biology - transport in humans

why can simple, unicellular organisms rely on diffusion for movement of substances in and out of the cell

they have a large surface area to volume ratio (large surface area compared to volume ratio)

oxygen, nutrients and waste can move directly across the cell membrane

distances to travel for absorption are short so diffusion is fast enough to carry around what the organism needs

what is the need for a transport system in multicellular organisms

multicellular organisms have a low surface area to volume ratio, so oxygen and nutrients would take too long to reach organs; need a specialised circulatory system to carry faster

describe the composition of the blood

red blood cells, white blood cells, platelets and plasma

what is the role of plasma in the transport of carbon dioxide, digested food, urea, hormones and heat energy

main transport medium

transports 5% of carbon dioxide

transports dissolved nutrients e.g. glucose, amino acids, vitamins

transports waste nutrients

transports hormones that are release directly into the bloodstream

regulates body temperature by redistributing heat that the water in plasma can absorb

adaptations of red blood cells to make them suitable for oxygen transport

no nucleus so more space for haemoglobin

filled with haemoglobin which attaches to oxygen

biconcave shape to increase SA:V ration for oxygen diffusion

small and flexible to fit in blood capillaries to carry oxygen

how does the immune system responds to disease using white blood cells

wbc discovers pathogen, takes a while to produce antibodies. the next time, it removes the pathogen and produces the antibody quicker and destroys the pathogen quicker

phagocytes

move towards bacteria or pathogens and engulf them (phagocytosis)

lymphocytes

produce antitoxins to neutralise the toxins from pathogens

are specific to particular toxins

vaccination

results in manufacturing of memory cells to enable future antibody production to the pathogen occur sooner, faster and in greater quantity

platelets

stick to the broken vessel wall

they release chemicals that activate clotting.

this causes fibrin (an insoluble protein) to form a mesh that traps blood cells and seals the wound.

adrenaline

a hormone released when danger is perceived

adrenaline increases heart rate because body needs to pump more blood around the body for the muscles

factors that may increase the risk of developing coronary heart disease

coronary arteries blocked by cholerstrol 

stress, blood pressure, high animal-fat diets, lack of excercise, the older the weaker the arteries are. smoking drugs, old age

arteries

carry blood away from heart

carries oxygenated blood except pulmonary artery

small lumen, elastic tissue and muscle, thick walls

veins

carry blood back to heart

carries deoxygenated blood except pulmonary veins

large lumen, valves, thin walls

capillaries

allow exchange of substances

one cell thick walls

structure of the circulation system

lungs → pulmonary vein → left atrium → left ventricle → aorta and valves → rest of body through capillaries to exchange oxygen → vena cava → right atrium → right ventricle → pulmonary artery → lungs