touch Flashcards

1
Q

where are touch receptors?

A

embedded in outer layer (epidermis) and underlying later (dermis) of skin

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2
Q

what are the three criteria of touch receptors?

A
  • type of stimulation to which they respond
  • size of receptive field
  • rate of adaption
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3
Q

what do tactile receptors respond to?

A

mechanical stimulation: pressure, vibration or movement

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4
Q

what are meissner corpuscles?

A

fast adaption with small receptive field

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5
Q

what are merkel cell neurite complexes?

A

slow adaption, small receptive field

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6
Q

what are pacinian corpuscles?

A

fast adaption, large receptive field

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7
Q

what are ruffini endings?

A

slow adaption, large receptive feild

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8
Q

what does the slow - adapting type 1 (SAI) mechanoreceptor do?

A

perceives pattern, texture and shape and responds to onset of stimulus and continues to respond at a lower level for the duration of stimulus

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9
Q

what do slow adapting types respond best to?

A

skin indention and allows identification of texture

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10
Q

what do merkel cells provide info on?

A

weight, form and surface features

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11
Q

what do fast adapting type 1 (FAI) mechanoreceptors perceive?

A

slip and maintaining grip control

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12
Q

what are meissner corpuscles responsible for?

A

detecting textures and edges as hand moves over surfaces - able to signal speed and direction and light touch

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13
Q

what do slow adapting type 2 (SAII) mechanoreceptors percieve?

A

skin stretch and hand conformation

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14
Q

what do SAII respond to?

A

for the duration of the stimulus and to the stretching of skin to help give information about movement and posture

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15
Q

what do fast adapting type 2 (FAII) mechanoreceptors percieve?

A

fine textures through transmitted vibration

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16
Q

what do the pacinian corpuscles do?

A

very sensitive to vibrations transmitted through an object and are the largest of the mechanoreceptors located deep in the dermis

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17
Q

how finely can we resolve temporal details?

A

two tactile pulses can be delivered over time, in a manner analogous to spatially separated two point threshold stimuli

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18
Q

what is the time sensitivity difference of touch?

A

5 ms

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19
Q

what is the time sensitivity difference of vision?

A

25 ms

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20
Q

what is the time sensitivity difference of audition?

A

0.01 ms

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21
Q

what is the two point threshold?

A

threshold smaller on fingertips and lips and larger on arms, legs and torso

22
Q

is there a brain pathway for tactile information?

A

there is inconclusive evidence that the mechanism by which
mechanoreceptors transduce mechanical force is analogous to
the mechanism by which hair cells in the cochlea transduce
movement of their stereocilia into neural signals sent through
auditory nerve fibers

23
Q

what is proprioception?

A

the unconscious perception of movement and spatial orientation

24
Q

what are kinesthetic receptors?

A

mechanoreceptors in muscles, tendons and joints

25
what do kinesthetic receptors do?
sense of where limbs are, what kinds of | movements are made
26
what is muscle spindle?
a sensory receptor located in a muscle that | senses its tension
27
what do the receptors in tendons do?
signal tension in muscles attached to tendons
28
what do receptors in joints do?
react when joint is bent to an extreme angle
29
what happened to ian waterman?
cutaneous nerves connecting Waterman’s kinesthetic mechanoreceptors to brain destroyed by viral infection so lacks kinesthetic senses, dependent on vision to tell limb positions
30
what is nociception?
introduced by sherrington with the intent of distinguishing between detection of a noxious or potentially harmful event and our responses to it
31
what are nociceptors?
sensory receptors that transduce the physical stimuli associated with damaging mechanical, thermal, or chemical events; are included among the free nerve endings in the epidermis and dermis
32
what is sensitization?
mechanism that decreases the response threshold | of nociceptors, so that even very low level stimulation of an injury site can cause pain
33
what are a-delta fibers?
myelinated axons of nociceptors that transmit pain signals relatively rapidly, to produce a rapid response to potentially damaging mechanical stimuli and to excessive heat
34
what are c fibers?
unmyelinated axons of nociceptors that transmit pain | signals relatively slowly
35
what do nociceptors transmit?
pain signals to the spinal cord via two | different types of fibers
36
what are the two fibers that nociceptors transmit via?
a delta fibers and c fibers
37
how fast do a delta fibers transmit action potentials?
relatively rapidly (about 2–4 m/sec), produce a rapid response to potentially damaging mechanical stimuli and to excessive heat
38
how fast do c fibers transmit action potentials?
``` relatively slowly (about 1 m/sec), produce a slower response to a wide range of pain stimuli ```
39
what do heat receptors detect?
temperatures over 25°, but they do not continue to detect heat when it gets too hot (e.g., extremely hot and harmful temperature of 45°C or hotter)
40
what do cold fibers respond to?
cool temperatures between 10°C and 20°C, but they do not respond to very cold temperatures, below 10°C
41
how numerous are cold and hot receptors in comparison?
cold are about 30 times more
42
do we notice thermal sensation when temp is maintained?
no
43
what happens if skin is abruptly warmed?
the firing rate of warm fibers increases
44
what happens if skin is abruptly cooled?
the firing rate of cold fibers increases
45
what is the dorsal column–medial lemniscal | pathway (DCML pathway)?
pathway for signals involved in tactile perception and proprioception; travels up the spinal cord on the ipsilateral side, crosses to the contralateral side in the medulla, and then goes through the ventral posterior nucleus of the thalamus and on to the somatosensory cortex
46
what is the spinothalamic pathway?
pathway for signals involved in nociception and thermoreception; crosses over to the contralateral side within the spinal cord and then goes through the ventral posterior nucleus of the thalamus and on to the cortex
47
how is touch sensations represented in the brain?
somatotopically
48
what is S1 and S2?
primary somatosensory cortex called S1; secondary | somatosensory cortex called S2
49
what are the two divisions of the vestibular system?
semicircular canals for rotary motion/balance and otolith organs (utricle and saccule) for linear acceleration/head tilt
50
what is movement of hair cells responsible for?
sending signals in each of the systems