Regulation of CO

Question 1

3 ways to change pacemaker potential

Answer 1

inc or dec HR

1) changing the slope of phase 4 funny current- how fast you are reaching threshold
2) changing maximal diastolic potential (how negative they are)
3) changing the threshold itself (change when Ca channels open)

Question 2

PSNS and HR

Answer 2

ACh activate cholinergic M2 muscarinic receptors

Negative chronotropy—>decreased HR

Question 3

SNS and HR

Answer 3

NE—>adrenergic B1–> positive chronotropy—> increase HR

Question 4

Effects of B1 agonists

Answer 4

Increases Na and Ca influx during funny current phase 4—>increases slope of phase 4—>reach threshold faster

adjusting Ca current makes threshold more negative (reached sooner)

increases HR

Question 5

Effects of M2 agonists

Answer 5

ACh mediates increased K conductance, decreases funny current, and decreases Ca conductance during phase 4

adjusting Ca current makes threshold more positive

increases time to reach threshold—>decrease HR

Question 6

Hormonal effects on HR

Answer 6

hyperthyroid—> increased HR
hypothyroid—>decreased HR
Catecholamines–> increased HR

Question 7

Ions and HR

Answer 7

hyperkalemia—>decreased HR (due to slowed K efflux during phase 3)
hypokalemia—>increased HR

Question 8

Conduction velocity: dromotropy

Answer 8

based upon the amplitude of AP: increase AP=increase CV

and rate: more rapid depol–>increased CV

Question 9

Factors increasing EDV

Answer 9

1) Increase CVP (venoconstriction increased thoracic blood volume, increased venous return)
2) decrease HR (more time in diastole for filling)
3) Increase ventricle compliance
4) increased atrial contractility
5) Increased aortic pressure inc afterload–>inc ESV–>decreased SV—>increased EDV (NOT GOOD)
6) Pathology (systolic failure, stenosis, regurgitation)

Question 10

decreasing EDV

Answer 10

1) Decreased CVP
2) increase HR
3) decrease atrial contractility
4) decrease afterload
5) diastolic failure
6) mitral or TC stenosis

Question 11

Factors decreasing ESV

Answer 11

increased preload (EDV)--->increased SV
increased contractility (increase Ca-independent of EDV) 
Increased HR (via increased contractility)

Question 12

increasing ESV

Answer 12

increased afterload—>decreased SV

increased HR—>decreased EDV—>increased ESV (less time for filing)

Question 13

Positive inotropic factors

Answer 13

increase contractility by increasing IC Ca concentration —> increased systolic function—> decreased ESV

Question 14

End systolic pressure volume relationship (ESPVR)

Answer 14

Lowest possible ESV that you can have for a given starting point (i.e. EDV)

indicator of contractility independent of preload

=increased contractility=increased slope of ESPVR= increased SV

Question 15

increasing contractility

Answer 15

B1
increased Ca influx via L type channels
increased Ca sensitivity of RYR
increasing SERCA–> increased Ca stores

Question 16

Postive inotropic agents

Answer 16

increase contractility

1) Beta 1 agonists: epi and NE
2) Cardiac glycosides (digitalis)—>increase Ca
3) Decrease ECF Na—>increase Ca extrusion
4) increased Ca ECF—>increased Ca into cell
5) increased HR —> increased Ca

Question 17

Anrep effect

Answer 17

compensatory mechanism of increased inotropy during times of increased afterload

Question 18

decreasing contractility

Answer 18

1) M2 agonists
2) decreased ECF Ca
3) Ca channel blockers
4) increased ECF Na
5) decreased affinity of troponin for Ca

Question 19

Positive Lusitropy (increased rate of relaxation)

Answer 19

1) B1 (SNS) agonists)—>increase SERCA activity—> sequester Ca