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PSL300 > Somatic Senses > Flashcards

Somatic Senses Flashcards

1
Q

somatic senses

A

touch, temperature, proprioception, and nociception

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2
Q

proprioception

A

awareness of the position of body parts relative to each other

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3
Q

nociception

A

detects tissue damage or threat of it and is perceived as pain or itch

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4
Q

Somatosensory Receptors

A

these receptor cells are neurons

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5
Q

where do receptors for somatic sensation below chin lie?

A

in the dorsal root ganglia

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6
Q

What are the different receptors in the skin

A

Free nerve endings, Merkel receptors/disks, encapsulated receptors

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7
Q

Free nerve endings

A

detect mechanical stimuli, temperature, and chemicals

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8
Q

Merkel Receptors

A

mechanoreceptor nerve endings in contact with specialized epithelial cells, Merkel cells

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9
Q

Encapsulated Receptors

A

mechanoreceptors sheathed in connective tissue

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10
Q

where is the location of Merkel disks

A

these lie at the bottom of the epidermis and they are very sensitive to deformation of the skin and are more tonic that phasic. Important for signalling contact

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11
Q

T/F. Most mechanoreceptors are phasic.

A

True because when given a constant stimulus, the nerve endings depolarize and then return to baseline in about 3 ms

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12
Q

Where are messier corpuscles located

A

at the top of the dermis.
they are mainly in the tongue and hairless skin, palms, and fingertips
they are phasic
detect sideways shearing by loop endings

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13
Q

pacinian corpuscles

A

deep in the dermis
they can detect tiny displacements if the motion is quick
phasic

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14
Q

Fill in the blank.

Palms, fingertips, and lips are the ______ of the somatosensory system

A

fovea

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15
Q

why are they considered the fovea

A

because they have more densely packed receptors and have higher acuity

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16
Q

2 point discrimination

A

the distance between 2 points of contact on your skin

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17
Q

what type of receptors are thermoreceptors

A

free nerve endings and they are phasic tonic

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18
Q

what is the max temperature cold receptors respond to

A

30 degrees

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19
Q

What is the max temperature warm receptors respond to

A

45 degrees

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20
Q

what happens when we come into contact with temperature above 45 degrees

A

our pain receptors are activated

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21
Q

paradoxical cold

A

when you touch a hot object it may briefly feel cold

22
Q

do we have more cold or warm receptors

A

cold

23
Q

how many fibres of thermoreceptors can carry info up the spinal cord to the brain

A

around 1000 fibres

24
Q

Nociceptors

A

free nerve endings that respond to noxious stimuli- damaging mechanical, temperature, or even chemicals released from damaged cells or serotonin released by platelets in response to injury

25
Q

what 2 groups do somatosensory afferents fall into

A

small: C or A-delta which come mainly from free nerve endings. C fibres are unmyelinated and conduct spikes at up to 2m/s. A delta are thicker (myelinated) and can conduct up to 30 m/s

Large:a beta come from Merkel disks or encapsulated mechanoreceptors like messier or pacinian. Thet are myelinated and conduct 70m/s

26
Q

where do large fibres project to

A

they turn upward on reaching the spinal cord and run sideways to the medulla in the dorsal columns. When they get to medulla they synapse on cells whose axons cross midline

27
Q

Where do small fibres project

A

they synapse directly or via interneurons on motoneurons (reflex) or on dorsal-horn neurons whose axons cross the midline and run in the spinothalamic tracts (lateral side of spine between ventral and Dorsal

28
Q

contralateral

A

whether it is small or large vibes the info arrives contra laterally, meaning they will cross to the other side

29
Q

function of large fibers

A

provide feedback to the brain, to motor cortex as it manipulates objects- controls motion

30
Q

function of small fibers

A

evoke simple responses to specific stimuli, withdrawing from pain, brushing away a bug- they handle specific stimuli with little levels of processing

31
Q

where do signals from the spinal cord travel

A

they travel via the ventroposterolateral nucleus of the thalamus to the cortex

32
Q

where do signals from the head travel

A

via ventroposteromedial nucleus

33
Q

somatotopic

A

neighbouring areas of skin project to neighbouring cells in cortex- the primary somatosensory cortex is somatotopic

34
Q

where is the primary somatosensory cortex located

A

in the parietal lobe

35
Q

what is the somatosensory version of chevreul illusion

A

if you step into a very hot bath and you feel the most discomfort not at the foot but at the line where the water forms around your leg due to temperature edge

36
Q

where do we perceive pain from

A

from signals that arrives from activity from nociceptors.

Nociceptors have ion channels of transient receptor potential (TRP) family

37
Q

what channel responds to damaging heat and chemicals like capsaicin

A

vanillin receptors (TRPV1)

38
Q

what channel responds to cold and menthol

A

TRPM8

39
Q

what fibres carry sharp pain

A

A delta fibers

40
Q

what fibres carry slow pain

A

C fibers

41
Q

why do we have 2 types of pain

A

due to quick withdrawal and prolonged immobilization (to promote healing)

42
Q

does trigger withdrawal receive input from brain

A

no it is a spinal reflex and skips the brain

43
Q

what reactions do we experience when nociceptive signals reach the limbic system

A

emotional distress, nausea, vomiting, and sweating

44
Q

when can you block nociceptive cells in the spinal cord

A

through descending pathways of the thalamus in emergencies that depend on ignoring pain

45
Q

Referred pain

A

pain in an internal organ being felt on the body surface

46
Q

where do we feel pain If we have gallstones or pain in our liver

A

in the upper right shoulder

47
Q

where do we feel pain when we experience a heart attack

A

our left arm

48
Q

how can alpha beta activity block pain signals

A

because c fibres contact secondary neurons and the interneurons can inhibit the secondary neurons from continuing to the brain

49
Q

how do analgesics work

A

aspirin inhibits prostaglandins and inflammation and slow the transmission of pain signals

opioids decrease transmitter released from primary sensory neurons and postsynaptically inhibit secondary sensory neurons

50
Q

what are the body’s natural painkillers

A

endorphins, enkephalins, and dynorphins

PSL300 (15 decks)

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