Central, Peripheral, Somatic, and Autonomic Nerves Flashcards
(109 cards)
1
Q
central nervous system
A
brain and spinal cord
2
Q
peripheral nervous system
A
spinal and cranial nerves
3
Q
vertebral canal spinal cord structure
A
where the spinal cord is located within the vertebral column
4
Q
meninges
A
3 layers of connective tissue coverings that extend around the spinal cord and brain
spinal meninges
cranial meninges
3 layers of meninges
5
Q
spinal meninges
A
protect the spinal cord; continuous with cranial meninges
6
Q
cranial meninges
A
protect the brain
7
Q
3 layers of meninges
A
dura mater
arachnoid mater
pia mater
8
Q
dura mater
A
outermost layer; tough, dense irregular connective tissue; protects the delicate structures of the CNS; extends to the second sacral vertebra (past the end of the spinal cord)
9
Q
arachnoid mater
A
middle layer; arrangement of its collagen and elastic fibers ressemble a spider’s web
10
Q
pia mater
A
innermost layer; transparent layer of collagen and elastic fibers that adheres to the surface of the spinal cord and brain; contains numerous blood vessels
11
Q
2 spaces
A
epidural space
subarachnoid space
12
Q
epidural space
A
space between the dura mater and vertebral column that contains a cushion of fat and connective tissue to protect the spinal cord
13
Q
subarachnoid space
A
space between the arachnoid mater and the pia mater; where cerebrospinal fluid circulates
14
Q
length of spinal cord
A
42-45 cm ( medulla oblongata to the second lumbar vertebra)
15
Q
cauda equina
A
horse’s tail; the roots of the spinal nerves that angle down the vertebral canal to
exit at vertebral levels before the level they exit the spinal cord
16
Q
conus medullaris
A
the tapered inferior end of the spinal cord
17
Q
enlargements
A
cervical
lumbar`
18
Q
cervical enlargement
A
contains cell bodies of nerves that supply the upper limbs
19
Q
lumbar enlargement
A
contains cell bodies of nerves that supply the upper limbs
20
Q
grooves
A
(divide the spinal cord into right and left halves)
anterior median fissure
posterior median sulcus
21
Q
anterior median fissure
A
deep
22
Q
posterior median sulcus
A
shallow
23
Q
central canal spinal cord structure
A
a small space in the center of the gray matter that extends the length of the cord; contains cerebrospinal fluid
24
Q
gray matter of the spinal cord * internal structure of spinal cord*
A
contains neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia
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horns
divisions of spinal cord gray matter; named relative to their location
anterior
lateral
posterior
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anterior horns
contain cell bodies of somatic motor neurons that provide nerve impulses for contraction of skeletal muscles
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lateral horns
between anterior and posterior horns; present only in thoracic and upper
lumbar segments; contains cell bodies of autonomic motor neurons that regulate
the activity of cardiac muscle, smooth muscle, and glands
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posterior horns
contain cell bodies and axons of interneurons as well as axons of incoming sensory neurons
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white matter of the spinal cord
consists primarily of myelinated axons of neurons
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white columns
regions of spinal cord white matter (anterior, lateral, and posterior); contains one or more tracts
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tracts
distinct bundles of axons having a common origin or destination and carrying similar information
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sensory ( ascending) tracts
consist of axons that conduct nerve impulses up the spinal cord toward the brain; continuous with sensory tracts in the brain
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motor ( descending) tracts
consist of axons that carry nerve impulses down the spinal cord away from the brain; continuous with motor tracts in the brain
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spinal nerves
paths of communication between the spinal cord and specific regions of the body
31 pairs or spinal nerves that emerge at regular intervals; named and numbered according to the region and level of the vertebral column
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cervical spinal nerves
8
36
thoracic spinal nerves
12
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lumbar spinal neves
5
38
sacral spinal nerves
5
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coccygeal spinal nerves
1
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intervertebral foramina
holes between vertebrae through which spinal nerves leave the vertebral column
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roots
bundles of axons that connect each spinal nerve to a segment of the cord (2 roots per
spinal nerve)
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posterior ( dorsal) root
contains only sensory axons (conduct nerve impulses from sensory receptors into the CNS)
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posterior ( dorsal ) root ganglion
a swelling which contains the cell bodies of sensory neurons
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anterior ( ventral) root
contains only motor axons (conduct nerve impulses from the CNS to effectors)
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spinal nerve =
| * internal spinal structure*
1 posterior root + 1 anterior root = mixed nerve
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spinal nerve coverings
endonerium
fascicles
perineurium
epineurium
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endoneurium
connective tissue that wraps individual axons of spinal and cranial nerves
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fascicles
bundles of axons wrapped in endoneurium
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perineurium
connective tissue that wraps fascicles; many blood vessels
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epineurium
the superficial covering over the entire nerve; fuses with the dura mater of the
spinal meninges; many blood vessels
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distribution of spinal nerves
After exiting through the intervertebral foramina, spinal nerves divide into several branches
Many of these branches form networks with adjacent branches from other spinal nerves forming a plexus
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plexus
a network of nerves or vessels
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major plexuses
cervical
brachial
lumbar
sacral
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cervical plexus
skin and muscles of the posterior head, neck, upper part of shoulders, and diaphragm
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brachial plexus
upper limbs and several neck and shoulder muscles
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lumbar plexus
abdominal wall, external genitals, and part of the lower limbs
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sacral plexus
buttocks, perineum, and lower limbs (contains sciatic nerve which is the
longest nerve in the body)
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intercostal nerves
spinal nerves at levels T2-T11 which do not form plexuses
Muscles between ribs, abdominal muscles, skin of the chest and back
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cranial nerves
numbered in order from anterior to posterior in which the nerves emerge from the brain
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3 sensory nerves
I, II, VIII
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5 motor nerves
III, IV, VI, XI, XII
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4 mixed nerves
V, VII, IX, X
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2 main functions of the spinal cord
white matter
| gray matter
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white matter
highways for nerve impulse conduction
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pathway
the route that nerve impulses follow from a neuron in one part of the body to
other neurons elsewhere in the body
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gray matter
receives and integrates incoming and outgoing information; site for integration of
reflexes
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reflex
a fast, involuntary sequence of actions that occurs in response to a particular stimulus
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spinal reflex
when integration takes place in the spinal cord gray matter
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cranial reflex
when integration occurs in the brain stem rather than the spinal cord
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reflex arc
the pathway followed by nerve impulses that produce a reflex
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components of a reflex arc
```
stimulus
sensory neuron
integrating center
motor neuron
effector
```
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stimulus
arrival of a stimulus at the sensory receptor
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sensory neuron
nerve impulses are conducted from the sensory receptor along the axon of a sensory neuron leading to the CNS
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integrating center
gray matter in the CNS relays the sensory information to a motor neuron
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motor neuron
an impulse is triggered from the spinal cord along a motor neuron to the part of the body that will respond
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effector
the part of the body that responds to the motor nerve impulse, receives the signal and an action occurs
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somatic reflex
if the effector is skeletal muscle
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autonomic ( visceral) reflex
if the effector is smooth or cardiac muscle,
| or a gland
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autonomic and somatic nervous system
together they compose the peripheral nervous system
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somatic nervous system
Produce conscious, voluntary movements; consciously perceived sensations
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autonomic nervous system
Not under conscious control
May use acetylcholine or norepinephrine (instead of only ACh)
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autonomic motor neurons
regulate ongoing activities in their effector tissues (cardiac muscle, smooth muscle, and glands)
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2 branches of the motor part of the autonomic nervous system
sympathetic nervous system
| parasympathetic nervous system
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sympathetic nervous system
increases
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parasympathetic nervous system
decreases
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autonomic pathway utilizes how many motor neurons?
2
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somatic pathway utilizes how many motor neurons?
1
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preganglionic neuron
the first of the two; cell body is in the brain or spinal cord and axon exits the CNS as part of a cranial or spinal nerve
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postganglionic neuron
the second neuron in the autonomic motor pathway; lies entirely outside the CNS; its cell body and dendrites are located in the autonomic ganglion; it terminates in an effector
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autonomic ganglion
Where the preganglionic neuron and the postganglionic neuron synapse
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organization of sympathetic nervous system
Also called the thoracolumbar division because the outflow of sympathetic nerve impulses comes from the thoracic and lumbar segments of the spinal cord
Sympathetic preganglionic neurons have their cell bodies in the 12 thoracic and the first 2-3 lumbar segments of the spinal cord; after exiting the cord extend to sympathetic ganglions
Once the axon of a preganglionic neuron of the sympathetic division enters a sympathetic trunk ganglion, it may follow one of four paths
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sympathetic trunk ganglia
in two vertical rows, one on either side of the vertebral column; short axons because they don’t have far to go
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prevertebral ganglia
lie anterior to the vertebral column and close to the large abdominal arteries
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4 paths a sympathetic trunk ganglion may follow
Synapse with postganglionic neurons in the sympathetic trunk ganglion it first reaches
Ascend or descend to a higher or lower sympathetic trunk ganglion before synapsing
Continue without synapsing through the sympathetic trunk ganglion to end at a
prevertebral ganglion
Extend to and terminate in the adrenal medulla
95
a single sympathetic preganglionic axon may
synapse with 20+ postganglionic neurons; can elicit change in several effectors at once
adrenal medulla
96
adrenal medulla
inner part of the adrenal gland; similar tissue to sympathetic postganglionic neurons
upon stimulation by sympathetic preganglionic neurons release epinephrine and norepinephrine to intensify responses around the body
97
organization of parasympathetic nervous system
Also called the craniosacral division because the outflow of parasympathetic nerve impulses comes from cranial nerve nuclei and sacral segments of the spinal cord
The cell bodies of parasympathetic preganglionic neurons are located in the nuclei of 4 cranial nerves (III, VII, IX, and X) in the brain stem and in the 2-4 sacral segments of the spinal cord
(S2-S4)
The vagus (X) nerve carries nearly 80% of the total parasympathetic outflow
One preganglionic neuron only synapses with 4-5 postganglionic neurons, all of which supply the same effector
98
terminal ganglia
where the preganglionic and postganglionic neurons synapse in the parasympathetic system; located close to or actually within the wall of the innervated organ
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functions of the autonomic nervous system
Autonomic neurons release neurotransmitters (acetylcholine or norepinephrine) at synapses: between or with autonomic effectors
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between neurons
preganglionic to postganglionic
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with autonomic effectors
smooth muscle, cardiac muscle, and glands
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ANS neurons that release acetycholine
All sympathetic and parasympathetic preganglionic neurons
All parasympathetic postganglionic neurons
A few sympathetic postganglionic neurons
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ANS neurons that release norepinephrine
Most sympathetic postganglionic neurons
104
parasympathetic effects are
short-lived and localized
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sympathetic effects are
long-lasting and widespread
106
balance between sympathetic and parasympathetic
is regulated by the hypothalamus
107
sympathetic activities
Favors body functions that can support vigorous physical activity and rapid production of ATP
Reduces body functions that favor the storage of energy
Stimulated by physical exertion, a variety of emotions (fear, embarrassment, rage, etc.)
Exercise, Emergency, Excitement, Embarrassment
Fight-or-flight
108
Fight-or-flight
pupils dilate, heart rate and blood pressure increase, airways dilate, blood vessels (supplying muscles, heart, lungs, and brain) dilate, slowing of digestion and urine formation, liver works on ATP production and increases blood glucose level,
nonessential processes are inhibited
109
parasympathetic activites
Rest and digest activities; blood vessels dilate/constrict to redirect blood flow
Support body functions that conserve and restore body energy during times of rest and recovery
In quiet intervals, parasympathetic impulses predominate over sympathetic impulses
SLUDD: salivation, lacrimation, urination, digestion, and defecation
Decreases: heart rate, diameter of airways, and diameter of pupils
