Peripheral Nervous System Flashcards
1
Q
PNS includes 3 things
A
Sensory receptors
Nerves and associated ganglia
Motor endings (neuromuscular junctions)
2
Q
Respond to mechanical force, such as touch, pressure (including blood pressure), vibration, and stretch
A
Mechanoreceptors
3
Q
Respond to temperature changes; there are both hot and cold receptors
A
thermoreceptors
4
Q
Respond to light (e.g., those found in retina)
A
photoreceptors
5
Q
Respond to chemicals in solution (e.g., molecules smelled or tasted, or changes in blood or interstitial fluid chemistry)
A
chemoreceptors
6
Q
Respond to pain; signals (e.g., acid, extreme heat) stimulate subtypes of thermoreceptors, mechanoreceptors, and chemoreceptors
A
nocicoreceptors
7
Q
Respond to stimuli arising outside body, so are located near or at body surface (e.g., touch, pressure, pain, temperature, special senses)
A
exteroceptors
8
Q
Respond to stimuli arising inside the body (e.g., from internal organs and blood vessels)
A
interoceptors
9
Q
Monitor variety of stimuli (e.g., stretch, chemical changes, temperature)
Generally unaware of their activity, but they can make us feel pain, discomfort, hunger, thirst, etc.
A
interoceptors
10
Q
Respond to internal stimuli;
monitor stretch in muscles, tendons, ligaments, joints, and connective tissue coverings of bones and muscles
allows awareness of positions and movements of body parts
A
proprioceptors
11
Q
modified dendrites; most common in body
A
sensory receptors
- -tactile sensation
- -temp
- -pain
- -proprioceptors
12
Q
“muscle sense”
A
proprioceptors
13
Q
Receptors for special senses (vision, hearing, smell, taste, equilibrium) are housed in
A
sense organs
14
Q
general sensory receptors
A
chemicals, temperature, pressure, and pain
15
Q
one receptor can respond to (blank) stimuli
A
various (a lot of overlap)
16
Q
modified free nerve ending (Merkel cells/tactile disc)
A
exteroceptors
mechanoreceptors
17
Q
hair follicle receptors
A
exteroceptors
mechanorecepetors
18
Q
itch
A
allergic response?
19
Q
nonencapsulated
A
Merkel/tactile discs
hair follicle receptors
free nerve endings of sensory neurons
20
Q
encapsulated
A
Neuron terminals are surrounded by connective tissue capsule
21
Q
most encapsulated are found in…
A
mechanoreceptors (skin)
22
Q
muscle spindle–muscle contracts
A
found in muscles
form of proprioceptor to let brain know how much muscle is stretching; play a role in reflex
23
Q
tendon organs–muscle relaxes
A
let brain know how much tendon is stretching
24
Q
3 levels of somatosensory neural integration
A
sensory receptor level
circuit level
perceptual level
25
A stimulus excites a receptor
sensory receptor level
26
Stimulus energy converted to graded potential
| Eventually, action potential is sent to CNS
Transducton (SR level)
27
Some sensory receptors have a change in sensitivity (and impulse generation) to a constant stimulus
Adaptation (SR level)
28
Adapt quickly; provide info about changes in environment
phasic receptors (SR level)
29
Little or no adaptation; nociceptors and proprioceptors almost always provide info; so we know we are in pain until pain is fixed
Tonic receptors (SR level)
30
stimulus is a graded potential to
action potential
31
Processing of sensory input along ascending pathways; delivers impulses to cerebral cortex
Circuit level (chain of 3 neurons)
32
are all receptors able to adapt?
no
33
which receptors can adapt?
phasic
34
Processing in cerebral cortex
perceptual level
35
perceptual level (processing in cerebral cortex)
Sensation identification depends on location of target neurons in brain’s somatosensory cortex (there is a map)
Each axon “labeled line” says “who” is calling and from “where”
Features: Detection, magnitude estimation, spatial discrimination (e.g., two-point discrimination), abstraction, quality discrimination (e.g., sweet vs. salty), and pattern recognition
36
- -Cell bodies in ganglion (dorsal root or cranial)
| - -transmit impulses from peripheral receptors to spinal cord or brain stem
First Order Neurons (super long)
37
- -Cell bodies reside in dorsal gray matter of spinal cord or nuclei of medulla oblongata
- -transmit impulses to thalamus or cerebellum
Second Order Neurons
38
- -Cell bodies in thalamus (no third-order neurons in cerebellum)
- -transmit impulses to somatosensory cortex of cerebrum
Third Order Neurons
39
Ascending Pathway has (blank) neurons
3
40
warns us of tissue damage
pain
41
triggered by chemicals and extremes of pressure and temperature
pain receptors
42
We all have the same pain threshold (stimulus intensity that causes us to feel pain) but different
pain tolerances
43
pain tolerance and response to pain medication determined by...
genetics
44
Intense or long-lasting pain activates...
NMDA receptors (special type of chemically-gated ion channels in synapses that are associated with learning)
spinal cord "learned pain"
cause of phantom limb pain
45
how to reduce phantom limb pain
Epidural anesthetics reduce incidence of phantom limb pain; must be managed early
46
Pain stimulus arising in one body part is interpreted by the brain as arising from another body part
Referred pain
47
why does referred pain occur?
Brain interprets pain as coming from more common somatic pathway
48
How can the somatosensory cortex tell the difference between hot and cold?
different thermoreceptors are parts of different “labeled lines” to the brain
49
How can the somatosensory cortex tell the difference between Cool and cold?
action potential frequency from cold stimulus greater than cool stimulus
50
How can the somatosensory cortex tell the difference between Ice on your arm or ice on your foot?
Signals from arms and feet are carried along different “labeled lines,” arriving in different parts of the somatosensory cortex
51
Loose connective tissue surrounds each axon (nerve fiber) and Schwann cells if present
endoneurium
52
Connective tissue surrounds groups of nerve fibers called fascicles
perineurium
53
Tough fibrous sheath encloses everything
epineurium
54
only sensory fibers toward CNS
sensory nerves
55
only motor fibers away from CNS
motor nerves
56
both sensory and motor fibers
mixed nerves
57
pure sensory and motor=rare
mixed=common
58
are mature neurons amitotic?
yes
59
nerve axons do not
regenerate
60
damage to cell body kills neuron and...
all neurons stimulated by it
61
if only axon is damaged (CNS)…it cannot regenerate
Oligodendrocytes suppress axon regeneration
| Astrocytes form scar tissue
62
if only axon is damaged (PNS)...it can regenerate
- -Schwann cells
- -slowly (1.5 mm/day)
- -must retrain
63
Post-trauma axon regrowth
never like before
64
know all 12 cranial nerves
yes
65
all cranial nerves attach to brain stem except...
1, 2, 12
66
All cranial nerves only serve head and neck except
vagus nerve
67
Only the tiny sensory nerves (“filaments”) are part of cranial nerve
Olfactory bulb and olfactory tract (which lead to primary olfactory cortex) are part of the brain
olfactory nerve (1)
68
partial crossover of fibers at the optic chiasma
optic nerve (2)
69
Trochlear nerve (IV) controls
eye movement
70
trochlear nerve means
“pulley”
| Cartilaginous structure
71
Trigeminal (V)
Largest cranial nerves
| involved in migraine
72
3 regions of Trigeminal (V)
V1: Ophthalmic
V2: Maxillary
V3: Mandibular
73
facial (VII) 5 branches
| Facial expressions not chewing
```
Temporal
Zygomatic
Buccal
Mandibular
Cervical
```
74
chewing controlled by
trigeminal nerve
75
vagus (X)
Medulla oblongata helps regulate cardiovascular and respiratory systems
serves visceral organs
76
“Gut-brain axis”
gut flora (bacteria in intestines) can communicate with our brain via vagus
77
gut bacteria can influence behavior
and vice versa (speculative)
78
how many pairs of spinal nerves
31
79
spinal nerves named according to...
vertebrae
80
8 cervical nerves, only 7 cervical vertebrae
first 7 exit superior to vertebrae, but at 8th comes out inferior to c7 (c8 nerve)
anything after that is inferior to vertebrae it's named after
81
cervical enlargement
larger than rest of spinal cord because service arms
82
lumbar enlargement
larger than rest of spinal cord because service legs
83
spinal nerves: CNS or PNS
part of PNS
84
Ventral roots
Motor (efferent) fibers
Somatic (voluntary) motor neurons
Visceral (autonomic; specifically, sympathetic) motor neurons
85
Dorsal roots
Sensory (afferent) fibers
Somatic sensory neurons
Visceral sensory neurons
86
: Cell bodies of sensory neurons cluster at
dorsal root ganglion
87
Spinal roots (blank) to form spinal nerves (both motor and sensory meet) inside vertebral column
merge
88
Spinal nerves emerge from foramina and split into
dorsal and ventral rami; now are mixed
89
roots
Strictly sensory or motor
90
rami
both sensory and motor fibers
91
Ventral rami for nerves T2-T11 become
intercostal nerves
92
T12 becomes
subcostal nerves
93
5 spinal plexuses
```
Cervical
Brachial
Lumbar
Sacral
Coccygeal
```
94
ventral nerve plexus redistribute because
each muscle in a limb supplied by more than one spinal nerve, so it is unlikely to completely paralyze any limb muscle
95
dorsal rami don't form
plexuses
96
don't need to know any of slide 34
yes
97
after fibers stop and form new nerves
yes
98
Innervates diaphragm (breathing muscle);
Phrenic nerve (cervical plexus):
99
Injury hard to use the pincer grasp (opposed thumb and index finger) ; damaged in wrist-slashing suicide attempts and compressed in carpal tunnel syndrome
Median nerve (brachial plexus)
100
ulnar nerve (brachial plexus)
“funny bone”
101
Herniated disc compressing lumbar plexus can cause gait problems
femoral nerve innervates leg muscles
Femoral nerve (lumbar plexus):
102
Thickest, longest nerve of body; supplies leg; sciatica is a stabbing pain that radiates from this nerve
Sciatic nerve (sacral plexus):
103
Area of skin innervated by cutaneous sensory fibers of a single spinal nerve
Dermatome
104
dermatome maps
people have different maps
105
all spinal nerves except C1 involved in
touch
106
can determine if spinal cord is damaged based on
dermatomes (if suddenly loses sensation)
107
destruction of a single spinal nerve will not cause complete numbness anywhere
because of overlap
108
in limbs, some skin only innervated by single spinal nerve
could lose all feeling
109
highest level of command for movement
cerebellum
110
cerebellum controls output of cortex and
brain stem
111
Where? unconscious planning occurs in advance of willful movement (sets pathway, we decide whether or not to act)
cerebellum
112
upper motor neurons (descending pathway)
Motor cortex and basal nuclei (subcortical motor nuclei)
113
lower motor neurons (descending pathway)
Ventral gray matter regions of spinal cord; directly innervate skeletal muscles
114
serial processing
Automatic response
115
parallel processing
awareness
116
Due to practice or repetition
learned (acquired) reflex
117
single synapse between sensory neuron and motor neuron; no interneuron
monosynaptic reflex (not common, but do exist)
118
More than one synapse; interneurons
polysynaptic reflex (common)
119
somatic reflex
Activate skeletal muscle
120
autonomic (visceral) reflex
Activate smooth or cardiac muscle or glands
121
spinal reflexes
somatic reflexes occur without input from higher brain centers
122
thinks muscle is being stretched too far, causes muscle to contract
muscle reflex
123
tendon reflex
helps muscle relax
124
stretch reflexes are generally...
monosynaptic and ipsilateral
125
part of reflex arc inhibits antagonist is...
polysynaptic
126
stretch reflex prevents knee from buckling, falling
patellar (knee-jerk) reflex
127
tendon reflex is...
polysynaptic
| muscles relax and lengthen in response to tension
128
flexor (withdrawal) reflex
Response to painful stimulus
Ipsilateral, polysynaptic
Can be overridden by brain (e.g., expecting a prick for blood draw)
129
crossed-extensor reflex often accompanies
flexor (withdrawal reflex)
130
crossed (extensor) reflex
one arm flexes, the other extends
E.g., if you step on broken glass, one leg flexes (withdraws), while the other extends (to support weight of body)
Helps maintain balance
Contralateral, polysynaptic
131
sympathetic
fight or flight
132
parasympathetic
rest and digest
133
autonomic myelinated?
not always
| it's ok to be slow
