Blood pressure Flashcards
What is hypertension?
High blood pressure
What is blood pressure a measure of?
The hydrostatic force of the blood against the walls of a blood vessel
When is pressure in arteries highest?
When the ventricles have contracted and forced blood into the arteries - systolic pressure
When is pressure in arteries lowest?
When the ventricles are relaxed - diastolic pressure
How is systolic pressure measured?
When the blood first starts to spurt through the artery that has been closed
How is diastolic pressure measured?
When the pressure falls to the point where no sound can be heard and it equals the lowest pressure in the artery
What is the top and bottom number of a blood pressure?
Top = systolic pressure, maximum blood pressure when heart contracts
Bottom = diastolic pressure, blood pressure when heart relaxes
What is peripheral resistance?
Contact between blood and the walls of the blood vessels causes friction and this impedes the flow of blood
What are the fluctuations in pressure in the arteries caused by?
Contraction and relaxation of the heart. As blood is expelled from the heart, pressure is higher.
Describe the roles of arterioles and capillaries in blood flow.
They offer a greater total surface area than the arteries, resisting flow more, slowing the blood down and causing the blood pressure to fall
Describe the effect of smooth muscle contraction in arteries and arterioles.
This contraction leads to vessel constriction, making the lumen narrower and increasing resistance, which raises blood pressure
How does smooth muscle relaxation affect blood pressure?
This relaxation dilates the lumen of blood vessels, so peripheral resistance is reduced and blood pressure falls
List some factors that contribute to the construction of arteries and arterioles and therefore elevated blood pressure.
• Natural loss of elasticity with age
• Release of hormones (adrenaline)
• High-salt diet
What is oedema?
Fluid building up in tissues and causing swelling. It may be associated with kidney or liver disease, or with restricted body movement.
What forms tissue fluid?
Pressure forces fluid and small molecules normally found in plasma out through the tiny gaps between the cells of the capillary wall into the intercellular space.
What happens to this tissue fluid?
The tissue fluid drains into a network of lymph capillaries which returns the fluid to the blood via a lymph vessel which empties into the vena cava
