Biology - Topic 6

unfinished

digestion

digestion

series of biochemical reactions that convert large ingested food molecules into small, soluble molecules that can be absorbed by the body

sequence of organs as food passes through

mouth oesophagus stomach small intestine large intestine anus

types of enzymes found in digestive juices

amylase, protease, pancreatic lipase

amylase

salivary glands or pancrease, and produces maltose and glucose

protease

gastric glands and pancrease, produced polypeptides and amino acids

lipase

found in pancrease, produced fatty acids and glycerol

peristalsis

food passes along alimentary canal via longitudinal and circular muscles (antagonistic pair)

villi structure

columnar epithelial cells, capillaries, lacteal, smooth muscle, arteriole and venule

arteries

carry blood under high pressure, have strong muscle and elastic fibres, only 2 have valves, and are large with narrow lumen

veins

carry blood at low pressure, contain few muscles and elastic fibres, have some valves preventing backflow, thin walls and wide lumen

capillaries

carry blood under low pressure, walls are only one cell thick, no valves, diameter is 5 micrometres

direction of blood flow, starting at RA

vena cava brings deoxygenated blood into RA, passes into RV through valve (bi), blood pumped through PA; oxygenated returns via PV into LA, into LV through valve (tri), into aorta to body

sinoatrial node

pacemaker of heartbeat, located in wall of right atrium; sends signals to atriums and atrioventricular node, which signals to ventricles

how does heart rate change

nerves of medulla connected to SA node; increases as active and decreases as resting; emotions can cause adrenal glands to release adrenalin to stimulate

cardiac cycle

sequence of events that takes place during one heartbeat

systole

contraction of the muscles of a chamber of the heart

diastole

relaxation of muscles of heart

pathogens

living organisms or viruses that cause disease. Most are bacteria and viruses but fungi and parasitic worms can also be pathogenic

first line of defence

unbroken skin prevents pathogens from entering the body at first, but openins in body are protected by mucous membranes that contain enzymes to attack

when skin is cut

clotting factors released from platelets and damaged tissue cells, prothrombin is turned into thrombin, which activated soluble fibrinogen with insoluble fibrin that creates a mesh to stop blood

antigen

protein found in membrane or cell wall of a bacterium that enables the body to recognise the pathogen

antibodies

proteins that are produced by lymphocytes in response to antigens.

what triggers antibody production

antigens stimulate cell division of lymphocytes that produce specific antibody; a clone of them is plasma cells that secretes antibody

how do antibodies kill pathogens?

cause bacterial cells to clump (agglutination), cause cell walls to rupture, prevent viruses from attaching to host cells

antibiotics

kill or block bacterial growth. Some: block protein synthesis inside, prevent cell wall formation, rupture membrane or inhibit enzymes

ventilation

maintains a concentration gradience of oxygen and carbon dioxide between the air in the alveoli and blood in capillaries

pneumocytes

type 1 are adapted to gas exchange (flattened and thing), and type 2 create a moist surface (pulmonary surfactant)

inhalation

lung pressure reduced, thorax volume increased, vacuum createrd. Diaphragm contracts to flatten, external intercostal muscles contract to raise ribs

exhalation

lung pressure increased, air forced out, internal intercostal muscles contract to lower ribs, abs contract and diaphragm relaxes, to reduce volume of thorax and force air out

lung cancer

tumours take up space in lungs, prevent gas exchanged and strain the heart (mitosis processes disturbed)

emphysema

small alveoli replaced with larger air sacs of thick and unelastic walls

neuron

a nerve cell that transmits electrical impulses along its length to the next neuron until it reaches a muscle

resting potential

the potential difference across the plasma membrane of a neuron when an impulse is not being transmitted. For most this is 70mV

action potential

rapid change in the membrane potential. It consists of two stages: depolarisation and repolarisation