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