Sensory System and Pain Flashcards

1
Q

How do anticonvulsant drugs effect GABA

A

agonists to chloride conductance, blocking GABA reuptake or inhibiting its metabolism by GABA transaminase

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2
Q

Why is the ear drum larger than the oval window

A

to allow the wave frequency to be transferred through the fluid of the cochlea

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3
Q

describe the A delta fibres

A

fast
large myelinated
up to 10m/sec
sharp stabbing pain

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4
Q

True or false: Low plasma drug = low Vd = drug not widely distributed

A

False

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5
Q

What happens when glutamate binds to a mGlu receptor

A

Gαq

PLC –> IP3 + DAG –> Ca2+ via IP3 R on ER–> Ca2+ + DAG –> PKC

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6
Q

State the 3 ionotropic glutamate receptors

A

NMDA
AMPA
Kainate

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7
Q

What are the two types of spontaneous pain

A

continuous and paroxysmal (intermittent) pain

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8
Q

What does ketamine antagonise to cause effects

A

NMDA- , which prevents excitatory stimuli inducing a state of euphoria/sleep

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9
Q

What do thermoreceptors sense

A

Temperature

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10
Q

Explain the steps of photoreception

A

Light activating photoreceptors –> conformational change –> decreased glutamate release

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11
Q

What does the organ of corti contain

A

hair cells and the auditory nerve

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12
Q

What is GABA converted to for breakdown

A

succinate

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13
Q

Describe non-depolarising neuromuscular blockers

A

Curare Derivatives
No Na influx, muscle is relaxed
Prevents ACh binding to receptors
Inhibits respiratory muscle such as the diaphragm

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14
Q

Give effects of opioids

A

analgesia, constipation, sedation, respiratory depression, and mood alteration

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15
Q

What are anticonvulsant drugs

A

a diverse group of drugs used in the treatment of seizures such as epilepsy. They suppress excessive rapid firing of neurons during seizures and prevent the spread through the brain.

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16
Q

What does Gi inhibit

A

adenylate cyclase

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17
Q

What is the role of glycine

A

potentiate NMDA signalling

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18
Q

What do photoreceptors sense

A

vision

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19
Q

What is the calculation for the volume of distribution

A

(amount of drug in body (dose))/(plasma concentration (extrapolated))

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20
Q

Does the ear canal or cochlea have cells with cilia

A

cochlea

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21
Q

When light hits the excitatory portion of the receptive field, what happens

A

the photoreceptor becomes hyperpolarised, and the process of photoreception occurs

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22
Q

What are the three layers of the retina

A
  • epithelial cells
  • photoreceptors
  • bipolar/ganglion/amacrine cells
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23
Q

Describe the withdrawal reflex

A
  • Pain signal travels along the Ad fibre, to the dorsal root ganglion
  • travels across an interneuron to the anterior horn cell
  • travels along a motor neuron to move e..g the hand
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24
Q

Define Peripheral sensitisation

A

sensory neuron expression of α-adrenoreceptors, so more stress means more pain, and overexpression of V-G Na+, which increases AP production and increases stimuli above the original injury.

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25
Q

describe the C fibres

A

slow
small unmyelinated
1.2m/sec
aching burning pain

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26
Q
How is the activity of NMDA receptors controlled?
A. voltage-gated
B. ligand-gated
C. enzyme antagonist
D. all of the above
A

D
NMDA receptors are both voltage-gated and ligand-gated: they will only open the ion channels if the membrane is depolarized and the neurotransmitters glutamate and glycine are attached. When the membrane is not depolarized the activity of the NMDA receptors is blocked as Mg2+ acts as an enzyme antagonist.

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27
Q

How does neostigmine work

A

inhibits AchE activity, so Ach is not broken down in the synaptic cleft and continues to activation the nicotinic ACHR, for Na+ to cause depolarisation and contraction.

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28
Q

what are the two types of pain conduction

A

fast response - A delta fibres

slow response - C fibres

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29
Q

What is the purpose of GABAa channels

A

Causes hyperpolarisation which reduces excitability

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30
Q

what is the pain pathway

A

injury –> peripheral nerve (afferent neurone, excitatory (glutamate and ATP release)) –> spinal cord - receptor binding, AMPA (fast), NMPA (slower, release block of prolonged depolarisation) –>
thalamus –>
cortex

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31
Q

What is glycine

A

Glycine is an inhibitory neurotransmitter

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32
Q

What is the retina

A

a thin layer of tissue, lining the back of the eye. It receives the light that the lens has focused and converts it to neural signals, sending these to the brain for visual recognition.

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33
Q

What type of channels are GABAa

A

Ligand gated chloride channels

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34
Q

what is a precursor of glutamate

A

glutamine

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35
Q

What happens when glutamate binds to a NMDA receptor

A

When glutamate and glycine bind to the NMDA receptors the conformation of the protein changes and Ca2+ permeable ion channels open.

36
Q

Symptoms of phantom pain

A
  • Continuous or paroxysmal pain
  • Often effects part of the limb furthest from the body
  • Shooting, stabbing, burning, throbbing pain
  • May be triggered by pressure on remaining part of the limb, or emotional stress
37
Q

What types of non-medication may be helpful for phantom pain

A
  • Acupuncture
  • Massage of the residual limb
  • Use of a shrinker
  • Repositioning of the residual limb by propping on a pillow or cushion
  • Mirror box therapy
  • Biofeedback
  • TENS (transcutaneous electrical nerve stimulation)
  • Virtual reality therapy
  • Imagery
38
Q

What do nociceptors sense

A

extremes of pain and temperature

39
Q

Which fibres are the fast pain conductance

A

A delta fibres

40
Q

what is the predominant precursor of GABA

A

glucose

41
Q

What is the receptive field

A

Areas of the retina which change membrane potential in the presence of light. Every cell of the retina has one.

42
Q

Describe depolarising neuromuscular blockers

A

Succinylcholine
Blockade for a few minutes
Metabolised by plasma cholinesterase
Causes persistent refractory depolarisation

43
Q

What can alter sensitivity (broadly), and give examples

A

inflammatory mediators such as K+, H+, histamine, ATP, prostaglandins, bradykinin, substance P, 5-HT.

44
Q

What types of medication may be helpful for phantom pain

A
  • Non-steroidal anti-inflammatory drugs (NSAIDs)
  • Opioids (narcotic pain medications)
  • Antidepressants
  • Anticonvulsants
  • Beta-blockers
  • Muscle relaxants.
45
Q

Is GABA an inhibitory or excitatory neurotransmitter

A

inhibitory

46
Q

True or False: Low plasma drug = high vd = drug widely distributed in other tissues

A

True

47
Q

what can the volume of distribution be affected by

A
  • Drug size
  • Drug lipophilicity (pKa/pH)
  • Plasma protein binding
  • Body composition
  • Patient age/gender
48
Q

State the metabotropic glutamate receptor

A

mGLu

49
Q

By blocking the sodium/calcium channels, how do anticonvulsant drugs help?

A

they reduce the release of glutamate as by stabilising the channels in an inactive state, they prevent the repetitive firing of the axons

50
Q

How does botox work

A

cleaves SNARE proteins to stop Ach vesicles fusing to the terminal bouton. This prevents exocytosis, and ‘freezes’ the muscle

51
Q

What is phantom pain

A

as ongoing painful sensations which seem to be coming from a body part which is no longer there

52
Q

Is glutamate essential or non-essential

A

non-essential

53
Q

What do chemoreceptors sense

A

olfaction, taste, arterial PO2,

54
Q

what are photoreceptor cells

A

light-sensitive cells responsible for detecting the intensity and colour of light.

55
Q

What do mechanoreceptors sense

A

touch, audition, vestibulation

56
Q

Which fibres are the slow pain conductance

A

C fibres

57
Q

Is glutamate an inhibitory or excitatory neurotransmitter

A

excitatory

58
Q

Which nerves do sensory receptors send signals along? and where to?

A

afferent nerves to the CNS

59
Q

What is a neuromuscular blocker

A

A molecule which acts at a neuromuscular junction to prevent normal action of ACh.

60
Q

Are glutamate receptors ionotropic or metabotropic

A

Both/either

61
Q

Define anesthesia

A

a state of temporary induced loss of sensation/awareness

62
Q

True or false: The brain shows activity when the person feels phantom pain, even if neurologically, it is no longer connected

A

True

63
Q

What is the calculation for clearance

A

([drug]in urine x urine flow rate)/([drug]in plasma)

64
Q

What do glutamate receptors synapse with

A

sensory neurons in the spinal cord

65
Q

how do opioids works

A

By inhibiting the descending pathway from the cortex and midbrain, they prevent pain signals from happening

66
Q
What neurological functions are not thought to be influenced by glutamate activity?
A. memory formation
B. learning
C. arousal
D. movement
A

C is correct. Glutamate is a very common excitatory neurotransmitter that is involved in memory formation, learning, and movement. Arousal is thought to be influenced by the excitatory neurotransmitter norepinephrine.

67
Q

Anaesthetics are agonists of which type of receptor

A

GABAa agonists

68
Q

What factors affect renal clearance

A
  • Renal blood flow/kidney function
  • Drug lipophilicity
  • Plasma protein binding
69
Q

What is the pKa

A

the pH at which 50% of the molecules exist in the tertiary form and 50% exist in the quaternary form

70
Q

What is the pKa value for all anaesthetics

A

> 7.4

71
Q

What does Go do

A

decrease the neuronal excitability, having an inhibitory effect. This opens K+ channels and causes membrane hyperpolarisation meaning they are less likely to fire action potentials

72
Q

What is the ionisation constant

A

(pKa) for an anaesthetic predicts the proportion of molecules which exist in each of the states

73
Q

What is the volume of distribution

A

The volumes in which total amount of drug would need to be dissolved to match plasma concentration.

74
Q

True or false: AchE can hydrolyse suxamethonium

A

False

75
Q

What is the precursor to glycine

A

Serine

76
Q

True or false: More than one photoreceptor can become hyperpolarised for each bipolar cell.

A

true

77
Q

What is the most abundant g protein in the CNS

A

Go

78
Q

What type of channels are GABAb

A

Gi/GO

79
Q

What is neuropathic pain

A

Caused by damage or disease of the somatosensory nervous system, rather than stimulation of pain receptors

80
Q

Which GCPR signalling pathway do opioids use

A

Gi/Go signalling pathway.

81
Q

Is the ear canal or cochlea fluid filled

A

cochlea

82
Q

what prevents the opening of the NMDA receptor ion channels when the membrane is not depolarized

A

a voltage-dependent Mg2+ block

83
Q
How many classes of glutamate receptor subunits are found in NMDA receptors?
A. two
B. five
C. ten
D. one
A

A is correct. While each NMDA receptor is made up of five subunits, these subunits fall into two classes of glutamate receptor subunit family.

84
Q

What is the purpose of GABAb channels

A

Inhibits VOCCs & opens K+ channels

=reduces excitability

85
Q

If there is a decrease in GiGo inhibitory VOCCs/K release, does this increase or decrease excitation?

A

Increase

86
Q

If there is less glutamate, and a decrease in NMDA and AMPA receptors, is there more or less excitation?

A

Less