Muscle Contraction

Question 1

motor unit

Answer 1

all the muscle fibers innervated by the same motor neuron

Question 2

all-or-none principle

Answer 2

all muscle fibers that make up a motor unit contract fully together

Question 3

the all-or-none principle holds true

Answer 3

at the sarcomere, myofibril, muscle fiber levels, and motor unit levels

Question 4

the all-or-none principle does not apply to

Answer 4

the muscle level; not all motor units always contract at the same time

Question 5

recruitment

Answer 5

the process by which the number of actively contracting motor units is increased

Question 6

types of muscle contraction

Answer 6

isometric and isotonic

Question 7

isometric contraction

Answer 7

a contraction where considerable muscle tension is generated without shortening the muscle

Question 8

isotonic contraction

Answer 8

contraction where shortening of the muscle occurs

Question 9

concentric isotonic contraction

Answer 9

overall length of a muscle decreases during contraction

Question 10

eccentric isotonic contraction

Answer 10

overall length of muscle increases during contraction

Question 11

myogram periods

Answer 11

latent, contraction, relaxation

Question 12

simple twitch

Answer 12

brief contraction of all fibers in a motor unit in response to a single stimulus

Question 13

wave summation

Answer 13

two stimuli that occur close together so that the second stimulus occurs before the muscle can completely relax

Question 14

unfused/incomplete tetanus

Answer 14

multiple stimuli causing repeated wave summations that increase force of contraction due to recruitment

Question 15

fused/complete tetanus

Answer 15

sustained max contraction in which individual contractions are not discernible and the muscle does not relax

Question 16

internal tension

Answer 16

force created by the shortening of sarcomeres and myofibrils within a muscle cell or fiber

Question 17

external tension

Answer 17

force transferred from contracting muscle cells to their connective tissues and the tendons they become a part of

Question 18

external tension transfers to

Answer 18

force at joints to move bones

Question 19

receptors in muscles

Answer 19

muscle spindle and golgi tendon organ

Question 20

muscle spindle

Answer 20

detects dynamic and static changes in muscle length

Question 21

stretch reflex

Answer 21

stretch on muscle causes reflex contraction

Question 22

golgi tendon organ

Answer 22

monitors tension developed in muscle and prevents damage during excessive force generation

Question 23

hormones that regulate muscle activity

Answer 23

growth hormone and testosterone, thyroid hormones, epinephrine

Question 24

growth hormone and testosterone

Answer 24

stimulate the synthesis of contractile proteins and enlarge skeletal muscles

Question 25

thyroid hormones

Answer 25

elevate the rate of energy consumption by resting and active muscles

Question 26

epinephrine

Answer 26

stimulates muscle metabolism and increases both duration and force of contraction