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Flashcards in Cardiac Function Deck (20):
1

Define cardiac output (CO)

Heart rate x Stroke vol

2

What occurs in diastole

This is the passive phase during which the heart refills with blood

3

What occurs in systole

This is the active phase during which the heart expels blood

4

What effect does adrenaline have on the heart? How?

Beta1-adrenergic receptors increase the force and rate of contraction and relaxation. GPCR activation increases cAMP. This activates protein kinase A which phosphorylates proteins

5

What effect does the alpha adrenoceptor have on the heart

Shorter action potential. Accelerated relaxation. Prevents Na overload.

6

What controls stroke volume

Stretch (of vessels) and force (of contraction)

7

How is the stretch of blood vessels determined

Skeletal muscle activity
Adrenergic effects on blood vessels (inc or dec)
Respiratory pump (inc/dec depth and frequency)

8

What does inotropic mean

The force of contraction

9

What does lusitropic mean

The force of relaxation

10

What does chronotropic mean

The rate of contraction

11

What are the sites of action of PKA and PKC for hormonal control of cardiac output

NCX (Na/Ca exchanger)
VGCC
RyR (ryanodine receptor)
SERCA channel
Sodium pump
Tn1 (troponin 1)

12

What is the function of voltage gated calcium channels and how are they regulated

Triggers calcium influx/efflux. Accounts for the plateau phase of an action potential
Regulated by:
Activation by depolarisaion. Phosphorylated by protein kinase. Involved in calcium induced calcium release

13

What is the function of ryanodine receptors and how are they regulated

Involved in calcium induced calcium release from the ER.
Regulated by:
pH, Protein kinases, calcium (intra and extra), Stretch/Nitric oxide, binding proteins

14

What is the function of SERCA and how is it regulated

Removes calcium from the cytoplasm (at end of AP) into the ER.
Regulated by Nitric oxide and phospholamban (PLB; reduces affinity for calcium)
PLB can be disinhibited by PKA phosphorylation.

15

What is the function of the NCX and how is it regulated

Triggers calcium influx at the start of an AP; triggers calcium efflux at the end.
Regulated by PKC (enhanced activity; more calcium influx and efflux)

16

What is the function of the sodium pump and how is it regulated

Active transporter. Removes sodium at end of an AP. Maintains ion gradients. Controls membrane potential
Regulated by phospholemman phosphorylation (PKA/PKC)(activates pump)

17

What is the function of the troponin 1 receptor and how is it regulated

Inhibits actin/myosin interaction. (inhibition removed by calcium binding)
Regulated by; PKA phosphorylation - reduces affinity for calcium (reduction in contraction, accelerates relaxation)

18

What is the downstream molecule associated with the beta-adrenoceptor

Protein kinase A

19

What is the downstream molecule associated with the alpha-adrenoceptor

Protein kinase C

20

What is the overall result of activation of either the alpha- or beta- adrenoceptor

Increased stroke vol
Increased ejection fraction
Quicker contraction/AP
More beats per min.