1. Comparative Vertebrate Physiology
Regulation of cardiac output and blood pressure

2. Cardiac output
Increasing preload pressure increases heart rate and stroke volume

3. Cardiac output Cardiac output = HR x SV
e.g. Humans: 80 beats/min. x 0.07l/beat = 5.6 l/min

4. Cardiac output
Most of the increase in C.O. is due to HR and not SV

5. Starling’s law Cardiac muscle is much shorter than its optimum length
The great the filling of the heart, the greater the amount pumped by the heart

6. Control of cardiac output
Heart is innervated by the ANS

7. Control of cardiac output
Sympathetic
Norepinephrine (Na+ and Ca+ + influx)
Parasympathetic
Acetylcholine (K+ efflux)

8. Blood pressure Determined by: Mean arterial pressure = CO x TPR
cardiac output
vascular resistance (TPR)
blood volume
Mean arterial pressure = CO x TPR

9. Changes in blood pressure

10. Blood pressure regulation
Short term
Control of heart rate
Vascular resistance
Altering blood flow
Altering vessel diameter

11. Blood pressure regulation
Vasodilation
Blood pumped faster
Venous return
Muscle pump
Respiratory pump

12. Blood pressure regulation
Long term (days)
Changes in blood volume (kidneys)

13. Blood pressure regulation
Baroreceptors
Nerve endings detect stretch
Most important (aortic arch, carotid arteries)
Information relayed to the brain

14. Blood pressure in divers
Air breathing vertebrates
Bradycardia
Reduction in cardiac output

15. Blood pressure in divers

16. Blood pressure in divers
Blood pressure unaffected
Vasoconstriction and shunting