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NEURO > Sensory systems (including physiology of pain) > Flashcards

Sensory systems (including physiology of pain) Flashcards

1
Q

what are different types of sensory information associated with

A

specific receptor types responding to a specific sensory modality

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2
Q

give some examples of specific receptors

A

mechanoreceptors, chemoreceptors, thermoreceptors, nociceptors, proprioceptors

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3
Q

what is the receptive field of a receptor

A

the area in which they respond to a stimulus

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4
Q

what are the different types of receptor structures

A

can be free nerve endings e.g. nociceptors

can be complex structures e.g. pacinian corpuscle, meissners corpuscle

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5
Q

list some receptor structures and what stimuli they respond to

A
  1. tactile meissners corpuscle - light tough
  2. tactile merkles corpuscle - touch
  3. free nerve ending - pain
  4. lamellated pacinian corpuscle - deep pressure
  5. ruffini corpuscle - warmth
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6
Q

what do all sensory receptors do the their adequate stimulus

A

transduce it into a depolarisation (the receptor generator potential)

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7
Q

what determines the size of the receptor generator potential

A

the intensity of stimulus

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8
Q

what does the receptor generator potential evoke

A

firing of APs for long distance transmission

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9
Q

what determines the frequency and duration of APs fired

A

the intensity of stimulus

porportionally

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10
Q

what does the receptive field encode

A

the location of the action potential

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11
Q

what determines neurotransmitter release

A

the pattern of action potentials arriving at the axon terminal

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12
Q

briefly summaries the steps in signal transduction

A
  1. stimulus
  2. transduction site = receptro generator potential
  3. trigger zone - receptor potential integrated
  4. myelinated axon - firing of APs - frequency and duration based on stimulus
  5. axon terminal - neurotransmitter release in response to AP
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13
Q

what determines acuity

A

density of innervation and size of receptive fields

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14
Q

what transmits action potentials to the CNS

A

axons

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15
Q

what 2 types of primary afferent fibres mediate proprioception

A

mechanoreceptive:

Aα & Aβ

eg muscle spindles, golgi tendon organs etc

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16
Q

what 3 types of primary afferent fibres mediate cutaneous sensation

A

thermoreceptive and nociceptive:

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

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17
Q

where do all the primary afferent fibres enter the spinal cord

A

at the dorsal root ganglion

or cranial ganglia for the head

18
Q

what do Abeta fibres mediate

A

touch pressure, vibration

19
Q

what do Adelta fibres mediate

A

cold, fast pain, pressure

20
Q

what do C fibres mediate

A

warmth, slow pain

21
Q

what is the route of transmission of Aa, Ab fibres

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

22
Q

what is the route of transmission of Adelta and C fibres

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

23
Q

what does the different pathways for transmission of sensory information explain

A

explains consequences of different spinal cord injuries

24
Q

what does damage to the dorsal column cause

A

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

25
what does damage to the anterolateral quadrant cause
causes loss of nociceptive & temperature sensation below lesion on contralateral side
26
where is the ultimate termination of the sensory fibres pathway
somatosensory corted (S1) of the post central gyrus
27
what produces the sensory homunculus
extent of representation - related to the density of receptors in each location
28
what are the three processes in sensory pathways
adaptation covergence lateral inhibition
29
what is adaptation
the change over time in the responsiveness of the sensory system to a constant stimulus
30
what is convergence
when non-specific ascending pathways combine e.g. touch and temperature responses so that there is one larger group of info arriving in the brain reduces acuity and may underlie referred pain
31
what is lateral inhibition
when activation of one sensory input causes synaptic inhibition of tis neighbours gives better definition of boundaries - cleans up sensory information enhances the perception of the stimulus
32
list some examples of different types of pain
sharp, stabbing vs diffuse, throbbing pain fast (initial) pain vs slow (delayed) pain acute vs chronic pain visceral pain referred pain phantom limb pain
33
what activate signal transduction in nociceptors
low pH, heat local chemical mediators (e.g. bradykinin, histamine, prostaglandins)
34
how does pressure alleviate pain
gate control theory: - pressure activates Aa/b fibres - activate inhibitory interneurones - interneurons release opioid peptides (endorphins) - endorphins inhibit transmitter relase from Adelta/C fibres = CLOSE THE GATE OF PAIN happens at the segmental level
35
how does the gate control theory work in the descending controls
same inhibitory interneurones are also cite by descending pathways from the peri-aqueductal grey matter and nuclus raphe magnus - also close the gate activated by opiates
36
what do prostaglandins do to nociceptors
sensitise them to bradykinin
37
how do NSAIDS work as an analgesic
they inhibit cyclo-oxygenase which converts arachidonic acid to prostaglandins they are also anti-inflammatory so work well with pain associated with inflammation
38
how does local anaesthetics block pain
block Na+ action potential and therefore all axonal transmission
39
how do opiates e.g. morphine work as an analgesic
reduce sensitivity to nociceptors block transmitter release from the dorsal horn (hence epidural administration) activate descending inhibitory pathways
40
what is TENS
trans cutaneous electric nerve stimulation

NEURO (51 decks)

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