Skeletal Muscle

Question 1

alpha-actinin

Answer 1

actin-binding protein; comprises the Z disk

Question 2

A-band

Answer 2

where actin and myosin overlap

Question 3

actin

Answer 3

thin filaments

Question 4

H band

Answer 4

band with myosin but no actin

Question 5

I band

Answer 5

actin but no myosin, attaches so Z disk

Question 6

M line

Answer 6

where myosin attaches; middle of sarcomere

Question 7

nebulin

Answer 7

regulates actin filament length during sarcomere assembly

Question 8

titin

Answer 8

helps maintain resting length of sarcomere

Question 9

Z disk

Answer 9

where actin attaches

Question 10

transverse tubule

Answer 10

invaginations of the plasma membrane that is open to the outside; where AP travels to release calcium

Question 11

What type of channel is located on the T tubule?

Answer 11

L-type Ca++ channel; opens due to chemical stimulation

Question 12

skeletal muscle contraction

Answer 12

AP travels down T tubule –> binds the L-type Ca++ channel and opens it –> L-type channel mechanically opens the Ca++ release channel on the SR –> calcium exits the SR and activates troponin C

Question 13

tropomyosin

Answer 13

regulates the binding of myosin head to actin –> troponin binds this to move it out of way

Question 14

troponin T

Answer 14

binds tropomyosin

Question 15

troponin C

Answer 15

binds calcium

Question 16

troponin I

Answer 16

binds to actin and inhibits contraction

Question 17

alkali light chains of myosin

Answer 17

stabilize the head region

Question 18

regulatory light chains of myosin head

Answer 18

regulate ATPase activity of myosin

Question 19

When does TnI cover the myosin binding site?

Answer 19

in the absence of Ca++

Question 20

phosphate release

Answer 20

power stroke

Question 21

cross bridge cycle

Answer 21

myosin head forms a cross bridge with actin (ADP and Pi are attached) –> myosin head bends, releasing ADP and Pi for the power stroke –> new molecule of ATP binds, causing myosin to detach –> ATP hydrolyzes to ADP and Pi, which returns myosin to cocked position

Question 22

termination of contraction

Answer 22

requires re-uptake of Ca++

Question 23

re-uptake of Ca++

Answer 23

calcium is stored in the SR via the Ca++/H+ pump (primary active); PMCA pump on membrane extrudes calcium (primary active); Na+/Ca++ pump on membrane extrudes calcium (secondary active)

Question 24

isotonic

Answer 24

same tension

Question 25

isometric

Answer 25

same length

Question 26

temporal summation

Answer 26

stimulation before complete relaxation causes a greater contraction (more tension)

Question 27

tetanus

Answer 27

no relaxation, plateau of tension

Question 28

motor unit

Answer 28

a single muscle neuron and the muscle fibers that it innervates

Question 29

motor neuron pool

Answer 29

all the motor neurons that innervate a single muscle

Question 30

skeletal synapses are _

Answer 30

chemical

Question 31

electrical synapse

Answer 31

directly link cytoplasm of adjacent cells; connexon channels of gap junctions

Question 32

chemical synapse

Answer 32

NTs synthesized and packaged in vesicles –> AP arrives at presynaptic terminal –> VG-Ca++ channels open and Ca++ enters –> rise of Ca++ causes fusion of synaptic vesicles with presynaptic membrane –> transmitter molecules diffuse across synaptic cleft and bind to receptors on postsynaptic cell

Question 33

action potential stimulation

Answer 33

Na+ enters cell and depolarizes it

Question 34

end of action potential

Answer 34

K+ exits cell for repolarization

Question 35

ionotropic receptors are _

Answer 35

skeletal; stimulate muscle contraction

Question 36

metabotropic receptors are found in _

Answer 36

heart; can inhibit muscle contraction with Ach binding