Sensory Systems

Question 1

What type of nerve endings does information from pain and cold temperatures have?

Answer 1

Free nerve endings

Question 2

What type of nerve endings does information from mechanoreceptors have?

Answer 2

Tactile nerve endings

Question 3

What is the receptive field?

Answer 3

Responding to a stimuli over a specific area

Question 4

What type of information and nerve endings does meissners and Merkel’s corpuscles have/recieve?

Answer 4

Both are tactile free nerve endings
contains information from tough - merkels
Contain information from light touch - meissner’s

Question 5

What type of nerve ending is warmth and cold temperatures associated with?

Answer 5

Warmth = ruffini corpuscle 
Cold = free nerve ending (nociceptor)

Question 6

Is activation of the receptor (generator) potential stimulated by hyperpolarisation or depolarisation?

Answer 6

Depolarisation

Question 7

regarding signal transduction, what determines the intensity of the stimulus?

Answer 7

the size of receptor potential which evokes firing of action potentials thus the frequency of action potentials

Question 8

regarding signal transduction what determines the location of the stimulus?

Answer 8

the receptive field

Question 9

regarding signal transduction, what determines acuity?

Answer 9

the density of innervation and size of receptive field

Question 10

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

Answer 10

A beta = large myelinated
A delta = small myelinated
C = unmyelinated

Question 11

what type of stimulus does the 3 types of primary afferent fibres receive?

Answer 11

A beta = touch, pressure, vibration
A delta =cold, ‘fast pain’, pressure
C = warmth, ‘slow pain’

Question 12

what type of fibres is proprioception mediated by?

Answer 12

Aalpha

A beta

Question 13

what type of fibres are thermoreceptors and nociceptors?

Answer 13

Adelta & C fibres

Question 14

what type of fibres are mechanoreceptors?

Answer 14

Aalpha & Abeta

Question 15

where does mechanoreceptors synapse and what type of fibres do they carry?

Answer 15

Aalpha and Abeta fibres

synapse in the cuneate and gracile nuclei in brainstem

Question 16

where type of fibres does thermoreceptors and nociceptors carry and where do they synapse?

Answer 16

Adelta & C fibres

they synapse in the dorsal horn at point of entry

Question 17

what receptors are Aalpha fibres?

Answer 17

mechanoreceptors

proprioceptors

Question 18

what receptors are Abeta fibres?

Answer 18

mechanoreceptors

proprioceptors

Question 19

what receptors carry Adelta fibres?

Answer 19

nociceptors and thermoreceptors

Question 20

what fibres are unmyelinated and what receptors are they found in?

Answer 20

C fibres in nociceptors and thermoreceptors

Question 21

what would result if there was damage to the dorsal columns?

Answer 21

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

Question 22

what would result if there was damage of the anterolateral quadrant?

Answer 22

loss of nociceptive and temperature sensation below lesion on contralateral side

Question 23

what horn does the nociceptor and thermoreceptor fibres travel up through the spinal cord in?

Answer 23

anterolateral tract

Question 24

what horn does the mechanoreceptor fibres travel up through the spinal cord in?

Answer 24

dorsal horn

Question 25

what is adaptation?

Answer 25

after there is a constant stimulus the mechanoreceptors get used to it so the firing of action potentials decreases - you get used to the senstion so you don't feel it i.e. putting a hat on

Question 26

regarding processing in sensory pathways, what is referred pain an example of?

Answer 26

convergence | multiple incoming mechanoreceptors synapse onto 1 neurone

Question 27

what is responsible for sharpening up stimuli?

Answer 27

lateral inhibition neurones inhibit nearby neurones so the information being sent to the cortex is more accurate by giving better definition of boundaries

Question 28

what is signal transduction in nociceptors activated by?

Answer 28

heat low PH local chemical mediators i.e. bradykinin, prostaglandins, histamine

Question 29

describe the gate control theory.

Answer 29

when mechanoreceptor information enters the dorsal horn, it also gives off an interneurone which releases opioid peptides that inhibits transmitter release from nociceptor fibres heme closing the gate

Question 30

what does NSAIDs inhibit?

Answer 30

cyclo-oxygenase

Question 31

how does NSAIDS work?

Answer 31

they inhibit cycle-oxygenase which converts arachidonic acid to prostaglandins (prostaglandins produce inflammation) therefore by inhibiting prostaglandin production you decrease the inflammation

Question 32

how does local anaesthetics work?

Answer 32

they block all Na action potentials and therefore all axonal transmission

Question 33

what are the 3 ways in which opiates work?

Answer 33

reduce sensitivity of nociceptors to bradykinin block transmitter release in dorsal horn activate descending inhibitory pathways