Topic 3E: The Mammalian Circulatory System Flashcards
Explain how the highest blood pressure is produced in the left ventricle. [1]
- Stronger contractions
Some babies are born with a hole between the right and left ventricles. These babies are unable to get enough oxygen to their tissues.
Suggest why. [2]
- Blood flows from left ventricle to right ventricle;
- Lower volume of (oxygenated) blood leaves left ventricle
Suggest how tendinous cords help to maintain the flow of blood in one direction through the heart. [2]
- (Valves close) when ventricles contract;
- Prevent valves from being inverted
Give two safety precautions that should be followed when dissecting a heart. [1]
- Use a sharp scalpel;
- Wash hands/wear gloves;
- Disinfect bench;
- Cover any cuts;
- Cut away from self/on a hard surface;
- Safe disposal by placing hearts in separate bin
Explain how atrioventricular valves help to maintain a unidirectional flow of blood. [2]
- Pressure in atrium is higher than in ventricle causing valve to open;
- Pressure in ventricle is higher than in atrium causing valve to close
Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs. [3]
- Renal vein;
- Vena cava to right atrium;
- Right ventricle to pulmonary artery
Name the blood vessels that carry blood to the heart muscle. [1]
- Coronary arteries
Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta. [5]
- Atrium has higher pressure than ventricle causing atrioventricular valves to open;
- Ventricle has higher pressure than atrium causing atrioventricular valves to close;
- Ventricle has higher pressure than aorta causing semilunar valve to open;
- Higher pressure in aorta than ventricle causing semilunar valve to close;
- (Muscles) contraction causes increase in pressure.
Suggest how the flow of some of the blood between the aorta and pulmonary artery due to Patau syndrome could cause children to die in the first 12 months. [3]
- (Some) oxygenated blood (from aorta) flows into pulmonary artery;
- Less oxygen delivered to cells;
- So less oxygen for aerobic respiration;
- Tissue dies
The cardiac cycle is controlled by the sinoatrial node (SAN) and the atrioventricular node (AVN).
Describe how. [5]
- SAN sends wave of electrical activity (across atria) causing atrial contraction;
- Non-conducting tissue prevents impulses reaching the ventricles;
- AVN delays (impulse) whilst ventricles fill;
- (AVN) sends wave of electrical activity down Bundle of His;
- Causing ventricles to contract from base up
Describe and explain the structure of arteries. [6]
- Lumen: space through which blood flows;
- Endothelium: smooth to reduce friction with blood;
- Elastic tissue: stretches due to high blood pressure when ventricle contracts then recoils when ventricle relaxes;
- This recoil help to maintain blood pressure and smooth blood flow;
- Muscle: contracts to constrict the lumen (vasoconstriction);
- Reduces blood flow
- Outer layer: tough to withstand high blood pressure and stop bursting;
- The aorta and pulmonary artery have semilunar valves to prevent back flow of blood into the ventricles.
State the structural differences between arteries and veins. [2]
- Narrow lumen vs wide lumen;
- More elastic tissue vs less elastic tissue;
- More muscle vs less muscle;
- Thicker wall vs thinner wall;
- No valves vs valves
Explain how arteries can reduce the blood flow to certain parts of the body. [2]
- Contracts;
- (Causing) vasoconstriction
Explain how elastic tissue in the walls of arteries help to even out the pressure of blood. [2]
- Stretches when pressure is high;
- Recoils to normal
Describe and explain the structural adaptations of capillaries. [5]
- Endothelium is one cell thick so diffusion pathway is short;
- Endothelium cells are flattened so diffusion pathway is short;
- Narrow lumen increases friction and therefore reduces rate of blood flow so there is more time for diffusion;
- Narrow lumen means red blood cells are in close contact with the endothelium so diffusion pathway for oxygen is short;
- Small diameter overall so large surface area to volume ratio;
- Pores between endothelial cells allow water and certain dissolved substances to leak out of blood and form tissue fluid.
Explain why the rate of blood flow decreases from the aorta to the capillaries. [1]
- Increases in friction
Efficient exchange of substances in the capillaries is linked to the rate of blood flow.
Explain how. [1]
- (More) time for exchange of substances
Explain how an arteriole can reduce the blood flow into capillaries. [2]
- Muscle contracts;
- Narrows lumen
Which blood vessel carries blood with the lowest pressure? [1]
- Vena cava
Describe two precautions a student should take when clearing away after a dissection. [2]
- Carry sharp instruments by the handle;
- Disinfect surfaces;
- Wash hands with soap (and water);
- Put organ in a (separate) bin to dispose
Describe how tissue fluid is formed and how it is returned to the circulatory system. [6]
Formation:
1. High blood pressure;
2. forces water out;
3. Large proteins remain in capillary;
Return:
4. Low water potential in blood;
5. Due to proteins;
6. Water enters blood;
7. (by) osmosis
8. (Any remaining excess) tissue fluid returns (to blood) via lymphatic system.
Explain the role of the heart in the formation of tissue fluid. [2]
- Contraction of ventricle(s) produces high blood pressure;
- Forces water (and some dissolved substances) out (of blood capillaries)
Suggest how a blockage in the lymphatic system could cause swelling. [1]
- Excess tissue fluid builds up
Explain why a lack of protein in the blood causes a build up of tissue fluid. [3]
- Water potential gradient is reduced;
- Less water removed (into capillary);
- By osmosis
The hydrostatic pressure of the blood at the arteriole end of the capillary helps to form tissue fluid.
Explain how. [2]
- Hydrostatic pressure higher than osmotic effect;
- Forces water out
A high concentration of sodium ions in the blood can raise blood pressure. Suggest how. [3]
- (Sodium ions) lower the water potential (of blood);
- Water moves into the blood by osmosis (from tissue fluid);
- Increasing the blood volume
What is the function of the coronary arteries? [2]
- (Carry) oxygen/glucose;
- (to) heart muscle
The rise and fall in blood pressure in the aorta is greater than in the small arteries. Suggest why. [3]
- Directly linked to the heart;
- (Aorta has) elastic tissue;
- Stretch / recoil
Although the speed of blood flow in an arteriole is greater than speed of blood flow in a capillary, blood does not accumulate in the arterioles.
Explain why. [1]
- Many capillaries;
- (Cross-sectional) area of capillaries (much) greater
An arteriole is described as an organ. Explain why. [1]
- Made of (different) tissues
Explain the difference in thickness between the pulmonary artery and the pulmonary vein. [1]
- Higher pressure in pulmonary artery
The thickness of the aorta wall changes all the time during each cardiac cycle.
Explain why. [3]
- (Wall) stretches because pressure increases;
- Recoils because pressure falls;
- Maintains pressure/smooth flow
Describe and explain the changes in the speed of flow of blood from the aorta to capillaries. [2]
- Slow decrease in speed until reaches arterioles then rapid decrease;
- More friction
Explain why the volumes of blood in the pulmonary artery and vein are the same but the speed of flow is different. [1]
- (Pulmonary vein has) wider lumen so greater volume carried
Describe how you would calculate cardiac output from heart rate and stroke volume. [1]
Heart rate x stroke volume
