Topic 1: 1.1 Flashcards
Structure of water molecules
Water is a dipolar molecules because it has uneven distribution of charges over the molecules
. Oxygen: slightly negative due to distribution of lone pairs
. Hydrogen: slightly positive due to the position of the electrons on one end of the atom only
Properties of water
. Very cohesive and form hydrogen bonds because they’re dipolar -> the slightly negative oxygen atoms are attracted to the slightly positive hydrogen atoms
- This helps water flow making it good for transporting substances
. Good solvent because its dipolar-> the slightly negative oxygen atoms are attracted to the positive ions and the slightly positive hydrogen atoms are attracted to negative ions, this means ions will get totally surrounded by water molecules and form hydrogen bonds (the ions dissolve)
- this allows metabollic reactions to occur
- allows transport of substances
Mass transport systems: single celled organisms and multicellular organisms
Cells need energy which they achieve via aerobic respiration so glucose and oxygen need to be delivered to cells
- Single celled organisms: diffusion alone is enough to exchange gasses due to short diffusion distance
- Multicellular organisms: higher metabolic rates than small organisms so diffusion alone isn’t enough to exchange gases due to larger distance to cells -> they have mass transport systems and specialised exchange surfaces
-> circulatory system: mass transport system in mammals -> individual cells get nutrients and oxygen from the blood and get rid of metabolic waste into the blood
Blood vessels: arteries -> function and adaptations
Carry oxygenated blood from the heart to the rest of the body
-> thick muscular walls with elastic tissue that allow the endothelium to expand and recoil to withstand high pressure
-> muscular walls contain collagen which strengthens the wall to maintain high pressure
-> contraction of muscular wall constricts lumen maintaining high pressure
-> narrow lumen to maintain high pressure
Blood vessels: veins -> function and adaptations
Carry deoxygenated blood back to the heart
-> large lumen and very little elastic or muscle tissue to maintain low pressure
-> surrounding skeletal muscles contract helping blood flow in them
-> they have valves to stop blood flowing backwards due to the low pressure
. Valves: only open one way
Open: higher pressure behind valve
Closed: higher pressure in front valve
Blood vessels: capillaries -> function and adaptations
Where metabolic exchange occurs (gas exchange occurs)
-> capillary cells are one cell thick, speeding up the rate of diffusion
-> there’s capillary beds (network of capillaries in tissue9 that increase surface area for gas exchange
-> they have pores in the cell membrane for diffusion of small molecules
Heart dissection: external examination
. Four main blood vessels
-> arteries are thick and rubbery
-> veins are thinner
. Left and right atria
. Left and right ventricles
. Coronary arteries
Heart dissection: internal examination
. Left ventricle wall is thicker that the wall of the right ventricle
. Atria wall are thinner than ventricle walls
. Septum is a thick wall separating the two side of the hearts
Functions of structures in the heart
. Left ventricle is thicker than the right ventricle because it needs to pump blood strongly to the rest of the body whilst the right ventricle only need to get blood to the lungs
. Ventricles have thicker walls than atria because they have to pump blood out of the heart whereas atria just needs to push blood into the ventricles within the heart
. Atrioventricular valves link atria to ventricles and stop blood from flowing back intro atria
-> valve tendons/ valves attach AV valves to ventricles to stop them being forced up into atria when ventricles contract
. Semilunar valves link ventricles to pulmonary artery and aorta and stop blood from flowing back into the heart
The cardiac cycle: stage 1: ventricle diastole, atrial systole
Ventricles relax and atria contract
-> VALVES: AV valves open and SL valves close
1. Atria volume decreases and pressure increases so AV valves open as there’s a higher pressure in the atria than in the ventricles
2. Blood flows into the ventricles increasing slightly its volume
The cardiac cycle: stags 2: ventricular systole, atrial diastole
Ventricles contract and atria relax
-> VALVES: AV valves close and SL valves open
1. Ventricular volume decreases and pressure increases so AV valves shut as there’s a higher pressure in the ventricles than atria and SL valves open as there’s a higher pressure in the ventricles than in the arteries
2. Blood flows out of the heart via the pulmonary artery and aorta
The cardiac cycle: stage 3: cardiac diastole
Ventricles and atria relax
-> VALVES: AV valves open and SL valves close
1. Higher pressure in the arteries than in the the ventricles so the SL valves shut
2. Blood re-enters the atria via the vena cava and pulmonary vein due to higher pressure in veins
-> some blood passively enters the ventricles due to gravity as AV valves are open as there’s a higher pressure in the atria than in the ventricles
