Chapter 9

Question 0

Myofibrils

Answer 0

thousands of rodlike bundles of contractile filaments, that run parallel to the length of the muscle fibers. They account for about 80% of cellular volume.

Question 1

Four important functions of muscle tissue

Answer 1

Produces movement, maintains posture, stabilizes joints and generates heat

Question 2

Sarcoplasmic reticulum

Answer 2

specialize endoplasmic reticulum of muscle cells

Question 3

T Tubules

Answer 3

Extension of the muscle cells plasma membrane (sarcolemma) that protrudes deeply into the muscle cell.

Question 4

How is action potential generated?

Answer 4

The inside of the cells is negatively charged while the outside is positively charged. Next Na+ (sodium) and K+ (potassium) ions in and surrounding the cell, there are more on the outside though (more positive on the outside). When a neuron is stimulated, an electric current stimulates a voltage gated sodium channel to open, and sodium ions rush into the cell, causing the charge inside to rise. In order for an action potential to be generated the sodium ions rushing in have to increase the charge in the cell to the threshold potential. once the cell depolarize the potassium channels open too, and constantly release potassium from the inside, causing the charge inside the cell to drop. potassium leaks out until the charge of the cell is below the resting action potential.

Question 5

Action Potential

Answer 5

A large transient depolarization event, including polarity reversal , that is conducted along the membrane of a muscle cell or a nerve fiber

Question 6

Motor Unit

Answer 6

a motor neuron and all the muscle cells it stimulates

Question 7

Muscle twitch

Answer 7

the response of a muscle to a single brief threshold stimulus.

Question 8

Isometric contractions

Answer 8

Contraction in which the muscle does not shorten (the load is too heavy) but its internal tension increases

Question 9

Isotonic Contraction

Answer 9

Contraction in which muscle tension remains constant at a given load, and the muscle shortens.

Question 10

Follow the events of excitation contraction coupling that lead to cross bridge activity

Answer 10

Sequence of events by which transmission of an AP along the sarcolemma leads to sliding of the myofilaments

Question 11

Describe three ways in which ATP is regenerated during skeletal muscle contraction

Answer 11

1. Direct phosphorylation of ADP by creatine phosphate (CP) couple reaction of creatine phosphate and ADP)
2. Anaerobic pathway (glycolysis and lactic acid formation), Aerobic respiration, Produces 95% of ATP during rest and light to moderate exercise,
3. Fuels: stored glycogen, then bloodborne glucose, pyruvic acid from glycolysis and free fatty acids.

Question 12

EPOC

Answer 12

Excess post-exercise oxygen consumption. The extra amount of oxygen that the body must take in for restorative processes, EPOC represents the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used.

Question 13

For a muscle to return to its resting state, all the following must occur

Answer 13

1. it’s oxygen reserves in myoglobin must be replenished
2. the accumulated lactic acid must be reconverted to pyruvic acid.
3. Glycogen stores must be replaced
4. ATP and creatine phosphate reserves must be resynthesized

Question 14

Muscle fatigue

Answer 14

a state of physiological inability to contract even though the muscle still may be receiving stimuli

Question 15

possible causes of muscle fatigue

Answer 15

problems in excitation-contraction or problems at the neuromuscular junction.

Question 16

Three types of skeletal muscle fibers

Answer 16

Slow oxidative fibers, fast oxidative fibers, fast glycolytic fibers

Question 17

Slow oxidative fibers

Answer 17

slow contraction, Aerobic, high myoglobin content, low glycogen, fatigue resistant. Best suited for endurance type activities (running a marathon, maintaining posture) red in color

Question 18

Fast oxidative fibers

Answer 18

fast contraction, Aerobic, high myoglobin content, Moderately fatigue-resistant, best suited for sprinting or walking. red to pink in color.

Question 19

Fast Glycolytic Fibers

Answer 19

Fast contraction, Anaerobic, fatigable, best suited for short-term intense or powerful movements (hitting a baseball) and white in color.

Question 20

effects of Aerobic excercise

Answer 20

also called endurance exercise such as swimming, jogging, biking, can result in several recognizable changes in skeletal muscle. the number os capillaries surrounding the muscle fibers increases, the number of mitochondria within the muscle fibers also increases. The fibers synthesize more myoglobin.

Question 21

Effects of resistant excercise

Answer 21

such as weight lifting, or isometric exercises which pit muscles against high-resistance or immovalbe forces. Here strength, not stamina, is important.