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CV exam 1 wk 1 > how does the heart work? > Flashcards

how does the heart work? Flashcards

1
Q

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

A

calcium handling and calcium sensitivity

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2
Q

How do we think about cardiac muscle physiology?

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

Force

A
  1. calcium relationships
    Biochemical interactions
  2. Highlights calcium regulation and biochemistry
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4
Q

Frank-Starling relationships

A
  1. Intact muscle physiology

2. Highlights length tension relationships

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5
Q

PV loops

A

Integrated cardiac performance

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6
Q

Mechanisms by which the heart moderates its performance

throughout the day include:

A
  1. Length dependent activation (Frank-Starling effects)
  2. Enhanced contractility,
  3. enhanced chronotropy.
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7
Q

The effect of increasing preload on force of contraction:

A
  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.
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8
Q

So, how does increasing preload affect cardiac performance?

A
  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.
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9
Q

phosphorylation of Ca channels (SA node cells) will cause

A
  1. ↑ Heart rate

2. Improved CO

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10
Q

Phosphorylation of Ca channels
(ventricular cells)
will cause

A
  1. ↑ Ca entry
  2. ↑ Force of contraction
  3. improved ejection fraction (+ inotropy)
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11
Q

Phosphorylation of Na pump

will cause

A
  1. ↑ Ca efflux (via Na-Ca exchange)

2. enhanced relaxation and diastolic filling

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12
Q

Phosphorylation of Phospholamban

will cause

A
  1. Disinhibition of SR calcium pump (SERCA2)
  2. Increased SR calcium load
  3. improved diastolic filling
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13
Q

Phosphorylation of FKB

will cause

A
  1. Enhances Ryr receptor mediated calcium release

3. enhanced contractility

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14
Q

Phosphorylation of troponin I

will result in

A
  1. ↓ Ca affinity for TnC

2. enhanced relaxation

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15
Q

How do we get through the day?!?!

A
  1. postural accomodation
  2. isotonic (exercise: cardio)
  3. isometric (weight training)
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16
Q

postural accomodation

A
  1. Venous pump: skeletal musculature
  2. Increase venous return
  3. Increased EDV → increased SV
17
Q

isotonic

A
  1. Decrease peripheral vascular resistance
  2. Increase venous return (Frank-Starling)
  3. Increase heart rate
  4. Increase inotropy
18
Q

Isometric (weight training)

A
  1. Increased peripheral vascular resistance (maintain blood flow to exercising muscle group)
  2. Increased HR
  3. No increase (or decrease) in CO
19
Q

What happens acutely during a heart attack?

A
  1. Loss of functional myocardium
  2. Increased catecholamine surge
  3. Increased inotropy to maintain CO despite increase BP (afterload)
  4. Heterogeneous cellular environment
20
Q

Increased catecholamine surge symptoms are

A

Sweating, tachycardia, ± hypertension

21
Q

Heterogeneous cellular environment symptoms are

A
  1. Local /regional changes in pH
  2. change in membrane potential
  3. secondary effect on cytosolic calcium
22
Q

Ca regulated by

A

phospholamban and serca 2a pump.

23
Q

Phospholamban

A
  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
Q

which part of myosin has ATPase activity?

A

head of myosin

muscle shortening is an ATP dependent process

25
Q

Diastole:

A

no interaction between actin and myosin

26
Q

Systole:

A

interaction between actin and myosin

27
Q

Regulation between actin and myosin is by

A

Calcium C on troponin C and phophosrylation of troponin molecules

28
Q

Factors that influence EC50 (calcium sensitivity) include

A
  1. pH
  2. temperature
  3. sarcomere length
  4. contractile protein phosphorylation
  5. caffeine
29
Q

PKA effect on pCa

A
  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
Q

PKC effect on pCa

A
  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

CV exam 1 wk 1 (48 decks)

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