10. 4 - 10.7

Question 1

resting membrane potential for skeletal muscle

Answer 1

NEGATIVE 85 mV (-85 mV)

Question 2

excitable membranes

Answer 2

permit rapid communication between different parts of a cell

Question 3

types of excitable membranes

Answer 3

depolarization
hyperpolarization
repolarization

Question 4

depolarization

Answer 4

membrane potential becomes less negative due to influx of sodium ions

Question 5

hyperpolarization

Answer 5

the membrane potential becomes more negative due to outflow of potassium ions

Question 6

repolarization

Answer 6

return to the resting membrane potential after depolorization

Question 7

neuromuscualar junction (NMJ)

Answer 7

the synapse between a motor neuron and a skeletal muscle fiber

Question 8

axon (synaptic) terminal

Answer 8

expanded end of the axons of the motor neuron

Question 9

motor end plate

Answer 9

folded membrane of the skeletal muscle fiber at the NMJ

Question 10

synaptic cleft

Answer 10

narrow space between the axon terminal and the motor end plate

Question 11

neurotransmitter

Answer 11

chemical released from the axon terminal into the synaptic cleft

Question 12

neurotransmitter at the NMJ is

Answer 12

acetylcholine (ACh)

Question 13

excitation-contraction coupling

Answer 13

link between the generation of an action potential in the sarcolemma and the start of muscle contraction

Question 14

steps of excitation-contraction coupling (5)

Question 15

contraction cycle

Answer 15

series of molecular events that enable muscle contraction

Question 16

contraction cycles involved the formation of

Answer 16

cross bridges: myosin heads bind to the active sites on actin

Question 17

power stroke

Answer 17

the myosin head uses energy from ATP to pivot and pull on active towards the M line

Question 18

steps that initiate a muscle contraction

Answer 18

-ACh released
-action potential reaches T tubule
-sarcoplasmic reticulum releases stored calcium ions
-active sites exposed and cross bridges form
- contraction cycle begins

Question 19

steps that end a muscle contraction

Answer 19

-ACh is broken down
- SR reabsorbs calcium ions
-active sites covered and cross bridge formation ends
- contraction ends
- muscle relaxation occurs

Question 20

rigor mortis

Answer 20

muscle stiffens after death resulting from a muscles being locked in a contracted position

Question 21

tension

Answer 21

pull force generated by the muscle when it contracts

Question 22

length tension relationship

Answer 22

tension produced by a muscle fiber relates to the length of the sarcomeres

Question 23

twitch

Answer 23

a single stimulus contraction relaxation sequence

Question 23

myogram

Answer 23

graph showing tension development in muscle fibers

Question 24

phases of a twitch

Answer 24

latent period
contraction phase
relaxation phase

Question 25

latent period

Answer 25

the time it takes from the stimulation to move across the sarcolemma and for the SR to release calcium ions

Question 26

contraction phase

Answer 26

tension increases as the muscle fiber is forming cross bridges and the myosin heads do power strokes

Question 27

relaxation phase

Answer 27

tension decreases as cytosolic calcium ion levels decrease, myosin binding sites on actin are covered by tropomyosin, and cross bridges detach

Question 28

treppe

Answer 28

an increase in peak tension caused by repeated stimulations which happen after the end of each relaxation phase

Question 29

wave summation

Answer 29

increasing tension due to successive stimuli that arrive before the relaxation phase has been completed

Question 30

tetanus

Answer 30

maximum tension

Question 31

incomplete tetanus

Answer 31

the muscle produces near maximum tension due to rapid cycles of contraction and very brief incomplete relaxation

Question 32

complete tetanus

Answer 32

the muscle is in continuous contraction due to high stimulation frequency which eliminates the relaxation phase

Question 33

motor unit

Answer 33

a motor neuron and all the muscle fibers it controls

Question 34

fasciculation

Answer 34

involuntary muscle twitch which is caused by the synchronous contraction of one motor unit

Question 35

recruitment

Answer 35

increase in muscle tension due to the increase of active motor units

Question 36

motor unit summation

Answer 36

“relay” approach in which some motor units are contracting, and some are resting and recovering

Question 37

muscle tone

Answer 37

the resting tension of a skeletal muscle

Question 38

types of muscle contractions

Answer 38

isotonic and isometric

Question 39

isotonic contractions

Answer 39

causes the skeletal muscle to change length

Question 40

isotonic concentric contraction

Answer 40

muscle tension exceeds the load (resistance) and the muscle shortens

Question 41

isotonic eccentric contraction

Answer 41

peak muscle tension is less than the load and the muscle elongates due to gravity or the contraction of another muscle

Question 42

isometric contractions

Answer 42

the skeletal muscle develops tension, but does not change length

Question 43

how does atp transfer energy

Answer 43

atp transfers energy (in the form of a phosphate) to create creatine phosphate (CP)
- catalyzed by the enzyme creatine kinase

Question 44

atp is generated by

Answer 44

glycolysis and aerobic metabolism

Question 45

glycolysis

Answer 45

anaerobic metabolism that breaks down glucose to pyruvate in the cytosol

Question 46

aerobic metabolism

Answer 46

oxygen dependent process in which mitochondria use organic substrates (ex: pyruvate) to produce atp

Question 47

recovery period

Answer 47

the time required for muscles to return to pre-exertion conditions

Question 48

oxygen debt/excess postexercise oxygen consumption

Answer 48

the amount of oxygen required to restore normal pre-exertion conditions