Skeletal Muscle II

Question 1

what is the outer coat made of

Answer 1

thin layer of material that contains many thin collagen fibers

Question 2

titin

Answer 2

large protein molecule that holds myosin and actin filaments in place

Question 3

what is titin attached to

Answer 3

Z line and myosin thick filament

Question 4

diseases caused by titin mutations

Answer 4

hereditary myopathy with early repiratory failure

familial dilated cardiomyopathy

Question 5

function of Sarcoplasmic reticulum

Answer 5

stores Ca++, releases Ca++ into muscle cytosol

Question 6

dystrophin

Answer 6

large protein that forms a rod that connects thin actin filaments to a transmembrane protein

Question 7

troponin I

Answer 7

has affinity to actin

Question 8

what happens when Ca++ binds to troponin C

Answer 8

acuses tropomyosin to move, expose active site on actin where myosin can bind

Question 9

what happens when ATP binds to head of myosin heaby chain

Answer 9

reduces affinity of myosin for actin.

Question 10

if all cross-bridges in the muscle have ATP bound to them, then the muscle is what

Answer 10

relaxed

Question 11

what happens when ATP is hydrolysized

Answer 11

myosin head pivots into cocked position,

Question 12

what happens during the cross bridge formation

Answer 12

myosin ADP-Pi complexbinds to new position of actin filament

Question 13

what happens with Pi is released from myosin

Answer 13

power stroke is triggered

Question 14

what happens when ADP is released from myosin

Answer 14

cycle is complete. actin and myosin are still bound so you have a rigid state

Question 15

how does end-plate-potential spread

Answer 15

passively to area of muscle cell membrane that has voltage regulated Na+ channels

Question 16

function of L-type Ca++ channels in T tubules

Answer 16

voltage sensors.

Question 17

what id another name of L-type Ca++ channels

Answer 17

DHP receptors

Question 18

what happens when DHP receptor channels open

Answer 18

cause Ca++ release channels to open, Ca++ rapidly leaves SR and spreads into myofibrisl

Question 19

another name for Ca++ release channels

Answer 19

ryanodine receptors

Question 20

what causes central core disease

Answer 20

muation in ryanodine receptor 1 gene

Question 21

what does excitatory pulse of Ca++ cause

Answer 21

contraction

Question 22

how is Ca++ pumped back into SR

Answer 22

Ca++ ATPase pump

Question 23

what inhibits Ca++ ATPase pump

Answer 23

high Ca++ conc in SR lumen

Question 24

most important binding protein in skeletal muscle SR

Answer 24

calsequstrin

Question 25

what happens when Ca++ levels fall in myofibirl

Answer 25

active sites on actin are covered, muscle cell stops contracting

Question 26

what is cross bridge cycling regulated by

Answer 26

Ca++ conc in myofibirls

Question 27

which is longer - duration of uscle action potential or the duration of conctraction caused by single action potential

Answer 27

duration of contraction

Question 28

how much ATP do muscle cells contral

Answer 28

only enough for a few seconds of max contractions

Question 29

ways muscle cells can regenerate ATP

Answer 29

• use phosphocreatine to rephosphorylate ADP to ATP
• glycogen metabolism
• oxidative and./or anaerovic metabolism

Question 30

usually an AP in motor neuron will cause what

Answer 30

AP in all the muscle fibers of that motor unit

Question 31

isometric contraction

Answer 31

muscle does not shorten

Question 32

isotonic contraction

Answer 32

muscle does shorten, but tension remains constant