EX1; Neuromuscular Junction Flashcards Preview

AU14 Physiology > EX1; Neuromuscular Junction > Flashcards

Flashcards in EX1; Neuromuscular Junction Deck (25):
1

The amount of contractile activity in a skeletal muscle is regulated by what

the nervous system; the site is the neuromuscular junction

2

Most skeletal muscles have now many NMJs

they have one NMJ on the surface membrane (sarcolemma)

3

The NMJ comprises what percentage of the sarcolemma area

less than 0.1%

4

True or False
The NMJ is a "synapse" a point of contact/communication between two excitable cells

True

5

What are the first two steps involving an AP in a motor neuron to an AP in the sarcolemma

AP travels along motor neuron axon and invades the motor neuron presynaptic terminal

6

What ion influx is in presynaptic terminal after the AP reaches

Calcium

7

These fuse to the membrane of the presynaptic terminal and release what

vesicles release acetylcholine

8

ACh diffuses across what (from the presynaptic terminal) to bind with receptors in the postsynaptic membrane (motor endplate)

neuromuscular cleft

9

Upon the binding of ACh to its receptors, this triggers the opening of what

Na and K channels which are chemically regulated (as opposed to voltage regulated) at the motor endplate, there is then a Na influx and a small K influx

10

Upon the Na and K influx, there is generation of what

endplate potential

11

The generation of the endplate potential causes the opening of what

voltage-regulated Na channels in the sarcolemma immediately surrounding the motor endplate (AP initiation in the sarcolemma)

12

True or False
Endplate potentials are graded, not an all-or-none response

True

13

Endplate potentials do not do this, but can undergo this

do not propagate
can undergo summation

14

These are small EPPs that occur spontaneously and result from the release of ACh from one or a few vesicles in the pre-synaptic terminal and subsequent binding to its receptor

miniature endplate potentials

15

Which one, EEP or MEPP occurs at rest

MEPPs at rest
EPPs occur following an AP in a motor neuron

16

Which one, EEP or MEPP is not sponatneous

EPPs
(MEPPs are spontaneous)

17

Which one, EEP or MEPP is confined to the end-plate region

Both!!

18

Which one, EEP or MEPP has an amplitude of 1-2mV

MEPPs
EPPs have an amplitude of ~10mV

19

Both EEPs and MEPPs can undergo summation, but which one usually leads to an AP in adjacent region of membrane

EPPs

20

This is located on the motor endplate membrane and in the basal lamina and is involved with the breakdown of ACh

acetylcholinesterases

21

What are the two products of ACh breakdown

choline and acetic acid

22

Where do the acetate and choline end up after breakdown of ACh

acetate; circulation
choline; taken up by presynaptic terminal where in it reacts with Acetyl-CoA and then back around to ACh

23

This is a plant derative that binds to AChR so ACh cannot bind; ACh will still be released, but APs will not occur

curare

24

This blocks ACh release so skeletal muscle activation will not occur

botulinum toxin

25

This blocks action of AChE so ACh will not be hydrolyzed; cannot activate skeletal muscle in its presence because Na channels remain in a refractory state

organophosphates (some, not all)