sensory systems including pain

Question 1

what is each type of sensory information associated with?

Answer 1

a specific receptor type responding to a specific sensory modality

Question 2

what is the receptive field?

Answer 2

the specific area over which a sensory receptor will respond to a stimulus

Question 3

what does a meissners corpuscle sense?

Answer 3

light touch

Question 4

what does a merkles corpuscle sense?

Answer 4

touch

Question 5

what does a free nerve ending sense?

Answer 5

pain

Question 6

what does a pacinian corpuscle sense?

Answer 6

deep pressure

Question 7

what does a ruffini corpuscle sense?

Answer 7

warmth

Question 8

what do all sensory receptors do to their adequate stimuli?

Answer 8

transduce them into depolarisation - which is the generator potential

Question 9

what encodes the intensity of a stimulus?

Answer 9

the size of the receptor potential

Question 10

what does the receptor potential evoke?

Answer 10

firing of action potentials for long distance transmission

Question 11

what does the frequency of action potentials encode?

Answer 11

intensity of stimulus

Question 12

what determines the acuity of a stimulus?

Answer 12

density of innervation and size of receptive field

Question 13

what 3 types of primary afferent fibres mediate cutaneous sensation?

Answer 13

large myelinated fibres
small myelinated fibres
unmyelinated fibres

Question 14

what type of information do large myelinated fibres convey?

Answer 14

touch
pressure
vibration

Question 15

what type of information do small myelinated fibres convey?

Answer 15

cold
fast pain
pressure

Question 16

what type of information do unmyelinated fibres conve/y

Answer 16

warmth

slow pain

Question 17

what fibres mediate proprioception?

Answer 17

2 types - large myleinated and A alpha

Question 18

where do all afferent fibre types enter the spinal cord?

Answer 18

via the dorsal root ganglia (or cranial nerve ganglia for head)

Question 19

how do mechanoreceptive (large myelinated) fibres project to the brain?

Answer 19

through ipsilateral dorsal columns

Question 20

where do the mechanoreceptive fibres decussate?

Answer 20

brainstem

Question 21

where do the mechanoreceptive fibres synapse?

Answer 21

in the cuneate and gracile nuclei

Question 22

where do mechanoreceptive fibres project to after they decussate?

Answer 22

thalamus, reticular formation and cortex

Question 23

where do the thermoreceptive and nociceptive fibres (short myelinated and unmyelinated)synapse?

Answer 23

dorsal horn

Question 24

where do the thermoreceptive and nociceptive fibres decussate?

Answer 24

in the spinal cord

Question 25

how do the mechanoreceptive and nociceptive fibres project to the brain?

Answer 25

through the controlateral spinothalamic tract

Question 26

where do the mechanoreceptive and nociceptive fibres project to within the brain?

Answer 26

thalamus, reticular formation and cortex

Question 27

what is the result of damage to the dorsal column?

Answer 27

loss of touch vibration proproception below the lesion on the IPSILATERAL side

Question 28

what is the result of damage to the anterolateral quadrant (spinothalamic)

Answer 28

causes loss of nociceptive and temperature sensation below the lesion on the contralateral side

Question 29

where is the ultimate termination point for sensory signals?

Answer 29

somatosensory cortex of the post central gyrus

Question 30

how are the nerve ending grouped in the post central gyrus?

Answer 30

according to the location of the receptors

Question 31

what are 3 ways that help process information in sensory pathways?

Answer 31

adaptation convergence lateral inhibition

Question 32

what is convergence?

Answer 32

when different neurones synapse in the same place?

Question 33

what are some of the effects of convergence?

Answer 33

saves on neurones reduces acuity may underlie referred pain

Question 34

what is lateral inhibition?

Answer 34

when activation of one sensory input causes synaptic inhibition of its neighbours

Question 35

what is the effect of lateral inhibition?

Answer 35

gives better definition of receptive field boundaries | cleans up sensory information

Question 36

what can activate signal transduction in nociceptors?

Answer 36

low pH, Heat | local chemical mediators (bradykinin, histamine, prostaglandins)

Question 37

in the gate control theory of pain, what do inhibitory interneurones release?

Answer 37

opioid peptides which inhibit transmitter release from pain fibres

Question 38

what can activate inhibitory interneurones in the gate control theory?

Answer 38

mechanoreceptive fibres nucleus raphe magnus pari-aqueductal grey matter

Question 39

how are NSAIDS analgesic?

Answer 39

they inhibit cyclo-oxygenase which converts arachidonic acid to prostaglanidins (prostaglandins sensitise nociceptors to bradykinin)

Question 40

how are local anaesthetics analgesic?

Answer 40

they block the Na+ action potential and therefore block all axonal transmission

Question 41

how are opiates analgesic?

Answer 41

they reduce the sensitivity of nociceptors block transmitter release in the dorsal horn and they activate descending inhibitory pathways