Mass Transport in Animals Flashcards
what is the cardiac cycle
a sequence of events that involves the coordinated contraction and relaxation of the walls of the atria and ventricles
how many phases does the cardiac cycle have?
three
what occurs in the first stage of the cardiac cycle? (4)
ventricles relax, atria contract
- ventricles relax and so have lower pressure
- atria contract; volume of chambers decreases, pressure increases
- atrioventricular valves open
- blood enters the ventricles down a pressure gradient
what occurs in the second phase of the cardiac cycle? (4)
ventricles contract, atria relax
- atria relax, and so pressure decreases
- ventricles contract; volume decreases, pressure increases
- atrioventricular valves close
- semi lunar valves open
what occurs in the third phase of the cardiac cycle? (2)
ventricles relax, atria relax
- pressure is now higher in the pulmonary artery and aorta
- semi lunar valves close to prevent backflow into the heart
CHARACTERISTICS: arteries (3)
- thick muscle to withstand high pressure
- elastic tissue to stretch and recoil
- inner lining called endothelium which is smooth and reduces friction
CHARACTERISTICS: arterioles
muscular layer is thicker than arteries to allow them to contract and constrict the lumen
CHARACTERISTICS: veins (3)
- thin muscle wall because the blood is at low pressure
- have valves to ensure no backflow of blood
- have a wide lumen which provides reduced friction
CHARACTERISTICS: capillaries (5)
- walls are one cell thick to allow short diffusion pathway
- wall is permeable
- fenestrations which allow large molecules to leave the blood vessel and be delivered to the cell
- narrow lumen to reduce flow rate, giving more time for diffusion
- endothelial cells are smooth and flat to reduce friction
what exactly is tissue fluid?
the fluid by which substances are exchanged between the blood and the cells
“in capillary beds, substances move out of the capillaries, into the tissue fluid, by _____________ ________________”
pressure filtration
“_____ _____, _______, _____, and ____ pass from the plasma into the tissue fluid and then from the tissue fluid into the cells”
amino acids
glucose
water
ions
explain the process of tissue fluid formation within the body (6)
- at the arterial end of the capillary, there is a higher hydrostatic pressure than in the tissue fluid
- an overall outward pressure forces fluid out of the capillaries and into the tissue space
- tissue fluid is formed
- at the venous end of the capillary, there is a lower hydrostatic pressure than in the tissue fluid
- tissue fluid is forced back into the capillaries
- water potential of the capillary is lower than the tissue fluid, so water re-enters by osmosis
what is the reason for a reduced water potential of the capillary at the venous end?
because large plasma proteins that are too big to leave the capillary remain
what happens to the tissue fluid that does not return to the capillaries?
it is drained away from the tissues via the lymphatic system - this fluid is now referred to as lymph
list the risk factors for cardiovascular disease (5)
age
due to gradual deposit over a lifetime
gender
men more at risk up until middle age - due to protective effect of oestrogen in women up until menopause
genetic factors
stress
causes increased blood pressure
smoking
nicotine is a vaso-constrictor - increases blood pressure
increases levels of cholesterol
what are lipoproteins?
made in the liver from fats, cholesterol and protein
what are the two types of lipoproteins that can be found within the blood?
LDL
low density lipoproteins
HDL
high density lipoproteins
LDL (2)
- the ‘bad’ cholesterol
- the greater the concentration of LDL, the greater the risk of CHD
HDL (2)
- the ‘beneficial’ cholesterol
- absorb excess cholesterol and return it to the liver where it is removed
how can high blood LDL be treated?
using statins
