Topic 9 - Blood vessels & blood flow Flashcards
(12 cards)
What are arteries?
High pressure tunnels
What are arterioles?
Regulate diameter to direct blood flow towards particular organs
*NOTE: MOST IMPORTANT SITE OF CARDIOVASCULAR DRUG ACTION
What are Capillaries?
Gas exchange occurs & other stuff
What are venules & veins?
Vessels bringing blood back to heart
What is blood flow dependent on?
It’s dependent on pressure gradient from A to B & resistance to flow
*Note: factors affecting resistance = length & diameter of tube & viscosity of fluid
What is Vascular resistance?
How wide or thin a tunnel is that changes in blood flow (contraction/relaxation of arteriolar smooth muscle)
What is the equation for flow rate into an organ?
(Mean arterial pressure - Venous pressure) / arteriolar resistance
What causes vasoconstriction?
- Angiotensin II
- Noradrenaline & adrenaline (a1 receptors)
- Local vasoconstrictors e.g vasopressin, vasoactive intestinal peptide, endothelin O2 etc.
What causes vasodilation?
- Adrenaline acting on Beta2 adrenoreceptors
- Local vasodilators e.g NO, K, histamine, adenosine, bradykinin etc.
What happens to blood flow as exercise occurs?
- It increases the total blood flow (5L -> 17.5L)
- It changes the proportion of the blood given to each organ (skeletal muscles go from 23% (X exercises) to 73%)
How does the blood flow actually increase?
- Autoregulation & active hyperaemia = Dilates coronary blood vessels inc Adenosine (ATP synthesis product) & H+/K+/Temp etc.
- Adrenaline activate beta 2 adrenoreceptors on vascular smooth muscle cells
How does that heart receive more blood from the veins?
- Increase skeletal muscle pump activity
- Increase respiration
- Sympathetic nerves cause increase of contraction of vascular smooth muscle cells = venomotor tone
