action potential to contraction in myocytes

Question 1

what causes eletrical potential across membrane

Answer 1

ions

Question 2

myocyte resting pot

Answer 2

-85mV

Question 3

how do APs vary between differen cells

Answer 3

number and type of ion channels

Question 4

how does Na channels change in purkinje vs. His

Answer 4

more Na channel as go down - faster propagation of signal

Question 5

how do diff. ion channel affect the AP

Answer 5

different refractory periods, pleateau, etc.

Question 6

what happens to start action potential

Answer 6

Na open, Ca open along the way

Question 7

what happens at top of AP

Answer 7

Na close

Question 8

what is Na threshold

Answer 8

-55mV

Question 9

what happens in plateau

Answer 9

Ca open, and fast K close

Question 10

what happens in repolarization

Answer 10

Ca close, slow K open

Question 11

what is Ca channel threshold

Answer 11

-45mV

Question 12

what leads to the refractory period

Answer 12

Na channels closing and not opening until -85

Question 13

what phase of AP is affected in long QT syndrome

Answer 13

repolarization

Question 14

what is P wave

Answer 14

atrial contraction

Question 15

what is Q wave

Answer 15

dip as travels down His

Question 16

what is R wave

Answer 16

entrance into purkinjes (early vent.)

Question 17

what is S wave

Answer 17

late vent depolarization

Question 18

what is sinus rhythm

Answer 18

heart rate

Question 19

normal HR

Answer 19

60-100bpm

Question 20

what is RR interval

Answer 20

heart rate

Question 21

what is PR interval

Answer 21

time of AV nodal conduction

Question 22

what is QRS interval/duration

Answer 22

time to depolarize heart

Question 23

what is QT interval

Answer 23

depolarization of ventricle

Question 24

what could cause QRS interval lengthing (2)

Answer 24

1. large heart

2. blocks

Question 25

steps for an AP to create a contraction

Answer 25

1. AP comes in
2. L-type channels open
3. Ca comes in
4. activated ryanadine receptor
5. RY gives Ca sparks
6. summed sparks give Ca signal
7. Ca troponin binding allows myosin to attach

Question 26

when does relaxation occur

Answer 26

what Ca unbinds

Question 27

what is important about short refractory period in skeletal muscle

Answer 27

allows mulitple contraction to build to eventual tetanus

Question 28

what is the ratio for muscle contraction to AP in cardiac muscle

Answer 28

almost the same, so can’t get contraction on top of each other