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year 2 neuro - Robbie > Sensory Systems (Including Physiology of Pain) > Flashcards

Sensory Systems (Including Physiology of Pain) Flashcards

1
Q

Each type of sensory information is associated with a specific receptor type responding to a specific sensory modality - name some examples?

A

mechanoreceptors

chemoreceptors

thermoreceptors

nociceptors

proprioceptors

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2
Q

sensory receptors may have free nerve endings or a complex structure, what are examples of each?

A

nociceptors, cold receptors

Pacininan corpuscle, Meissner’s corpuscle

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3
Q

What is the response over a specific area called?

A

receptive field

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4
Q

Image showing the different strucutres of neurons

Some have multiple nerve endings, others have fancy structures attached to the end of them

A
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5
Q

What are the 2 different sensory receptors in the body?

A

difference between physiological (sensory) receptors vs pharmacological (protein) receptors

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6
Q

all sensory receptors transduce their adequate stimulus into a depolarisation, what is i that causes this depolarisation?

A

the receptor (generator) potential

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7
Q

the size of the receptor potential encodes what?

A

intensity of stimulus

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8
Q

receptor potential then evokes firing of _____________ for long distance transmission

A

action potentials

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9
Q

frequency of action potentials encodes ________________

A

intensity of stimulus

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10
Q

What do the receptive fields encode

A

location of stimulus

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11
Q

What does the receptive field give information on?

A

gives information on the modality, intensity & location of the stimulus

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12
Q

Image showing graded and action potentials

A

Generated potentials are local so don’t reach the end but action potentials reach all the way to the end

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13
Q

What determines acuity of a sensory neuron?

A

density of innervation

size of receptive field

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14
Q

Explain this image

A

Two pointed both activated by the right sensory field - no 2 point discrimination

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15
Q

Action potentials are transmitted to the CNS by what?

A

axons

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16
Q

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

A

Aβ

Aδ

C

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17
Q

Are Aβ, Aδ, C fibres myelinated or not?

A

Aβ - large myelinated (30-70m/s)

Aδ - small myelinated (5-30m/s)

C - unmyelinated fibres (0.5-2m/s)

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18
Q

What is the function of the Aβ, Aδ, C fibres?

A

Aβ = touch, pressure, vibration

Aδ = cold, “fast” pain, pressure

C = warmth, “slow” pain

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19
Q

Proprioception is mediated by what 2 types of primary afferent fibres?

A

Aα & Aβ

eg muscle spindles, golgi tendon organs etc

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20
Q

Where do all primary afferent fibres enter the spinal cord?

A

all enter spinal cord via the dorsal root ganglia (or cranial nerve ganglia for head)

21
Q

Transition of sensory information is done through what types of fibres?

A

mechanoreceptive (Aα & Aβ) fibres

thermoreceptive & nociceptive (Aδ & C) fibres

22
Q

What type of fibres are mechanoreceptive fibres?

A

Aα & Aβ

23
Q

What is the course of mechanoreceptive 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

24
Q

What type of fibres are thermoreceptive & nociceptive fibres?

A

Aδ & C

25
Q

What is the course of thermoreceptive & nociceptive 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

26
Q

Is the left or the right:

mechanoreceptive (Aα & Aβ) fibres

thermoreceptive & nociceptive (Aδ & C) fibres

A

left - thermoreceptive and nociceptive fibres

right - mechanoreceptive fibres

27
Q

different pathways for transmission of sensory information explains consequences of spinal cord injuries

What does damage to the dorsal columns lead to?

A

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

28
Q

different pathways for transmission of sensory information explains consequences of spinal cord injuries

What does damage to anterolateral quadrant lead to?

A

causes loss of nociceptive & temperature sensation below lesion on contralateral side

29
Q

Where does the transmission of sensory information end?

A

ultimate termination is in the somatosensory cortex (S1) of the postcentral gyrus

30
Q

How is the sensory information stored and arranged?

A

endings are grouped according to the location of the receptors

extent of representation is related to the density of receptors in each location

produces the sensory homunculus

31
Q

Adaptation is one of the processes in the sensory pathway, explain this?

A

gradual decrease over time in the responsiveness of the sensory system to a constant stimulus

usually experienced as a change in the stimulus e.g. if a hand is rested on a table, the table’s surface is immediately felt against the skin but the sensation of the table surface against the skin gradually diminishes until it is virtually unnoticeable

sensory neurons that initially respond are no longer stimulated to respond; this is an example of neural adaptation

32
Q

Convergenge is another process of the sensory pathway, what is it and its effects?

A

saves on neurones

reduces acuity - as if 2 neurons go onto one then you don’t know where the stimulus is coming from

may be the cause of reffered pain

in nonspecific ascending pathways, different stimuli can get merged together

33
Q

lateral inhibition is another process in the sensory pathway, what is it?

A

activation of one sensory input causes synaptic inhibition of its neighbours

gives better definition of boundaries, can localize a stimulus on the skin better

cleans up sensory information

34
Q

What are 3 main processes that happen in the sensory pathway?

A

adaptation

convergence

lateral inhibition

35
Q

What are the 2 different types of pain that can be experienced?

A

sharp, stabbing vs diffuse, throbbing pain

36
Q

What are the 2 different speeds of pain?

A

fast (initial) pain vs slow (delayed) pain

37
Q

What are the different lengths of time that pain can persist?

A

acute vs chronic pain

38
Q

What is visceral pain?

A

occurs when pain receptors in the pelvis, abdomen, chest, or intestines are activated

when our internal organs and tissues are damaged or injured

vague, not localized, and not well understood or clearly defined

often feels like a deep squeeze, pressure, or aching

39
Q

What is referred pain?

A

pain percieved in another location form the site of the painful stimulus/origin

40
Q

What is phantom limb pain?

A

ongoing painful sensations that seem to be coming from the part of the limb that is no longer there

the limb is gone, but the pain is real

the onset of this pain most often occurs soon after surgery

41
Q

What is responsible for signal transduction in nociceptors?

A

low pH, heat (via ASIC, TRPV1 etc)

local chemical mediators (eg bradykinin, histamine, prostaglandins)

42
Q

How can pain be blocked form nocioceptors?

A

Nociceptors are the bottom left fibres

Gate control theory – can control information through the mechanoreceptor fibres and has an inhibitory interneuron in red, to block the gate in the pain neurons

Descending controls form the brain, called the PAG and their neurons activate neurons in the NRM and they travel down the spinal cord and also close the gate in the same exact way

Descending control work by inhibiting the same interneurons

Descending controls are activated during things like battlefield injuries

43
Q

Slide showing the same as before

A

SG is the (red) interneuron

44
Q

What is analgesia?

A

inability to feel pain

medicine that acts to relieve pain

45
Q

What is a type of analgesia?

A

Non-steroidal anti-inflammatory drugs (NSAIDs)

46
Q

How do NSAIDS work?

A

prostaglandins sensitise nociceptors to bradykinin

work by reducing the production of prostaglandins. Prostaglandins are chemicals that promote inflammation, pain, and fever

NSAIDs are analgesic (and antipiretic & anti-inflammatory) because they inhibit cyclo-oxygenase which converts arachidonic acid to prostaglandins

so NSAIDs work well against pain associated with inflammation

47
Q

How do local anaesthetics work as analgesics?

A

block Na+ action potential and therefore all axonal transmission

48
Q

How does trans cutaneous electric nerve stimulation (TENS) work as an analgesic?

A

electrical stimulus activating the A beta fibres to inhibit the others so electrically rubbing the skin

Rubbing the skin activates interneuron

49
Q

How do opiates (eg morphine) work as a analgesic?

A

reduce sensitivity of nociceptors

block transmitter release in dorsal horn (hence epidural administration)

activate descending inhibitory pathways (to close the gate)

Opiate receptors activate potassium channels to hyperpolarize membrane to stop action potentials being fibres in the first place, also block transmitter release in the dorsal horn

year 2 neuro - Robbie (48 decks)

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