CV system + haemodynamic (wk6)

Question 1

What are the main functions, structure and challenge’s of the CV system?

Answer 1

-Transportation of oxygen, nutrients and metabolites to the tissues, and the removal of metabolic waste products. Helps to produce energy in the body.
-Involvement in homeostatic mechanisms. Key role in the regulation of body temperature.
-Distribution of hormones to the tissues, and secretion of some hormones. How and when they operate.

Question 2

What are the main functions and structure of the CV system?
-Pulmonary and systematic circulation

Answer 2

-The pulmonary circulation is connected to the heart ‘in series’, which means that the entire blood volume has to pass through it every time it circulates the body. Circulation of blood in our lungs.
-The systematic circulation is connected to the heart ‘in parallel’, which means that there is a choice of which part of the body receive more or less of the available blood volume

Question 3

What are the main functions, structure and challenge’s of the CV system?
-Values and pulmonary and systematic circulation

Answer 3

-Typical values and implications -> Typical values of total blood volume -> roughly 5 litres + cardiac output -> roughly 5 litres/min. The implications for these numbers on;
1. The pulmonary circulation (upper half of diagram)-> It need to accommodate the entire blood volume every minute, even at rest. During peak exercise it needs to accommodate up to 5x the entire blood volume (roughly 25L) every minute..
2. The systemic circulation (lower half of diagram) -> There is not enough blood to fully support the metabolic needs of every tissue. Because of this, blood supply to inactive tissues is reduced and blood supply to active tissues is increased.

Question 4

Flow, pressure and resistance
-Darcy’s Law

Answer 4

-Fluid are incompressible. Fluid can only move out of the way and not decrease in size.
-Contractions of the ventricles of the heart generates pressure which is transferred to the blood causing it to flow along the blood vessels
-Driving pressure -> Flow is created by the pressure difference between 2 points. A pressure difference between 2 points has to be made to move fluid around.
-Flow (Darcy’s Law) = Pressure difference (symbol) / resistance
-Flow requires a pressure difference, but the amount of flow depends on pressure difference, not the absolute values of pressure
-The resistance and driving pressure has to be regulated to allow ‘flow’.

Question 5

Flow, pressure and resistance
-Poiseuille’s Law and combining the laws

Answer 5

-Use equation from 29/10
-Poiseuille’s Law (determines resistance to flow)
-Combining Darcy’s and Poiseuille’s Laws -> Flow = pressure difference x r4. Flow relation to pressure and vessel radius is directly proportional. This means that the higher the driving pressure and the larger the radius of a vessel, the higher the flow is (and vice versa)
-Doubling the vessel radius reduces resistance by a factor of 16. Halving the vessel radius would increase resistance by a factor of 16.
-Flow is proportional to driving pressure and the radius

Question 6

Velocity of blood flow in the CV system
-The relationship of CSA and velocity

Answer 6

-Velocity = flow rate/ cross-sectional area
-Units -> Velocity = distance/ time (cm/min, m/sec), Flow rate = volume/time (cm3/min), Cross-sectional area (CSA) = cm2,m2
-The narrower the vessel, the faster the flow
-Dot on top of a unit = a flow rate

Question 7

Velocity of blood flow in the CV system
-Relationship of total CSA and velocity

Answer 7

-Flow velocity of blood in the CV system depends on the cumulative radius of all vessels at a similar distance from the heart
-In tissues, the larger CSA and very low blood flow velocity is very important for diffusion of gases and exchange of nutrients/ waste
-Aorta through to capillaries