Transcript Cranial Nerves

PowerPoint Lecture Outlines
to accompany
Hole’s Human
Anatomy and Physiology
Eleventh Edition
Shier w Butler w Lewis
Chapter
11
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1
CNS
• Brain
- largest and most complex part of NS
- composed of 2 cerebral hemispheres, the
diencephalon, the brain stem, & cerebellum
-houses about 100 billion motor neurons
• Spinal Cord
-communicates between CNS & PNS
2
Chapter 11
Nervous System II
Meninges
• membranes
surrounding CNS
• protect CNS
• three layers
• dura mater – outer,
tough, dense CT, BV’s
& nerves
• arachnoid mater –
thin, weblike, lacks
BV’s
• pia mater – inner,
very thin, has nerves &
BV’s, nourishes brain
& SC
3
Meningitis
• Inflammation of the meninges (usually
arachnoid and pia maters)
• Bacteria or virus invades CSF
• Complications includes loss of vision, loss
of hearing, paralysis, and mental retardation
• Can be fatal
4
Dura mater
• Extends inward b/w lobes of the brain and forms
supportive and protective partitions
• 1) Falx cerebelli-separates the L & R cerebellar
hemispheres
• 2) Falx cerebri-extends downward into the
longitudinal fissure, and separetes the L & R
cerebral hemispheres
• 3) Tentorium cerebelli-separates the occipital
lobes of the cerebrum from the cerebellum
5
Dura mater
• Also splits into two layers, forming
channels called dorsal sinuses
• Venous blood flows through the channels as
it returns from the brain to vessels leading
to the heart
6
Epidural Space
• Between bony walls of vertebra and dura
mater
• Contains BV’s, loose CT, and adipose that
pad the spinal cord
7
Subdural Hematoma
• Caused by a blow to the head
• Brain bleed-blood collects beneath the dura
mater and increases pressure
• Pressure must be relieved or compression of
the brain may lead to function loss or death
8
Subarachnoid space
• Between the arachnoid and pia maters
• Contains cerebrospinal fluid (CSF)
9
Meninges of the Spinal Cord
10
Ventricles
• interconnected cavities
• within cerebral
hemispheres and brain
stem
• continuous with central
canal of spinal cord
• filled with cerebrospinal
fluid (CSF)
• 2 lateral ventricles largest
• third ventricle
• fourth ventricle
• cerebral aqueduct
11
Cerebrospinal Fluid
• secreted by choroid
plexus- specialized
capillaries from pia mater
• circulates in ventricles,
central canal of spinal
cord, and subarachnoid
space
• completely surrounds
brain and spinal cord
• clear liquid
• nutritive and protective
• helps maintain stable ion
concentrations in CNS
•Reabsorbed by arachnoid
granulations
12
Lumbar Puncture
• Also known as a spinal tap
• Measures CSF pressure
13
Spinal Cord
• slender column of
nervous tissue
continuous with brain
• extends downward
through vertebral
canal
• begins at level of
foramen magnum
and terminates near
first and second
lumbar
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Structure of the Spinal Cord
• 31 segments-each gives rise to a pair of spinal
nerves (p.423)
• Cervical enlargement: in neck; gives rise to nerves
that are in the upper limbs
• Lumbar enlargement: gives off nerves to the lower
limbs
• Two grooves extend the length of the SC: anterior
median fissure & posterior median sulcus
15
Cross Section of Spinal Cord
16
Functions of Spinal Cord
Two main functions:
• center for spinal reflexes
• conduit for nerve impulses to and
from the brain
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Reflex Arcs
Reflexes – automatic, subconscious responses to stimuli
within or outside the body; help maintain homeostasis
18
Reflex Arcs
19
General Components of a Spinal
Reflex
20
Reflex Behavior
• example is the knee-jerk reflex
• simple monosynaptic reflex
• helps maintain an upright posture
21
Reflex Behavior
• example is a withdrawal reflex
• prevents or limits tissue damage
22
Reflex Arc
• example crossed extensor reflex
• crossing of sensory impulses within the reflex center
to produce an opposite effect
23
Tracts of the Spinal Cord
• Ascending tracts conduct sensory impulses to the brain
• Descending tracts conduct motor impulses from the brain to
motor neurons reaching muscles and glands
24
Ascending Tracts
• major ascending spinal cord
tracts
• fasciculus gracilis and
fasciculus cuneatus (skin,
muscles, tendons, joint to
brain)
• spinothalamic
• lateral and anterior
(sensations of pain &
temperature)
• spinocerebellar
• posterior and anterior
(muscles of lower limbs &
trunk to cerebellum)
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Descending Tracts
• major descending spinal cord
tracts
• corticospinal
• lateral and anterior
(motor impulses from
brain to SC to muscles)
• reticulospinal
• lateral, anterior and
medial (muscle tone &
sweat glands)
• rubrospinal (brain to
skeletal muscles-coordinate
& control posture
26
Nerve Tracts of the Spinal Cord
27
Lou Gehrig’s Disease
• Motor neurons degenerate within the SC,
brainstem, and cerebral cortex
• Replaced with fibrous tissue
• Affects speech, muscle twitches
28
Brain
Functions
Major Parts
• interprets sensations
• cerebrum
• two hemispheres
• determines perception
• basal nuclei
• stores memory
• diencephalon
• reasoning
• brainstem
• makes decisions
• cerebellum
• coordinates muscular
movements
• regulates visceral activities
• determines personality
29
Brain
30
Brain Development
Three Major Vesicles
1. Forebrain
2. Midbrain
3. Hindbrain
31
Brain Development
32
Structure of Cerebrum
• corpus callosum
• connects cerebral
hemispheres
• convolutions
• bumps or gyri
• sulci
• grooves
• longitudinal fissure
• separates hemispheres
• transverse fissure
• separates cerebrum from
cerebellum
33
Lobes of Cerebral Hemispheres
• Frontal
• Parietal
• Temporal
• Occipital
• Insula
34
Functions of the Cerebrum
• interpreting impulses
• initiating voluntary movements
• storing information as memory
• retrieving stored information
• reasoning
• seat of intelligence and personality
35
Functional Regions of
Cerebral Cortex
Cerebral Cortex – thin layer of gray matter that
constitutes the outermost portion of cerebrum; contains
75% of all neurons in nervous system
36
Sensory Areas
• Cutaneous Sensory
Area
• parietal lobe
• interprets sensations
on skin
• Visual Area
• occipital lobe
• interprets vision
• Auditory Area
• Sensory Area for Taste
• near bases of the central
sulci
• Sensory Area for
Smell
• arise from
centers
deep within
the cerebrum
• temporal lobe
• interprets hearing
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Sensory Areas
38
Association Areas
• regions that are not primary motor or primary sensory areas
• widespread throughout the cerebral cortex
• analyze and interpret sensory experiences
• provide memory, reasoning, verbalization, judgment, emotions
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Association Areas
Frontal Lobe Association Areas
• concentrating
• planning
• complex problem solving
Temporal Lobe Association Areas
• interpret complex sensory
experiences
• store memories of visual scenes,
music, and complex patterns
Parietal Lobe Association Areas
• understanding speech
• choosing words to express
thought
Occipital Lobe Association Areas
• analyze and combine visual
images with other sensory
experiences
40
Hemisphere Dominance
• The left hemisphere is dominant in most individuals
• Dominant hemisphere
controls
• speech
• writing
• reading
• verbal skills
• analytical skills
• computational skills
• Nondominant hemisphere
controls
• nonverbal tasks
• motor tasks
• understanding and
interpreting musical and
visual patterns
• provides emotional and
intuitive thought processes
41
Memory
Short Term
• working memory
• closed neuronal circuit
• circuit is stimulated over
and over
• when impulse flow
ceases, memory does also
• unless it enters longterm memory via
memory consolidation
Long Term
• changes structure or
function of neurons
• enhances synaptic
transmission
42
Motor Areas
• Primary Motor Areas
• frontal lobes
• control voluntary muscles
• Broca’s Area
• anterior to primary motor
cortex
• usually in left hemisphere
• controls muscles needed for
speech
• Frontal Eye Field
• above Broca’s area
• controls voluntary
movements of eyes and
eyelids
43
Motor Areas
44
Functions of the Cerebral Lobes
45
Basal Nuclei
• masses of gray matter
• deep within cerebral
hemispheres
• caudate nucleus, putamen,
globus pallidus
• produce dopamine
• control certain muscular
activities
• primarily by inhibiting
motor functions
46
Diencephalon
• between cerebral hemispheres and above the brainstem
• surrounds third ventricle
• thalamus
• hypothalamus
• optic tracts
• optic chiasma
• infundibulum
• posterior pituitary
• mammillary bodies
• pineal gland
47
Diencephalon
Thalamus
• gateway for sensory impulses heading to cerebral cortex
• receives all sensory impulses (except smell)
• channels impulses to appropriate part of cerebral cortex
for interpretation
Hypothalamus
• maintains homeostasis by regulating visceral activities
• links nervous and endocrine systems
48
Diencephalon
Limbic System
Consists of
• portions of frontal lobe
• portions of temporal lobe
• hypothalamus
• thalamus
• basal nuclei
• other deep nuclei
Functions
• controls emotions
• produces feelings
• interprets sensory impulses
49
Brain Stem
Three Parts
1. Midbrain
2. Pons
3. Medulla Oblongata
50
Midbrain
• between diencephalon and
pons
• contains bundles of fibers
that join lower parts of
brainstem and spinal cord
with higher part of brain
• cerebral aqueduct
• cerebral peduncles –
bundles of nerve fibers
• corpora quadrigemina –
centers for visual and
auditory reflexes
51
Pons
• rounded bulge on underside of
brainstem
• between medulla oblongata
and midbrain
• helps regulate rate and depth
of breathing
• relays nerve impulses to and
from medulla oblongata and
cerebellum
52
Medulla Oblongata
• enlarged continuation of
spinal cord
• conducts ascending and
descending impulses between
brain and spinal cord
• contains cardiac, vasomotor,
and respiratory control
centers
• contains various nonvital
reflex control centers
(coughing, sneezing,
swallowing, vomiting)
53
Reticular Formation
• complex network of
nerve fibers scattered
throughout the brain stem
• extends into the
diencephalon
• connects to centers of
hypothalamus, basal
nuclei, cerebellum, and
cerebrum
• filters incoming sensory
information
• arouses cerebral cortex
into state of wakefulness
54
Types of Sleep
Slow Wave
Rapid Eye Movement (REM)
• non-REM sleep
• paradoxical sleep
• person is tired
• some areas of brain active
• decreasing activity of
• heart and respiratory rates
reticular system
irregular
• restful
• dreaming occurs
• dreamless
• reduced blood pressure and
respiratory rate
• ranges from light to heavy
• alternates with REM sleep
55
Cerebellum
• inferior to occipital lobes
• posterior to pons and medulla
oblongata
• two hemispheres
• vermis connects hemispheres
• cerebellar cortex – gray matter
• arbor vitae – white matter
• cerebellar peduncles – nerve fiber
tracts
• dentate nucleus – largest nucleus in
cerebellum
• integrates sensory information
concerning position of body parts
• coordinates skeletal muscle activity
• maintains posture
56
Major Parts of the Brain
57
Peripheral Nervous System
• Cranial nerves arising from the brain
• Somatic fibers connecting to the skin and skeletal muscles
• Autonomic fibers connecting to viscera
• Spinal nerves arising from the spinal cord
• Somatic fibers connecting to the skin and skeletal muscles
• Autonomic fibers connecting to viscera
58
Nervous System Subdivisions
59
Structure of a Peripheral Nerve
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Nerve Fiber Classification
• Sensory Nerves – conduct impulses into brain or spinal
cord
• Motor Nerves – conduct impulses to muscles or glands
• Mixed Nerves – contain both sensory nerve fibers and
motor nerve fibers; most nerves
61
Nerve Fiber Classification
General somatic efferent fibers
• carry motor impulses from
CNS to skeletal muscles
General visceral efferent fibers
• carry motor impulses away from
CNS to smooth muscles and
glands
General somatic afferent fibers
• carry sensory impulses to
CNS from skin and skeletal
muscles
General visceral afferent fibers
• carry sensory impulses to CNS
from blood vessels and internal
organs
62
Nerve Fiber Classification
Special somatic efferent fibers
• carry motor impulses from brain to muscles
used in chewing, swallowing, speaking, and
forming facial expressions
Special visceral afferent fibers
• carry sensory impulses to brain from olfactory and
taste receptors
Special somatic afferent fibers
• carry sensory impulses to brain from receptors of
sight, hearing, and equilibrium
63
Cranial Nerves
64
Cranial Nerves I and II
Olfactory (I)
• sensory
• fibers transmit
impulses associated
with smell
Optic (II)
• sensory
• fibers transmit
impulses associated
with vision
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Cranial Nerves III and IV
Oculomotor (III)
• some sensory
• proprioreceptors
• primarily motor
• motor impulses to
muscles that
• raise eyelids
• move the eyes
• focus lens
•adjust light entering
eye
Trochlear (IV)
• some sensory
• proprioreceptors
• primarily motor
• motor impulses to
muscles that move the
eyes
66
Cranial Nerve V
Trigeminal (V)
• mixed
• opthalmic division
• sensory from surface of eyes,
tear glands, scalp, forehead, and
upper eyelids
• maxillary division
• sensory from upper teeth,
upper gum, upper lip, palate,
and skin of face
• mandibular division
• sensory from scalp, skin of jaw,
lower teeth, lower gum, and
lower lip
• motor to muscles of mastication
and muscles in floor of mouth
67
Cranial Nerves VI and VII
Abducens (VI)
• primarily motor
• motor impulses to
muscles that move
the eyes
• some sensory with
proprioreceptors
Facial (VII)
• mixed
• sensory from taste
receptors
• motor to muscles of
facial expression,
tear glands, and
salivary glands
68
Cranial Nerves VIII and IX
Vestibulocochlear (VIII)
• sensory
• vestibular branch
•sensory from
equilibrium receptors of
ear
• cochlear branch
•sensory from hearing
receptors
Glossopharyngeal (IX)
• mixed
• sensory from pharynx,
tonsils, tongue, and carotid
arteries
• motor to salivary glands
and muscles of pharynx
69
Cranial Nerve X
Vagus (X)
• mixed
• somatic motor to
muscles of speech
and swallowing
• autonomic motor to
viscera of thorax and
abdomen
• sensory from
pharynx, larynx,
esophagus, and
viscera of thorax and
abdomen
70
Cranial Nerves XI and XII
Accessory (XI)
• primarily motor
• cranial branch
• motor to muscles of
soft palate, pharynx,
and larynx
• spinal branch
•motor to muscles of
neck, and back; some
proprioreceptor
Hypoglossal (XII)
• primarily motor
• motor to muscles of
the tongue; some
proprioreceptor
71
Functions of Cranial Nerves
72
Spinal Nerves
• mixed nerves
• 31 pairs
• 8 cervical
•(C1 to C8)
• 12 thoracic
•(T1 to T12)
• 5 lumbar
•(L1 to L5)
• 5 sacral
•(S1 to S5)
• 1 coccygeal
•(Co)
73
Spinal Nerves
Dorsal root (posterior
or sensory root)
• axons of sensory
neurons in the
dorsal root
ganglion
Dorsal root ganglion
• cell bodies of sensory
neurons whose axons
conduct impulses inward
from peripheral body
parts
74
Dermatome
• an area of skin that the sensory nerve fibers of a particular
spinal nerve innervate
75
Spinal Nerves
Ventral root (anterior or
motor root)
• axons of motor
neurons whose cell
bodies are in spinal
cord
Spinal nerve
• union of ventral root
and dorsal root
76
Cervical Plexuses
Nerve plexus – complex networks formed by anterior branches
of spinal nerves; fibers of various spinal nerves are sorted and
recombined
Cervical Plexus
• formed by anterior
branches of C1-C4
• lies deep in the neck
• supply muscles and
skin of the neck
• C3 – C5 contribute to
phrenic nerves
77
Brachial Plexuses
• C5-T1
• lies deep within shoulders
• musculocutaneous nerves
• supply muscles of anterior arms
and skin of forearms
• ulnar and median nerves
• supply muscles of forearms and
hands
• supply skin of hands
•radial nerves
• supply posterior muscles of
arms and skin of forearms and
hands
• axillary nerves
• supply muscles and skin of
anterior, lateral, and posterior
arms
78
Lumbosacral Plexuses
• T12 – S5
• extend from lumbar
region into pelvic cavity
• obturator nerves
• supply motor impulses
to adductors of thighs
• femoral nerves
• supply motor impulses
to muscles of anterior
thigh and sensory
impulses from skin of
thighs and legs
• sciatic nerves
• supply muscles and skin
of thighs, legs, and feet
79
Plexuses
80
Autonomic Nervous System
• functions without conscious effort
• controls visceral activities
• regulates smooth muscle, cardiac muscle, and glands
• efferent fibers typically lead to ganglia outside CNS
Two Divisions
• sympathetic – prepares body for fight or flight
situations
• parasympathetic – prepares body for resting
and digesting activities
81
Autonomic Nerve Fibers
• all are neurons are
motor (efferent)
• preganglionic fibers
• axons of preganglionic
neurons
• neuron cell bodies in
CNS
• postganglionic fibers
• axons of postganglionic
neurons
• neuron cell bodies in
ganglia
82
Sympathetic Division
• thoracolumbar divison –
location of preganglionic
neurons
• preganglionic fibers leave
spinal nerves through white
rami and enter
paravertebral ganglia
• paraverterbral ganglia
and fibers that connect
them make up the
sympathetic trunk
83
Sympathetic Division
• postganglionic fibers
extend from sympathetic
ganglia to visceral organs
• postganglionic fibers
usually pass through gray
rami and return to a spinal
nerve before proceeding to
an effector
• Exception: preganglionic
fibers to adrenal medulla do
not synapse with
postganglionic neurons
84
Sympathetic Division
85
Parasympathetic Division
• craniosacral division –
location of preganglionic
neurons
• ganglia are near or
within various organs
• terminal ganglia
• short postganglionic
fibers
• continue to
specific muscles or
glands
• preganglionic fibers of the
head are included in nerves
III, VII, and IX
• preganglionic fibers of
thorax and abdomen are
parts of nerve X
86
Parasympathetic Division
87
Autonomic Neurotransmitters
Cholinergic Fibers
• release acetylcholine
• preganglionic
sympathetic and
parasympathetic
fibers
• postganglionic
parasympathetic
fibers
Adrenergic Fibers
• release
norepinephrine
• most
postganglionic
sympathetic
fibers
88
Actions of Autonomic
Neurotransmitters
• depend on receptors in the membrane
Cholinergic receptors
• bind to acetlycholine
• muscarinic
• excitatory
• slow
• nicotinic
• excitatory
• rapid
Adrenergic Receptors
• bind to epinephrine
and norepinephrine
• alpha and beta
• both elicit different
responses on various
effectors
89
Actions of Autonomic
Insert figure 11.39
Neurotransmitters
90
Control of Autonomic
Activity
• Controlled largely by CNS
• Medulla oblongata regulates cardiac, vasomotor and
respiratory activities
• Hypothalamus regulates visceral functions, such as body
temperature, hunger, thirst, and water and electrolyte
balance
• Limbic system and cerebral cortex control emotional
responses
91
Life-Span Changes
• Brain cells begin to die before birth
• Over average lifetime, brain shrinks 10%
• Most cell death occurs in temporal lobes
• By age 90, frontal cortex has lost half its neurons
• Number of dendritic branches decreases
• Decreased levels of neurotransmitters
• Fading memory
• Slowed responses and reflexes
• Increased risk of falling
• Changes in sleep patterns that result in fewer sleeping hours
92
Clinical Application
Cerebral Injuries and Abnormalities
Concussion
• brain jarred against cranium
• loss of consciousness
• temporary loss of memory
• mental cloudiness
• headache
• recovery usually complete
Cerebral Palsy
• motor impairment at
birth
• caused by blocked
cerebral blood vessels
during development
• seizures
• learning disabilities
Cerebrovascular Accident
• stroke
• sudden interruption in blood
flow
• brain tissues die
93