Muscle and Nerve Physiology and Response to Electric Current

Question 1

What does a motor unit consist of?

Answer 1

One motor neuron and all the muscle fibers it stimulates

Question 2

Describe the process of neuromuscular transmission

Answer 2

1) an action potential is carried along the alpha motor neuron and releases Ach into the synaptic cleft
2) Ach diffuses across the cleft and binds to nicotnic receptors on the end plate region of the skeletal muscle cell
3) an action potential is initiated in the skeletal muscle cell

Question 3

Describe what occurs in the muscle cell once the action potential initiates it

Answer 3

1) the AP generated at the motor end plate region spreads along the membrane of the skeletal muscle cell and into the T tubules
2) these T tubules have receptors that connect to the Ca2+ channels
3) contraction of the muscle results from the interaction of the actin and myosin filaments (which can occur once the Ca2+ has been released through channels)

Question 4

Describe the order in which nerves are depolarized. How does this relate to phase duration?

Answer 4

1) Sensory nerves
2) Motor nerves
3) Pain nerves
4) Muscle fibers

Nerves that take less to stimulate (depolarize) have a short phase duration, whereas those that take longer to stimulate have long phase durations

Question 5

What must the phase duration be in order to depolarize a muscle fiber?

Answer 5

direct current

Question 6

In order for a nerve to depolarize what must happen to the intensity stimulus if the duration is decreased?

Answer 6

The intensity will have to increase

Question 7

Compare and contrast muscle contractions in skeletal and smooth muscle

Answer 7

Skeletal muscle contractions develop quickly but fatigue occurs
Smooth muscle contractions develop slowly and last longer

Question 8

Compare and contrast ATP in skeletal and smooth muscle contractions

Answer 8

Skeletal muscle contractions use a lot of ATP whereas smooth muscle contractions use less

Question 9

What is the primary source of calcium in skeletal muscle?

Answer 9

Sarcoplasmic Reticulum

Question 10

What is the primary source of calcium in smooth muscle?

Answer 10

Extracellular Ca2+ stores

Question 11

What are spontaneous depolarizations called in smooth muscle?

Answer 11

slow wave contractions

Question 12

What connects cardiac muscle cells?

Answer 12

gap junctions (electrical current)

Question 13

What controls cardiac muscle contractions?

Answer 13

The autonomic nervous system, hormones, and other intrinsic factors

Question 14

Compare and contrast stimulus propagation in physiologically stimulated muscle and electrically stimulated muscle

Answer 14

In physiologically stimulated muscle the stimulus moves in one direction
In electrically stimulated muscle the stimulus propagates in both directions

Question 15

Which muscle type is activated first physiologically?

Answer 15

Smaller, slow twitch Type I fibers are activated first

Question 16

Which muscle type is activated first electrically?

Answer 16

Largest diameter Type II muscle fibers are activated first

Question 17

Should GTOs be electrically stimulated?

Answer 17

No

Question 18

Are electrically stimulated contractions effective at strengthening muscle fibers weakened by disuse?

Answer 18

Yes

Question 19

Electrically stimulated contractions are ____ fatiguing, thus ___ rest times are needed between contractions.

Answer 19

more

long

Question 20

Where is the place in a muscle in which electrical stimulation will produce the greatest contraction with the least amount of electricity? Why?

Answer 20

Over the middle of the muscle belly, because this is where the muscle is the most superficial

Question 21

How far apart must electrodes be placed in order for a current to form?

Answer 21

2 inches

*Make sure the size of one of your electrodes can fit in the space between the electrodes

Question 22

Describe monopolar electrode application

Answer 22

One or more small active electrodes are placed over a treatment area and a large dispersive electrode is placed somewhere else on the body

Question 23

When utilizing monopolar electrode application where should the higher current density be?

Answer 23

Under the one electrode over the treatment area

Question 24

Describe quadripolar electrode application

Answer 24

Two sets of bipolar electrodes; each of which comes from a completely separate channel on the electrical stimulator.

Question 25

What is the purpose/proposed benefit of the crisscross pattern?

Answer 25

You can treat the area more focally and deeper

Question 26

The _____the load placed on a muscle, and the ____ force contraction it produces, the more strength that muscle will gain.

Answer 26

greater

higher

Question 27

How do you increase the force of muscle contraction electrically?

Answer 27

Increase the intensity

Question 28

What are the 3 Physiologic Responses to Electric Current?

Answer 28

• Thermal
• Chemical
• Physiologic

Question 29

What are electrical currents used to do?

Answer 29

Produce muscle contractions and modify pain impulses

Question 30

When would you use muscle re-education over muscle strengthening?

Answer 30

When someone has a decent quality contraction, but require more cueing

Question 31

How does electrical current activate the receptor cites on nonexcitable cells?

Answer 31

It stimulates the cellular changes that occur naturally with chemical molecular stimulation

Question 32

Denervated muscle must be stimulated via what type of current?

Answer 32

Continuous direct current

Question 33

Stimulation of denervated muscle must last more than __ ms

Answer 33

10

Question 34

When stimulating denervated what must the ratio of stimulus to pause be?

Answer 34

1:4 or 1:5

Question 35

What happens when a muscle membrane receives a second stimulus?

Answer 35

There is an increased mechanical shortening of the muscle fiber, due to the superimposing of one twitch contraction on another. This can lead to tetanus

Question 36

What common stimulant can block the affect of TENS?

Answer 36

Caffeine blocks the nicotinic receptors on the effector organ

Question 37

How does botulinum affect neuromuscular potential transmission?

Answer 37

It inhibits Ca2+ induced vesicle release from presynaptic terminals and degeneration of the terminals

Question 38

How does lidocaine and other local anesthetics affect neuromuscular potential transmission?

Answer 38

It prevents the generation and transmission of action potentials by blocking Na+ channels

Question 39

What neurons are the first to be blocked by lidocaine?

Answer 39

Small-diameter neurons that transmit pain information are the first to be blocked

Question 40

Myasthenia Gravis is a pathology characterized by a lack of what type of receptor? What does this result in?

Answer 40

ACh

Therefore, muscles are not able to contract as well, and when they do they fatigue quickly. This means that they will be greatly impacted by the use of TENS

Question 41

What is multiple sclerosis?

Answer 41

The demyelination of nerves in the CNS

Question 42

How are nerves in the CNS demyelinated?

Answer 42

By autoimmune factors or scarring/sclerosis on the myelin of the nerves

Question 43

What is the result of multiple sclerosis?

Answer 43

There is slow or absent conduction of impulses

Question 44

Can you use e-stim on patients who are on blood thinners? Why or why not?

Answer 44

No, because their potential for bleeding is higher

Question 45

Can you use e-stim on patients who with sickle cell anemia or hemophiliacs? Why or why not?

Answer 45

No, because it may cause clot deformation

Question 46

What is one of the most important things to do when preparing a patient for electrical stimulation?

Answer 46

assess sensation