Cardiovascular system pt.2

Question 1

How does SV and HR recover?

Answer 1

1. SV is maintained during early stages of recovery, as HR rapidly reduces
2. This will maintain blood flow and the removal of waste products while lowering the stress and workload on the cardiac muscle.

Question 2

How does CO recover?

Answer 2

CO decreases rapidly followed by a slower decrease to resting levels.

Question 3

What is the cardiac control centre?

Answer 3

1. Controlled by the autonomic nervous system (ANS) and determines the firing of the SA node
2. Located in the medulla oblongata of the brain
3. Responsible for regulating the heart via motor nerves:
   - The sympathetic nervous system which increases HR via the accelerator nerve
   - The parasympathetic nervous system which decreases HR via the vagus nerve.

Question 4

Which 3 factors control the activity of the cardiac control centre?

Answer 4

1. Neural control:
   - Proprioceptors, located in muscles, tendons and joints, they inform the CCC that movement has increased
   - Chemoreceptors, located in the aorta and carotid arteries, these detect a decrease in blood pH due to an increase in lactic acid and carbon dioxide
   - Baroreceptors, located in blood vessel walls, these inform the CCC of increased blood pressure
2. Intrinsic control:
   - Temperature, changes will affect blood viscosity and the speed of nerve impulse transmission
   - Venous return, changes will affect the stretch in ventricle walls, force of contraction and therefore SV
3. Hormonal control:
   - Adrenaline and noradrenaline, these are released from the adrenal glands and increase SV and HR.

Question 5

What is the vascular system?

Answer 5

The vascular system is a network of blood vessels and the blood they carry. Blood is 45% cells and 55% plasma.

Question 6

What is the function/structure of arteries and arterioles?

Answer 6

1. Carry oxygenated blood from the heart to muscles and organs
2. Contain blood under high pressure, so have thick walls
3. Have a large layer of smooth muscle to vasodilate and vasoconstrict, regulating blood flow and pressure
4. Arterioles have a ring of smooth muscle surrounding the capillary bed, called pre-capillary sphincters, which dilate and constrict to control blood flow.

Question 7

What is the function/structure of capillaries?

Answer 7

1. Capillary walls are 1 cell thick to allow gas to diffuse faster meaning gas exchange is easier
2. Gas exchange takes place:
   - Oxygen passes through the capillary wall and into the tissue
   - Carbon dioxide passes from the tissues into the blood through the capillary wall.

Question 8

What is the function/structure of veins and venules?

Answer 8

1. Carry deoxygenated blood form the muscles and organs back to the heart.
2. They contain blood under low pressure, so they have thin walls
3. Contain a smaller layer of smooth muscle allowing them to venodilate and venoconstrict
4. They have one-way pocket valves to prevent blood flowing backwards against gravity.

Question 9

What is meant vasodilation, vasoconstriction?

Answer 9

1. Vasodilation is the widening of arteries, arterioles and pre-capillary sphincters
2. Vasoconstriction is the narrowing of arteries, arterioles and pre-capillary sphincters.

Question 10

What are the mechanisms of venous return?

Answer 10

1. Pocket valves, located in the veins to stop the backflow of blood
2. Smooth muscle, the wall of each vein contains smooth muscle which venoconstricts, squeezing blood to the heart
3. Gravity, blood from the upper body, above the heart, is aided by gravity in its return to the heart
4. Muscle pump, many veins are situated between skeletal muscles, during exercise these muscles squeeze on the veins and help pushes the blood back towards the heart
5. Respiratory pump, helps return blood in thoracic cavity and abdomen back to the heart. While exercising, we inspire and expire faster and more deeply, this rapidly changes the pressure within the thorax between high and low to help squeeze the blood in the area back to the heart.

Question 11

What is the vascular shunt mechanism, at rest/during exercise?

Answer 11

1. As exercise begins, muscles demand more oxygen so blood flow is diverted to the working muscles away from non-essential organs
2. At rest:
   - Arterioles to organs vasodilate, increasing blood flow
   - Arterioles to muscles vasoconstrict, limiting blood flow
   - Pre-capillary sphincters vasodilate, opening up the capillary beds to allow more blood flow to the organ cells
   - Pre-capillary sphincters of capillary beds of muscle vasoconstrict
3. During exercise:
   - Arterioles to organs vasoconstrict, decreasing blood flow
   - Arterioles to muscles vasodilate to increase blood flow
   - Pre-capillary sphincters vasoconstrict, closing capillary beds to decrease blood flow to the organ cells
   - Pre-capillary sphincters of capillary beds of muscle vasodilate.

Question 12

What is vasomotor control?

Answer 12

1. Vasomotor control centre (VCC) is located in the medulla oblongata of the brain
2. The smooth muscle in the walls of arterial blood vessels is always in slight state of constriction, known as vasomotor tone
3. The VCC alters the level of stimulation sent to arterioles and pre-capillary sphincters at different sites in the body, allowing the vascular shunt mechanism
4. The VCC receives information from chemoreceptors and baroreceptors
5. In receipt of this information, is either increased to limit blood flow to an area of decreased to increase blood flow to an area.