Muscle Physiology Pt. 2

Question 1

It is the force generated by muscle fiber in order to oppose a force (load) exerted on the muscle by an object

Answer 1

Tension

Question 2

It is the mechanical response of a muscle fiber to a single action potential

Answer 2

Twitch

Question 3

What are the three phases of twitch contraction?

Answer 3

1. Latent Period
2. Contraction Period
3. Relaxation Period

Question 4

This period is the time from action potential to the onset of contraction

Answer 4

Latent period

Question 5

This period is the time that tension is developing due to cross-bridge cycling of actin and myosin filaments

Answer 5

Contraction period

Question 6

This period is the time the tension is decreasing due to the time it takes to receive all Ca2+

Answer 6

Relaxation period

Question 7

What are the two types of twitch contraction?

Answer 7

Isometric and Isotonic Twitch

Question 8

This twitch generates tension but does not shorten muscle; tension is high, but there is not much change in the muscle

Answer 8

Isometric twitch

Question 9

This twitch shortens the muscle; tension is not as high, but the muscle contracts

Answer 9

Isotonic twitch

Question 10

This relationship indicates that:
- The lighter the load, the less shortening of muscle, the bigger the distance, while
- The heavier the load, the shorter the time a person is able to carry it, the smaller the distance

Answer 10

Load-Velocity Relationship

Question 11

This relationships is when single action potentials lasts only 1-2 ms; twitch may last for 100 ms

Answer 11

Frequency-Tension Relationship

Question 12

Increase in muscle tension from successive action potentials occurring during the phase of mechanical activity

Answer 12

Summation

Question 13

Maintained contraction in response to repetitive stimulation

Answer 13

Tetanus

Question 14

This occurs when skeletal muscle fiber is repeatedly stimulated, causing tension to eventually decrease even if stimulation continues

Answer 14

Muscle fatigue

Question 15

In muscle fatigue, velocity __________ and rate of relaxation __________

Answer 15

Shortens; Slows down

Question 16

What are the three potential causes of muscle fatigue?

Answer 16

1. Conduction failure
2. Lactic acid build-up
3. Inhibition of cross-bridge recycling

Question 17

This is a result from build-up of K+ in T-tubule during repolarization of repetitive action potentials

Answer 17

Conduction failure

Question 18

Acidification of muscle by lactic acid may change muscle proteins, causing __________

Answer 18

Lactic Acid Build-up

Question 19

Build-up of ADP + PI within muscle fibers during intense activity may inhibit cross-bridge

Answer 19

Inhibition of Cross-Bridge Recycling

Question 20

Classification of muscle fibers:

Answer 20

1. Oxidative fibers
2. Glycolytic fibers

Question 21

Type of muscle fiber that has combined low myosin-ATPase activity with high oxidative capacity

Answer 21

Slow-oxidative fibers (Type I)

Question 22

Type of muscle fiber that has combines high myosin-ATPase activity within high glycolytic capacity

Answer 22

Fast-glycolytic fibers (Type IIB)

Question 23

Type of muscle fiber with combined high myosin-ATPase activity within high oxidative capacity and intermediate glycolytic capacity

Answer 23

Fast-oxidative-glycolytic fibers (Type IIA)

Question 24

Fourth possibility of muscle fiber that is generally not found

Answer 24

Slow-glycolytic fibers

Question 25

Muscle tension is affected by two factors. What are they?

Answer 25

1. Amount of tension developed by each fiber
2. Number of fibers contracting at any time

Question 26

Two types of muscle atrophy

Answer 26

1. Disuse atrophy
2. Denervation atrophy

Question 27

Type of atrophy in which nerves are intact and appearance becomes small if not used in a long time

Answer 27

Disuse atrophy

Question 28

Type of atrophy that causes muscles to become smaller in diameter and decreases in the number of contractile proteins

Answer 28

Denervation atrophy

Question 29

Muscle disorder with involuntary tetanic contraction of skeletal muscles and action potentials fire at abnormally high rates

Answer 29

Muscle cramps

Question 30

Muscle disorder with involuntary tetanic contraction of skeletal muscles, in which extracellular Ca2+ concentration falls to +- 40% of normal value

Answer 30

Hypocalcemic Tetany

Question 31

Muscle disorder that is also referred to as “Polio”; It is a viral disease that destroys motor neurons and leads to the paralysis of skeletal muscles

Answer 31

Poliomyelitis

Question 32

Muscle disorder with progressive degeneration of skeletal and cardiac muscle fibers

Answer 32

Muscular dystrophy

Question 33

It is a sex-linked recessive disorder (X chromosome) that is often seen in children

Answer 33

Duchenne Muscular Dystrophy (DMD)

Question 34

This is due to the destruction of nicotinic ACh receptor proteins of the motor end plate due to autoimmunity

Answer 34

Myasthenia gravis

Question 35

This type of muscle is spindle/fusiform-shaped with thick myosin-containing filaments and thin actin-containing filaments and tropomyosin

Answer 35

Smooth muscle

Question 36

What are the two sources of Ca2+ in smooth muscles?

Answer 36

1. Sarcoplasmic reticulum
2. Extracellular Ca2+ entering the cell through plasma membrane Ca2+ channels

Question 37

This is done by Myosin Light Chain Kinase (MLCK)

Answer 37

Cross-bridge activation

Question 38

This is influenced by autonomic neuron endings and does not have a specialized motor end plate region

Answer 38

Neural and hormonal control

Question 39

Membrane potential change occurring during the spontaneous depolarization to threshold

Answer 39

Pacemaker potential

Question 40

Membrane potential drifts up and down due to regular variation in ion influx across the membrane

Answer 40

Slow waves

Question 41

This type of smooth muscle responds to stimuli as a single unit because cells are connected by gap junctions

Answer 41

Single-unit

Question 42

This type of smooth muscle contains cells that respond to stimuli independently and contain few gap junctions

Answer 42

Multi-unit

Question 43

This type of muscle is striated and uses sliding filament to contract

Answer 43

Cardiac muscle

Question 44

This prevents tetanic contraction in cardiac muscles

Answer 44

Absolute Refractory Period (250 ms)