher mental functions of memory and
reasoning
– Seat of intelligence and personality
• Functions to control skeletal muscles, vision, hearing,
taste, and skin sensations
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Cerebrum
• cerebral cortex
– gyrus
– sulcus
– fissure
• lobes
– Frontal – Motor. Association areas- high intellectual processes.
– Parietal – Sensory. Association- speech, thoughts feelings.
– Occipital – Sensory- Vision. Association – Combine visual images
with other senses
– Temporal – Sensory – Hearing and smelling. Assoc – visual senses,
music, complex sensory
• primary motor cortex
• primary somatic sensory cortex
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Cerebrum
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Diencephalon
• Thalamus – Pain, touch, and temperature
• Hypothalamus – Controls and integrates
autonomic NS
• Epithalamus – Connects limbic system to other
parts of the brain
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Brain Stem
• Midbrain – relay station for sensory and motor
impulses
– Relays info over vision, hearing, motor activity, sleep/wake
cycles, alertness, and temp regulation
• Pons – regulates breathing
• medulla oblongata – regulates heart rate, blood
pressure, and breathing. Controls reflexes for
coughing, sneezing, and vomiting.
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Medulla Oblongata
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Medulla Oblongata
• Medulla Oblongata – enlarged continuation of
spinal cord
– All nerve fibers pass through
– Contains
• Cardiac center – increases/decreases heart rate
• Vasomotor center – stimulates smooth muscle in blood
vessels to contract.
– Constriction
– Vasodilation
heart rate increases. (vasoconstriction)
• Respiratory center – adjusts rate and depth of breathing
– Works with pons
• Reflex center – coughing, sneezing, swallowing, vomitting
– Injuries to the medulla oblongata are often fatal
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The Brain
• Cerebellum – balance
• Blood-brain barrier
– Blood vessels supply
nutrients
• Meninges
– dura mater
– arachnoid mater
– pia mater
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Spinal Cord
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Myths
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Pain
• an unpleasant awareness of a noxious stimulus or
bodily harm
• General info
– highly subjective to person experiencing it
– pain of some type is the most frequent reason for
physician consultation in the US, causing half of all
Americans to seek medical care annually
– pain that stops without treatment or responds to simple
measures is called acute
– pain is part of the body’s defense system
– pain that becomes pathological rather than beneficial is
called chronic
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Pain
• Intensity
– some have used a numeric scale ranging from 0-10
• Localization
– usually named according to area or region of
association(HEADACHE, BACKACHE)
– Radiating pain occurs when stimulus of a nerve at one
site is perceived as pain in the sensory distribution of
that nerve
• Sciatica– involves pain running down the back of the
buttock, leg, and bottom of foot (it is caused by
compression of the nerve root in the lumbar spine)
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Pain
• Referred pain usually happens when sensory
fibers from the viscera enter the same segment of
the spinal cord as nerves from superficial tissue
– heart attack—pain in left arm
• Phantom pain is the sensation of pain from a limb
or organ that has been lost or from which a person
no longer receives signals
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Review and Assessment
True or False?
1. The gyri divide the brain into 4 regions.
2. The hypothalamus regulates blood pressure.
3. The meninges has 3 layers.
4. The cerebellum coordinates balance.
5. The pons is also called the interbrain.
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Chapter 6: The Nervous System
Lesson 6.4
Functional Anatomy
of the Peripheral
Nervous System
Functional Anatomy of the Peripheral
Nervous System
•
•
•
•
nerve structure
cranial nerves
spinal nerves and nerve plexuses
autonomic nervous system
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Nerve Structure
• endoneurium
– covers axons
• perineurium
– bundles fascicles
• epineurium
– wraps nerves
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Cranial Nerves
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Spinal Nerves and Nerve Plexuses
•
•
•
•
31 pairs
dorsal root
ventral root
dorsal ramus – carry nerve impulses to muscle
and skin of trunk
• ventral ramus – carry nerve impulses to muscle
and skin of trunk
• Plexuses – complex interconnection of nerves
formed by ventral rami
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Autonomic Nervous System
• preganglionic and postganglionic neurons
• sympathetic nerves
– fight-or-flight action
• parasympathetic nerves
– resting or digesting action
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Review and Assessment
Match these words with 1–4 below: efferent,
ganglion, optic, perineurium.
1. wraps fascicles
2. motor
3. a cranial nerve
4. enlarged junction
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Chapter 6: The Nervous System
Lesson 6.5
Injuries and Disorders of
the Nervous System
Injuries to the Brain and Spinal Cord
• traumatic brain injury – occurs during violent
impacts to the head
• cerebral palsy – group of nervous system
disorders caused by dmg to the brain early on
• spinal cord injury – fractures or displacements of
the vertebrae can result in injury to the spinal cord
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Zika Virus
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Traumatic Brain Injury
• violent impact to head
– Mild – may remain conscious or lose consciousness for a short bit.
• Symptoms: headache, confusion, dizziness, disrupted vision, ringing ears,
bad taste in mouth, fatigue, abnormal sleep, behaviour changes, trouble
with intellectual functions
– Moderate
Same symptoms as above with worse/longer headache,
repeated nausea/vomitting, seizures, slurred speech,
weakness, numbness in extremities
– severe
• 50% require surgical repair
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Cerebral Palsy
• damage to brain
– before birth
– during birth
– during infancy
• motor function impairment
• Caused by several conditions
– Brain infections
– Head injury
– Impaired liver function
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Spinal Cord Injuries
•
•
•
•
C1–C3: usually fatal
C1–C4: quadriplegia – loss of function below neck
C5–C7: paralysis of lower extremities
T1–L5: paraplegia
– Loss of function in
Trunk and legs
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Common Diseases and Disorders of the
CNS
• Meningitis – inflammation of meninges
surrounding brain and spinal cord
• multiple sclerosis – autoimmune disease that
destroys myelin sheaths
• Epilepsy - group of brain disorders characterized
by repeated seizures
• Parkinson’s disease
– Common amongst elderly
– tremors and difficulty moving
• Dementia and Alzheimer’s disease – loss of
function in 2 or more areas of cognition
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Review and Assessment
Match these words with 1–4 below: quadriplegia,
multiple sclerosis, dementia, cerebral palsy.
1. inflammation destroys myelin sheath
2. loss of memory and thinking
3. loss of function below the neck
4. may begin before birth
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Brains
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