B2.1.3 The Heart
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Give some ways in which cardiac output is increased during vigorous exercise
Increased heart rate Increased stroke volume More adrenaline
Explain what causes the blood pressure in the aorta to be higher than the blood pressure in the pulmonary artery
Left ventricle has thicker muscle
Explain why a vein is described as an organ
It’s made of tissue
Explain how the elastic tissue helps even out the pressure of the blood going through the arteries
Elastic tissue stretches when pressure gets too high And recoils when pressure returns to normal
The Cardiac cycle is controlled by the sinoatrial node (SAN) and the atrioventricular node (AVN). Describe how
The SAN initiates heartbeat SAN sends waves of electricity across the atria causing atrial contraction AVN delays to allow the atria to empty (and the ventricles to fill up) before the ventricles contract AVN them sends a wave of electrical impulses down “bundle of His” This causes the ventricles to contract from the base up (ventricular systole)
An increase in respiration in the tissues of a mammal affects the oxygen dissociation curve of haemoglobin. Describe and explain how
Increase in carbon dioxide so the curve moves to the right
People living in high altitudes have more red blood cells than people living at sea level l. Explain the advantage of this to people living at high altitudes
They will have more haemoglobin so can pick up more oxygen in the lungs
Explain how fluids leave the capillaries at the arterial end
Hydrostatic pressure is greater than the osmotic effect so molecules are forced out
Explain how the shape of a red blood cell allows it to take up a large amount of oxygen in a short time
It’s has a large surface area to volume ratio for diffusion It is flat and thin so oxygen can reach all haemoglobin rapidly
Describe how the increase in pressure of the blood in the arteries is a result from the events in the cardiac cycle
Increase in blood pressure caused by blood leaving the heart and entering the arteries This is a result of ventricular systole
Describe the part played by proteins in the plasma in returning tissue fluid to the capillaries
A high concentration of protein produces a lower water potential so water moves into the capillaries by osmosis
Give some changes that will increase blood flow through the skeletal muscles
Increase in heart rate Increased volume of blood pumped per beat Dilation of vessels Increased blood pressure
Explain some advantages of increasing the blood flow through the skeletal muscles during exercise
More oxygen supplied for respiration so less anaerobic respiration More glucose supplies for respiration Carbon dioxide rapidly removed from respiring cells
Describe how the regular contractions of the atria and the ventricles is initiated and coordinated by the heart itself
Cardiac muscle is myogenic SAN sends a wave of electrical impulses across the atria This initiates the contraction of the atria AVN then spreads an electrical signal across the ventricles causing the ventricles to contract once they have filled with blood
Describe how haemoglobin loads and unloads oxygen in the body
Haemoglobin picks up oxygen at high partial pressures e.g. In the lungs Haemoglobin unloads oxygen at low partial pressures e.g. In respiring tissues
Explain how the structure of arterioles enables the regulation of blood flow to different parts of the body
Muscles in the walls for the arterioles contact increasing blood flow
When is the arterial pressure at its maximum value?
When the ventricles are contracting
give 2 ways the aorta structure is suited to function
• Elastic tissue - stretch and recoil /spring back • muscle layer for contraction • Thick walls to resist pressure and stop it bursting • smooth endothelium - reduces friction • semi lunar valve - prevents back flow
name the blood vessels that carry blood to the heart muscle
coronary arteries