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Flashcards in how does the heart work? Deck (30):
1

At the level of the myocyte and myofibril, _____ are key determinants of contractile performance

calcium handling and calcium sensitivity

2

How do we think about cardiac muscle physiology?

1. Force – calcium relationships
2. Frank-Starling relationships
3. PV loops
Integrated cardiac performance

3

Force

1. calcium relationships
Biochemical interactions
2. Highlights calcium regulation and biochemistry

4

Frank-Starling relationships

1. Intact muscle physiology
2. Highlights length tension relationships

5

PV loops

Integrated cardiac performance

6

Mechanisms by which the heart moderates its performance
throughout the day include:

1. Length dependent activation (Frank-Starling effects)
2. Enhanced contractility,
3. enhanced chronotropy.

7

The effect of increasing preload on force of contraction:

1. the greater the volume of blood entering the heart during diastole (end-diastolic volume),
2. the greater the volume of blood ejected during systolic contraction (stroke volume) and vice versa.

8

So, how does increasing preload affect cardiac performance?

1. This is the basis of the Frank-Starling law of the heart.
2. The Frank-Starling law of the heart describes the effect of increasing preload on the force of contraction.
3. the greater the volume of blood entering the heart during diastole, the greater the volume of blood ejected during contraction.
4. due to increase the fiber length, the force of contraction for a given stimulus is increased.

9

phosphorylation of Ca channels (SA node cells) will cause

1. ↑ Heart rate
2. Improved CO

10

Phosphorylation of Ca channels
(ventricular cells)
will cause

1. ↑ Ca entry
2. ↑ Force of contraction
3. improved ejection fraction (+ inotropy)

11

Phosphorylation of Na pump
will cause

1. ↑ Ca efflux (via Na-Ca exchange)
2. enhanced relaxation and diastolic filling

12

Phosphorylation of Phospholamban
will cause

1. Disinhibition of SR calcium pump (SERCA2)
2. Increased SR calcium load
3. improved diastolic filling

13

Phosphorylation of FKB
will cause

1. Enhances Ryr receptor mediated calcium release
3. enhanced contractility

14

Phosphorylation of troponin I
will result in

1. ↓ Ca affinity for TnC
2. enhanced relaxation

15

How do we get through the day?!?!

1. postural accomodation
2. isotonic (exercise: cardio)
3. isometric (weight training)

16

postural accomodation

1. Venous pump: skeletal musculature
2. Increase venous return
3. Increased EDV → increased SV

17

isotonic

1. Decrease peripheral vascular resistance
2. Increase venous return (Frank-Starling)
3. Increase heart rate
4. Increase inotropy

18

Isometric (weight training)

1. Increased peripheral vascular resistance (maintain blood flow to exercising muscle group)
2. Increased HR
3. No increase (or decrease) in CO

19

What happens acutely during a heart attack?

1. Loss of functional myocardium
2. Increased catecholamine surge
3. Increased inotropy to maintain CO despite increase BP (afterload)
4. Heterogeneous cellular environment

20

Increased catecholamine surge symptoms are

Sweating, tachycardia, ± hypertension

21

Heterogeneous cellular environment symptoms are

1. Local /regional changes in pH
2. change in membrane potential
3. secondary effect on cytosolic calcium

22

Ca regulated by

phospholamban and serca 2a pump.

23

Phospholamban

1. typically inhibitits the pump
2. Ryanodine receptor is how ca gets out.
3. A little leaks out then a lot flows out of the SR

24

which part of myosin has ATPase activity?

head of myosin

muscle shortening is an ATP dependent process

25

Diastole:

no interaction between actin and myosin

26

Systole:

interaction between actin and myosin

27

Regulation between actin and myosin is by

Calcium C on troponin C and phophosrylation of troponin molecules

28

Factors that influence EC50 (calcium sensitivity) include

1. pH
2. temperature
3. sarcomere length
4. contractile protein phosphorylation
5. caffeine

29

PKA effect on pCa

1. causes an increase in velocity,
2. Force calcium relationship shifts to the Left.
3. Ca sensitivity increase,
4. this is the positive inotrope.

30

PKC effect on pCa

1. causes a negative inotropic effect.
2. Force calcium relationship shift to the right.
3. The same amount of calcium results in LESS generation.
4. Causes a decrease in velocity