Download Nervous System Notes 1_12

Bellwork 1/11/17
 Objective: SWBAT describe the anatomy of the
spinal cord.
 What are the three meninges, from most superficial
to most deep? Describe what the middle layer is like
and how its description relates to its name.
 Where is CSF produced and where is it resorbed?
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Spinal Cord
 Extends from the foramen magnum of the skull to
the first or second lumbar vertebra
 Provides a two-way conduction pathway to and from
the brain
 31 pairs of spinal nerves arise from the spinal cord
 Ends around vertebra L1 or L2
 Cauda equina is a collection of spinal nerves at the
inferior end
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Figure 7.20 Anatomy of the spinal cord, posterior view.
Cervical
enlargement
Cervical
spinal nerves
C8
Dura and
arachnoid
mater
Lumbar
enlargement
Thoracic
spinal nerves
T12
End of spinal cord
Lumbar
spinal nerves
Cauda equina
End of
meningeal
coverings
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L5
S1
S5
Sacral
spinal nerves
Spinal Cord Anatomy
 Internal gray matter is mostly cell bodies
 Dorsal (posterior) horns house interneurons
 Receive information from sensory neurons in the
dorsal root
 Anterior (ventral) horns house motor neurons of the
somatic (voluntary) nervous system
 Send information out ventral root
 Gray matter surrounds the central canal, which is
filled with cerebrospinal fluid
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Spinal Cord Anatomy
 Exterior white mater—conduction tracts
 Dorsal, lateral, ventral columns
 Sensory (afferent) tracts conduct impulses toward
brain
 Motor (efferent) tracts carry impulses from brain to
skeletal muscles
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PNS
Sensory (afferent)
fiber
Spinal
nerve
Motor (efferent)
fiber
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CNS
Gray matter
Short unmyelinated
interneurons
Cell bodies of
interneurons and
motor neurons
Neuroglia
White matter
Fiber tracts of
myelinated and
unmyelinated axons
Hollow central cavity
Figure 7.21 Spinal cord with meninges (three-dimensional view).
Dorsal root
ganglion
White matter
Central canal
Dorsal (posterior)
horn of gray matter
Lateral horn of
gray matter
Spinal nerve
Dorsal root of
spinal nerve
Ventral root
of spinal nerve
Ventral (anterior)
horn of gray matter
Pia mater
Arachnoid mater
Dura mater
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Figure 7.22 Schematic of ascending (sensory) and descending (motor) pathways between the brain and the spinal cord.
Interneuron carrying
sensory information
to cerebral cortex
Cerebral cortex
(gray matter)
White matter
Integration (processing
and interpretation of
sensory input) occurs
Interneuron carrying
response to motor
neurons
Cerebrum
Thalamus
Interneuron
carrying response
to motor neuron
Cell body of sensory
neuron in sensory
ganglion
Nerve
Skin
Sensory
receptors
Brain stem
Interneuron carrying
sensory information to
cerebral cortex
Cervical spinal cord
Muscle
White matter
Gray matter
Motor output
Interneuron
Motor neuron cell body
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Spinal Cord Anatomy
 Meninges cover the spinal cord
 Spinal nerves leave at the level of each vertebra
 Dorsal root
 Associated with the dorsal root ganglia—collections of
cell bodies outside the central nervous system
 Ventral root
 Contains axons
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Bellwork 1/12/17
 SWBAT describe the anatomy of the spinal cord.
 Draw a very simple sketch of the spinal cord and
label the ventral and dorsal horns of the gray matter,
as well as the central canal.
 What function do the ventral and dorsal horns
have?
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Peripheral Nervous System (PNS)
 PNS consists of nerves and ganglia outside the
central nervous system
 Nerve  bundle of neuron fibers
 Neuron fibers are bundled by connective tissue
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PNS: Structure of a Nerve
 Endoneurium surrounds each fiber
 Groups of fibers are bound into fascicles by
perineurium
 Fascicles are bound together by epineurium
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Figure 7.23 Structure of a nerve.
Axon
Myelin sheath
Endoneurium
Perineurium
Epineurium
Fascicle
Blood
vessels
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Concept Link
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PNS: Classification of Nerves
 Mixed nerves
 Both sensory and motor fibers
 Sensory (afferent) nerves
 Carry impulses toward the CNS
 Motor (efferent) nerves
 Carry impulses away from the CNS
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PNS: Cranial Nerves
 12 pairs of nerves that mostly serve the head and
neck
 Only the pair of vagus nerves extends to thoracic
and abdominal cavities
 Most are mixed nerves, but three are sensory only:
1. Optic
2. Olfactory
3. Vestibulocochlear
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PNS: Cranial Nerves Mnemonic Device
 Oh – Olfactory
 Oh – Optic
 Oh – Oculomotor
 To – Trochlear
 Touch – Trigeminal
 And – Abducens
 Feel – Facial
 Very – Vestibulocochlear
 Green – Glossopharyngeal
 Vegetables – Vagus
 A – Accessory
 H – Hypoglossal
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Table 7.2 The Cranial Nerves (1 of 6)
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Table 7.2 The Cranial Nerves (2 of 6)
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Table 7.2 The Cranial Nerves (3 of 6)
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Table 7.2 The Cranial Nerves (4 of 6)
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Table 7.2 The Cranial Nerves (5 of 6)
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Table 7.2 The Cranial Nerves (6 of 6)
Cervical
nerves
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Figure 7.24 Distribution of cranial nerves.
III Oculomotor
IV Trochlear
VI Abducens
I Olfactory
V Trigeminal
V Trigeminal
II Optic
VII Facial
Vestibular
branch
Cochlear
branch
VIII Vestibulocochlear
X Vagus
IX Glossopharyngeal
XII Hypoglossal
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XI Accessory
PNS: Spinal Nerves
 There is a pair of spinal nerves at the level of each
vertebra, for a total of 31 pairs
 Formed by the combination of the ventral and dorsal
roots of the spinal cord
 Named for the region from which they arise
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Figure 7.25a Spinal nerves.
C1
Cervical
nerves
2
3
4
5
6
7
8
T1
2
Ventral rami form
cervical plexus
(C1 – C5)
Ventral rami form
brachial plexus
(C5 – C8; T1)
3
4
Thoracic
nerves
5
6
7
8
9
10
Lumbar
nerves
Sacral
nerves
11
No plexus
formed
(intercostal
nerves)
(T1 – T12)
12
L1
2
3
4
Ventral rami form
lumbar plexus
(L1 – L4)
5
S1
2
(a)
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3
4
Ventral rami form
sacral plexus
(L4 – L5; S1 – S4)
PNS: Anatomy of Spinal Nerves
 Spinal nerves divide soon after leaving the spinal
cord
 Ramus—branch of a spinal nerve; contains both
motor and sensory fibers
 Dorsal rami—serve the skin and muscles of the
posterior trunk
 Ventral rami—form a complex of networks (plexus)
for the anterior
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Figure 7.25b Spinal nerves.
Dorsal
root
Dorsal
root
ganglion
Spinal
cord
Ventral
root
Spinal nerve
(b)
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Dorsal
ramus
Ventral
ramus
PNS: Spinal Nerve Plexuses
 Plexus–networks of nerves serving motor and
sensory needs of the limbs
 Form from ventral rami of spinal nerves in the
cervical, lumbar, and sacral regions
 Four plexuses:
1.
2.
3.
4.
Cervical
Brachial
Lumbar
Sacral
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Table 7.3 Spinal Nerves Plexuses (1 of 3)
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Figure 7.26a Distribution of the major peripheral nerves of the upper and lower limbs.
Axillary nerve
Humerus
Radial
nerve
Musculocutaneous
nerve
Ulna
Radius
Ulnar nerve
Radial nerve
(superficial
branch)
Median
nerve
(a) The major nerves
of the upper limb
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Table 7.3 Spinal Nerves Plexuses (2 of 3)
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Figure 7.26b Distribution of the major peripheral nerves of the upper and lower limbs.
Femoral
Lateral
femoral
cutaneous
Obturator
Anterior
femoral
cutaneous
Saphenous
(b) Lumbar plexus, anterior view
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Table 7.3 Spinal Nerves Plexuses (3 of 3)
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Figure 7.26c Distribution of the major peripheral nerves of the upper and lower limbs.
Superior
gluteal
Inferior
gluteal
Sciatic
Posterior
femoral
cutaneous
Common
fibular
Tibial
Sural (cut)
Deep
fibular
Superficial
fibular
Plantar
branches
(c) Sacral plexus, posterior view
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PNS: Autonomic Nervous System
 Motor subdivision of the PNS
 Consists only of motor nerves
 Also known as the involuntary nervous system
 Regulates activities of cardiac and smooth muscles
and glands
 Two subdivisions:
1. Sympathetic division
2. Parasympathetic division
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PNS: Differences Between Somatic
and Autonomic Nervous Systems
Somatic Nervous
System
Autonomic Nervous
System
Nerves
One-neuron system; it
originates in the CNS,
and axons extend to
the skeletal muscles
served
Two-neuron system
consisting of
preganglionic and
postganglionic
neurons
Effector organ
Skeletal muscle
Smooth muscle,
cardiac muscle,
glands
Subdivisions
None
Sympathetic and
parasympathetic
Neurotransmitter
Acetylcholine
Acetylcholine,
epinephrine,
norepinephrine
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Figure 7.27 Comparison of the somatic and autonomic nervous systems.
Central
nervous
system
Peripheral nervous system
Effector organs
Acetylcholine
Somatic nervous
system
Skeletal
muscle
Acetylcholine
Autonomic
nervous
system
Sympathetic
division
Smooth muscle
(e.g., in stomach)
Norepinephrine
Ganglion
Epinephrine and
Acetylcholine
norepinephrine
Blood
vessel
Parasympathetic
division
KEY:
Preganglionic
axons
(sympathetic)
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Postganglionic
axons
(sympathetic)
Glands
Acetylcholine
Cardiac
muscle
Ganglion
Myelination
Preganglionic
axons
(parasympathetic)
Postganglionic
axons
(parasympathetic)
PNS: Anatomy of the Parasympathetic
Division
 Preganglionic neurons originate from the
craniosacral regions:
 The cranial nerves III, VII, IX, and X
 S2 through S4 regions of the spinal cord
 Because it is the site of preganglionic neuron
origination, the parasympathetic division is also
known as the craniosacral division
 Terminal ganglia are at the effector organs
 Neurotransmitter: acetylcholine
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Figure 7.28 Anatomy of the autonomic nervous system.
Parasympathetic
Sympathetic
Eye
Brain stem
Salivary
glands
Heart
Eye
Skin
Cranial
Cervical
Sympathetic
ganglia
Salivary
glands
Lungs
Lungs
T1
Heart
Stomach
Stomach
Thoracic
Pancreas
Liver
and gallbladder
Pancreas
L1
Liver and
gallbladder
Adrenal
gland
Lumbar
Bladder
Genitals
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Bladder
Sacral
nerves
(S2–S4)
Genitals
PNS: Anatomy of the Sympathetic Division
 Preganglionic neurons originate from T1 through L2
 Ganglia are at the sympathetic trunk (near the
spinal cord)
 Short preganglionic neuron and long postganglionic
neuron transmit impulse from CNS to the effector
 Neurotransmitters: norepinephrine and epinephrine
(effector organs)
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Figure 7.28 Anatomy of the autonomic nervous system.
Parasympathetic
Sympathetic
Eye
Brain stem
Salivary
glands
Heart
Eye
Skin
Cranial
Cervical
Sympathetic
ganglia
Salivary
glands
Lungs
Lungs
T1
Heart
Stomach
Stomach
Thoracic
Pancreas
Liver
and gallbladder
Pancreas
L1
Liver and
gallbladder
Adrenal
gland
Lumbar
Bladder
Genitals
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Bladder
Sacral
nerves
(S2–S4)
Genitals
Figure 7.29 Sympathetic pathways.
Lateral horn of
gray matter
Dorsal ramus
of spinal nerve
Dorsal root
Sympathetic
trunk
Spinal
nerve
(a)
(b)
(c)
Ventral root
Sympathetic
trunk
ganglion
Splanchnic
nerve
Ventral ramus
of spinal nerve
To effector:
blood vessels,
arrector pili
muscles, and
sweat glands
of the skin
Gray ramus
communicans
White ramus
communicans
Collateral ganglion
(such as the celiac)
Visceral effector organ
(such as small intestine)
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PNS: Autonomic Functioning
 Sympathetic—“fight or flight” division
 Response to unusual stimulus
 Takes over to increase activities
 Remember as the “E” division:
 Exercise
 Excitement
 Emergency
 Embarrassment
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PNS: Autonomic Functioning
 Parasympathetic—“housekeeping” activites
 Conserves energy
 Maintains daily necessary body functions
 Remember as the “D” division
 Digestion
 Defecation
 Diuresis
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Table 7.4 Effects of the Sympathetic Divisions of the Autonomic Nervous System (1 of 2)
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Table 7.4 Effects of the Sympathetic Divisions of the Autonomic Nervous System (2 of 2)
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Developmental Aspects of the Nervous
System
 The nervous system is formed during the first month
of embryonic development
 Any maternal infection can have extremely harmful
effects
 Oxygen deprivation destroys brain cells
 The hypothalamus is one of the last areas of the
brain to develop
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Developmental Aspects of the Nervous
System
 Severe congenital brain diseases include:
 Cerebral palsy
 Anencephaly
 Hydrocephalus
 Spina bifida
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Developmental Aspects of the Nervous
System
 Premature babies have trouble regulating body
temperature because the hypothalamus is one of
the last brain areas to mature prenatally.
 Development of motor control indicates the
progressive myelination and maturation of a child’s
nervous system.
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Developmental Aspects of the Nervous
System
 Brain growth ends in young adulthood. Neurons die
throughout life and are not replaced; thus, brain
mass declines with age.
 Healthy aged people maintain nearly optimal
intellectual function.
 Disease—particularly cardiovascular disease—is
the major cause of declining mental function with
age.
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