Properties of vessels

Question 1

Arteries: a pressure reservoir

Answer 1

• Not all of the blood that enters arteries flows into the smaller, high- resistance arterioles
• Elastin allows arteries to expand like a balloon & temporarily hold excess blood
• When the heart is in diastole, stretched arterial walls recoil & exert pressure on the blood, ensuring continued flow even when the heart is relaxed & not pumping

Question 2

Elastin fibres in arteries

Answer 2

Elastin fibers allow arteries to expand during systole and passively recoil during diastole.

Question 3

Arteries: blood pressure fluctuates during the cardiac cycle

Answer 3

– Blood pressure is the force exerted by blood against a vessel wall. It depends on:
• Volume of blood
• Compliance of vessel

Question 4

during ventricular contraction

Answer 4

During ventricular contraction, the volume of blood that enters the arteries (stroke volume) is about one third greater than what leaves & enters the arterioles

Question 5

during ventricular relaxation

Answer 5

– During ventricular relaxation, blood does not enter arteries although blood flow from arteries into arterioles continues due to the elastic recoil

Question 6

Arteries: blood pressure fluctuates during the cardiac cycle

Answer 6

– Systolic pressure is the max pressure in arteries when blood is pumped into them *during contraction
– Diastolic pressure is the min pressure in arteries when there is no heart contraction & blood continues to flow into arterioles * HEART IS RELAXING - NEVER GETS TO 0 IN ARTERY

Question 7

Arteries: blood pressure fluctuates during the cardiac cycle

2

Answer 7

– Pulse pressure is the difference between systolic & diastolic pressures. It is this pressure difference we can feel when taking our pulse
– Mean arterial pressure is the average pressure during each cardiac cycle. This is the pressure that the body monitors & regulates

Question 8

Arteries: blood pressures at rest

Answer 8

– Systolic pressure 120 mmHg
– Diastolic pressure 80 mmHg
– Pulse pressure? 40 mmHg – MAP 93mmHg

Question 9

MAP

Answer 9

MAP = diastolic pressure + 1/3 (systolic-diastolic)

MAP isn’t halfway because in diastolic phase 2/3 longer compared to systolic which is 1/3

Question 10

Blood pressure throughout the systemic circulation

Answer 10

Arteries: 80 - 120
- pressure
resevoir so doesn’t
go to 0

Arterioles: starts about 93 and then drops due to adding high resistance

Arterial pressure never drops to zero unlike ventricular pressure as next contraction fills arteries again, before all
the blood has flowed out