Motor Unit Recruitment

Question 1

Features of muscle contraction can be demonstrated by eliciting single muscle __________

Answer 1

Twitches

Question 2

What are some characteristics of muscle contractions

Answer 2

Involuntary
Visible under the skin
Arises from spontaneous discharge of a bundle of skeletal muscle fibers

Question 3

In the latent period of a single fiber contraction, there is a delay of how much

Answer 3

1-2ms

Question 4

What occurs in the latent period of a single fiber contraction

Answer 4

Impulse travels along sarcolemma and down the t-tubules to sarcoplasmic reticulum (traids)
Ca is released and binds to troponin
Actin active site is exposed 
Myosin binds to actin
Tension is observed

Question 5

How long is the contraction period of a single fiber contraction

Answer 5

10-100 ms

Question 6

What occurs in the contraction period of a single fiber contraction

Answer 6

Tension rises as cross-bridges swivel and pull actin filaments towards the M line
Sarcomere length shorten

Question 7

How long is the relaxation period of the single fiber contraction

Answer 7

10-100ms

Question 8

What occurs in the relaxation period of a single fiber contraction

Answer 8

Muscle relaxes as tension decreases with unflexing of myosin heads and calcium sequestration
Sarcomere length returns to its original length

Question 9

What are the two ways in which muscle can contract

Answer 9

Isometric contraction, Isotonic Contraction

Question 10

What does isometric contraction involve

Answer 10

Maintenance of constant muscle length

Question 11

True or false, isometric contraction involves a contracted muscle against a load as it is unable to shorten because load is great

Answer 11

True

Question 12

In Isometric Contraction, Energy is released as _______ rather than through performance

Answer 12

Heat

Question 13

Give examples of isometric contraction

Answer 13

Pushing against a wall
Holding a weight in fixed position
Holding a stack of books
Body building Pose

Question 14

Isotonic contraction, involves maintenance of ________

Answer 14

Constant muscle tension

Question 15

True or false, Isotonic Contractions involve contracted muscle against a load due to the muscles maximal force of contraction exceeding the total load on the muscle

Answer 15

True

Question 16

True or false, in isotonic contraction, muscle shortens in length (concentric), or lengthens (eccentric)

Answer 16

True

Question 17

Give examples of isotonic contraction

Answer 17

Bicep curls, swimming, cycling, running

Question 18

What is the term given to the adding of individual twitch contractions to increase the intensity of overall muscle contract

Answer 18

Summation

Question 19

What are the two ways in which summation occurs

Answer 19

Multiple fibers (motor unit) summation
Frequency (wave) summation

Question 20

What type of summation occurs when there is an increasing number of motor units contracting simultaneously

Answer 20

Multiple fiber (motor unit) summation

Question 21

What type of summation occurs when there is an increase in the frequency of contraction

Answer 21

Frequency wave summation

Question 22

True or false, frequency summation occurs when there is a series of twitch contractions occurring one after the other at low frequency of stimulation

Answer 22

True

Question 23

Frequency summation leads to

Answer 23

Treppe (the staircase effect)

Tetany/tetanization/tetanus

Question 24

How does tetany arise

Answer 24

When enough calcium ions are maintained in the muscle sarcoplasm, even between APs, so that full contractile state is sustained without allowing any relaxation between the APs

Question 25

What is treppe

Answer 25

Gradual increase in the strength of a muscle contraction to a plateau following rapidly repeated stimulation after a quiescent period

Question 26

True or false, When a muscle begins to contract after a long period of rest, it’s initial strength of contraction may be as little as one half of its strength to 10 to 50 muscle twitches later

Answer 26

True

Question 27

What is the primary cause of treppe ie the staircase effect

Answer 27

Increasing Ca2+ in the cystol because of the release of more and more ions from the SR with each successive muscle AP Failure of SR to recapture the ions immediately

Question 28

True or false, fatigue increases almost directly proportional to the rate of deletion of glycogen in the muscle

Answer 28

True

Question 29

What causes muscle fatigue

Answer 29

Prolonged and strong contraction of muscles

Question 30

According to Columbia university, what is the cause of fatigue

Answer 30

Calcium leaking into the muscle cells

Question 31

True or false, treppe can lead to fatigue

Answer 31

True

Question 32

If blood flow is interrupted while a muscle is contracting, almost complete muscle fatigue occurs within _________ minutes, due to a low supply of ________

Answer 32

1 or 2 minutes, oxygen

Question 33

What can muscles provide alterations in, in order to better suit the function that is required

Answer 33

``` Diameter Length Strength Vascular supply Type of muscle fibers ```

Question 34

What is muscle hypertrophy

Answer 34

When the total muscle mass increases due to an increase in size of fibers

Question 35

I’m fiber Hyperplasia, though rare may arise in _____

Answer 35

Increase in fiber number

Question 36

In Denervation sensitivity, there is promoted expression of _________ receptors on the sarcolemma

Answer 36

Nicotiinc acetylcholine receptors

Question 37

True or false, rigor Mortis occurs when muscle fibers are completely depleted of ATP

Answer 37

True

Question 38

True or false, in rigor mortis, nearly all the myosin heads are attached to actin but in a fixed abnormal and resistant manner

Answer 38

True

Question 39

Muscles remain in rigor until the muscle proteins deteriorate in _________, this is as a result from ________

Answer 39

15-25 hours later, Enzymic autolysis

Question 40

True or false, temperature increases the speed of the effects of rigor mortis

Answer 40

True