B1A 1.1 RESPONDING TO CHANGE
Hormones, secreted by special glands, are chemicals that control internal processes in the body.
The nervous system responds to changes in the environment
- receptor cells detect stimuli such as
- light
- sound
- temperature
- impulses from the receptor travels along the sensory neurone
- the brain then co-ordinates a response
- impulses from the brain travel back along motor neurones to the effector
RECEPTOR > SENSORY NEURONE > CO-ORDINATOR > MOTOR NEURONE > EFFECTOR
B1A 1.2 REFLEX ACTION
- Reflexes are reactions to change that happen unconsciously
- Reflex actions include pulling your hand away from a hot object to protect your body
- the receptor detects the change then an impulse travels along a sensory neurone to the spinal chord, not the brain
- it then passes over a synapse and along a relay neurone, then straight back to the effector along the motor neurone
- this reaction is very quick and requires no conscious thought
Impulses travel synapses by sacs containing chemicals passing the gap which starts another impulse on the relay neurone.
B1A 1.3 THE MENSTRUAL CYCLE
- the menstrual cycle is controlled by hormones
- once a month, the pituitary gland secretes FSH
- this makes eggs mature in the ovary
- it stimulates the secretion of oestrogen from the ovaries
- this causes the womb lining to thicken
- it stimulates the pituitary gland to produce LH
- this stimulates the release of the matured egg
B1A 1.4 ARTIFICIAL CONTROL OF FERTILITY
THE CONTRACEPTIVE PILL
- contain mainly oestrogen
- oestrogen inhibits the release of FSH
- without FSH no eggs can mature
- must be taken regularly
- can cause health problems
FERTILITY TREATMENTS
- fertility drugs containing FSH can be taken
- this stimulates eggs to mature in the ovary
- also triggers the release of oestrogen
- can result in many babies
- IVF treatments remove eggs from the ovaries and fertilize them with sperm in a test tube
- good if fallopian tubes are damaged
- expensive
- low success rate
- raises ethical questions about interfering with god's plan and what to do with extra embryos
B1A 1.5 CONTROLLING CONDITIONS
WATER AND IONS
- if too much water moves in or out of cells they could be damaged
- you lose water in sweat, urine and when you breath out
- you lose salt in sweat and urine
- kidneys control water and salt levels
TEMPERATURE
BLOOD SUGAR
- blood sugar levels must be kept constant
- controlled by the pancreas
- secretes insulin
- a healthy diet consists of:
- carbohydrates
- proteins
- fats
- vitamins
- minerals
- fibre
- water
- the right amount of energy
- if your diet isn't balanced you will become malnourished
- in rich countries such as the UK, there are not many malnourished people, but some don't get the right amount of energy
- the amount energy a person needs depends on:
- gender
- age
- amount of exercise they do
- the temperature of where they live
- their metabolic rate
- this is affected by proportion of fat to muscle and your genes
- BMI = WEIGHT / (HEIGHT)2
- if you take in more energy than you use, the excess is stored as fat
- fat is useful but too much can lead to obesity
- being obese causes health problems such as:
- arthritis
- diabetes
- high blood pressure
- heart disease
- you can lose weight by cutting back the amount of energy you take in
- you can increase the amount of energy you use up
- some people join slimming groups
- in some parts of the world there is not enough food. this could be due to:
- wars
- draughts
- crop failure
- people in these countries have starvation. the main symptoms are:
- looking very thin
- muscles wasting away
- immune system failure
- periods stopping
- sometimes these symptoms are seen in the developed world due to a mental disorder called anorexia nervosa
CHOLESTEROL
- the amount and type of fat eaten seems to affect cholesterol
- cholesterol is made in the liver
- it makes cell membranes and some hormones
- too much cholesterol can increase risk of heart disease and blocked arteries
the amount of cholesterol is a persons blood depends on:
- the way their liver works which is genetic
- the amount of fat in their diet
- low density lipoproteins (LPDs) are "bad" cholesterol, increasing risk of heart problems
- high density lipoproteins (HPDs) are "good" cholesterol, reducing risk of heart disease
- saturated fats
- found in meat and dairy products
- raises cholesterol levels
- mono-unsaturated fats
- found in olive oils and nuts
- decreases cholesterol levels and improves the LPD to HPD balance
- poly-unsaturated fats
- found in oily fish and sunflower oil
- even better than mono-unsaturated fats
- salt is essential to life
- however, too much can lead to health problems such as:
- high blood pressure
- heart disease
- kidney damage
- increased risk of stroke
- a drug is a substance that alters the way in which your body works
- they change the chemical processes in the body
- they can be addictive
- some drugs, such as caffeine, tobacco and alcohol, are legal
- other drugs such as cannabis, cocaine and heroin are illegal
- drugs change the chemical processes in the body
- the body can become dependent on them
- the body can also build up a tolerance, meaning more of the drug is needed to feel normal
- trying to stop taking a drug can cause withdrawal symptoms such as:
- cravings
- shaking
- headaches
- alcohol, tobacco and illegal drugs can cause the body harm
- smoking cannabis can lead to mental problems
- drugs are addictive and expensive which can lead to:
- crime
- not eating properly
- thinking of nothing but the drug
- most medical drugs have little or no effect on the nervous system
- however, all recreational drugs (legal or illegal) affect the brain
- nicotine and caffeine are legal stimulants
- this means they speed up brain activity
- cocaine, ecstasy and LSD are illegal stimulants
- alcohol is a legal depressant
- this means it slows down brain activity
- it can help people relax
- cannabis and heroin are illegal depressants
- heroin stops impulses in the nervous system
- drugs are a big problem in sport with people cheating
- sporting drugs can:
- build up muscle mass
- make an athlete more alert and have faster responses
- give an athlete more energy
- alcohol slows down reactions
- it can cause loss of self control
- this means people put themselves in dangerous situations
- people make bad decisions
- too much alcohol can cause alcoholic poisoning
- severe vomiting
- unconsciousness
- coma
- death
- alcoholics are addicted to alcohol
- brain damage
- liver cirrhosis
- liver cancer
- being under the influence of alcohol makes accidents more likely
- 20% of fatal road accidents are caused by alcohol
- heavy drinking is linked to crime and domestic violence
- alcohol-related illness puts a large strain on the NHS
- cigarette smoke contains around 4000 chemicals
- nicotine is the highly addictive drug in tobacco smoke
- other chemicals in the smoke can cause:
- lung cancer
- emphysema
- more likely to get infections
- a build up of mucus - smokers cough
- blocked arteries
- raised blood pressure
- heart disease
- carbon monoxide is found in cigarette smoke
- it is highly poisonous
- smoking while pregnant can increase the risk of:
- a premature birth
- a baby with low birth mass
- a stillbirth
- diseases are caused by pathogens
- pathogens are micro-organisms that cause disease
- they passed from one person to another
- this means they are infectious
- single celled organisms
- no nucleus, genetic material just in cytoplasm
- not all bacteria cause disease
- split in two which releases toxins
VIRUSES
- even smaller than bacteria
- genetic material in protein coat
- all cause disease
- take over body cells and reproduce within them until they burst
IGNAZ SEMMELWEISS
- realized disease could be spread
- encouraged doctors to wash hands between operations
EXTERNAL MECHANISMS
- skin
- impermeable
- barrier for sensitive tissue
- platelets
- clot when skin is broken
- forms a scab which seals break in skin
- mucus
- line inside of lungs and tubes, trapping pathogens
white blood cells defend the body internally
- ingesting pathogens
- producing antibodies
- these target particular pathogens and destroy them
- each type of antibody is specific to the type of pathogen
- once the WBCs have produced an antibody, they can remake them very quickly if need be
- antitoxins
- counteract the toxins produced by bacteria
- lots of drugs just relieve symptoms of disease
- antibiotics cure diseases by killing bacteria
- can't destroy viruses as these reproduce inside cells
- the first antibiotic was penicillin and was discovered by Alexander Fleming
- many bacteria have become resistant to antibiotics through natural selection
- to prevent resistance, it is important not to over-prescribe antibiotics
- if bacteria or viruses mutate new strains could cause an epidemic or pandemic
- a good medicine is:
- effective
- safe
- stable
- at first new drugs are tested in labs
- next is animal testing
- then its tested on healthy volunteers
- then people with the disease
- medicine will be monitored while in use
- thalidomide was used as a sleeping pill before it was found to stop morning sickness
- it was assumed to be safe for babies but many had limb deformities
- testing is much more rigorous now
- all cells have antigens on their surface
- pathogens' antigens are different from our own
- WBCs recognise this and make antibodies to attack them
- once this antibody has been made the WBC know how to make it quickly for the next time the pathogen enters the body
- a weakened version of the pathogen is injected, so it won't cause disease
- the WBCs produce the antibody to kill it
- once they have done this they will be able to kill that particular disease next time it enters the body before it causes disease
- this means the person is immune
- vaccines can be used on viruses as well as bacteria
- no medicines are risk free
- a very small minority of babies react badly to the injection
- vaccines are good for society because if enough people are immune, the disease will no longer be able to exist in a country..
Source: http://getrevising.co.uk/revision-notes/aqa_science_b1ae:
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