Vascular physiology

What are the three main components of the cardiovascular system?

Heart pump

Why is the circulatory system called “closed”?

Blood remains within vessels and does not directly contact tissues.

What are the two circulations?

Pulmonary oxygenation and systemic distribution.

What lines all blood vessels?

A single layer of endothelial cells.

What are the three layers of arteries and veins?

Tunica intima

What is the tunica intima?

Endothelial layer lining the lumen.

What is the tunica media?

Smooth muscle and elastin layer controlling tone.

What is the tunica adventitia?

Connective tissue with collagen

Do veins have elastic lamina?

They have thin or absent elastic laminae.

What are capillaries composed of?

A single endothelial layer with a basement membrane and pericytes.

What are fenestrated capillaries?

Capillaries with pores allowing larger molecules to pass.

What are anastomoses?

Direct arteriole‑venule shunts bypassing capillary beds.

What are elastic arteries?

Large arteries with high elastin content for pulsatile recoil.

What are muscular arteries?

Distribution vessels with thick smooth muscle layers.

What are arterioles?

Resistance vessels controlling vascular tone and blood pressure.

What helps venous return?

Valves

What determines movement across capillaries?

Hydrostatic pressure and oncotic (colloid osmotic) pressure.

What is hydrostatic pressure?

Pressure pushing fluid out of capillaries.

What is oncotic pressure?

Protein‑driven osmotic force pulling fluid into capillaries.

What regulates vascular resistance?

Arteriolar tone controlled by local factors and sympathetic innervation.

What are baroreceptors?

Stretch receptors in aorta and carotid arteries regulating blood pressure.

What are chemoreceptors?

Sensors detecting pH

What factors affect blood pressure?

Cardiac output

What is preload?

End‑diastolic ventricular wall stress determined by venous tone.

What is afterload?

Systolic ventricular wall stress determined by arteriolar resistance.

Where does coronary perfusion occur?

During diastole.

What causes myocardial ischemia?

Imbalance between oxygen supply and demand.

What are endothelial cells?

Flat cells lining blood vessels with roles in transport

How do endothelial cells sense shear stress?

Via cytoskeleton and glycocalyx.

What are vascular smooth muscle cells?

Non‑striated muscle cells controlling vessel diameter.

Do vascular smooth muscle cells have sarcomeres?

No

What protein replaces troponin in smooth muscle?

Calmodulin.

What activates smooth muscle contraction?

Ca²⁺ binding to calmodulin activating myosin light chain kinase.

What causes smooth muscle relaxation?

Dephosphorylation of myosin light chain and reduced Ca²⁺.

What is the contraction style of smooth muscle?

Slow

What regulates vascular tone?

Neural

What is nitric oxide (NO)?

A potent vasodilator released by endothelial cells.

How does NO cause vasodilation?

Activates soluble guanylate cyclase increasing cGMP in smooth muscle.

What does NO do in blood?

Inhibits platelet adhesion and aggregation.

What is prostacyclin (PGI₂)?

An endothelial vasodilator and inhibitor of platelet aggregation.

What is EDHF?

Endothelium‑derived hyperpolarizing factor causing vasodilation.

What is endothelin?

A potent vasoconstrictor peptide produced by endothelial cells.

Which endothelin receptor causes vasoconstriction?

ETA receptor.

Which endothelin receptor causes vasodilation?

ETB receptor via NO and prostacyclin release.

What is the renin‑angiotensin‑aldosterone system?

Hormonal system regulating blood volume and vascular tone.

What does angiotensin II do?

Causes vasoconstriction via AT1 receptors and increases Ca²⁺ release.

How do ACE inhibitors reduce blood pressure?

Prevent formation of angiotensin II.

How do AT1 receptor blockers reduce blood pressure?

Block angiotensin II binding.

What are natriuretic peptides?

Hormones (ANP

How does ANP cause vasodilation?

Increases cGMP leading to myosin light chain dephosphorylation.

What does epinephrine do to most vessels?

Causes vasoconstriction.

What does vasopressin do?

Causes vasoconstriction and water retention.

What does EPO do?

Stimulates red blood cell production and can cause vasoconstriction.

What does sympathetic activation do to vessels?

Causes vasoconstriction via α1‑adrenergic receptors.

Does parasympathetic innervation strongly affect vessels?

No

Why do calcium channel blockers affect vascular tone?

Ca²⁺ is essential for smooth muscle contraction.