Hypertension

Question 1

State how blood flow through a vessel is influenced by pressure, length, viscosity and vessel radius

Answer 1

flow = delta pressure/resistance

vessel length doesn’t change and under normal conditions, viscosity remains relatively constant, and resistance is largely determined by the radius of blood vessels.

Question 2

Define the term total peripheral resistance in relation to mean systemic arterial blood pressure and cardiac output

Answer 2

tpr = arterial pressure - venous pressure/cardiac output

Question 3

Describe the capacitance function of veins and how venomotor tone can influence venous return

Answer 3

Venous return is affected by venomotor tone (constriction), venous valve competence, the skeletal muscle pump and respiration. This is because inspiration decreases intrathoracic pressure and increases intra-abdominal pressure, and hence provides a pressure gradient to assist blood flow to the heart.

Question 4

Describe how major hormones e.g. adrenaline, angiotensin II affect vascular contractility

Answer 4

angiotensin contracts, adrenaline dialates.

Question 5

Describe how factors released from the endothelium can modulate vascular tone

Answer 5

Endothelium-derived vasorelaxations are prostacyclin (PGI2), nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF). An endothelium-derived vasoconstrictor is endothelin.

Question 6

Describe how myogenic mechanisms contribute to autoregulation of blood flow

Answer 6

The myogenic response is important in the cerebral vasculature. Stretch, imposed by increased pressure, causes vasoconstriction.