Chapter 10 - Muscles & Muscle Tissue (Continued)

Question 1

Muscle physiology

Answer 1

how muscles contract

Question 2

Sliding filament model

Answer 2

filaments do not shorten; proteins do not shorten; thin filaments slide toward center of thick filaments & cause the sarcomeres to shorten

Question 3

Fully contracted muscle

Answer 3

thin & thick filaments completely overlap each other & shortens the myofibrils & the muscle fibers shorten; entire muscle shortens causes bone to move bc muscle is attached to tendons which is attached to bones

Question 4

Physiology of skeletal muscle fiber contraction (all 3 triggers need to happen)

Answer 4

1. Acetylcholine
2. Action potentials
3. Ca++ (Calcium released)

Question 5

Location/Events of 1st trigger - Acetylcholine

Answer 5

Neuromuscular junction - nerve cells stimulates muscle fiber; junction between neuron & muscle fiber

Question 6

Location/Events of 2nd trigger - Action Potentials

Answer 6

generation of electrical signal along sarcolemma & t-tubules; gets inside cell; cause sarcoplasmic reticulum to be “leaky” & Ca is released (high to low concentration)

Question 7

Location/Events of 3rd trigger - Ca++

Answer 7

sarcoplasmic reticulum releases Ca++ into sarcoplasm; muscle fiber contraction–thin filaments slide past thick filaments

Question 8

Neurotransmitter

Answer 8

chemical released by neurons; 100 known released in body

Question 9

Contraction Cycle/Cross Bridge Cycle

Answer 9

smaller scale what is happening between actin & myosin; Ca binds to one protein - Troponin & troponin changes shape & pushes on tropomyosin & essentially unblocks all binding sites & begins contractions; every actin has a binding site for myosin

Question 10

Steps of Contraction Cycle/Cross Bridge Cycle

Answer 10

1. BINDING step/ATTACHMENT - myosin head binds to the actin
2. MOVEMENT due to bending of myosin head
3. DETACHMENT - requires ATP; causes myosin head to detach; actin & myosin separate
4. RESETTING of myosin head (so it can bind again); ATP is hydrolyzed; phosphate comes off & now ADP; releases chem energy that reenergizes myosin head so it can bind again

Question 11

Contraction cycle starts again & binds @ a different spot

Answer 11

after many, many contraction cycles, the myosin head moves along the actin (thick & thin filaments slide across each other)

Question 12

Rigor mortis

Answer 12

body gets rigid after death; no ATP; actin & myosin are attached permanently & causes muscle to stiffen & harden

Question 13

Control of muscle tension

Answer 13

the more motor units activated, the more muscle fibers & myofibrils shorten & the greater the force of muscle contraction

Question 14

motor unit

Answer 14

motor neuron & all the muscle fibers it stimulates; stimulates myofibrils to shorten

Question 15

muscle twitch

Answer 15

contraction of all muscle fibers of the motor unit when stimulated

Question 16

latent period

Answer 16

delay time between stimulus & contraction; 3 triggers must occur before muscle contracts; that’s why there is a delay

Question 17

contraction period

Answer 17

period of time when muscle is contracting

Question 18

relaxation period

Answer 18

period of time when muscle is relaxing; begins when a stimulus is stopped; acetylcholine is no longer released

Question 19

refractory period

Answer 19

period of time when muscle cannot contract even when stimulated; period of unresponsiveness; muscle is responding to 1st stimulus & disrupts initial contraction; to protect 1st contraction

Question 20

acetylcholine

Answer 20

neurotransmitter released at the neuromuscular junction; chemical; causes action potentials to occur

Question 21

Action potential

Answer 21

electrical impulse generated along the sarcolemma (and axolemma); causes Ca to be released