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Flashcards in sensory systems Deck (25)
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1
Q

what does meissner’s corpuscle sense

A

light touch

2
Q

what does merkle’s corpuscle sense

A

touch

3
Q

what does paciniain corpuscle sense

A

deep pressure

4
Q

what does ruffini’s corpuscle sense

A

warmth

5
Q

sensory signal transduction

A

all sensory receptors transduce their adequate stimulus into a depolarisation
–> receptor (generator) potential

6
Q

what does receptor (generator) potential evoke

A

firing of action potentials for long distance transmission

7
Q

what does sensory signal transduction give info on

A

modality, intensity and location of stimulus

8
Q

primary afferent fibres: A-beta

A

touch, pressure, vibration

large, myelinate

9
Q

primary afferent fibres: A-delta

A

cold, fast pain, pressure

small myelinated

10
Q

primary afferent fibres: C

A

warmth, slow pain

unmyelinated

11
Q

which primary afferent fibres mediate proprioception

A

A-alpha and A-beta

muscle spindles, golgi tendon organs etc

12
Q

what do primary afferent fibres enter spinal cord via

A

dorsal root ganglia

or cranial nerve ganglia for head

13
Q

mechanoreceptive fibres

A

A-alpha
A-beta

project striaght up ipsilateral columns, synapse in cunate and graciel nucleu
2nd order fibres decussate in brainstem + project

14
Q

thermoreceptive + nociceptive fibres

A

A-delta
C

synapse in dorsal horn
2nd order fibres decussate in spinal cord
project up through contralateral spinothalamic tract

15
Q

damage to dorsal columns

A

loss touch, vibration, proprioception below lesion on ipsilateral side

16
Q

damage to anterolateral quadrant

A

loss of nociceptiev and temp sensation below lesion on contralateral side

17
Q

ultimate termination of sensory info

A

somatosensory cortex (S1) of poscentral gyrus

endings are grouped according to location of receptors –> sensory homunculus

18
Q

types of processing in sensory pathways

A
adaptation 
convergence
lateral inhibition 
not all info reaches brain 
perception
19
Q

convergence

A

saves on neurones
reduces acuity
underlies referred sensations

20
Q

lateral inhibition

A

activation one sensory fibre causes synaptic inhibition of its neighbours
gives better boundary definition, cleans up sensory info

21
Q

what are nociceptors activated by

A

low pH
heat
local chemical mediators: bradykinin, histamine, prostaglandins

22
Q

gate control theory of pain

A

acitivy of A-alpha/beta fibres activate inhibitory interneurones which release endorphines which inhibit transmitter release from A-delta/C fibres

same inhibitory pathways are activated from desc pathways from peri-aqueductal grey matter and nucleus raphe magnus

23
Q

NSAIDs

A

NSAIDs are analgesics because they inhibit cyclo–oxygenase which converts arachindonic acid to prostaglandins

(prostaglandins sensitise nociceptors to bradykinin)

24
Q

local anaesthetics

A

block Na+ action potential and so all axonal transmission

25
Q

opiates

A

reduce sensitivity of nociceptors
block transmitter release in dorsal horn
activate desc inhibitory pathways