OCR GCSE Biology B1a-h

B1a - Fitness and HealthHealthy = Free from diseaseFitness = The ability to do physical activityMeasuring fitness: Stamina Agility Muscle Mass Speed Cardiovascular activity (how well the heart copes with physical activity i.e. how quickly your heart rate returns to normal) Blood pressure = A measure of the force of blood pushing against an artery wall, indicates how hard the heart is having to work to pump blood through the blood vessels.Systolic is the top number, caused when the heart CONTRACTSDiastolic is the bottom number, caused when the heart RELAXESHigh Blood pressure: Causes: Obesity, smoking, lots of salt, too much alcohol, lack of exercise Risks: Kidney disease/damage, cardiovascular disease, burst blood vessels, stroke Low Blood pressure: Causes: Dehydration. blood loss, lack of nutrients Risks: Anaemia, cold hands and feet, medical shock, fainting, dizziness, blurred vision Cholesterol = Comes from saturated animal fats, can lead to heart disease by blocked up the coronary arteries and preventing blood flow to the heart causing heart disease.Heart Disease = When cholesterol blocks the arteries, stopping blood flow to the heart and causing the heart to stop working.Angina = When the coronary arteries get blocked causing chest pains.Cardiac Arrest = When the heart stops beating altogether.Heart Attack = When one part of the heart cannot get oxygen and stops working; left arm goes numb.Components of cigarette smoke: Nicotine Tar Carbon Monoxide

B1b - Human Health and DietFood is broken down by enzymes: Proteins into amino acids Fats in fatty acids and glycerol Complex sugars into simple sugars Essential amino acids = Cant be made in the body; animal proteins (first class); 8 typesNon-essential amino acids = Can be made in the bodyBMI = Mass(kg/) / Height (m2)<18.5 = Underweight18.5-24.9 = Ideal weight25-29.9 = Overweight>30 = Obese (could lead to type 2 diabetes, arthritis, breast cancer, and heart disease)Balance diet includes: Minerals Vitamins Fibre Water Carbohydrates and fats to provide energy Proteins for growth and repair of tissues EAR (amount of protein to be eaten daily) = 0.6 x Body Mass (kg) (Can vary depending on age, pregnancy and lactation)

B1c - Staying HealthyCancer: Non-infectious (cannot be caught from another person) Benign tumour = grows in one place and doesn't spread Malignant tumour = starts to grow in other places of the body Reducing the likelihood: Don't smoke; Don't drink excess alcohol; Avoid sunburn; Healthy diet. Infectious diseases can spread from one person to another, caused by pathogens. Fungi/Fungus = Athlete's foot Virus = Flu Bacteria/Bacterium = Cholera Protozoa/Protozoan = Malaria Malaria: A mosquito (the vector) sucks blood from the human (the host) If there are malaria parasites in the blood, they mate and move from the mosquito's gut to its salivary glands The mosquito bites another human and passes the malaria parasites into their bloodstream The malaria parasites move to the liver where they mature and reproduce The new generation migrates to the blood and replicates in red blood cells, bursting them open, this leads to malaria fever, sometimes death We can prevent this by: Sleeping under mosquito nets Using insect repellents Killing them with insecticide Defences against pathogens: The skin acts as a barrier against micro-organisms The blood clots in wounds preventing micro-organisms from entering the blood stream The respiratory system is lined with cells that produce a sticky mucus to trap micro-organisms The stomach produces hydrochloric acid which kills micro-organisms in the food we eat Pathogens show symptoms of disease in 2 ways: Physically damaging cells Producing toxins There are two different types of white blood cells that tackle pathogens Lymphocytes (produce anti-bodies) Phagocytes (engulf pathogens) Active Immunity = If you've been infected by a particular pathogen, your white blood cells make antibodies to kill them. This means they can produce the necessary antibodies much quicker if the same pathogen is detected again. This provides future protection.Immunisation = Provides natural immunity from a disease A person is injected with a weakened or dead strain of pathogen The antigens trigger the production of specific antibodies by the white blood cells Afterwards the white blood cells remain in the blood (memory cells). This means more antibodies can be produced very quickly is the same pathogen is detected again Passive Immunity = Occurs when antibodies are put into an individual's body. This is used as a quick response or when a person has a weak immune systemDiseases caused by bacteria or fungi can be treated using antibiotics. Antiviral drugs are used to treat diseases caused by viruses only. New drugs have to be tested to make sure they are safe and effective. A new drug can be tested using: Computer models (to predict how it will effect cells) Animals (to see how it affects living organisms) Human tissue, grown in a laboratory (to see how it affects human cells) Healthy Volunteers (either the placebo or or the actual drug) Blind trial = the volunteers don't know whether they have been given the new drug or the placeboDouble Blind trial = neither the volunteers nor the doctors know which drug has been given, eliminates bias.

B1d - The Nervous SystemMain components of the nervous system: Brain (CNS) Spinal Cord (CNS) Neurones that make up the peripheral nervous system Locations of receptors: Light receptors in eyes Sound and balance receptors in ears Taste receptors on tongue Smell receptors in nose Touch, pressure, pain and temperature receptors in skin Neurones are specially adapted cells that can carry a nerve impulse (an electrical message/signal)3 types of neurone: Sensory neurones = carry nerve impulses from receptors to brain Relay neurones = make connections between brain and spinal cord Motor neurones = carry nerve impulses from your brain to muscles and glands These neurones are adapted to their job. They have: An elongated axon to make connections throughout the body A 'myelin' or insulated sheath to speed up nerve impulses Dendrites to allow a single neurone to act on many muscle fibres Synapses: An electrical impulse travels down a neurone until it reaches a synapse (small gap between neurones) A transmitter substance is made at the pre-synaptic end and diffuses across the synapse The transmitter binds with the receptor molecules on the next neurone, causing an electrical impulse to be initiated in that neurones. The reflex arc: Stimulus (change in environment) Receptor Sensory Neurone Relay Neurone Motor neurone Effector Response e.g. knee jerk, pupil size change, withdrawing hand from hot object The eye:Iris = controls amount of light entering the eyeCornea = refracts rays of lightLens = focuses light onto the retina, so the rays converge and produce a clear image on the retinaLight receptors in the retina = cause nerve impulses to pass along sensory neurones in the optic nerve to your brainCommon eye defects include: Long (corrected by a CONVEX lens) and short sight (corrected by a CONCAVE lens) Red - green colour blindness Cones = colourRods = Black and WhiteTypes of vision: Binocular (eyes close together on front of head; each eye has limted field of view; can judge distance and speed accurately; humans and prey) Monocular (eyes postioned on either side of head; each eye has wide field of view; cannot judge distance and speed as there in little overlap in the fields; prey) NEAR OBJECT: Ciliary muscles CONTRACT, Suspensory ligaments SLACKEN, Lens is SHORT AND FATDISTANT OBJECT: Ciliary muscles RELAX, Suspensory ligaments PULL TIGHT, Lens is LONG AND THIN

B1e - Drugs and youDrug categories: Stimulants (e.g. Caffeine, nicotine, ecstasy) Increases brain activity, causes more neuro-transmitter to cross the synapse Depressants (e.g. Alcohol, solvents, tranquillisers) Decreases brain activity, bind with receptor molecules and blocks the transmission of the next impulse Painkillers (e.g. Aspiring, paracetamol, heroin) Blocks nerve impulses Performance-enhancing drugs (e.g. Anabolic steroids) Increases muscle development Hallucinogens (e.g. LSD) Distorts what is seen and heard Class A = most dangerous, heavy prison sentences and large fines (heroin, cocaine)Class B = lower penaltiesClass C = less dangerous, lowest penalties (steroids and tranquillisers)Addiction = physiological or physical need for the drugTolerance = needing a higher dosage to get the same effectRehabilitation = the process in which an addict learns to live without the drugWithdrawal symptoms = symptoms an addict experiences during rehabilitation e.g. cravings, sweating, shaking, nausea.Short term effects of alcohol: lack of balance and muscle control blurred vision and slurred speech poor judgement and drowsiness vasodilation Long term effects of alcohol: liver damage brain damage Tobacco: Smoking can lead to disease such as cancer of the mouth, throat, oesophagus and lungs, heart disease, emphysema and bronchitis. It damages the cilia which line the airways (trachea, bronchi and bronchioles) This prevents the movement of cilia, tar and dirt from the lungs, leading to 'smokers cough'. Cigarettes contain tar, nicotine, and produces carbon monoxide. Tar contains carcinogens (cancer-causing chemicals)

B1f - Staying in balanceHomeostasis = maintaining a constant internal environment. e.g. steady temperature, water levels and carbon dioxide in the blood.Temperature control mechanisms: Vasoconstriction (blood vessels constrict and raise body temperature) Vasodilation (blood vessels dilate and lower body temperature) Piloerection (hairs stand on end and raise body temperature) Shivering (raises body temperature) Sweating (lowers body temperature) Hormones = chemical messages released by glands directly into the blood streamDiabetes:The hormone insulin is released by the pancreas to control blood sugar levels. Type 1 diabetes is when the pancreas fails to produce insulin. Type 2 diabetes affects the cells that respond to insulin, they become unresponsive to the insulin.

B1g - Controlling plant hormonesPlant hormones are chemical that control: The growth of shoots and roots Flowering and the ripening of fruits Auxin affects the plant's growth by responding to gravity/light (geo/phototropism)Shoots grow: Towards light (positive phototropism) Against gravity (negative geotropism) Roots grow: Away from light (negative phototropism) Towards gravity (positive geotropism) Auxin works in 3 steps: The hormones in direct sunlight are destroyed The hormones on the shaded side continue to function causing the cells to elongate The shoot bends towards the light Commercial uses of hormones: Rooting powder Fruit-ripening hormone Control of dormancy Selective weedkillers

B1g - Variation and inheritanceGenetic variations = Nose shape, Eye colourEnvironmental variation = Language, ScarsCombination = Body mass, Intelligent, HeightAlleles: Dominant alleles = control the development of a characteristic even if a recessive allele is present Recessive alleles = Only control the development of a characteristic if a dominant allele is not present If both chromosomes in a pair contain the same allele of a gene they are HomozygousIf both chromosomes in a pair contain different alleles of a gene they are HeterozygousGametes = contain half the number of chromosomes of a normal cellGender in mammals is determined by the sex chromosomes (XX = female; XY = male)Inherited diseases : Cystic Fibrosis is caused by a faulty recessive allele