Exam 2: PNS Flashcards
(99 cards)
1
Q
Central nervous system consists of:
A
Brain + spinal cord
2
Q
Peripheral nervous system consists of
A
12 cranial nerves (+ their ganglia) + 31 spinal nerves, (+ their ganglia), autonomic NS (+ their ganglia), enteric NS
3
Q
Gives rise to the CNS:
A
Neural tube
4
Q
Gives rise to the PNS:
A
Neural crest cells
5
Q
Give rise to sensory head & neck structures like nasal, lens, otic (auditory):
A
Ectodermal Placodes
6
Q
Describe sensory afferent (arrive) nerves:
A
Convey info TO the CNS from organs + body receptors
7
Q
Describe motor efferent (exit) nerves:
A
Convey info FROM the CNS to the organs, muscles, glands
8
Q
How do sensory + motor nerves further divide?
A
Somatic (body wall) and visceral (organs, glands, smooth muscle)
9
Q
What are the two main types of nerves?
A
Cranial + spinal
10
Q
Describe cranial nerves:
A
Bilateral pairs (R/L) which exit the cranial cavity through the foramina (opening) in the skull
11
Q
Describe spinal nerves:
A
Bilateral pairs (R/L) from a specific segment in the spinal cord
12
Q
How are spinal nerves identified
A
Letter + number (example: T5)
13
Q
How many spinal cord levels are there?
A
31
14
Q
How many cervical spinal nerves are there?
A
8; C1-C7 for vertebra inferior to their exit; C8 exits between C7 and T1
15
Q
How are the remaining spinal nerves named (non-cervical)?
A
Named by the vertebra superior to their point of exit (12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal)
16
Q
How are cranial nerves identified?
A
Either by name (ex: vagus nerve) or Roman numeral (CN X)
17
Q
What are the spinal nerves responsible for?
A
Conveying info to/from the horns of the spinal cord
18
Q
How many cervical vertebrae are there?
A
7
19
Q
How many thoracic vertebrae are there?
A
12
20
Q
How many lumbar vertebrae are there?
A
5
21
Q
How many sacral vertebrae are there?
A
5 but they fuse to form the sacrum
22
Q
How many Coccygeal vertebrae are there?
A
3-4 but they fuse to form the coccyx
23
Q
What are rootlets?
A
Fibers emerging from the spinal cord
24
Q
What are nerve roots?
A
Rootlets that converge to form 2 nerve roots
25
Describe the anterior (ventral) spinal nerve root:
Responsible for MOTOR function
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Describe the posterior (dorsal) spinal nerve root:
Responsible for SENSORY function
27
How does the final spinal nerve form?
Rootlets --> 2 roots --> 1 spinal nerve
28
What does the spinal nerve consist of?
Mixed fibers (motor and sensory)
29
Where is the final spinal nerve formed?
Near or at the intervertebral foramen
30
What does the spinal nerve divide into?
Posterior (dorsal) + anterior (ventral) ramus
31
What does a ramus consist of?
Mixed motor + sensory fibers
32
What does the ramus become?
A peripheral nerve (example: radial never, sciatic nerve)
33
What is an intervertebral foramen?
An opening in the vertebrae
34
What is the function of the dorsal (posterior) rami?
Carry somatic (body wall) motor, somatic sensory, and postganglionic sympathetic fibers to all 31 spinal levels
35
What do the dorsal (posterior) rami innervate?
Deep (true) muscles of the back, skin overlying those muscles, arteries supplying these structures
35
Do the dorsal (posterior) rami converge with the spinal cord?
No they remain separate the entire length of the spinal cord
36
What is the function of the anterior (ventral) rami?
Carry somatic (body wall) motor, somatic sensory, and postganglionic sympathetic fibers to all 31 spinal levels
37
Where do the anterior (ventral) rami innervate?
Anterior and lateral trunk, upper and lower limbs
38
What structure can form plexuses (network) for the limbs?
Anterior (ventral) rami
example: brachial plexus (arm) and cervical plexus (neck)
39
Do anterior (ventral) rami converge with each other in the trunk?
No, they remain separate (segmented)
40
Why do peripheral nerves arising from a plexus contain fibers from multiple spinal nerve levels?
The anterior (ventral) rami that form plexuses contribute fibers to multiple peripheral nerves arising from the plexus
41
Branches of the dorsal and ventral rami (peripheral nerves) have mixed components of?
Somatic motor fibers (skeletal muscles), somatic sensory fibers (skin, joint, muscle), and postganglionic sympathetic fibers (smooth muscle of arteries and sweat glands)
42
Do peripheral nerves (dorsal + ventral rami) have equal amounts of sensory and motor fibers?
No, some have more motor than sensory and vice versa. The name of the fiber type (motor or sensory) refers to what the majority type of fiber in that nerve is
43
Do spinal nerves supply the head?
No, they only supply the body wall and limbs. They do not supply structures within the body cavities either (thoracic, abdominal, or pelvic cavities) only the ANS does
44
Are 1st-order cell bodies of the sensory system located inside or outside the CNS?
Outside the CNS; located in the dorsal root (spinal) ganglion and the ganglia associated with cranial nerves
45
Where do sensory (afferent) peripheral (distal) processes extend to?
From target to the cell body
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Where do sensory (afferent) central (proximal) processes extend to?
From cell body to spinal cord
47
How do sensory (afferent) PNS fibers enter the CNS?
Via posterior (dorsal) root of spinal nerve or via specific cranial nerves
48
Are the motor neuron cell bodies of the motor system located inside or outside the CNS?
Located INSIDE the gray matter of the CNS; specifically the ventral + lateral horns of the spinal cord and the nuclei of the brainstem
49
How do motor (efferent) axons exit the CNS?
Via the anterior (ventral) root of spinal nerves or specific cranial nerves
50
What does the somatic system within the PNS do?
Conveys information between the CNS and body wall + extremities
51
What does the visceral system within the PNS do?
Conveys information between the CNS and internal organs, glands, blood vessels
52
What are the 4 main functional divisions of the PNS?
Somatic motor, somatic sensory, visceral motor, visceral sensory
53
Where is the somatic sensory 1st-order cell body located?
Within a dorsal root (spinal) ganglion, or ganglia associated with cranial nerves
54
Describe the somatic sensory system:
Info TO the CNS from body walls (skin, joints, skeletal muscle)
Relays info regarding: pain, temp, touch, pressure, proprioception
55
Does a synapse occur in a sensory ganglion?
No, it's 1 neuron 2 processes
56
What are the two processes of a 1st order sensory neuron?
Distal (peripheral) process from target to cell body and a central (proximal) process from cell body to CNS
57
What is a dermatome?
Unilateral area of skin innervated by the somatic sensory fibers of a single spinal nerve
58
Dermatome landmark: C4
Lateral neck/superior shoulder
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Dermatome landmark: C5
Lateral arm
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Dermatome landmark: C6
Lateral forearm and thumb (1st digit)
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Dermatome landmark: C7
Middle and ring fingers (3rd + 4th digits)
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Dermatome landmark: C8
Little finger (5th digit) and medial hand
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Dermatome landmark: T1
Medial forearm + armpit
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Dermatome landmark: T2
Medial arm
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Dermatome landmark: T4
Nipple
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Dermatome landmark: T10
Umbilicus (belly button)
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Which two ways can spinal nerves reach a dermatome?
A single peripheral nerve (thoracic and abdominal walls) or multiple peripheral nerves (upper + lower limbs)
68
Peripheral nerve innervation map
Looks similar to a dermatome map at the level of the trunk; no plexus formation so dermatomes and peripheral nerve distributions are the same
69
Describe shingles:
Affects: dorsal root (spinal) ganglion
After invading the dorsal root (spinal ganglion), the virus produces a sharp, burning pain in the dermatome supplied by the involved nerve. This follows the peripheral process of the 1st order cell bodies located in that ganglion to the area of skin distribution
70
Describe the somatic motor system:
Voluntary motor system that transmits signals to the skeletal (voluntary) muscles from the CNS
71
How many neurons are between the somatic motor system's CNS and end-organ/target?
Only one known as the lower motor neuron
72
Describe the visceral motor system:
Contains the autonomic nervous system (ANS) which conveys signals to smooth muscle and glands. ANS includes parasympathetic and sympathetic systems
End organs include:
-Smooth muscle: arteries, hollow organ + duct, arrector pili, intrinsic eye
-Glands: sweat, salivary, lacrimal
-Modified cardiac muscle
-SA and AV node of the heart
73
What are the two neuron systems that make up the visceral motor (ANS)
Preganglionic neurons and postganglionic neurons
74
Describe the preganglionic neuron of the visceral motor (ANS)
Cell body located within grey matter of CNS; axon terminates only within an autonomic ganglia upon the cell body of a postganglionic neuron (SYNAPSE)
75
Describe the postganglionic neuron of the visceral motor (ANS)
Cell body located outside the CNS and makes up the autonomic ganglia; axon terminates on target (end) organ
76
In the sympathetic ANS pathway, where do fibers go?
Everywhere
77
In the parasympathetic ANS pathway, where do the fibers go?
They are restricted and do not go everywhere. They also do not go to the body wall or limbs
78
Describe the visceral sensory system:
Input to CNS from hollow organs and blood vessels from sensory receptors
Symptoms: pain and subconscious visceral reflex sensation (stretch/distension), blood gas, blood pressure levels, blood pH
79
How do visceral sensory system fibers enter the CNS?
Via posterior (dorsal) root of spinal nerves or cranial nerves
80
Does a synapse occur in the visceral sensory system ganglion?
No
81
Where are the 1st order cell bodies in the visceral sensory system?
Either the spinal (dorsal) root ganglion or specific cranial nerve ganglion
82
At certain levels, the dorsal root ganglion of the visceral sensory system contains cell bodies for both:
Somatic sensory and visceral sensory (pain)
*referred pain: pain felt in one area of the body but is caused by a different part of the body
83
Neurons destroyed through disease or trauma are ___
Not replaced
84
Do neurons proliferate in the adult NS?
No, the only exception is the olfactory epithelium
85
What happens to neurons when they are stretched, cut, or crushed?
Axons degenerate distal to the damage because they were dependent on the cell body to survive
86
What happens to neurons when their axons are damaged but the cell body is intact?
Regeneration and return of function may occur
87
Describe stretching nerve injury:
Nerves (axons) can stretch but only to a certain degree. Once their limit is exceeded the nerve can be torn (ex: bone fractures + dislocations). Recovery depends on the extent of the stretch
88
Describe crushing nerve injury:
Result of an acute traumatic compression of a nerve. Only damages the axons so with cell bodies still intact the nerve can regenerate
89
Describe severed (cut) nerve injury:
Not likely to regenerate. Sprouting may occur but it will likely not reach its target. Surgical intervention may bring the two nerve ends back together
90
Describe compression nerve injury:
Compromises blood supply to the nerve (ischemia). May result in permanent paresthesia (pins & needles sensation), numbness, and/or muscle weakness. If ischemia is not prolonged, only temporary numbness will occur (foot falling asleep)
91
What is peripheral neuropathy?
Damage to one or more of the nerves outside of the brain and spinal cord
92
What is the result of peripheral neuropathy?
Numbness, pain, weakness, usually in the hands or feet, or body functions such as digestion, urination, circulation
93
Common causes of nerve damage:
Diabetes (most common), autoimmune disease, infection, medication, nerve injury (fall), vitamin deficiency
94
What is the Roman numeral for the vagus nerve?
X (ten)
95
A plexus is best described as:
Network of nerves (or other structures) with each axon maintaining its own identify
96
How many neurons are between the CNS (brain & spinal cord) and the somatic sensory targets?
1
97
Where do spinal nerves exit the vertebral column?
Near or at the vertebral column (spine) through intervertebral foramina
98
Which nerve supplies the head?
Cranial nerve
