intro to the CVS

Question 1

why do we need a CVS ?

Answer 1

• temperature regulation
• human reproduction
• pump blood through lungs and carry oxygen
• transport nutrients to muscles and organs
• circulates hormones and immune mediators
• connection to lymphatic system

Question 2

what is typical resting blood pressure ?

Answer 2

120/80 mmHg

Question 3

how is cardiac output calculated ?

Answer 3

heart rate x stroke volume

Question 4

what are 3 factors that impact cardiac output ?

Answer 4

• filling pressure ( starlings law)
• sympathetic and parasympathetic autonomic nerves
• chemical factors and hormones ( adrenaline)

Question 5

what are the 4 major blood vessels and their functions ?

Answer 5

arteries
* partially elastic to Accommodate stroke volume and provide a constant flow.
arterioles
* Control arterial BP & regulate local blood flow.
capillaries
*Nutrient delivery to cells tissue water & lymph formation removal of metabolic waste.
venules and veins
* Control the filling pressure of the heart & provide a reservoir of blood.

Question 6

how are cardiac output and oxygen consumption distributed around the body?

Answer 6

• liver and GI have the most consumption
• oxygen consumption of the brain and myocardium is higher than its cardiac output, which means that if the cardiac output drops, it can cause problems as they can’t afford to lose blood

Question 7

How does pressure vary through the circulation system?

Answer 7

• Highest Pressure (Arteries) – The highest pressure is in the aorta and large arteries due to the forceful contraction of the left ventricle.
• Gradual Decline (Arterioles) – Pressure drops significantly in arterioles, which regulate blood flow using vasoconstriction and vasodilation.
• Low Pressure (Capillaries) – In the capillaries, pressure is lower to allow nutrient and gas exchange.
• Even Lower (Veins & Venules) – Venules and veins have much lower pressure, aided by valves and muscle contractions to return blood to the heart.
• Lowest Pressure (Right Atrium) – The right atrium has the lowest pressure, ensuring continuous blood return to the heart.

Question 8

Why is blood flow faster in the aorta and slowest in the capillaries?

Answer 8

• Aorta (Fast Flow): The aorta has a small total cross-sectional area, so blood moves quickly under high pressure from the heart.
• Capillaries (Slow Flow): Capillaries collectively have a large total cross-sectional area, causing blood to slow down, allowing sufficient time for gas and nutrient exchange.

Question 9

Why does blood speed up again when it gets into the venous system?

Answer 9

Blood speeds up in the venous system because the total cross-sectional area decreases as venules merge into larger veins.

• Capillaries (Slow Flow): Blood moves slowly due to a large total cross-sectional area.
• Veins (Faster Flow): As capillaries converge into venules and then veins, the total cross-sectional area decreases, increasing blood velocity.
• Aided by External Forces: Venous return is also helped by skeletal muscle contractions, respiratory movements, and valves that prevent backflow.

Question 10

Where is blood volume distributed in blood vessels and why?

Answer 10

• Veins (~60-70%) – The majority of blood is in the veins because they are high-capacitance vessels that can expand and store blood.
• Arteries (~10-15%) – Arteries hold less blood since they have thicker walls and function mainly for high-pressure distribution.
• Capillaries (~5%) – A small portion is in capillaries, allowing efficient exchange of gases and nutrients.
• Heart & Lungs (~10-15%) – The heart and pulmonary circulation hold a moderate amount to maintain continuous circulation.
• Veins act as a blood reservoir, adjusting blood return to the heart as needed.