Cardiovascular system

Question 1

What materials are carried by the blood?

Answer 1

• O2 and CO2
• Energy substrates
• Hormones
• Waste metabolites
• Drugs and drugs metabolites

Question 2

What direction does blood occur in pulmonary circulation?

Answer 2

Through right ventricle to lung to collect oxygen and then into left ventricle

Question 3

What direction does blood travel in systemic circulation?

Answer 3

From left ventricle through all organs and tissues - except lungs - delivers oxygen, back to right atrium

Question 4

Describe the blood flow in the hepatic portal system

Answer 4

1. Atrial blood enters the first capillary bed in the stomach and small intestine where nutrients and toxin are absorbed into the bloodstream
2. Various veins from these organs transport blood and join at the hepatic portal vein where the blood is taken to the liver
3. In the liver blood is taken to the second capillary bed in the liver sinusoids where nutrients and toxins leave the bloodstream and diffuse into the hepatocytes.
4. The blood then travel out of the liver via the hepatic vein and then the inferior vena cava to the heart.

Question 5

Describe the left and right sides of the heart

Answer 5

Right heart

• Low pressure
• Receives deoxygenated blood from vena cava
• Pumps deoxygenated blood to lungs to remove CO2 and pick up O2 (gas exchange)

Left heart

• High pressure
• Receives oxygenated blood from the pulmonary vein and pumps it out of the aorta to the rest of the body
• Walls of left ventricle are thicker and more muscular due to being needed to pump the blood further than the right side.

Question 6

Explain the cardiac cycle,

Include electrical and mechanical processes.

Answer 6

1. At complete cardiac diastole - Atria are continuously filling with blood which causes an increase in pressure in the atria, which is higher than in the ventricles and cause the atrioventricular valves to open. This allows blood to passively flow into ventricles.
2. Sino Atrial nodes trigger a wave of contraction across the myocardium of both atria causing Atrial systole –> causing the atria to empty and complete ventricular filling. The electrical impulse from the SA nodes is slowed when arriving at the AV nodes due to it allowing atrium contraction to complete before sending the next impulse.
3. Once atrial systole is completed the AV nodes send the impulse via the Bundle of His to the Purkinje fibres which surround the ventricles. This electrical impulse causes the mechanical response of the ventricles contracting.
4. As the pressure in the ventricles is higher than the atria the atrioventricular valves shut, and as its higher than in the pulmonary artery and aorta, the pulmonary artery and aortic valves open. Allow the contraction the send the blood through the pulmonary artery and aorta. This is ventricular systole.
5. Ventricular contraction is followed by complete cardiac systole, where the pressure in the ventricles fall so the pulmonary and aortic valves shut. Both the atria and ventricles are relaxed. Myocardium recovers and is ready for next heart beat. Atria re-fills ready for next cycle.
6. Cycle begins again

Question 7

What factors control stroke volume?

Answer 7

• End diastole volume - how much blood has entered the ventricles and is available for ejection
• Sympathetic regulation - degree of ventricular contraction

Question 8

What are some examples of the body regulating cardiac output?

Answer 8

• Exercise - energy demands of increase increased blood flow to active tissues - increasing stroke volume and heart rate
• Control of blood pressure - regulated to ensure adequate blood to tissues

Question 9

Describe arteries
(3 types)

Answer 9

• Elastic artery –> expand and relax as blood is pumped into them
• Muscular artery –> less elastic, limited ability to expand, vasoconstriction
• Arteriole –> small, critical in slowing down blood flow before capillaries, primary site of blood pressure regulation, can vasoconstrict and vasodilate, specialised for controlling blood flow into capillary beds

Question 10

Describe the different types of capillaries

Answer 10

Continuous - most common, continuous endothelial lining, tight junctions between cells, not found in the brain

Fenestrate - has pores, permeable to some larger molecules, found in small intestine and kidney

Sinusoid - least common, incomplete basement membrane, large opening, found in the liver and spleen.

Question 11

Describe the function of the capillaries and how they are adapted for their role

Answer 11

Capillaries in capillary bed have a one cell thick endothelial walls, designed for material to the pass from blood to tissue (and visa verca), quick and easily

• Blood travels slowly through them to increase time for diffusion of gases, nutrients, and waste metabolites.
• Large number of them to increase surface area
• At rest on 25% are open, when metabolic activity increases then more open up
• Cannot change diameter

Question 12

Describe venules and veins

Answer 12

• Very thin walls in comparison to arteries and arterioles
• Collagen fibres make up walls
• Able to accommodate an increase in blood volume without much rise in blood pressure

Question 13

Describe capillary exchange

Answer 13

Lipid soluble materials pass through cell membrane
Non-lipid soluble materials pass through tight junctions between cells or pores in fenestrated capillaries

Movement is driven by pressure and concentration

Question 14

What are the main factors that affect heart rate?

Answer 14

Autonomic activity
Circulating hormones
Activity and exercise
Gender
Age
Temperature
Baroreceptor reflex
Emotional states