Physiology of Muscle

Question 1

Z line to Z line indicates…

Answer 1

sarcomere, functional unit of skeletal muscle

Question 2

T tubules invaginate the sarcolemma and are adjacent to…

Answer 2

sarcoplasmic reticulum, providing Ca storage

Question 3

thick vs thin filaments

Answer 3

thick- myosin, tail of heavy chains and multiple heads with heavy and light chains

thin- actin/troponin/tropomyosin complex, binding sites on actin blocked by tropomyosin and troponin (sensitive to Ca)

Question 4

motor end plate def

Answer 4

post synaptic region of skeletal muscle cell at NMJ

Question 5

motor unit

Answer 5

all muscle fibers innervated by one somatic motor neuron

Question 6

type of receptor at motor end plate

Answer 6

nicotinic Ach receptor, increases permeability to Na and K to propograte action potential

Question 7

describe end plate potential

Answer 7

Na influx exceeds K efflux, creates depolarizing graded potential

threshold reached every time in human skeletal muscle, voltage gated Na channels open

Question 8

describe skeletal muscle process in response to action potential in sarcolemma/T tubules

Answer 8

L type Ca channels in T tubules (DHP) open, cause Ca to be released from SR via ryanodine receptors (these receptors are coupled mechanically)

Ca diffuses out of SR, causes cross bridging of filaments

Question 9

a single action potential is enough to bind all ____ for cross bridgning in skeletal muscle

Answer 9

troponin sites

allows for actin binding

Question 10

ATP is needed for which part of cross bridging

Answer 10

detachment of the myosin head from actin

Question 11

H Zone

Answer 11

myosin alone

Question 12

A band

Answer 12

zone of overlap of thick and thin filaments w/i a sarcomere

Question 13

I band

Answer 13

only thin actin filaments, centered around Z disc

Question 14

which bands shorten during contraction

Answer 14

HIZ bands

Question 15

how is Ca removed from cytosol

Answer 15

mostly from SERCA, reuptake into SR

Question 16

describe tetanus mechanism

Answer 16

response to repeated stimulation- intracellular Ca never returns to low levels causing continued cross bridging

sustained contraction is called tetanus as opposed to single twitch followed by relaxation

Question 17

Type 1 skeletal muscle has lots of ___

Answer 17

mitochondria, relies on oxidative phosphorylation (low on glycogen)

myoglobin- more of a red color

Question 18

fn of type 1 skeletal muscle

Answer 18

slow twitch- oxidative phosphorylation is a slow process

good for sustained contraction, fatigue resistant

1 SLOW red ox

Question 19

contrast type 2B skeletal muscle to type 1

Answer 19

fewer mitochondria, less myoglobin (appear white)

relies more on glycolysis for energy

fast twitch and fatigues quickly, sprinting and extra ocular muscles

Question 20

describe type 2a skeletal mucles

Answer 20

features of both red and white

fast twitch but has high myoglobin content, relies on oxidative metab

but has lots of glycogen so fatigue resistant

Question 21

action potentials in skeletal muscle don’t summate, but _____ can

Answer 21

contractions can summate to cause tetany if Ca levels remain elevated