Cardiovascular Biology Overview

Vasovagal Syncope (Fainting)

• Syncope is another name for fainting, which is also known as vasovagal syncope.

Blood Vessel Structure & Function

• Arteries act as pressure reservoirs in the cardiovascular system.
• Endothelium is the inner lining of blood vessels.
• Smooth muscle is found in vessel walls except capillaries.
• Pericytes are highly branched, contractile cells that regulate permeability.
• Arterioles have a continuous smooth muscle layer in their walls, unlike metarterioles.
• Venules and capillaries permit exchange between blood and interstitial fluid.
• Angiogenesis is the growth of new blood vessels.
• Angiostatin and endostatin may treat some cancers.

Blood Pressure & Regulation

• Blood pressure (e.g., 120/80) reflects arterial pressure during ventricular systole and diastole.
• Systole involves increased blood pressure and stress on arterial walls.
• Mean arterial pressure (MAP) is the driving force for blood flow.
• Blood flow increases with higher tissue CO2 levels.
• Blood pressure measures blood force in a vessel.
• Pulse pressure is the difference between systolic and diastolic pressures.
• Factors increasing blood pressure include sympathetic stimulation, decreased arterial diameter, and increased resistance.
• Arterioles are the main variable resistance vessels, contributing significantly to overall resistance (over 60%).
• Increased cardiac output (with no change in arteriolar resistance) leads to increased blood pressure.
• Increased blood volume increases blood pressure.
• The kidney, while not part of the cardiovascular system, is critical in blood pressure regulation.
• Local control of blood flow matches it to tissue metabolism.
• Myogenic autoregulation describes reflexive constriction of stretched smooth muscle in blood vessels.
• Calcium ions (Ca2+) do not cause vasodilation.
• Reactive hyperemia involves increased flow after reduced flow, triggered by local paracrine accumulation.
• Preeclampsia is elevated blood pressure during pregnancy.
• Vasodilation of most vascular smooth muscles is caused by reducing sympathetic stimulation.
• Fenestrated capillaries have higher permeability (fluid passage) than continuous capillaries, which have selective permeability.
• Sinusoids replace capillaries in some tissues.
• Capillary blood flow is significantly slower than arterial flow.
• Net filtration occurs at the arteriolar end of most capillaries, followed by net absorption at the venous end.
• The lymphatic system returns lost capillary fluid to the circulatory system.
• Oncotic/colloid osmotic pressure is osmotic pressure exerted by plasma proteins.
• The medulla oblongata controls blood pressure.
• When blood pressure decreases, baroreceptors reduce firing rate.
• A drop in blood pressure triggers the baroreceptor reflex, increasing sympathetic activity and cardiac output.
• Bedridden individuals may have a weak baroreceptor reflex upon standing due to reduced blood volume.
• Hypertension diagnosis occurs with systolic pressure above 140 mm Hg or diastolic pressure above 90 mm Hg.
• Compensation for low blood volume involves increased sympathetic stimulation, water intake, and sympathetic activation of the heart.
• Fenestrated capillaries are found in the liver.
• Kidneys minimize fluid loss and maintain blood pressure through a balance of blood volume.
• The cardiovascular control center in the brain directly controls arteriolar dilation/constriction and heart rate.
• Edema occurs when the heart is an insufficient pump.
• Increased blood CO2 results in reduced parasympathetic heart stimulation.
• Drugs blocking beta receptors in cardiac muscle might treat hypertension.