Lower Motor Neurons and the Neuromuscular Junction

Question 1

what does the amount of intracellular calcium determine?

Answer 1

number of vesicles that can be released

Question 2

what is the target of peripheral muscle relaxants used during surgery?

Answer 2

nicotinic receptors at the motor end plate

Question 3

without appropriate ______________ conductance the muscle will be hyperexcitable

Answer 3

chloride

Question 4

what do alpha motor neurons innervate?

Answer 4

extrafusal muscle fibers

Question 5

what do gamma motor neurons innervate?

Answer 5

intrafusal muscle fibers

Question 6

how can activation be initiated at the spinal level?

Answer 6

incoming sensory afferents from muscle spindle (Ia fiber) or golgi tendon organs (Ib) or descending fibers (UMN)

Question 7

what do upper motor neurons provide to gamma motor neurons?

Answer 7

inhibitory inputs

Question 8

how many muscle fibers does a motor neuron innervate in a motor unit?

Answer 8

hundreds of muscle fibers

Question 9

what breaks down acetylcholine in the neuromuscular junction?

Answer 9

acetylcholinesterase

Question 10

is calcium involved in uptake of choline from the synaptic cleft?

Answer 10

yes

Question 11

how does uptake of acetylcholine into storage vesicles occur?

Answer 11

vesicular acetylcholine transporter

Question 12

how does magnesium impact vesicular release?

Answer 12

inhibits vesicular release
less magnesium leads to more release

Question 13

what are the side effects of acetylcholinesterase inhibitors like?

Answer 13

parasympathetic activation
more acetylcholine left in cleft to bind

Question 14

what are found in different combinations in different types of nicotinic acetylcholine receptors?

Answer 14

five polypeptide subunits

Question 15

what does activation of DPH (L-type calcium channels) receptors result in?

Answer 15

conformation change of ryanodine receptors
release of calcium from sarcoplasmic reticulum

Question 16

what maintains the resting conductance of muscle fibers?

Answer 16

chloride channels

Question 17

what is happening in synaptic fatigue?

Answer 17

reuptake, synthesis, and transport mechanisms cannot keep up with neuromuscular demand

Question 18

when might synaptic fatigue be seem?

Answer 18

following myoclonic seizures

Question 19

what is happening in denervation hypersensitivity?

Answer 19

in response to injury, nicotinic receptors spread out over larger part of motor end plate

Question 20

what ion conductance is decreased in myotonia?

Answer 20

chloride conductance

Question 21

acquired myasthenia gravis involves generation of antibodies that bind ____________________

Answer 21

nicotinic receptors