L14 Blood Pressure Flashcards
Which blood vessel is under the most blood pressure?
The arteries
What does compliance/ capacitance mean?
The ability of blood vessels to expand and hold a larger volume of blood without a significant increase in blood pressure
Do arteries have a low or a high compliance/capacitance?
They have a lower compliance
Which blood vessel has the highest resistance to blood flow?
Arterioles
What type of muscles does arterioles have?
Tonically active vascular smooth muscles.
Give me examples of alpha 1 adrenergic receptors
The skin, mucous membrane, splanchnic arterioles
What happens when alpha 1 adrenergic receptors contract in the VSM?
The diameter of arterioles decreases
The resistance to blood flow increases
What does VSM stand for ?
Vascular smooth muscle
Where are beta 2 adrenergic receptors?
Skeletal muscle and heart arterioles
What 3 things increases resistance to blood flow in the arterioles?
- Sympathetic nerves
- Circulating catecholamines e.g. adrenaline
- Other vasoactive substances (NO)
What does balance of alpha and beta receptor do?
Balance of α1 + β2 receptor activation plays a crucial role in regulating blood flow to different organs and tissues in changing conditions.
How is the blood flow within the capillaries controlled?
Controlled by dilation/ constriction of arterioles.
What is the pressure like in capillaries and why?
Capillaries have low pressure and slow flow because this would facilitate the diffusion of nutrients and oxygen
What is the blood pressure like in the venules and veins?
They have low blood pressure
The walls contain much less elastic tissue than arteries
Do veins/venules have a small or large capacitance?
They have a large capacitance
How do venules and veins increase activity via α1- adrenergic receptors?
Contraction to reduce capacitance - decrease in ‘unstressed volume’ .
Unstressed volume - no pressure exerting on the vessel walls. Vessels = relaxed and not stretched
How do you calculate the velocity of blood flow?
V = Q/A
V - Velocity of blood flow (cm/s)
Q - flow (mL/s)
A - cross-sectional area (cm^2)
What happens to the velocity when you increase the cross sectional area of a blood vessel?
Velocity decreases as cross sectional area increases
Inverse relationship between velocity and cross sectional area (total)
How would you calculate the blood volume per unit of time?
Q = DeltaP/R
- Q - blood vol per unit of time
- Delta P - Pressure difference
- R = Resistance
What two factors affect blood flow (Q)?
Pressure difference between two points in a vessel
Resistance - vessel opposition to blood flow
What is the significance of the relationship between blood flow, resistance and pressure? (Wtf)
- BP regulation - Vasoconstriction increases resistance and then increases BP, Vasodilation decrease resistance and decreases BP.
- Blood flow distribution - Adjustments due to resistance.
- Disease states
What does NB mean?
Fran says it means important
What does TPR mean?
Total peripheral resistance
(Resistance of entire systemic vasculature)