Cardiology physiology Flashcards
What volume of blood is present in circulation in an average 70kg man?
5.5L
How can arteries dampen the pulsatile oscillations in pressure that result from intermittent outflow of blood from the left ventricle?
As they are elastic
Smaller arteries and arterioles are the primary vessels involved in what?
Regulation of arterial blood pressure and blood flow within organs
Smaller arteries and arterioles are innervated by what?
Autonomic nervous system
What are the primary exchange vessels in the body?
Capillaries
What are the main differences between arteries and veins?
Veins are larger in diameter
Veins provide less resistance
Vein walls are thin and distensible
What percentage of blood volume is contained within veins?
70%
Why are veins known as capacitance vessels?
Because veins act as a blood volume reservoir
What are the 3 layers of large and medium sized arteries?
Tunica intima
Tunica media
Tunica adventitia
What is the tunica intima composed of?
Thin layer of endothelial cells
Sub endothelium connective tissue
Elastic lamina
What is the tunica media composed of?
Fenestrated elastic membranes
Smooth muscle cells
Collagen
What is the thickest part of arterial walls?
Tunia media
What is the tunica adventitia composed of?
Thin layer of connective tissue
Lynphatics
Nerves
Vasa Vasorum (blood vessels that supply smooth muscle)
Arteries with a diameter less than what are classed as arterioles?
<0.1mm
What are the walls of capillaries made up on?
Single endothelial cells
What are the 3 main types of capillary?
Continunous
Fenestrated
Sinusoidal
Which vessels are the preferred site of white blood cell migration I inflammation and infection?
Veins
What do most vasoconstrictors bind to and cause?
Receptors that cause a G-protein mediated rise in intracellular calcium levels = contraction of vascular smooth muscle.
Where does intracellular calcium arise from?
Sarcoplasmic reticulum
Entry across sarcolemma through calcium channels
Name some vasoconstrictors.
Endothelin-I
Angiotensin-II
Noradrenaline
What do calcium channel blockers do?
Prevent or reduce opening of calcium channels = reduction in vasoconstriction.
How do most endogenous vasodilators cause vessel relaxation?
By increasing cGMP (E.G. NO) or cAMP (prostacyclin/ beta agonists)
Removal of which ions causes vasodilation?
Calcium ions
Which aspect of vessels plays an important role in regulation of vascular tone?
Vascular endothelium (as it is a source of important vasoactive mediators)