Regulation of Blood Flow and Pressure

What drives tissue perfusion?

Arterial blood pressure.

What is Darcy's Law for blood flow?

Q = ΔP ÷ R (flow equals pressure gradient over resistance).

What is Ohm's Law in the context of circulation?

Pressure gradient (ΔP) equals flow (Q) multiplied by resistance (R).

What is intrinsic regulation of vascular tone?

Local control via mechanical stimuli, endothelium, metabolites, and autocoids.

What is extrinsic regulation of vascular tone?

Systemic control via sympathetic nerves and circulating hormones.

What is the normal systemic arterial pressure?

120/80 mmHg.

What is the normal pulmonary arterial pressure?

25/10 mmHg.

Why is pulmonary resistance much lower than systemic resistance?

To accommodate the same volume of blood at a much lower pressure.

How does hypoxia affect pulmonary arteries?

It causes hypoxic pulmonary vasoconstriction for V/Q matching.

Where are baroreceptors located?

In the walls of the aortic arch and carotid sinus.

Which brain region acts as the central relay for the baroreceptor reflex?

The medulla oblongata.

How does the baroreceptor reflex respond to a drop in blood pressure?

Decreased vagal outflow, increased sympathetic outflow, and increased heart rate and vascular tone.

How is Grade I hypertension defined?

Consistent readings of systolic >140 mmHg or diastolic >90 mmHg.

What is vascular tone?

The constriction applied across blood vessels, balancing constrictors and dilators.

What is the myogenic response in vascular smooth muscle?

Smooth muscle constricts when stretched, contributing to basal tone and autoregulation.

What is a major vasodilator produced by the vascular endothelium?

Nitric oxide (NO).

Name two endothelial vasoconstrictors.

Endotelins (ET), Angiotensin II, and thromboxane (TxA2).

Which local metabolites promote vasodilation?

Increased CO2, K+, H+, adenosine, and decreased O2.

When does most coronary blood flow occur?

During diastole, as arteries are compressed during systole.

What is the primary cause of cerebral autoregulation?

Myogenic activity and local mediators like K+, adenosine, and NO.

How is cerebral perfusion pressure (CPP) calculated?

Mean arterial pressure (MAP) minus intracranial pressure (ICP).