Sensory Systems (Including Physiology of Pain) Flashcards Preview

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Flashcards in Sensory Systems (Including Physiology of Pain) Deck (24)
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1
Q

true or false:

all sensory receptors transduce their adequate stimulus into a depolarisation, the receptor potential

A

true

2
Q

the size of the receptor potential encodes the what of a stimulus?

A

intensity

3
Q

where are action potentials transmitted to?

A

CNS by axons

4
Q

cutaneous sensation is mediated by 3 types of primary afferent fibres, what are they?

A

Aβ = large myelinated (30-70m/s) touch, pressure, vibration

Aδ = small myelinated (5-30m/s) cold, “fast” pain, pressure

C = unmyelinated fibres (0.5-2m/s) warmth, “slow” pain

5
Q

what is proprioception mediated by?

A

2 types of primary afferent fibres

Aα & Aβ eg muscle spindles, golgi tendon organs etc

6
Q

what are the mechanoreceptive fibres?

A

Aα & Aβ

7
Q

what do the mechanoreceptive fibres do?

A

project straight up through ipsilateral dorsal columns

synapse in cuneate & gracile nuclei

the 2nd order fibres cross over midline (decussate) in the brain stem & project to reticular formation, thalamus and cortex

8
Q

what are the thermoreceptive and nociceptive fibres?

A

Aδ & C

9
Q

what do the thermoreceptive and nociceptive fibres do?

A

synapse in the dorsal horn

the 2nd order fibres cross over the midline in the spinal cord

project up through the contralateral spinothalamic (anterolateral) tract to reticular formation, thalamus and cortex

10
Q

what does damage to dorsal columns cause?

A

causes loss of touch, vibration, proprioception below lesion on ipsilateral side

11
Q

what does damage to anterolateral quadrant cause?

A

causes loss of nociceptive & temperature sensation below lesion on contralateral side

12
Q

where is the ultimate termination of the postcentral gyrus?

A

somatosensory cortex

13
Q

what produces the sensory homunculus?

A

postcentral gyrus

14
Q

how are sensory pathways processed?

A

adaptation
convergence
lateral inhibition

15
Q

how does adaptation process sensory pathways?

A

gradual decrease over time in the responsiveness of the sensory system to a constant stimulus

16
Q

how does convergence process sensory pathways

A

saves on neurones
but reduces acuity
may underlie referred pain

17
Q

how does lateral inhibition help to process sensory pathways?

A

activation of one sensory input causes synaptic inhibition of its neighbours
gives better definition of boundaries
cleans up sensory information

18
Q

what are all the different types of pain?

A

sharp, stabbing vs diffuse, throbbing pain
fast (initial) pain vs slow (delayed) pain
acute vs chronic pain
visceral pain
referred pain
phantom limb pain

19
Q

what is signal transduction in nociceptors activated by?

A

low pH, heat (via ASIC, TRPV1 etc)

local chemical mediators (eg bradykinin, histamine, prostaglandins)

20
Q

what is analgesia?

A

Non-steroidal anti-inflammatory drugs (NSAIDs)

21
Q

why are NSAIDS analgesic?

A

because they inhibit cyclo-oxygenase which converts arachidonic acid to prostaglandins

22
Q

how does analgesia work as a local anaesthetic?

A

block Na+ action potential and therefore all axonal transmission

23
Q

what do opiates do to nociceptors?

A

reduce sensitivity

24
Q

what are the functions of opiates?

A

block transmitter release in dorsal horn (hence epidural administration)
activate descending inhibitory pathways

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