Muscular System

Question 1

skeletal muscle

Answer 1

• voluntary movement
• somatic NS
• actin and myosin in repeating units called sarcomeres
• striated
• red and white fibers

Question 2

red fibers

Answer 2

• skeletal muscle slow twitch fibers
• high myoglobin content, derive energy aerobically
• contain mitochondria and carry out oxidative phosphorylation

Question 3

white fibers

Answer 3

• skeletal muscle fibers fast-twitch
• less myoglobin

Question 4

smooth muscle

Answer 4

• involuntary action
• autonomic NS
• single nucleus at the center of the cell
• actin and myosin but fibers not as well seen, no striations
• sustained contractions, tonus

Question 5

myogenic activity

Answer 5

• smooth and cardiac muscle can contract without NS input

Question 6

cardiac muscle

Answer 6

• smooth and skeletal muscle types
• uninucleated primarily, some cells may have two nuclei
• involuntary contraction, autonomic NS
• striated

Question 7

how do cardiac cells communicate?

Answer 7

• they are connected through intercalated discs and contains many gap junctions through which ions flow and allow for rapid depolarization
• maintain their own rhythm
• SA node, AV node, bundle of His, Purkinje fibers

Question 8

how does NS affect heart rate?

Answer 8

• vagus nerve provides sympathetic outflow to the heart and slows HR

Question 9

how does endocrine system affect HR?

Answer 9

NE from sympathetic neurons of Epi from adrenal medulla binds to adrenergic receptors in the heart which causes inc HR and greater contractility

Question 10

thick filament made of

Answer 10

myosin

Question 11

thin filament made of

Answer 11

actin

Question 12

in a sarcomere, titin acts as a…

Answer 12

spring and anchors actin and myosin together to prevent XS stretching

Question 13

Z line of sarcomere

Answer 13

end of sarcomere

Question 14

M line of sarcomere

Answer 14

• center of sarcomere
• middle of myosin filaments

Question 15

I band

Answer 15

• exclusively thin filaments

Question 16

H zone

Answer 16

• contains only thick filaments

Question 17

A band

Answer 17

contains any thick filaments in their entirety including overlap with thin

Question 18

during contraction of a sarcomere…

Answer 18

• H zone and I band become smaller
• Z lines and M lines get closer
• A band remains constant

Question 19

sarcomeres attach end to end to form

Answer 19

myofibrils

Question 20

myofibrils are surrounded by…

Answer 20

sarcoplasmic reticulum

Question 21

sarcoplasm lies…

Answer 21

outside the SR

Question 22

cell membrane of a myocyte is known as…

Answer 22

• sarcolemma, capable of propagating an action potential using T-tubules

Question 23

each myocyte consists of…

Answer 23

many myofibrils arranged in parallel and can also be called a muscle fiber

Question 24

muscle contraction

Answer 24

• motor neuron sends AP down to the NMJ and releases Ach to attach to the motor end plate
• Ach binds to sarcolemma receptors causing depolarization
• AP travels down to T-tubules to the SR, causing Ca2+ release
• Ca2+ binds to troponin
• change in tropomyosin which exposes the myosin-binding sites on actin
• myosin binds to the actin w a hydrolyzed ATP (ADP + Pi) and causes cross-bridge formation, sarcomere shortening
• power stroke, contraction, ADP + Pi dissociates
• ATP binds to myosin head and it is now free and relaxation is now achieved

Question 25

each nerve terminal…

Answer 25

controls a group of myocytes and this consists of a motor unit

Question 26

muscle cells, like neurons…

Answer 26

exhibit an all-or-nothing response

Question 27

simple twitch

Answer 27

response of a single muscle fiber to a brief stimulus at or above threshold, consists of a latent period

Question 28

if a muscle fiber is exposed to frequent and prolonged stimulation…

Answer 28

it will have insufficient time to relax

Question 29

frequency summation

Answer 29

combined strong prolonged contractions due to frequent stimulation

Question 30

tetanus

Answer 30

- if the contractions become so frequent that the muscle is unable to relax at all - results in muscle fatigue

Question 31

creatine phosphate

Answer 31

- transferring phosphate group from ATP to creatine during times of rest to make it easier to then generate ATP in the reverse rxn

Question 32

what happens to the lactic acid after lactic acid fermentation occurs in both white and red muscle fibers

Answer 32

lactic acid then converted into pyruvate to enter the TCA cycle