Circulatory Systems Flashcards
Purpose of heart
Contract to pump blood to different areas of the body and supply cells with oxygen and glucose as well as remove waste
Diffusion
Random net movement of molecules from a region of their high concentration to a region of their low concentration
Why can’t complex multicellular organisms rely on diffusion to transport substances
They have a low SA:volume ratio, more cells so need more nutrients and need quicker gas and waste produce exchange. Have a higher metabolic rate so use more nutrients and need this carried over larger distances
What is mass flow
How particles in a liquid move on one direction through tubes due to a different in pressure created by contractions of the heart, move down pressure gradient
Open circulatory system
No blood vessels to transport blood, organs and tissues are directly fed with blood which is pumped by a simple heart into cavities. When heart relaxes, blood drawn from cavity back into heart through valved openings
Which animals have open circulatory systems
Small animals such as insects
Why can certain animals have open circulatory systems
They have a relatively low metabolic rate meaning a sufficient amount of oxygen and glucose diffuse into body cells without the need for blood vessels. Blood does not need to travel far so can have lower pressure.
Closed circulatory system
Blood enclosed within blood vessels, generating higher blood pressures as blood forced along narrow channels-travels faster so more efficient.
Path of blood in terms of blood vessels in a closed circulatory system
Leaves heart under pressure and flows along arteries then arterioles(small arteries) to capillaries. Capillaries come into close contact with body cells where substances are exchanged between blood and cells. Returns to heart by venules(small veins) and veins.
Single circulatory systems and path of blood in fish
Heart contracts once for circuit of body. Heart pumps deox blood to gills where gaseous exchange occurs with diffusion of carbon dioxide from blood into water and diffusion of oxygen from water into gills. Oxygenated blood then flows around rest of body before returning to heart.
Which animals have single circulatory systems and why can they afford to have this
Fish as they are smaller so blood does not need to travel as far and have lower metabolic activity so do not need as much nutrients. Concentration gradients do not need to be as high
How many chambers of heart in single circulatory system
Two chambers , one ventricle and one atrium
Double circulatory systems
Heart contracts twice for each circuit of the body. Creates higher pressure meaning blood can travel further and gets to body cells faster and deliver oxygen. Means higher concentration gradients for gas exchange= allows higher metabolic rates. No mixing of deox and ox blood= higher concen gradients.
Path of blood in double circulatory system
Right ventricle of heart pumps deoxygenated blood to lungs where receives oxygen, oxygenated blood returns to heart second time to be pumped by left ventricle to rest of body.
Which animals have double circulatory systems
Birds and mammals
What does systole mean
Contraction
What does diastole mean
Relaxation
What is a cardiac cycle
A sequence of alternating contraction and relaxation of the atria and ventricles in order to pump blood throughout the body
What happens in atrial systole
Atria contract which forces open atrioventricular valves allowing blood to enter ventricles
What happens in ventricular systole
Ventricles contract which increases pressure in the ventricles, forcing closed the atrioventricular valves due to pressure. This also forces open the semilunar valves and pushed blood up and out through pulmonary arteries and aorta.
What happens in diastole
Atria and ventricles relax, elastic recoil of relaxing heart walls lowers pressure in atria and ventricles. Blood under higher pressure in pulmonary arteries and aorta drawn back towards ventricles which closes semilunar valves and prevents back flow. Coronary arteries fill. Low pressure in atria draws blood into heart from veins
Which valves open and closed during atrial systole
Atrioventricular open, semi lunar closed
Are atrioventricular valves open during diastole
Yes
