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Nervous System > Sensory Systems > Flashcards

Sensory Systems Flashcards

1
Q

what is the receptive field?

A

the specific area that a receptor responds to

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2
Q

what do all sensory receptors transduce the adequate stimulus into?

A

a depolarisation, the receptor generator potential

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3
Q

what does the size of the receptor potential encode?

A

the intensity of the stimulus

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4
Q

what does the receptor potential then evoke?

A

firing of action potential for long distance transmission

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5
Q

what does the frequency of the action potential encode?

A

the size of the stimulus

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6
Q

what determines acuity?

A

the density of innervation and size of receptive fields

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7
Q

what are A beta afferent fibres?

A

they are large myelinated fibres sensing touch, pressure and vibration

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8
Q

what are A omega afferent fibres?

A

small myelinated fibres sensing cold, fast pain and pressure

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9
Q

what are C afferent fibres?

A

unmyelinated fibres sensing warmth, slow pain

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10
Q

what primary afferent fibres mediate proprioception?

A

a alpha and A beta fibres

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11
Q

what type of fibres are mechanoreceptive fibres?

A

> A alpha

> A beta

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12
Q

where do mechanoreceptive fibres synapse in?

A

the cuneate and gracile nuclei

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13
Q

where do the 2nd order mechanoreceptive fibres project to?

A

> reticular formation
thalamus
cortex

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14
Q

what fibres are the thermoreceptive and nociceptive fibres?

A

A omega and C fibres

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15
Q

where do thermoreceptive and nociceptive fibres synapse?

A

in the dorsal horn

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16
Q

where do second order mechanoreceptor fibres cross over?

A

in the brainstem

17
Q

where do thermoreceptive and nociceptive fibres cross the midline?

A

in the spinal cord

18
Q

where do the thermoreceptive and nociceptive fibres project to?

A

reticular formation
thalamus
cortex

19
Q

how will damage to the dorsal column affect sensory information?

A

there will be loss of touch, vibration, proprioception below lesion on the ipsilateral side

20
Q

how will damage to the anterolateral quadrant affect transmission of sensory information?

A

there will be loss of nociceptive and temperature sensation below the lesion on contralateral side

21
Q

where is the ultimate termination of sensory information?

A

the somatosensory cortex of the postcentral gyrus

22
Q

how are the endings of sensory fibres grouped together?

A

they are grouped according to the location of the receptors

23
Q

what produces a sensory homunculus?

A

grouping of ending of sensory nerve fibres according to the location of their receptors. the extent of the representation is related to the density of receptors in each location.

24
Q

describe the action potential firing rate in a rapidly adapting neuron when there is a prolonged stimulus

A

action potential are fired at the beginning of the stimulus then after a brief period of time they stop firing. they fire again when the stimulus stops.

25
Q

what does convergence reduce?

A

acuity

26
Q

what is lateral inhibition?

A

activation of one sensory input causes synaptic inhibition of its neighbours giving a better definition of boundaries and cleaning up sensory information

27
Q

describe how opioid peptides (endorphins) “close the gate” and inhibit A omega and C neurons

A

inhibitory interneurons release opioid peptides that inhibit transmitter release from A omega and C fibres

28
Q

describe gate closing in segmental control

A

activity in A alpha and beta fibres activates inhibitory interneurons that inhibit neurotransmitter release from A omega and C fibres

29
Q

what do prostaglandins sensitise?

A

nociceptors to bradykinin

30
Q

how do NSAIDs work as an analgesic?

A

they block cyclo-oxygenase that generates prostaglandins

31
Q

how do local anaesthetic work?

A

they block Na+ action potential and therefore all axonal transmissions

32
Q

how do opiates work?

A

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

33
Q

how does trans cutaneous electrical nerve stimulation?

A

> activation of large diameter mechanoreceptor fibres in the same segment as the stimulus
this stimulates the release of endogenous opioid peptides from interneurons in the dorsal horn
this inhibits synaptic transmission between primary afferent fibres and other fibres.

Nervous System (45 decks)

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