Regulation of stroke volume and heart rate Flashcards Preview

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Flashcards in Regulation of stroke volume and heart rate Deck (10):
1

how to increase heart rate

Tachycardia
-sympathetic system
-Release of adrenaline from sympathetic fibres
-release of noradrenaline from adrenal medulla
-acts of B1 receptors of SA node
-increases slope of pacemaker potential

2

How to decrease heart rate

Bradycardia
-Parasympaththetic
-release of ACH from vagus nerve
-acts of muscarinic receptors of SA node
-decrease slope of pacemaker potential

3

how to increase stroke volume

1-Neural
- release of adrenaline from sympathetic fibres
-release of noradrenaline from adrenal medulla
-act on B1 receptors of myocetes
-increases contractility-longer and shorter
2-increase preload
3-decrease afterload

4

How to decrease stroke volume

1- neural- parasympathetic has little effect
2-decrease preload
3-increase afterload

5

what is pre-load

-how far the muscle can stretch before contraction
-depends on sarcomere length- cannot be measured
-EDV measured
-when venous returns increase= EDV increases so stroke volume increases

6

what is afterload

the pressure the heart has to combat to release blood
-Total peripheral resistance: Aortic pressure
the greater the A.P., less energy is available for stroke volume as more used to overcome this
-Amount of blood being pushed out of ventricles

7

Pathologies of control

Hypercalcemia: increases stroke volume per given EDV- shifts curve up and left
Hypocalcemia
Barbituates
Ischemia- reduced blood flow to the heart

8

How to increase cardiac output

1-Electric fibrillation:
-temporarily increases C.o. by increasing heart rate
-S.V. falls as the E.D.V. decreases (cuts rapid filling phase)
-C.O. then falls
2-increase H.R. BY METHODS LISTED
3-increase S.V. BY METHODS LISTED

9

Starlings law

The energy of contraction of the muscle is dependant on the initial length of the cardiac muscle- the greater the length, the greater the tension

10

How to increase pre-load

-Skeletal muscle pump
-Respiratory pump
-Venocontriction