GCSE biology unit 1 - the nervous system

The nervous system

Its job is to detect stimuli so we can coordinate our behaviour. Stimuli are changes in the environment.
Receptors sense these changes:

• eyes contain light receptors that detect light
• noses contain chemical receptors that detect smells
• mouths contain chemical receptors that detect tastes
• skin has various receptors that are sensitive to touch, temperature, pressure and pain
• ears contain sound receptors and also receptors that detect position (balance)

once the receptor has detected the stimulus, the sensory neurone passes an electrical impulse to the central nervous system (brain + spinal chord), where relay neurones pass the signals from one nerve cell to another. The CNS then passes an impulse through the motor neurone to the effectors  and a response happens.

e.g. sound stimulus - sound receptors - sensory neurone - CNS - motor neurone - effector - response.

The CNS contains synapses which are junctions between the three neurones. that pass the electrical impulses through gaps by using chemical signals.

Reflexes miss out the CNS and go straight through the three neurones. This way they are quicker so protect you. If the brain was involved, there would be a delay.

GCSE biology unit 1 - growing microbes

Growing Microbes

Also referred to as "culturing" microbes. We grow microbes to investigate what medicines can kill it. we do this under ASEPTIC CONDITIONS (make sure nothing gets contaminated that might effect the results)

STEP 1: sterilise the agar jelly inside the Petri dish
STEP 2: transfer microbes to the agar jelly using a inoculating hoop and place in neat, straight lines. The inoculating hoop should be heated first to kill any bacteria then left to cool before transferring the microbes.
STEP 3: quickly place lid on Petri dish and seal the container with tape to prevent any further contamination.
STEP 4: incubate at 25 degrees if in a school or 37 degrees if in a safe lab with scientists incase a pathogen is grown at the higher temperatures.

testing for disinfectants or antibiotics

use the microbes grown and place different sorts of disinfectants or antibiotics on the patch of microbes. once the microbes die, the agar jelly turns clear so the most effective disinfectant of antibiotic will have the largest clear area.

GCSE biology unit 1 - antibiotic resistance

Antibiotic Resistance

Medicines and Antibiotics

Pathogens infect the body and, after a while, cause symptoms. people's options are to wait for the white blood cells kick in or they can take medicines (pain killers) to relieve the symptoms. Medicines such as painkillers only relieve the symptoms - they don't effect the pathogens.

Antibiotics are medicines that relieve symptoms, have an effect on bacteria and can actually kill pathogens. These are good but...

If a doctor prescribes too many and too often the bacteria get a lot of exposure to the antibiotics and a mutation occurs (a random, spontaneous change in tis DNA) that causes the bacteria to become antibiotic resistant. This mutation is caused by natural selection. as this new bacteria multiplies, the person ends up with a population of antibiotic resistant bacteria.

scientists are developing new antibiotics that will actually kill that bacteria as opposed to just having an effect on them. These, again should not be prescribed too much.

GCSE biology unit 1 - vaccinations

vaccinations

protecting against future diseases

• vaccines contain dead pathogens that still have antigens (codes or shapes on the cell wall)
• the white blood cells will produce antibodies to attack the antigens
• in the future, if these pathogens enter the body, the white blood cells will be able to produce antibodies quicker as it will recognise the antigens

The more people that are vaccinated, the harder it is for the disease to spread as there are fewer people who can catch it.

MMR

• measles, mumps and rubella
• linked to autism (condition that effects people's communication and social interaction skills)

Ignas Semmelweis (1850s) noticed that there were fewer cases child bed fever (a common birth disease) in the wards where only the midwives worked and the were more cases of child bed fever in the wards where the medical students dealt with child birth. 

He noted that the medical students were also working on dead bodies whereas the midwifes only dealt with child birth. He also noted that the medical students didn't wash their hands after carrying out investigations on dead bodies.

He recorded results and there were indeed many more cases of the disease on the medical student wards. Semmelweis predicted that something from the dead bodies was passing on causing child bed fever. He asked the medical students to wash their hands and the number of deaths reduced but his ideas were rejected because he could not explain what was passing on. Nowadays we know this is bacteria and it is normal procedure for doctor and nurses to wash their hands continually.

GCSE CHEMISTRY - unit 1 - compounds and bonding

REACTIONS AND COMPOUNDS

New substances are formed by chemical reactions. When elements react together to form compounds their atoms join to other atoms using chemical bonds.

Ionic bonds

Compounds formed from metals and non-metals consist of ions. Ions are charged particles that form when atoms (or clusters of atoms) lose or gain electrons:

• metal atoms lose electrons to form positively charged ion
• non-metal atoms gain electrons to form negatively charged ions

The ionic bond is the force of attraction between the oppositely charged ions. 

Covalent bonds

Two non-metals share an electron to form covalent bonds that hold the atoms together to form molecules.

Chemical formulas

The chemical formula of a compound shows how many of each type of atom join together to make the units which make up the compound. For example, in iron sulfide every iron atom is joined to one sulfur atom, so we show its formula asFeS. In sodium oxide, there are two sodium atoms for every oxygen atom, so we show its formula as Na₂O. Notice that the 2 is written as a subscript, so Na2O would be wrong.

GCSE biology unit 1 - infectious diseases

Infectious diseases

Microorganisms

• E.g bacteria, viruses, fungi
• Not all cause diseases
• Ones that cause diseases are called pathogens 

Pathogens

Microorganisms that cause disease

Bacteria

Produce toxins (poisons)

Viruses

Much smaller

Infect body cells by getting inside and reproducing so many times that the cell explodes/breaks so is permanently damaged

DEFENCE - white blood cells

They ingest bacteria and release enzymes to digest pathogens

They produce antibodies to latch onto the antigens (small shapes on cell walls) of the pathogen and start destroying them. Different diseases have different antigens.

They produce antitoxins which neutralise bacteria toxins, making them harmless.

GCSE biology unit 1 - balanced diets

Balanced diet

Proteins

• Meat, fish, eggs, pulse veg. Etc.
• Build new tissue (important if still growing)
• Repairs damaged tissues
• Made up of amino acids

Carbohydrates

• Potatoes, breat, rice, sugars, etc.
• Provide energy
• Can lead to obesity if not balanced with exercise 

Fats

• Butter, oil, etc.
• Provides stored energy to be used later when needed
• Can lead to obesity if not balanced with exersise

Fibre

• Veg, fruit, etc.
• Not absorbed by body/ blood so not a nutrient
• Helps prevent constipation

Vitamins and minerals

• For general health
• Can't get energy from them
• A lack of them leads to deficiency disease

If you take in more energy compared with what you release, you will put on weight.

MALNUTRITION is caused by a non-balanced diet.

You can either be underweight or overweight.

Metabolism

Total of the chemical reactions that are going on in your body

Affected by

• Amount of exersise you do
• Genetics
• Muscle to fat ratio (muscle requires energy)
• Gender (females tend to have lower)

Cholesterol 

Required in the body to make cell membranes

Too much can lead to blocked arteries (especially around the heart), restricting the blood flow

This can lead to a heart attack.

Type 2 diabetes

Linked to being overweight

Means you cannot control blood sugar levels

Insulin is not recognised by body cells so cells don't take sugar out of the blood.