Heart & circulation Flashcards
What are cardiovascular diseases?
Diseases of the heart and circulation
What are the main forms of cardiovascular diseases?
• Coronary heart disease
• Stroke
What is the function of the heart and circulation?
To move substances around the body
How do unicellular organisms move substances around?
As distances are short, substances such as oxygen, carbon dioxide and digestive products move around the organism by diffusion
What is diffusion?
The movement of molecules from a region of high concentration to a region of low concentration
Why can’t multicellular organisms rely on diffusion?
They are too large for diffusion to move substances around their bodies quickly enough
How do multicellular organisms move substances around?
They rely on a mass transport system to move substances efficiently over long distances by mass flow
What does a circulatory system consist of?
Animals usually have blood to carry vital substances around their bodies and a heart to pump it
How do open circulatory systems work?
Blood circulated in large open spaces. A simple heart pumps blood out into cavities surrounding the animals organs. Substances can diffuse between the blood and cells.
How do closed circulatory systems work?
Blood is enclosed within tubes - blood vessels. This generates higher blood pressures as the blood is forced along fairly narrow channels. This means the blood travels faster and so the blood system is more efficient at delivering substances around the body.
Where does the blood travel in a closed circulatory system?
• The blood leaves the heart under pressure and flows along arteries and then arterioles to capillaries
• The capillaries come into close contact with most of the cells in the body where substances are exchanged between blood and cells
• The blood then returns to the heart by means of benumbed and then veins
What is the function of valves?
To ensure that blood flows only in one direction
How does blood flow in single circulatory systems? (fish example)
• The heart pumps deoxygenated blood to the gills
• Gaseous exchange takes place in the gills; there is diffusion of CO2 from the blood into the water that surrounds the gills, and diffusion of oxygen from this water into the blood within gills
• The blood leaving the gills then flows round the rest of the body before eventually returning to the heart
How many times does the blood flow through the heart in single circulatory systems?
Once for each complete circuit of the body
How does blood flow in double circulatory systems?
• The right ventricle of the heart pumps deoxygenated blood to the lungs where it receives oxygen
• The oxygenated blood then returns to the heart to be pumped a second time (by the left ventricle) out to the rest of the body
How many times does the blood flow through the heart in double circulatory systems?
Twice for each complete circuit of the body
What does the heart do to the blood returning from the lungs?
Gives the blood an extra ‘boost’ that reduces the time it takes for the blood to circulate round the whole body
What does the extra ‘boost’ allow birds and mammals to have?
To have a high metabolic rate, as oxygen and food substances required for metabolic processes can be delivered more rapidly to cells and meet the needs of the organism
What is the transport medium in animals?
Blood
What does plasma contain?
• Mainly water
• Digested food molecules (glucose)
• Oxygen
• Carbon dioxide
• Proteins
• Amino acids
• Salts
• Enzymes
• Hormones
• Antibodies
• Urea
What cells are carried in blood?
• Red blood cells
• White blood cells
• Platelets
What is the heart made of?
Cardiac muscle
What is the function of the right side of the heart?
It receives deoxygenated blood from the body and pumps it to the lungs
What is the function of the left side of the heart?
It receives oxygenated blood from the lungs and pumps it to the body
Label a diagram of the heart
What is the function of the arteries?
Carry blood from the heart to the rest of the body
What is the function of the veins?
Take blood back to the heart
What is the function of the capillaries?
Where metabolic exchange occurs - substances are exchanged between cells and capillaries
What common features do arteries and veins have?
• Walls contain collagen
• Elastic fibres
• Smooth muscle cells in walls
What does collagen do?
Makes them strong and durable
What do elastic fibres do?
Allows them to stretch to accommodate high pressure and recoil to maintain pressure on blood
What does the smooth muscle do?
Allows them to constrict and dilate
How are arteries adapted to carry out their function?
• Thick smooth muscular walls: maintain high pressure without damage - contract/exert pressure
• Folded endothelium: allows stretching to accommodate high pressure
• Narrow lumen: maintains blood at high pressure
• Smooth lining: reduces friction to blood flow
How are veins adapted to carry out their function?
• Thinner walls: allows skeletal muscle movement and low heart pressure to draw blood towards heart
• Valves: ensures blood continues to move towards the heart
• Large lumen: blood flows back to the heart under low pressure
How are capillaries adapted to carry out their function?
• One cell thick walls: reduces diffusion distance, higher rate of diffusion
• Large network near all cells: increases surface area which allows a higher rate of diffusion
• Narrow lumen: reduces diffusion distance between RBC and tissue cells
Label diagrams of arteries, veins and capillaries
What happens to the blood vessels during systole?
The heart contracts, blood is forced into arteries and their elastic walls stretch to accommodate the blood
What happens to the blood vessels during diastole?
The heart relaxes, the elasticity of the artery walls causes them to recoil behind the blood, helping to push the blood forward and smoothing blood flow
How is the heart muscle supplied with blood?
Through its own coronary circulation; two vessels called the coronary arteries, a network of capillaries and two coronary veins
How does the heart work?
The chambers of the heart alternately contract (systole) and relax (diastole) in a rhythmic cycle. One complete sequence of filling and pumping blood is called a cardiac cycle.
What happens to the heart during systole?
Cardiac muscle contracts and the heart pumps blood out through the aorta and pulmonary arteries
What happens to the heart during diastole?
Cardiac muscle relaxes and the heart fills with blood
What are the 3 phases of the cardiac cycle?
- Atrial systole
- Ventricular systole
- Diastole
What happens in the atrial systole phase?
Blood under low pressure flows into the left and right atria from the pulmonary veins and vena cava. As the atria fill, the increasing pressure of blood against the atrioventricular valves pushes them open and blood begins to leak into the ventricles. The atria walls contract forcing more blood into the ventricles.
What happens in the ventricular systole phase?
The ventricles contract from the base of the heart upwards, increasing the pressure in the ventricles. The pressure forces open the semilunar valves and pushes blood up and out through the pulmonary arteries and aorta. The pressure of blood against the atrioventricular valves closes them and prevents blood flowing backwards into the atria.
What happens in the cardiac diastole phase?
The atria and ventricles relax. Elastic recoil of the relaxing heart walls lowers pressure in the atria and ventricles. Blood under higher pressure in the pulmonary arteries and aorta is drawn back towards the ventricles, closing the semilunar valves and preventing further back flow into the ventricles. The coronary arteries fill during diastole. Low pressure in the atria helps draw blood into the heart from the veins.
Describe the roles of arterioles and capillaries in blood flow.
They offer a greater total surface area than the arteries, resisting flow more, slowing the blood down and causing the blood pressure to fall
