muscles, control of body movement (ch 12, ch 13)

Question 1

muscle unit

Answer 1

all the muscle fibers innervated by a single motor neuron
all the fibers in an unit are of a single twitch type

Question 2

types of muscle fibers

(skeletal muscle)

Answer 2

slow-twitch - dark red muscle, fatigue resistant, more myoglobin, more capillaries, thinner fibers - used for maintaining posture, walking, standing
fast-twitch (oxidative-glycolytic - middle
and glycolytic - white muscle, less fatigue resistant, less myoglobin) - used for fast fine movement

Question 3

multiple muscle cells form

(skeletal muscle)

Answer 3

a muscle fascicle

Question 4

multiple myofibrils form …
myofibrils are formed from …

(skeletal muscle)

Answer 4

a muscle cell (along with other cell components - multiple nuclei, mitochondria, sarcoplasmatic reticuli)
sarcomeres

Question 5

sarcolemma

Answer 5

plasma membrane of muslce cell

Question 6

T tubules

Answer 6

invaginations of the sarcolemma that reach deep into the muscle cell, circulating the action potential to the interior of the cell (sarcoplasmatic reticulum)

Question 7

sarcomere (components)

Answer 7

thin actin fibers connected to the Z disk, associated with tropomyosin and troponin, thick myosin fibers, elastic elements (titin and nebulin)

Question 8

twitch

Answer 8

a single contraction-relaxation cycle

Question 9

neuromuscular junction + EC coupling events

skeletal muscle

Answer 9

action potential reaches the end of the somatic motor neuron; voltage gated Ca2+ channels open, influx of calcium triggers exocytosis of ACh-filled vesicles; ACh is released onto motor end plate of the muscle cell; ACh binds ligand gated monovalent cation channels (more Na out than K in -> depolarization of sarcolemma), action potential is triggered, it travels down the T tubule, where it opens a voltage gated Ca2+ channel that is mechanically linked to Ca2+ channels in the SR -> cytoplasmatic calcium influx -> contraction -> Ca2+ pumped back into SR by Ca2+-ATPase pump

Question 10

sliding fialment theory

Answer 10

Ca2+ binds to troponin, which dislodges tropomyosin from the grooves of the F-actin, revealing binding sites for myosin
the myosin heads each bind G-actin and release Pi (orthophosphate) upon binding, executing a power stroke that pulls the actin fiber towards the M line (with the stored energy from ATP hydrolysis)
ADP is released
myosin binds ATP which reduces its affinity for G-actin
myosin hydrolyses the ATP and restarts the cycle

Question 11

epinephrine binding alpha adrenergic receptors on smooth muscle cells causes….1
epinephrine binding beta 2 adrenergic receptors on smooth muscle cells causes….2

Answer 11

1 smooth muscle contraction
2 smooth muscle relaxation