AUTOREGULATION-ON STANDING UP

SUMMARY

Remember: BP = CO * SVR = HR * SV * SVR

1. Standing increases venous pooling in the dependent parts of the body. This causes reduction in venous return to the heart, causing reduction in stroke volume (SV).

2. Carotid baroreceptor stimulation is reduced due to reduced pulse pressure upon standing.

3. This leads to reduced vagal tone & increased sympathetic stimulation leading to increased HR & peripheral arteriolar vasoconstriction (SVR).

4. SNS stimulation causes decreased peripheral blood pooling.

5. SNS also has an inotropic effect on myocardium, increasing SV, hence CO.

6. Normally, arterial pressure may increase slightly upon standing.

Reference(s)

Barrett, K.E., Barman, S.M., Brooks, H.L., X, J. and Ganong, W.F. (2019). Ganong’s review of medical physiology. 26th ed. New York: Mcgraw-Hill Education