Contraction/Conduction

Question 1

resistance =

Answer 1

resistance =(mean art p - central venous p)/CO

Question 2

blood flow =

Answer 2

blood flow = diff pressures/resistance

Question 3

blood flow is proportional to

Answer 3

the driving force; pressure difference

Question 4

relative refractory period

Answer 4

greater than normal stimulus needed to generate a propogated AP

Question 5

effective action potential

Answer 5

propagated AP cannot be elicited

Question 6

absolute refractory period

Answer 6

AP cannot be elicited NO matter what

Question 7

fast APs occur in

Answer 7

contracting regions (atrial and ventricular mm)
fast conduction (his/purkinje)
LEFT side

Question 8

slow APs occur in

Answer 8

pacemaking (SA node)
slow conduction (AV node)
RIGHT side

Question 9

AP is fast or slow depending on

Answer 9

speed of initial depolarization

Question 10

Fast; Phase 0

Answer 10

rapid depol, Na inward

Question 11

Fast; Phase 1

Answer 11

initial repolarization;
inactivation of Na
open outward K (Ito)
activ

Question 12

Fast; Phase 2

Answer 12

Plateau
slowly act inward Ca currents
(atrial and ventricular contraction)

Question 13

Fast; Phase 3

Answer 13

repolarization
inactivation of Ca currents
act of several K out currents (Ikr, Iks)

Question 14

Fast; Phase 4

Answer 14

resting mem potiential due to

inward K channels (Ik1)

Question 15

Slow; Phase 0

Answer 15

slow depol

slowly activating Ca channels

Question 16

Slow; Phase 1

Answer 16

absent

Question 17

Slow; Phase 2

Answer 17

absent

Question 18

Slow; Phase 3

Answer 18

repolarization
Ca channel deactivation
act of outward K channels

Question 19

Slow; Phase 4

Answer 19

slowly depolarizing resting potential

Question 20

pacemaking

Answer 20

due to slowly depol phase 4

rate of depol sets time it takes to reach threshold and thus firing rate

Question 21

spontaneous depolarization

Answer 21

imbalance between
Outward; ACh act K channels (Ik,ACh, Igirk)
- hyperpolarize the cell
Inward; nonsel cation channel HCN (If)
- depolarize the cell

In>out = depolarization

Question 22

PNS - acetylcholine & phase 4

Answer 22

ACh + muscarinic ACh receptors
increases Igirk K+ currents
reduces rate of depolarization (phase 4) - hyperpolarizes
reduces heart rate
(negative chronotropic effect)

Question 23

SNS - epinephrine/NE & phase 4

Answer 23

beta 1 adrenergic receptors
increases If and ICa (inward currents
increase rate of phase 4 depol
increases heart rate
(postive chronotropic effect)

Question 24

rate of SA nodal pacing can also be changed by changing diastolic resting pot/threshold;

Answer 24

changing the diastolic resting potential/threshold
PNS - diastolic pot more Neg -> increases threshold, reduces firing rate
SNS - diastolic pot more Pos ->

Question 25

overdrive suppression

Answer 25

pacemaker w fastest rate of phase 4 depol and shortest AP controls heart rate

Question 26

intrinsic rates (beats/min):

Answer 26

SA node 100 AV 40-60 His/P 30-40

Question 27

slowest AP is in the

Answer 27

AV node provides delay bet atrial and ventricular AP important for pumping - allows for more efficient filling of ventricles before contraction Autonomic NS can alter conduction velocity here too

Question 28

positive dromotopic effect

Answer 28

increase conduction velocity of AV node | SNS

Question 29

negative dromotopic effect

Answer 29

decrease conduction velocity of AV node | PNS