Muscle Contraction

Question 1

The latent period is marked by an

Answer 1

action potential reaching the T tubule

Question 2

Relaxation phase

Answer 2

Ca2+ flow back into the NMJ, myosin detaches from action.

Question 3

Treppe

Answer 3

an increase in peak tension with each successive stimulus delivered shortly after the completion of the relaxation phase of the preceding twitch (allows relaxation).

Question 4

Complete tetanus

Answer 4

stimulus frequency is so high that the relaxation phase is eliminated. Tension plateaus at a maximum level. (complete fatigue)

Question 5

Wave summation

Answer 5

occurs when successive stimuli arrive before the relaxation phase has been completed (doesn’t allow it to relax).

Question 6

incomplete tetanus

Answer 6

occurs if the stimulus frequency increases further, but you’re giving them a break before then. Tension production rises to a peak, and the periods of relaxation are very brief.

Question 7

All the fibers in a motor unit all

Answer 7

contract at the same time

Question 8

motor units controlling few muscle fibers activate ____ while those with a lot activate ____.

Answer 8

first, last

Question 9

Recruitment is the

Answer 9

increase in the number of motor neurons.

Question 10

The smaller the load, the ____ the contraction.

Answer 10

bigger

Question 11

small fibers lack ____ and ___

Answer 11

myoglobin and blood

Question 12

Because small fibers lack ___ and ___, they rely on ____

Answer 12

myoglobin, blood, anaerobic metabolism

Question 13

Three types of skeletal muscle fibers:

Answer 13

fast, slow, intermediate

Question 14

muscle hypertrophy aims to

Answer 14

strength muscles by growth; increases diameter of muscle fibers (not making more) number of myofibrils, number of mitochondria, glycogen reserves, higher concentration of glycolytic enzymes to make ATP

Question 15

Muscle Atrophy

Answer 15

reduction of muscle size, tone, and power due to lack of activity. This is an adaptation trait.

Question 16

Muscle Fatigue

Answer 16

Depletion of metabolic reserves, damage to sarcolemma + sarcoplasmic reticulum, decline in pH, which affects calcium ion binding and alters enzyme activities.

Question 17

Anaerobic endurance

Answer 17

uses fast fibers and stimulates hypertrophy and is I imported by frequent, brief, intensive workouts

Question 18

Aerobic endurance (prolonged activities)

Answer 18

supported by mitochondria does not stimulate muscle hypertrophy, training involves sustained, low levels of activity

Question 19

Differences between Cardiac and Skeletal muscles

Answer 19

Smaller, branched with one nucleus, almost completely dependent on aerobic metabolism; many mitochondria and myoglobin, contact each other via intercalated discs.

Short, wide T tubules; no triad
have SR with no terminal cisternae.

Question 20

Automaticity

Answer 20

Contraction without neural stimulation
Controlled by pacemaker cells

Question 21

Nervous system can alter heart rate by

Answer 21

altering pace and tension of contractions

Question 22

Cardiac muscles stay at _______ that are longer than skeletal muscles

Answer 22

refractory periods

Question 24

Characteristics of a smooth muscle:

Answer 24

spindle-shaped cells
single, central nucleus
no T tubules, myofibrils, or sarcomeres
nonstriated muscle
thin filaments attached to dense bodies
no tendons

Question 25

T tubules send action potentials transversely into the

Answer 25

muscle fiber