Receptors and Primary Afferents Flashcards Preview

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Flashcards in Receptors and Primary Afferents Deck (25)
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1
Q

Describe peripheral nerve structure (3 layers)

A

endonerium: connective tissue around axons and Schwann cells
perinerium: connective tissue around nerve fasicles
epinerium: connective tissue around the entire nerve

2
Q

Describe blood supply in the nerve.

A

arterioles in the epinuerium yield a capillary plexus in the perineurium. blood vessels have tight junctions in that space.

3
Q

What are the fastest nerve fibers?

A

Ia (or A-alpha)

primary muscle spindle afferentes

4
Q

What are the fibers that sense pressure and pain?

A

III or A-delta

5
Q

What are the fibers that sense slow pain?

A

IV or C fibers. unmyelinated.

6
Q

What is the one part of the PNS with primary sensory bodies that are NOT in the PNS ganglia?

A

mesencephalic nucleus of V- primary cell bodies in lower midbrain

7
Q

What is another name for epicritic senses?

A

dorsal column/medial lemnisucs

8
Q

What is another name for protopathic senses?

A

anterolateral spinothalamic tracts

9
Q

What are two kinds of receptors>

A

quickly adapting and slowly adapting. quickly adapting generate an AP in response to a change in stimuli. slowly adapting transuduce a signal as long as the stimulus is still around

10
Q

What are differences in receptors between gabrous skin and hairy skin?

A

hairy skin has unique receptors associated with hair follicles.

11
Q

What two quickly adapting receptors that I should know about? What is the difference?

A

Meissner’s corpuscles (superficial, glabrous), hair follicle (superficial, hairy) and PAcinian corpuscle (deep)

12
Q

What two slowly adapting receptors should I know about ?

A

Merkel cell/neurite complex (superficial), ruffini (deep, relatively rare in glabrous skin but common in hairy skin)

13
Q

What is the purpose of free nerve endings in skin?

A

detect pain, warmth, tickle, cool

14
Q

What is a fast fatigable fiber?

A

rapid contraction and relaxation, but depend on glycolysis and anaerobic breakdown of glycogen for energy. relative lack of mitochondria and myoglobin (“white fibers”).

15
Q

What is a slow fiber?

A

longer, weaker contractions. resistnat to fatigue: high levels of mitochondria and myoglobin (“red fibers”)

16
Q

What is a fast fatigue resistant fiber?

A

intermediate. short contraction times but resistant to fatigue

17
Q

What is the general arrangement of fast to slow fibers?

A

fast fatibuable closer to the surface (less vascular access); slow fibers closer to the internal part of the msucle

18
Q

What is the size principle of recruitment?

A

small motor neurons are recruited first. they usually innervate slow/red fibers first. then, larger alpha motor neurons are recruited: fast fatigue0resistant fiber associated nuerns recruited next, than fast fatiguable neurons.

19
Q

What arhe the 3 functional consequenses of the size principle of recruitment?

A
  1. output for m UMN dictates desired amt of force
  2. contraction force incr. smoothly
  3. preferential use of lower energy slower motor neurons.
20
Q

What is the name for the post synaptic terminal of the NMJ?

A

end-plate

21
Q

What are special features of the NMJ end plate?

A

junctional folds to incr. membrane area, basement membrane, and nACh receptors

22
Q

What is the specialized region of the NMJ where transmitter is released?

A

dense bars

23
Q

How does the muscle influence its innervating neuron?

A

releases neurotrophic factors that allow for survival. without this factor, neurons die

24
Q

How does an innervating neuron influence its muscle? (molecular level)

A

allows for specialization of the end-plate and the accumulation of ACh receptors. Also determines the makeup of ACh receptor subunits.
Axons release agrin, which binds to MuSK receptors on the muscles to mediate these effects.

25
Q

How does an innervating neuron influence its muscle (bigger level)? How is this seen in pathological states?

A

neuron firing rate influences development. slow firing induces differentiation into red fibers
ALS: denervation/renervation changes the normal checkerboard gropuing of muscle fiber tibes to a more grouped appearance