CHAP: 7 EXCITATION OF SKELETAL MUSCLE

Question 1

Each nerve ending makes a junction called?

Answer 1

Neuromuscular junction

Question 2

The nerve fiber forms a complex of _________ that invaginates into the surface of the muscular fiber but lie outside the muscle plasma membrane.

Answer 2

Branching nerve terminal

Question 3

The entire structure is called ?

Answer 3

Motor end plate

Question 4

invagintaed membrane is called?

Answer 4

Synaptic gutter or Synaptic trough

Question 5

The space between the terminal & fiber membrane is called _____this space is 20-3 nm.

Answer 5

Synaptic space or synaptic cleft

Question 6

At the bottom of the gutter are numerous smaller folds of the muscle membrane, which greatly increase the surface area at which the synaptic transmitter can act.

Answer 6

Subneural cleft

Question 7

In the axon terminal are many mitochondria that supply ATP, the energy source that is used for synthesis of an excitatory transmitter, what is this?

Answer 7

Acetylcholine

Question 8

In the synaptic space are large quantities of the enzyme________ that destroys acetylcholine a few milliseconds after it has been released from the synaptic vesicles.

Answer 8

Acetylcholinesterase

Question 9

The vesicles then fuse w/ the neural membrane & empty their acetylcholine into the synaptic space by the process?

Answer 9

Exocytosis

Question 10

Each receptor is a protein complex that has a total molecular weight of 275,000. The complex is composed of of 5 subunits protein, what are those?

Answer 10

1. Alpha protein
2. Beta
3. Delta
4. Gamma proteins

Question 11

this do not pass through because of strong negative charges in the mouth of the channel that repel these negative ions.

Answer 11

1. Chloride ions

Question 12

what are the only 2 positive ions in large concentration?

Answer 12

1. sodium ions in ECF
2. potassium ion in ICF

Question 13

the negative potential on the inside of the muscle membrane ______ this millivolts, pulls the positevely charged sodium ions to the inside of the fiber, while simultaneously preventing efflux of the positively charged potassium ions when they attempt to pass outward.

Answer 13

-80 to 90 millivolts

Question 14

What is the principal effect of opening the acetylcholine-gated channels

Answer 14

is to allow large number of sodium ion to pour to the inside of the fiber, carrying with them large numbers of positive changes

Question 15

when the principal effect happens this creates a local positive potential change inside the muscle fiber membrane called?

Answer 15

end plate potential.

Question 16

Acetylcholine is removed by 2 means:

Answer 16

1. Destryoed by enzyme acetylcholinesterase
2. Small amount of acetylcholine diffuses out in the synaptic space & is then no longer available to act on the muscle fiber membrane.

Question 17

this millivolts creats a local potential called the end plate potential.

Answer 17

50 to 75 millivolts

Question 18

a drug that blocks the gating action of acetylcholine on the acetylcholine channels by competing for the acetylcholine channels by competing for the acetylcholine receptor sites.

Answer 18

Curare

Question 19

a bacteria poison that decreases the quantity of acetylcholine release by the nerve terminals.

Answer 19

Botulinum toxin

Question 20

what are the drugs that stimulate the muscle fiber by acetylcholine like action.

Answer 20

1. Methacoline
2. Carbachol
3. Nicotine

Question 21

drugs that stimulate the neuromuscular junctions by inactivating acetylcholinesterase:

Answer 21

1. Neostigmine
2. Physostigmine
3. Diisopropyl fluorophosphate

Question 22

This 2 is combine w/ acetylcholinesterase to inactive the acetylcholinesterase for up to several hours , after it displaced the esterase once again become active.

Answer 22

1. Neostigmine
2. physostigmine

Question 23

______ is a powerful nerve gas poison, inactive cholinesterase for weeks, which makes this a particularly lethal poison

Answer 23

diisopropyl fluorophosphate

Question 24

drugs that block transmission at the neuromuscular junction:

Answer 24

1. Curariform drugs- it can prevent the passage of impulses from the nerve ending to the muscle.

Question 25

______ occurs in about 1 in every 20,000 person, it causes muscle paralysis because of inablity of the neuromuscular junction to transmit enough signals form the nerve fibers to the muscle fibers.

Answer 25

Myasthenia gravis

Question 26

Myasthenia gravis is believed to be an?

Answer 26

autoimmune disease in which the patients have developed antibodies that block or destroy their own acetylcholine receptors at the postsynaptic neuromuscular junction.

Question 27

if myasthenia gravis is intense this is ameliorated for several hours after admenistering?

Answer 27

Neostigmine

Question 28

What are the 3 quantitative aspects of muscle poetential:

Answer 28

1. resting membrane potential
2. duration of action potential
3. Velocity of conduction

Question 29

What is the resting membrane potential?

Answer 29

-80 to -90 millivolts in skeletal fiber- same as in large myelinated nerve fiber

Question 30

What is the duration of action potential?

Answer 30

1 to 50 milliseconds in skeletal muscle- 5x as long as in large myelinated fiber

Question 31

What is the velocity of conduction?

Answer 31

3 to 5 m/sec-about 1/13 the velocity conduction in large myelinated nerve fibers that excite skeletal muscle.

Question 32

what is the step to get the maximum muscle contraction?

Answer 32

The current must penetrate deeply into the muscle fiber to the vicinity of the separate myofibrils.

Question 33

Maximum muscle contraction is achieved by transmission of action potential along ______ that penetrate all the way through the muscle fiber from one side of the fiber to the other.

Answer 33

Transverse tubules

Question 34

The T-tubele action potenials causes the release of ______ inside the muscle fiber in the immediate vicinity of the myofibrils & causes cotraction.

Answer 34

Calcium ions

Question 35

From pentrating to achieved maximum mudcle contraction, & release of calcium in the T-tubules, this whole process is called ?

Answer 35

excitation-contraction coupling

Question 36

As the action potenial reaches the T tubule, the voltage changed is sensed by ___________ that are linked to calcium channels, also called _______

Answer 36

1. dihydropyridine receptors
2. ryanodine receptor channels

Question 37

activation of this ______ triggers the opening of the calcium release channels in the cisternae, as well as in their attached longitudinal tubules.

Answer 37

Dihydropyridine receptors

Question 38

Inside the reticulum is a protein called ______ that can bind up to 40x more calcium.

Answer 38

Calsequestrin

Question 39

the total duration of this calcium pulse i the usual skeletal muscle fiber last about how many second?

Answer 39

1/20 sec

Question 40

about how many vesicles of acetylcholine are released from the terminals into the synaptic space?

Answer 40

125 vesicles