Peters' Physiology

Question 1

With regards to the alpha motor neurone and innervation of skeletal muscle fibres, where is the ACh receptor concentrated?

Answer 1

At the endplate region of the muscle fibre

Question 2

Which receptors are located at the endplate of the muscle fibre?

Answer 2

Nicotinic ACh receptors

Question 3

What subunits make up the nicotinic ACh receptor?

Answer 3

2x alpha1
1x beta1
1x delta
1x epsilon

Question 4

What generates a miniature endplate potential (mepp) at muscle fibres?

Answer 4

One vesicle of ACh activating nictonic ACh receptors at the endplate

Question 5

What do many successive mepps produce?

Answer 5

Graded epp which, if above threshold, triggers an action potential that will initiate contractions

Question 6

Once threshold epp is achieved, which channels open to cause an action potential to be fired?

Answer 6

Voltage-gated sodium channels - these also allow for the action potential to propagate down the muscle fibre

Question 7

Which enzyme hydrolyses ACh at the endplate to terminate neuromuscular transmission?

Answer 7

Acetylcholinesterase

Question 8

Neuromyotonia involves muscle twitches, stiffness, cramps and slow relaxation. How does it arise?

Answer 8

Antibodies produced against K channels in the motor neurone, resulting in repeated firing/hyperexcitation

Question 9

Which drug blocks Na channels and may be useful in neuromyotonia?

Answer 9

Carbamazepine - an anticonvulsant that blocks voltage activated sodium channels

Question 10

Lambert-Eaton Myasthenic Syndrome is associated with muscle weakness and small cell carcinoma of the lung. How does it arise?

Answer 10

Antibodies produced against Ca channels causing reduced Ca entry and thus reduced ACh vesicle release (which is needed to initiate muscle contraction)

Question 11

Which drugs increase ACh concn in the synaptic cleft?

Answer 11

Anticholinesterases (pyridostigimine)

Question 12

Myasthenia gravis involves muscle weakness during activity. How does it arise?

Answer 12

Antibodies produced againsts nicotinic ACh receptors, causing reduced amplitude of epp and less AP generation

Question 13

What are the 3 types of pain?

Answer 13

Nociceptive
Inflammatory
Pathological

Question 14

What is nociceptive pain?

Answer 14

Acute sensory; arises to limit further damage

Question 15

What is inflammatory pain?

Answer 15

Persistent; outlives initial injury but can heal over time

Question 16

Which receptors are activated in the presence of noxious stimuli?

Answer 16

Nociceptors (sensory afferents)

Question 17

Nociceptive pain requires threshold to be achieved to activate nociceptors. True/False?

Answer 17

True

Question 18

Give an example of heightened pain sensitivity in inflammatory pain

Answer 18

Touching an inflamed joint would be sorer than touching the joint when it is not inflamed

Question 19

What is pathological pain?

Answer 19

Abnormal nervous system function causes normal stimuli to be felt as noxious

Question 20

What are the 2 main subtypes of nociceptors?

Answer 20

A-delta-fibres

C-fibres

Question 21

What is the difference between A-delta-fibres and C-fibres?

Answer 21

A-delta-fibres mediate initial/fast pain; C-fibres mediate the second/aftermath pain

Question 22

C-fibres conduct faster than A-delta-fibres. True/False?

Answer 22

False

A-delta-fibres conduct faster

Question 23

Peptidergic polymodal nociceptors are a subset of C-fibres. What are their efferent function?

Answer 23

Release pro-inflammatory mediators from peripheral terminals; contribute to neurogenic inflammation

Question 24

Peptidergic polymodal nociceptors are a subset of C-fibres. What are their afferent function?

Answer 24

Transmit nociceptive stimuli to the CNS via glutamate and peptides

Question 25

Axon of primary afferents terminate centrally in the dorsal horn of the spinal cord in various laminae of Rexed. Where do A-delta-fibres and C-fibres terminate?

Answer 25

Laminae I, II

also V for A-delta-fibres

Question 26

Second order neurones ascend the spinal cord in a system comprised of which two tracts?

Answer 26

Spinoreticular

Spinothalamic

Question 27

What is the spinothalamic tract concerned with?

Answer 27

Pain perception - where it is, how bad is it

Question 28

What is the spinoreticular tract concerned with?

Answer 28

Autonomic/emotional response - fear of pain, what can I do to stop it

Question 29

What is skeletal muscle innervated by?

Answer 29

fast conducting alpha motor neurones with myelinated axos and cell bodies in the spinal cord or brain stem

Question 30

What are the key steps in neuromuscular transmission

Answer 30

synthesis of ACh in cytoplasm of bouton, uptake of ACh in synpatic vesicles, Ca2+ dependant release of ACh into synpatic cleft by exocytosis, brief activation of nicotinic ACh receptors by reverse binding of ACh then rapid termination of transmitter action by ACE within synaptic cleft

Question 31

What does each vesicle of ACh contain?

Answer 31

a quantum of neurotransmitter

Question 32

What does the botulinum toxin do?

Answer 32

Extremely potent exotoxin - acts at motor neurone terminals to irreversibly inhibit ACh release

enters presynaptic nerve terminal to enzymatically modify proteins involved in the docking of vesicles containing ACh - preventing exocytosis

Question 33

What do curate-like compounds do?

Answer 33

Interfere with postsynaptic action of ACE by acting as competitive antagonists of the nicotinic ACh receptor - reduce amplitude of the end plate potential