Stimulus - receptor - sensory - CNS - motor - effector - response
Sensory has small cell body, motor has crazy one
Resting potential maintained by sodium/potassium pumps (3Na+ out, 2K+ in) by active transport, K+ diffuse out by facilitated diffusion - keeps overall negative charge
Waves of depolarisation, Na+ moves along neurone
Saltatory conduction in myelinated neurones is fast, impulses jumps between nodes of Ranvier
Bigger stilumi increase frequency (all of nothing, can't be bigger APs)
Speed increased by increasing temp (up to 40oC), and larger axon diameters (less resistance of ionas in flow)
Some chemicals can affect synaptic transmission by:
- mimicking neurtoransmitter action, actiavting more receptors
- Block receptors - paralysis
- Inhibit enzyme that breaks down neurotransmitters - loss of muscle control
- Inhibit neurotransmitter relsease
One neurone to many = divergence
Many neurones to one = convergence
Spatial summation - many release a small amount of neurotransmitter all at once, adds up to reach threshold potential
Temporal summation - many arrive in quick succession, more neurotansmitter in the cleft at one time, reaches threshold
Unidirectional transmission controlled by the presynaptic release, binding to postsynaptic membrane
Hormones can be proteins or peptides
Exocrine - secrete chemicals through ducts, endocrine secrete chemicals into blood, only affect target tissue
Hormones are first messengers - takes chemical to receptor, binds, activates enzyme in cell
Second messanger is the signalling molecule which the enzyme catalyses the production of, involved in other parts of the cell by causing a cascade (work of lots of different enzymes)
Adrenaline (first messenger) adenylate cyclase (enzyme) cAMP (signalling molecule) releases glucose
Adrenal (exocrine) glands - cortex secretes steroid hormones like cortisol, medulla secretes catechloamine hormones like adrenaline
Pancreas as endo - islets of Langerhans (clusters in blood capillaries) a's secrete glucagon, b's secrete insulin
Pancreas as exo - acinar cells (clusters around pancreatic duct) secrete digestive enzymes into duct
The maintenance of a constant internal environment
High temp - more KE, more collisions, more reactions
Too high temp - vibration of ensyme molecules denature the protein
Too low temp - Enzyme activity reduced, slowing metabolic reaction
Negative Feedback - Change in environment, receptor detects it, communication between nervous/hormonal system, effectors respond to counteract, back to normal
Positive Feedback - will amplify a change. Change in environment, receptor detects it, communication, effectors respons, higher change in environment - used to rapidly activate processes in body, e.g. form a blood clot
Ectotherms - Control their body temperature through changing behaviour - internal temp depends on external temp - variable metabolic rate and activity level, but save energy
Endotherms - Mainly controlled internally by homeostasis, less effected by external temperature - constatntly high metabolic rate, can be active at any time, use lots of energy all the time
Reducing body temp - sweating (evaporating heat), hairs lie flat (less insulation of heat), vasodilation (blood flows closer to skin surface with wider arterioles, heat lost by radiation)
Increasing - Shivering (heat from respiration of muscle spasms), hormones (adrenaline and thyroxine increase metabolism), sweat less, hairs lie flat, vasoconstriction
Hypothalamus - recieves information from thermoreceptors, detect temp of blood, peripheral receptors (in skin) detect external temp.
Blood Glucose Control
Concentration monitored by the pancreas to be 90mg per 100cm3 of blood
INSULIN - Secreted by beta cells in islets of Langherhans, lowers BGC, increases permeability of cell membranes to glucose, so the cells take up more of it - activates enzymes that convert glucose to glycogen to be stored in cells, by glycogenesis. Insulin increases rate of respiration of glucose.
Glucagon - Increases BCG, released from alpha cells. Breaks down glycogen into glucose through glycogenolysis. It also forms glucose from glycerol and amino acids by gluconeogenesis, decreasing rate of respiration of glucose.
BGC too high - detected by pancreas, insulin secreted, glucagon secretion stopped, cells take up more glucose, glycogenesis, more glucose respiration.
BGC too low - detected by pancreas, glucagon secreted, insulin not, gluconeogenesis, glycogenolysis, cells respire less glucose.
Type 1 - Body attacks own beta cells, doesn't produce insulin, BGC stays high. Treated by regular injections of insulin, and controlling eating habits.
Type 2 - Beta cells don't produce enough insulin or body doesn't respond properly, because insulin receptors on membranes don't work. Linked with obesity, or certain ethnicities, e.g. Asian. Treated by controlling carb intake and losing weight.
GM Insulin - cheaper than extraction from animals, larger quanitites made, human insulin can be made which is more effective than animal insulin, fewer ethical issues.
Stem Cells - Could be grown into beta cells to cure diabetes - implanted into pancreas of a person with type 1 diabetes.
Control of Heart Rate
CNS - Brain and Spinal Cord / Peripheral Nervous System - neurones connecting CNS to body
PNS divided into autonomic (unconscious) and somatic (conscious) nervous systems
Autonomic further divided into sympathetic (fight or flight, noradrenaline released) and parasympathetic nervous system (rest and digest, acetlycholine)
SAN controlled by medulla oblogata in the brain
Baroreceptors - detect internal stimuli of pressure in aorta, vena cava and carotid arteries /Chemoreceptors - detect stimuli of chemicals in the aorta carotid arteries and medulla oblongata
High Blood Pressure, O2, low CO2 or high PH - acetlycholine from parasympathetic neurones slow heart rate
Low Blood Pressure, O2, high CO2, low PH - Noradrenaline from sympathetic neurones increase heart rate
Adrenal glands secrete adrenaline when stressed, binds to cardiac muscle and increases contractions with more force
The Liver and Excretion
Excretion - Removal of waste products of metabolism from the body
Liver breaks down metabolic waste into less harmful substances
Hepatic artery - Supplies oxygenated blood for energy and respiration in the liver
Hepatic vein - Takes away deoxygenated blood
Hepatic Portal Vein - Brings blood from duodenum and ileum (intestines) so it has products of digestion in, so any ingested harmful substances are filtered out
Bile Duct - Takes bile to gall bladder to store
Liver lobules made of hepatocytes, hepatic vein in middle with branches of the others, connected by capillaries called sinusoids, and Kupffer cells attached to sinusoids remove bacteria and break down red blood cells. Bile duct connected to central vein by canaliculi.
Detoxification - insulin, paracetamol, alcohol (into ethanal, then acetic acid)
Ultrafiltration - Filtration of the blood through the kidneys, takes place in the thousands of nephrons (long tubules with blood capillaries).
Blood travels from renal artery - afferent arteriole in cortex - glomerulus (capillaries looped inside a renal capsule) - efferent arteriole (has a smaller diameter, blood under pressure, so forces blood into renal capsule).
The filtrate passes from capillary endothelium, to basement membrane, to epithelium of renal capsule - then filtrate passes along nephron, being selectively reabsorbed.
Selective Reabsorption - Takes place in PCT, LoH, and DCT - useful substances leave nephron tubules and enter capillary network around them.
PCT epithelium has microvilli for larger surface area to reabsorb solutes like glucose, salts, amino acids by active transport and facilitated diffusion.
Kidneys and Water
Regulation of water content takes place in LoH, DCT and Collecting Duct - volume absorbed is controlled by release of antidiuretic hormone by the pituitary gland when water content is low, through osmoreceptors in hypothalamus.
LoH Length - alters in different animals, a longer one means more solutes pumped out, low water potential in medulla, so gives concentrated urine, usually in desert animals who need water.
ADH molecules bind to receptors on membranes of cells in DCT and collecting duct, causing aquaporins to go on the membrane and allow water to pass through by osmosis, making the DCT and collecting duct more permeable to water. So more is reabsorbed back into the blood, so urine is concentrated.
Dehydration: little water - detected by osmoreceptors - pituitary gland release ADH - makes DCT and collecting duct permeable - more water reabsorbed - highly concentrated pee
Hydration: too much water - detected by osmoreceptors - pituitary gland releases less ADH - DCT and CD less permeable - less water reabsorbed - diluted pee
Infections - Kidneys swell, damage cells, intereferes with filtering/reabsorption High Blood Pressure - Damage glomerulus, larger molecules can get through capillary walls
Problems: Build up of waste products = vomiting and weight loss. Accumulation of fluid = Swelling of legs, face, abdomen Imbalance of ions = Brittle bones, water retention Long term kidney failue = anaemia
Solution 1: Renal Dialysis - How it Works: Patient's blood filtered through dialysis machine (dialysis fluid and blood, either side of partially permeable membrane, flow in opposite directions to keep high concentration gradient, waste products from blood flow into dialysis fluid) - Problems: patients feel unwell between sessions, time consuming, expensive, less risky tho
Solution 2: Transplant - How it Works: New one put in from someone with the same blood and tissue type - Advantages: Cheaper, more convenient, don't feel unwell - Disadvantages: Risky, need immunosuppressants
- Stick used with antibodies for hCG attached to coloured bead, any hCG from urine will attach
- Urine moves up strip carrying beads with it, and test strip has immobilised antibodies to hCGs
- If hCG is present then strip turns blue because the immobilised antibody binds to hCG, will concentrate blue beads in the immobilised area.
- With no hCG, it wont attach to anything and so wont go blue
- Drugs that build up muscle tissue, banned in athletics, as its unfair and dangerous
- Steroids are removed from blood in urine, so athletes have urine tests
- Urine is vaporised for gas chromatography, and is passed up a column containing a liquid
- Length of time taken for substances in sample to move up is compared to time taken for a steroid to move up, if time is the same, urine contains steroids.
Storing and Releasing Energy
Photosynthesis is a metabolic pathway in which autotrophs make glucose from CO2 and water.
ATP is the cell's immediate source of energy, synthesised from ADP and Pi using ATP synthase enzyme and energy from an energy releasing reaction, and is stored as chemical energy.
Using energy makes ATP go back to ADP + Pi, using ATPase, and is known as hydrolysis as it uses water.
Properties of ATP:
- Stores/releases small amounts of energy
- small molecule
- easily broken down
- transfers energy by the transfer of a phosphate
- can't pass out of the cell.
- A double membrane (chloroplast envelope)
- Thylakoids (fluid filled sacs), which are stacked to form grana, joined by thylakoid membranes called lamellae
- Photosynthetic pigments (chlorophyll a, b, carotene) coloured substances that absorb light and are found in lamellae (attached to protein) protein + pigment called a photosystem
- Stroma - gel like substance surrounding thylakoids containing enzymes, sugars, organic acids - starch is stored here
- Photosystems have 2 photosynthetic pigments, primary (reaction centre, where electrons are excited when photons of light hit, usually chlorophyll a) and...
- accesory pigments - surround, and transfer light energy to, primargy pigments.
- PS1 - absorbs light best at 700nm, PS2 - absorbs light best at 680nm.
Adaptations for Photosynthesis:
- Chloroplast envelope keeps reactants for photosynthesis close to reaction sites
- Thylakoids have large surface area to absorb lots of light
- Lots of ATP synthase molecules in thylakoid membranes
- Stroma contains necessary enzymes/sugars/organic acids for light independent reaction.
Reduction - Gained electrons, may have gained hydrogen or lost oxygen Oxidation - Lost electrons, may have lost hydrogen or gained oxygen.
Coenzyme - a molecule that aids the function of an enzyme, transfers a chemical group from one molecule to another. NADP - coenzyme in photosynthesis, transfers hydrogen between molecules.
Light Dependent Reaction - takes place in thylakoid membranes, light is absorbed by photosynthetic pigments and converted to chemical energy - used to form ATP (transfers energy) from ADP and reduce NADP (transfers hydrogen)
Light Independent Reaction - Uses products of LDR, takes place in stroma
Products of Photosynthesis
- Calvin Cycle needs to turn six times to make one hexose sugar (one TP molecule each time)
Carbs, Lipids, Aminos
- Larger carbs (like starch) are made by joining hexose sugars
- Lipids made using glycerol (synthesised by TP) and fatty acids (Synthesised from GP)
- Amino Acids can be made from GP
- ATP - Adenine Triphosphate
- TP - Triose Phosphate
- RuBP - Ribulose Bisphosphate
- GP - Glycerate 3-Phosphate
- Rubisco - Ribulose bisphosphate carboxylase
Limiting Factors in Photosynthesis
- Light - High light intensity of red and blue light in sunlight needed for photosynthetic pigments
- Temp of 25 - Optimum for rubisco and ATP synthase, and keeps stomata open
- CO2 at 0.4% - Higher rate of photosynthesis, but not too high that stomata close
- Water - constant supply (too little, no photosynthesis, too much, waterlogged soil)
Saturation Point - Where a limiting factor is not longer limiting
- CO2 - Added to the air in a greenhouse, e.g. burning propane in CO2 generator
- Light - Light can get in through glass, lamps at night
- Temp - Glass traps heat from sunlight warming the air, can set up heaters/coolers
Limiting Factors in Calvin Cycle
Light Intensity - Low Light = less ATP and reduced NADP. Conversion of GP to TP and RuBP is slower, so more GP.
Temperature - Low temp = slower enzyme reactions - all levels will fall.
CO2 Concentration - Less CO2 = Less GP, as RuBP can't combine with CO2, so RuBP levels rise, GP and TP fall as they're being used to make RuBP.
- Inner mitochondrial membrane is folded into cristae, increases surface area
- ATP Synthase molecules in inner mitochondrial membrane
- Mitochondrial matrix contains reactants and enzymes for LR and KC.
- NAD and FAD - transfer hydrogen atoms
- Coenzyme A - transfers acetate
- Should be 32 molecules per molecule of glucose, but is lower as:
- Some NAD+ is used in other reactions
- Some ATP is used up in actively transporting these substances
- Inner mitochondrial membrane is leaky, some protons may get into matrix without making ATP
Any biological molecule that can be broken down in respiration to release energy, e.g. glucose, other carbs, lipids and proteins.
Respiratory Quotient - The volume of Carbon Dioxide produced when that substance is respired, divided by volume of oxygen consumed.
RQ = Volume of CO2 released / Volume of O2 consumed
Roughly: Carbs = 1, Lipids = 0.7, Proteins = 0.9
C6H12O6 + 6O2 = 6CO2 + 6H2O + Energy /// 6/6 = 1
- You can find the respiratory quotient for a whole organism
- This means you can find out which substances they respire and what type of respiration (an/aerobic)