Anatomy and Physiology of the CVS

Question 1

Define the function of the cardiovascular system

Answer 1

The CVS is s bulk flow system which transports oxygen, carbon dioxide, nutrients, metabolites, hormones and heat around the body through the bloodstream.

Question 2

Justify the significance of pressure, resistance and capacitance with respect to the cardiovascular system

Answer 2

Pressure is the force exerted by blood on the walls of blood vessels or heart chambers, indicating the speed and force of the circulation.
Resistance is exertion in the bloodstream from the walls of the vessel which dictates the rate of flow.
Capacitance is the ability of blood vessels (primarily veins) to store blood until needed when not in circulation.

Question 3

Indicate the significance vascular beds being arranged in parallel or in series

Answer 3

The majority of vascular beds are in parallel meaning they all receive blood directly from the heart at the same time.
Some beds are in series, example organs are the kidney and liver. This means that blood pumped from the heart first goes through another organ before reaching the other, generally to improve specialised functions.

Question 4

List the sequence of events occurring during excitation-contraction coupling in cardiac muscle

Answer 4

1. Action potentials travel along the sarcolemma, down into the T-tubule system depolarising the cell membrane
2. Voltage sensitive DHP receptors open to allow calcium to enter the cell during phase 2 of the action potential
3. Calcium influx triggers the release of calcium stored in the SR through calcium release channels, increasing intracellular calcium concentration
4. Free calcium binds to to actin thin filaments, causing a conformational change. This causes ATP hydrolysis by myosin which supplies energy for conformational change in the actin-myosin complex
5. This causes a movement between the myosin heads and actin, shortening the sarcomere length. The cycle continues as long as the calcium concentration remains high.
6. Calcium entry slows, calcium is returned to the SR through active transport and expelled from the cell through active transport, lowering calcium concentration. This causes the conformational change in the troponin complex, returning the sarcomere to its initial length.

Question 5

Compare the basis of action potential in pacemaker and non-pacemaker tissue

Answer 5

Pacemaker tissue has a slower rate of depolarisation in response to action potentials in comparison to non-pacemaker tissue.