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Anatomy & Physiology > Peripheral Nervous System > Flashcards

Peripheral Nervous System Flashcards

1
Q

By definition, what is a stimulus?

A

a thing or event that evokes a specific functional reaction in an organ or tissue

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2
Q

What types of stimuli are received and transduced by each of the following types of
receptors: mechanoreceptors, thermoreceptors, nociceptors, photoreceptors, and
chemoreceptors?

A

mechanoreceptors- detect mechanical pressure or stretching
(blood pressure, vibration, perception, hearing)

thermoreceptors- detect changes in temperature

nociceptors- respond to stimuli that could potentially cause mechanical or chemical damage to tissues

  • except the brain
  • Input the brain receives as extreme cold gets interpreted as pain

photoreceptors- detect light energy
* in retina of the eye

chemoreceptors- responds to chemicals in solution
*mouth, nasal cavity, blood vessels

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3
Q

Describe the location and stimulus selectivity of exteroceptors, interoceptors, and proprioceptors.

A

exteroceptors- information about stimulus at originated outside the body

interoceptors- located in walls of the viscera and blood vessels
*includes visceral receptors (sends signals to the CNS) , detects when youre full

proprioceptors- located in skeletal muscles, tendons, joints, ligaments and CT coverings of bones & muscles
*muscle tension, position and activity at joints

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4
Q

Identify and describe the main difference between the two subcategories of simple
receptors.

A

simple & complex

simple receptors - modified dendritic endings, serve as receptors for the general sense

complex receptors - the sense organs have the special senses (smell, taste, vision, hearing/equilbrium)

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5
Q

What is the function of free dendritic nerve endings? In what tissues is this type of
receptor especially abundant?

A

Abundant in ET and CT

sensitive to painful stimuli, to hot and cold, and to light touch.

1.) Merkel discs- tactile/touch discs

  1. ) hair follicle receptor (root hair plexus)
    ex: when a mosquito lands on your skin
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6
Q

Identify and describe two specialized types of free (non-encapsulated) nerve endings.

A

1.) Merkel discs- tactile/touch discs

  1. ) hair follicle receptor (root hair plexus)
    ex: when a mosquito lands on your skin
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7
Q

Locate and describe the structure and function of the encapsulated dendritic endings:
Meissner’s corpuscles (aka tactile corpuscles)
Krause end bulbs
Pacinian corpuscles (aka lamellar corpuscles)
bulbous corpuscles (aka Ruffini’s endings)
muscle spindles
(Golgi) tendon organs
joint kinesthetic receptors

A
  1. ) Meissner’s corpuscles (aka tactile corpuscles) - rapidly adapting light touch receptors(activated at the onset of touch)

Location: Exteroceptors
*found in dermal papillae, especially of hairless skin (nipples, fingertips, soles. of feet etc)

2.) Krause end bulbs -
Location: Extero, Intro, Prop
mechanoreceptors, located in mucous membrane

3.) Pacinian corpuscles (aka lamellar corpuscles) -

Location: Extero, Intro, Prop
mechanoreceptors that respond to deep pressure and stretch
*single dendrite, surrounded by many layers of fattened Schwann cells in a CT capsule

4.) bulbous corpuscles (aka Ruffini’s endings) -
LocationL Extero, Prop
mechanoreceptors ; spray of dendritic endings enclosed by a flattened capsule

muscle spindles-
Location: proprioceptors; monitor muscle stretch and length

5.) (Golgi) tendon organs-
Location: Prop
monitor stretch within and around symmetrical capsule joints

6.) joint kinesthetic receptors
Location: Prop
mechanoreceptors and nociceptors in joint capsules of synovial joints

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8
Q

Describe the energy conversion that occurs in transduction.

A

transduction - process through which a sense receptor/organ converts stimulus energy to into a graded potential (electrical energy)

step 1) begins when a stimulus creates a graded potential in the receptor cell (depolarizing usually which causes an influx of sodium)

  • on a first order neuron - generator potential
  • on a separate cell - receptor potential
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9
Q

What is a receptor potential? How does a receptor potential produce an AP in a first-
order afferent neuron?

A

a graded potential that occurs at a separate cell

the receptor potential changes the amount of neurotransmitter released by the receptor cell onto the sensory neuron. the neurotransmitters then generate graded potential in the sensory neuron

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10
Q

What is a generator potential? How does a generator potential produce an AP in a first-order afferent neuron?

A

when the receptor region is part of a sensory neuron the general potential is Called this because it causes AP’s in sensory neurons

*generates action potential in a sensory neuron

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11
Q

Define the term receptor specificity.

A

its receptive field is only to monitor a small area of there body, cant respond if the stimulus is outside the receptive field

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12
Q

Define the term receptive field.

A

the area the receptor monitors

*The smaller the receptive field, the greater the ability of the brain to accurately localize the stimuli site

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13
Q

What is sensory adaptation?

A

decreased sensitivity during a long-lasting & unchanging stimulus due to adaptation of a stimulus decreases, although the stimulus is still present

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14
Q

What is the difference between phasic and tonic receptors?

A

phasic receptors - fast adapting, give bursts of impulses at the end and beginning of the stimulus.
*report changes in the internal or external environment.

ex: getting used to bad smells

tonic receptors - provide a sustained response with little or no adaption
*nociceptors and most proprioceptors are tonic because of the protective importance of their information

ex: detecting pain, body position, chemicals in the blood etc

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15
Q

Identify and describe the three main levels of neural integration in the somatosensory
system.

A

receptor level
circuit level
perceptual level

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16
Q

Explain how the receptive field influences discriminative ability.

A

the circumscribed body area (usually the skin) is monitored by a single receptor

the size of the receptor field varies inversely with the density of receptors in the area

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17
Q

Identify and describe the connective tissue sheaths which are associated with a nerve.

A

Axon

  • Then myelin
  • *Then Endoneurium- encloses the fibers associated Schwann cells
  • **Perineurium- binds groups of axons into bundles called fascicles
  • ***Epineurium- Encloses all the fascicles to form the nerves
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18
Q

What is a mixed nerve?

A

contain both sensory and motor nerve fibers and transmit impulses to and from the CNS

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19
Q

What type of fibers is present in the dorsal root?

A

sensory

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20
Q

What type of fibers is present in the ventral root?

A

autonomic motor neurons

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21
Q

Name and identify the general function of each of the initial three branches of a spinal nerve.

A
22
Q

What is a dermatome?

A

a skin segment innervated by the fibers of a single pair of spinal nerves

23
Q

Describe the neural pathway for pain, beginning with activation of nociceptors.

A

step 1) nociceptors are activated by noxious stimuli (anything that damages tissues) - can be mechanical, thermal, or chemical stimuli

step 2) tissues become inflamed

step 3) type A delta fibers- carry pain related to chemical and thermal damage, arises at the cerebral cortex and results in rapid pain senses

type C fibers - carries chemical, mechanical, and thermal stimuli conducts impulses more slowly. (involved in chronic pain sensations)
ex: aching, burning, throbbing, dull pain

step 4) first-order neuron synapses in dorsal horn of spinal cord

step 5) second-order neurons synapses int thalamus in third order neuron

step 6) this order neuron carries input into the primary somatosensory cortex

24
Q

At what point in the neural pathway (#31) is pain modulation likely?

A

step 4, when the first order neuron synapses

25
Q

At what point in the neural pathway (#31) can one localize the pain to a specific part of
the body?

A

step 5 and 6

26
Q

What is the difference (structurally and functionally) between the two types of first-
order neurons, type A-delta and type C, in the pain pathway?

A

type A delta fibers- carry pain related to chemical and thermal damage, arises at the cerebral cortex and results in rapid pain senses

type C fibers - carries chemical, mechanical, and thermal stimuli conducts impulses more slowly. (involved in chronic pain sensations)
ex: aching, burning, throbbing, dull pain

27
Q

Name and describe the three main categories of pain.

A
  1. ) somatic pain -
  2. visceral pain
  3. neuropathic pain
28
Q

Describe the process of nerve fiber regeneration in the PNS. How is it similar to or different from nerve fiber regeneration in the CNS?

A

Schwann cells actively help PNS axons regenerate

step 1) the axon fragments

step 2) Schwann cells and macrophages clean out the dead axon distal to the injury

step 3) axon filaments grow through a regeneration tube
(Schwann cells release a growth factor and CAM that guide the regeneration tube)

step 4) the axon regenerates and a new myelin sheath forms

while oligodendrocytes actively suppress CNS axon regeneration ( have growth-inhibition proteins so the damage ends collapses and the axon fails to grow)

29
Q

What factors inhibit the process of nerve fiber regeneration in the CNS?

A

mature neurons do not divide

however, if the cell body remains intact, axons of the PNS can regenerate but axons on the CNS cannot.

30
Q

Where does somatic pain arise? Where does visceral pain arise?

A

joints, skin muscles, mucus membranes

organs of the thorax and abdominal cavity

31
Q

Identify the three levels in the hierarchy of motor control and describe the activities
performed at each level.

A

step 1) Recommend level - programs and instructions (modified by feedback)
*cerebellum and basal nucleotides (highest)

step 2) Projection Level - Conveys instructions to spinal cord motor neurons and sends a copy of that information to higher levels
*motor cortex (middle)

step 3) segmental level- contains central pattern generators
*spinal cord (lowest) —– reflex activity

32
Q

What parts of the CNS are associated with each level of the motor control hierarchy?

A

step 1) Recommend level - programs and instructions (modified by feedback)
*cerebellum and basal nucleotides (highest)

step 2) Projection Level - Conveys instructions to spinal cord motor neurons and sends a copy of that information to higher levels
*motor cortex (middle)

step 3) segmental level- contains central pattern generators
*spinal cord (lowest) —– reflex activity

33
Q

Describe the difference between a reflex and a reflex arc.

A

reflex- rapid, automatic responses to specific (threshold) stimuli (result of a motor output)

reflex arc - the specific neural pathways/circuits involved in producing reflex behavior

34
Q

The reflex arc is an example of what type of processing –serial or parallel?

A

serial processing

35
Q

What are the five components of all reflex arcs?

A
  1. ) Receptor
  2. ) Sensory neron
  3. ) Integration center - single synapse (monosynaptic reflex or multiple synapses (polysynaptic reflex)
  4. ) Motor neuron
  5. ) Effector organs (muscles or glands)
36
Q

Where is the integration center for the reflex arc always located?

A

in the CNS

37
Q

Identify and describe the two functional types of reflex.

A
  1. ) Somatic reflexes - those that activate skeletal muscles
  2. ) Automatic (visceral) reflexes - those that activate smooth or cardiac muscle and/or glands
38
Q

What are the five components of all reflex arcs?

A
  1. ) Receptor
  2. ) Sensory neron
  3. ) Integration center - single synapse (monosynaptic reflex or multiple synapses (polysynaptic reflex)
  4. ) Motor neuron
  5. ) Effector organs (muscles or glands)
39
Q

Describe the structure and function of the muscle spindle.

A

structure - bundle of modified skeletal muscle fibers (intrafusal fibers) enclosed in CT capsule

the contractile fibers of the muscle are called extramural fibers ( intervated by alpha motor fibers)

40
Q

What is the function of alpha motor efferents? of gamma motor efferents?

A

alpha motor efferents - stimulate efferent fibers of the alpha motor neurons to contract
- innervating extramural fibers to contract

gama motor efferents - innervate intramural fibers in the contracting regions at the end of the muscle spindle

  • important for regulating tension when the skeletal muscle contracts
    ex: patellar reflex
41
Q

Describe the function of the primary sensory ending of the muscle spindle.

A

primary sensory endings/ anulospiral : end of type 1 afferent fibers - respond to both length/stretch AND the rate of change in length/stretch in muscle

secondary sensory ending/flower spray endings: end of type 2 afferent fibers- respond ONLY to the length/stretch (not the change in length/stretch) of the muscle

42
Q

Describe the structure and function of the Golgi tendon organ.

A

a muscle stretch receptor

  • proprioceptors located in the tendons
  • stimulated by increased tension in the tendon (occurs during muscle contraction or stretch)

involved in reciprocal activation - when contracting muscles are inhibited and antagonists muscles are activated

43
Q

Describe the stretch reflex and the tendon reflex. Be sure to include all five components of the reflex arc in your description.

A

stretch reflex - cause muscle contraction in response to increased muscle length (stretch). vs tendon flex - muscles relax and lengthen in response to tension

stretch reflex
the patellar reflex
1.) Receptor

  1. ) Sensory neron
    - tapping the patellar ligament stretches the quadriceps and excites its muscle spindle
  2. ) Integration center - single synapse (monosynaptic reflex or multiple synapses (polysynaptic reflex)
    - afferent impulses travel to the spinal cord, where synapses occur with motor neurons and interneurons
  3. ) Motor neuron
    - send activating impulses to the quadriceps causing it to contract, extending the knee
  4. ) Effector organs (muscles or glands)
    - there interneurons make inhibitory synapses with ventral horn neurons that prevent the antagonist muscles (hamstrings) from resisting the contraction of the quads

tendon reflexes
1.) quads strongly contract. tendon organs are activated

  1. ) afferent fibers synapse with interneurons in the spinal cord
  2. ) efferent impulses to muscle with stretched tendon are damped. muscle relaxes, reducing tension.

at the same time-Efferent impulses to antagonist muscle cause it to contract.

44
Q

Which of the above reflexes (#50) is monosynaptic? Which is polysynaptic?

A

stretch - monosynaptic and ipsilateral (same side)

tendon- polysynaptic

45
Q

Describe the phenomena of reciprocal activation and reciprocal inhibition? Which of these is associated with the stretch reflex? which is associated with the tendon reflex?

A

reciprocal activation, tendon reflex- afferent impulses are transmitted to the spinal cord, and the to the cerebellum, where the information is used to adjust muscle tension. Simultaneously, motor neurons in spinal cord circuits supplying the contracting muscle are inhibited and antagonist muscles are activated.

reciprocal inhibition, stretch reflex - afferent impulses of alpha motor neurons cause the stretched muscle to contract. This resists or reverses the stretch. At the same time, afferent impulses of alpha motor neurons to antagonist muscles are reduced.

46
Q

Describe the discriminative sensation techniques utilized to test the ability of the sensory cortex to correlate, analyze and interpret sensations.

A

perceptual detection - ability to detect a stimulus requires summation of inputs from several reports

magnitude estimation- ability to detect how intense the stimulus is (remember that intensity is coded in frequency of Abs)

spatial discrimination - identifying site or pattern of stimulus (assessed by two-point discrimination)

feature abstraction - identification of more complex aspects and several stimulus properties

quality discrimination - ability to identify sub-modalities of sensation (sweet or sour taste)

pattern recognition - recognition of familiar or significant patterns in stimulus ( melody in piece of music)

47
Q

Regarding assessment of dermatome T4 and T10: what is the location and the significance of each?

A

T4 - nipple eline

T10 - Abilocus

48
Q

What is the role of alpha-gamma co-activation in ensuring that the muscle spindle functions effectively?

A

Alpha-gamma coactivation ensures that muscle spindles maintain sensitivity to stretch over a wide range of muscle lengths.

49
Q

Identify 4 deep tendon reflexes and the 1 stretch reflex (often known as a DTR) and
tell which segmental level is tested by each.

A

biceps

triceps

bracioradialis

patella

calcanea

50
Q

Understand how to rate a patient, using the scale for grading reflexes.

A

0 to +4

0 - no response

+1 - slight but present response (may or may not be normal)

+2- brisk response, normal

+3 - a very brisk response (may or may not be normal)

+4 - repeated reflex (abnormal)

51
Q

Identify 4 deep tendon reflexes and the 1 stretch reflex (often known as a DTR) and
tell which segmental level is tested by each.

A

biceps - cervical C5-C6

triceps - cervical C6, C7, C8

bracioradialis = cervical C5 - C6

patella (stretch) - Lumbar L2 , L3, L4

calcaneal - sacral - S1, S2

52
Q

Regarding assessment of dermatome T4 and T10: what is the location and the significance of each?

A

dermatome - a skin segment innervated by the fibers of a single pair of spinal nerves

T4 - nipple line

T10 - Abilocus

Anatomy & Physiology (10 decks)

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