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Y2 Neurology > Sensory Systems > Flashcards

Sensory Systems Flashcards

1
Q

state 5 types of sensory receptors

A

mechanoreceptors, chemoreceptors, thermoreceptors, nociceptors, proprioceptors

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2
Q

what is the area where the sensory neuron will respond to a stimulus called?

A

receptive field

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3
Q

what does it mean when a sensory receptors transduces a stimulus ?

A

changes the stimulus into electrical energy

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4
Q

what is the stimulus called which is required to causes an AP to be produced and for the neuron to depolarise ?

A

an adequate stimulus

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5
Q

what is the potential called which is produced when the neuron depolarises?

A

receptor potential

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6
Q

what variable of the receptor potential conveys the intensity of the stimulus?

A

the size of the receptor potential

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7
Q

what variable of the action potential conveys the intensity of the stimulus?

A

the frequency of the AP

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8
Q

are APs all the same size?

A

yes

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9
Q

if a sensory neuron has a large receptive field then is the acuity small or large ?

A

acuity is small

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10
Q

are APs self propagating ?

A

yes

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11
Q

if there is a higher frequency of APs then will there be more neurotransmitters released ?

A

yes

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12
Q

what are the three types of afferent cutaneous sensation fibres?

A

A beta
A delta
C

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13
Q

what are the two types of primary afferent fibres fibres for proprioception?

A

A alpha

A beta

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14
Q

describe the appearance of A beta fibres?

A

Large myelinated

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15
Q

describe the appearance of A delta fibres?

A

small myelinated

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16
Q

what do A beta fibres detect?

A

touch, pressure, vibration

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17
Q

what do A delta fibres detect?

A

cold, “fast” pain, pressure

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18
Q

describe the appearance of C fibres

A

unmyelinated fibres

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19
Q

what do C fibres detect?

A

warmth, “slow” pain

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20
Q

what are the speeds of the three fibres used for cutaneous sensation?

A

A beta = 30-70m/s
A delta = 5-30 m/s
C = 0.5-2 m/s

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21
Q

where abouts for the A alpha and A beta fibres project up the spinal cord?

A

project straight up through ipsilateral dorsal columns

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22
Q

what does A alpha and A beta fibres detect?

A

mechanoreceptive

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23
Q

where do the A delta and C fibres project up the spinal cord ?

A
  1. the fibres synapse in the dorsal horn and cross over to the opposite side and then
  2. project up through the contralateral spinothalamic (anterolateral) tract to reticular formation, thalamus and cortex
24
Q

where abouts do the A alpha and A beta fibres decussate ?

A

in the brain stem

25
Q

where do the primary afferent fibres enter the spinal cord?

A

dorsal root ganglia

26
Q

which afferent fibre type is used for detecting warmth

A

C fibres

27
Q

which afferent fibre type is used for detecting cold

A

A delta fibres

28
Q

which afferent fibre type is used for detecting proprioception

A

A alpha

A beta

29
Q

which afferent fibre type is used for detecting touch?

A

A beta

30
Q

which of the fibres is large and myelinated ?

A

A alpha

A beta

31
Q

what sensory information would be lost if the dorsal column of the spinal cord was damaged ?

A

touch
vibration
proprioception
- these would be lost below the lesion on the ipsilateral side

32
Q

what sensory information would be lost if the anterolateral column of the spinal cord was damaged ?

A

pain
temperature
- these would be lost below the lesion on the contralateral side

33
Q

where abouts is the somatosensory cortex located?

A

post-central gyrus

34
Q

what is adaptation of sensory pathways ?

A
  1. with a stimulus APs are fired
  2. with a rapidly adapting fibres the APs will decrease quickly after the stimulus has remained for a certain amount of time and it not harmful
35
Q

give an example of the adaptation of sensory pathways

A

when you put on a hat you first feel it then you can’t tell its there anymore

36
Q

what is convergence of neurons?

A

when several first neurons synapse with second neurons

37
Q

what is the advantage of the convergence of neurons?

A

reduces the number of neurons required

38
Q

what is the disadvantage of the convergence of neurons?

A

reduces acuity

39
Q

convergence can be specific or non specific

- what are the differences ?

A

specific
- when the same type of fibres synapse together so increase the sensory field

non-specific
- when fibres of different types synapse together for example touch and temperature

40
Q

what is lateral inhibition of sensory pathways ?

A

activation of one sensory input causes inhibition to the fibres near by

41
Q

what is the advantage of inhibition of sensory pathways?

A

gives better definition to the boundaries of the stimulus

42
Q

what is perception of sensory pathways?

A

different responses to stimuli in different people

e.g. picture of a scary dog and being in the same room as a scary dog

43
Q

when a cell depolarises are the Na channels open or closed?

A

Na channels are open

44
Q

what sensory fibres carry pain and temperature?

A

A delta and C fibres

45
Q

what are the two ways that nociceptors and tempereceptors can be inhibited?

A

Segmental Control

Descending Control

46
Q

Describe how segmental control of nociceptors work?

A
  1. Activity in Aα/β fibres activates inhibitory interneurones
  2. Inhibitory interneurones release opioid peptides (endorphins) that inhibit transmitter release from Aδ/C fibres, hence “closing the gate”
47
Q

Describe how descending control of nociceptors work?

A

The same inhibitory interneurones used in segmental control are also activated by descending pathways from PAG via NRM, hence also “closing the gate”

48
Q

How do NSAIDs work?

A
  1. They inhibit Cyclo-oxygenase enzyme
  2. COX converts arachidonic acid to prostaglandins
  3. Therefore, less prostaglandins are being produced
  4. This decreases the sensitivity of bradykinin
  5. This decreases the number of APs fired to the A delta and C fibres
  6. the perception of pain is less
49
Q

what three properties do NSAIDS decrease?

A
  • pain
  • inflammation
  • pyrexia
50
Q

how do local anaesthetics work?

A

block Na+ action potential and therefore all axonal transmission (sensory transmission)

51
Q

how does Trans cutaneous electric nerve stimulation (TENS) work?

A

stimulate PAG area and therefore stimulate the inhibitory interneuron which releases endorphins and inhibits the A delta and C fibres

52
Q

how do opiates work?

A
  1. reduce the sensitivity of nociceptors
  2. block transmission release in dorsal horn
  3. activate descending inhibitory pathways
53
Q

how does tissue damage result in pain?

A
  1. tissue damage results in an inflammation process where prostaglandin is released
  2. prostaglandins increase the sensitivity of nociceptors to bradykinin
  3. which causes depolarisation in the A delta and C fibres
54
Q

how does referred pain occur?

A
  1. when there is a large sensory field

2. when neurons converge so a large area of skin will only stimulate one neuron

55
Q

what is the gate control hypothesis of pain modulation?

A

when A alpha neurons are stimulated which stimulate an inhibitory interneuron which releases endorphins and causes inhibition in the nociceptor fibres

Y2 Neurology (52 decks)

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