Cardiac homeostasis
- Created by: kpritchard16
- Created on: 29-12-18 21:04
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- Cardiac homeostasis
- Preload
- passive stretch placed on a muscle prior to an active contraction; initial passive length to which muscle is stretched prior to the start of a contraction
- Frank-Starling curve
- Normal heart - As you increase preload, you increase stroke volume
- Failing heart - this relationship is lost, heart loses its ability to pump increased blood round body
- Afterload
- force a muscle experiences (exerts) after it has begun to shorten, force heart has to beat against (aortic pressure)
- Frank-Starling law
- The stroke volume of the heart increases in response to an increase in the volume of blood filling the heart when all other factors remain constant.
- Caculations
- MABP= CO x TPR
- Fall in MABP is detected by arterial baroreceptors
- Causes reflex
- sympathetic arteriolar constriction in skin and viscera
- sympathetic cardiostimulation
- sympathetic veno-constriction
- Causes reflex
- Fall in MABP is detected by arterial baroreceptors
- CO = SV x HR
- CO can increase 4-5 fold during exercise
- This is cardiac reserve. In HF this is diminished or abolished
- CO can increase 4-5 fold during exercise
- MABP= CO x TPR
- Haemodynamics
- physics of blood flow and distributions
- Ventricular function curves
- A biological property of muscle increases in resting length causes increase in development of tension/contractionMore you stretch cardiomyocytes, the more tension they have
- Contractility and venous return
- Increased cardiac contractility (Sympathetic stimulation) and decreased resistance (as occurs during exercise) will produce maximum increases in CO.
- Sympathetic venoconstriction may further enhance venous return. Note that changing cardiac contractility (pump output) also changes Rt Atrial Press
- Preload
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