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1. Neurology > Physiology of Sensation > Flashcards

Physiology of Sensation Flashcards

1
Q

What are the 3 divisions of the somatosensory system?

A

exteroceptive
proprioceptive
enteroceptive

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2
Q

Describe the exteroceptive division?

A

cutaneous senses - registers information from the surface of the body

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3
Q

Describe the proprioceptive division?

A

monitors posture and movement of the body

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4
Q

Describe the enteroceptive division?

A

reports upon the internal state of the body and closely relates to autonomic function

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5
Q

How are stimuli passed on through the nerves?

A

open a cation selective ion channel in the peripheral terminal of the primary sensory afferent - this elects a depolarising receptor potential
this triggers an action potential
action potentials cause a graded neurotransmitter release

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6
Q

What do low threshold receptors respond to?

A

low intensity non damaging stimuli

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7
Q

What do high threshold receptors respond to?

A

high intensity, potentially damaging stimuli

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8
Q

What do thermal nociceptors respond to?

A

extremes of heat = >45 or <10-15

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9
Q

What do chemical nociceptors respond to?

A

substances in the tissue eg serotonin, histamine, prostaglandin

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10
Q

What do polymodal receptors respond to?

A

two or more different stimuli

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11
Q

What is a receptive field?

A

target area where a sensory unit can be excited

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12
Q

How do receptive fields relate to innervation density and sensory acuity?

A

inversely proportional

i.e. high receptive field = low innervation density and low sensory acuity

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13
Q

What is two point discrimination?

A

minimum distance required between two simultaneous stimuli for them to be registered

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14
Q

Do regions with high descriminative capacity have big or small RFs?

A

small

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15
Q

What stimulates messiners corpuscles?

A

fine touch

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16
Q

What stimulates merkels discs?

A

pressure

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17
Q

What stimulates ruffini endings?

A

stretch

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18
Q

What stimulates pacinian capsules?

A

pressure and vibration

19
Q

What is gray matter divided into?

A

10 laminae of Rexed

20
Q

What laminae do nociceptors go to?

A

laminae 1 and 2

21
Q

What laminae do low threshold mechanoreceptors go to?

A

laminae 3 - 6

22
Q

What laminae do properioceptors go to?

A

laminae 7 - 9

23
Q

What are the two dorsal columns?

A

fasciculus gracilis

fasciculus cunate

24
Q

Which is more medial - fasciculus gracilis or fasciculus cunate?

A

fasciculus gracilis

25
Q

What nerves does the fasciculus gracilis carry through the dorsal column?

A

sensory input from T6 and downwards

eg FROM THE LEGS

26
Q

What nerves does the fasciculus cunate carry through the dorsal column?

A

sensory input from T6 upwards

eg FROM THE UPPER BODY

27
Q

What order does information from the spinal section come in? Laterally to medially?

A

cervical
thoracic
lumbar
sacral

28
Q

What is stereognosis?

A

the ability to recognise an object just by feeling it

29
Q

What is fine touch?

A

the ability to recognise the exact location of something just by light touch

30
Q

What is concious proprioception?

A

awareness of body movements and posture

31
Q

What is contrast enhancement?

A

when information is conveyed from one neuron to the next, the differences in adjacent neurons is amplified - meaning the main signal is wishy washy

32
Q

How is contrast enhancement combatted?

A

lateral inhibition

33
Q

What is lateral inhibition?

A

works via inhibitory interneurons to sharpen stimulus perception

34
Q

Where is the somatosensory cortex located?

A

post central gyrus of the parietal cortex

35
Q

What makes up the somatosensory cortex?

A

brodmann areas

36
Q

What makes up 1, 2, 3a and 3b of brodmann areas?

A

1 - cutaneous and 3a
2 - 3a,3b,joint afferents, deep tissue, golgi tendon organs
3a - proprioceptors
3b - cutaneous and 3a

37
Q

What does S1 stand for?

A

Brodmann areas

38
Q

What does S2 stand for?

A

Posterior parietal cortex

39
Q

What would a lesion in brodmann area 1 present as?

A

loss of texture discrimination

40
Q

What would a lesion in brodmann area 2 present as?

A

impaired grasping and size and shape discrimination

41
Q

What would a lesion in brodmann area 3a present as?

A

deficits in texture, shape and discrimination

42
Q

How is the somatosensory cortex arranged?

A

in columns - each column consisting of neurons with simlar inputs and responses - fast/slow adapting

43
Q

What is the role of the posterior parietal cortex (S2)?

A

recieves and integrates information from S1, other cortical areas (visual, auditory) and subcorticle areas (thalamus) and deciphers the deeper meaning - i.e. inputs the texture size context etc then tells its a key

44
Q

What can damage to the posterior parietal cortex cause/

A

neglect syndrome - patients believe that one side of their body doesnt exist

1. Neurology (32 decks)

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