CARDIAC MUSCLE

Question 1

what is a myocyte

Answer 1

cardiac muscle cell

Question 2

what do myocytes have

Answer 2

branches

Question 3

what connects individual myocytes

Answer 3

intercalated disks

Question 4

what is located in intercalated disks

Answer 4

1. desmosomes

2. gap junctions

Question 5

what is the function of desmosomes

Answer 5

mechanically / physically couple myocytes

Question 6

what are gap junctions

Answer 6

trasnmem channels linking cyto of adjacent cells

Question 7

what is the function of gap junctions

Answer 7

electrically couple myocytes

Question 8

what is the structure of thin filaments in cardiac muscle

Answer 8

2 strands of F actin wrapped together to form alpha helix

Question 9

what is the structure of tropomyosin in cardiac muscle

Answer 9

2 alpha helices

Question 10

what is the structure of troponin in cardiac muscle

Answer 10

TnT binds tropomyosin
TnC binds Ca
TnI binds actin to inhibit contraction

Question 11

how does nebulin in cardiac muscle differ from nebulin in skeletal muscle

Answer 11

smaller

Question 12

what is the function of titin in cardiac myocytes

Answer 12

provides recoil after contraction

Question 13

what regulates contraction of myocytes

Answer 13

Ca conc

Question 14

how do t tubules and ST of myocytes differ from that of skeletal muscle fibres

Answer 14

less organized

Question 15

how do invaginations in myocytes differ from that of skeletal muscle fibres

Answer 15

bigger

Question 16

how many SR cisternae associated w T tubules in myocytes

Answer 16

1 (dyad)

Question 17

what innervates heart

Answer 17

1. parasympathetic division of ANS

2. sympathetic division of ANS

Question 18

what happens when there is increase in intracellular Ca

Answer 18

contraction

Question 19

how is TnC in cardiac muscle diff from TnC in skeletal muscle

Answer 19

• cardiac ==> 1 low affinity Ca binding site

- skeletal ==> 2 low affinity Ca binding sites

Question 20

what source of Ca is cardiac muscle dependent on

Answer 20

extracellular

Question 21

what source of Ca is skeletal muscle dependent on

Answer 21

SR

Question 22

in skeletal muscle what is required for Ca release from ryanodine receptors

Answer 22

mechanical coupling w L type receptors

Question 23

in skeletal muscle what is not required for Ca release form ryanodine receptors

Answer 23

Ca influx through L type receptors

Question 24

in cardiac muscle what is required for Ca release from ryanodine receptors

Answer 24

Ca influx through L type receptors

Question 25

what is calcium release channel in skeletal muscle // what is calcium release channel in cardiac muscle

Answer 25

ryanodine // RyR2

Question 26

what is the function of triad and dyad

Answer 26

excitation contraction coupling

Question 27

what does excitation contraction coupling mean

Answer 27

couple AP to release of Ca

Question 28

when it comes to excitation contraction coupling how does cardiac muscle differ from skeletal muscle

Answer 28

mechanism of Ca release

Question 29

what happens when AP travels down sarcolemma of cardiac muscle to T tubule

Answer 29

1. AP causes L type channels to open
2. Ca enters myocyte through L type channels
3. Ca binds to ryanodine receptors
4. SR releases Ca into cyto through ryanodine receptors
5. Ca interacts with contractile proteins in sarcomere

Question 30

what does Ca bind to in SR of myocyte

Answer 30

calsequestrin

Question 31

in cardiac muscle what is mechanism for excitation contraction coupling

Answer 31

calcium induced calcium release

Question 32

what are the mechanisms for decreasing Ca conc in cyto

Answer 32

1. NCX

2. SERCA 2A (90%)

Question 33

what is phospholamban

Answer 33

regulator of SERCA 2A

Question 34

how does phospholamban regulate SERCA

Answer 34

phosphorylation through cAMP second messenger system enhancer SERCA 2A activity