Regulation of stroke volume and heart rate Flashcards Preview

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

how to increase heart rate

A

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
Q

How to decrease heart rate

A

Bradycardia

  • Parasympaththetic
  • release of ACH from vagus nerve
  • acts of muscarinic receptors of SA node
  • decrease slope of pacemaker potential
3
Q

how to increase stroke volume

A

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
Q

How to decrease stroke volume

A

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

5
Q

what is pre-load

A
  • 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
Q

what is afterload

A

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
Q

Pathologies of control

A

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

8
Q

How to increase cardiac output

A

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
Q

Starlings law

A

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
Q

How to increase pre-load

A
  • Skeletal muscle pump
  • Respiratory pump
  • Venocontriction