Science

Sense organs dectect Stimuli- a stimulas is a change in your enviroment which you may need to react to.

Your Five sense organs are:

Eyes, Ears, Nose, Tounge and Skin

A stimulus can be light sound touch pressure chemical or a change in position or temperature.

The nervous system consits of the spinal cord, sensory neurones, effectors(muscles) and motor neurones

Responses can be voluntary or involuntary(reflex)

Reflex actions are there to save your body from injury. eg your eyes changing to focus under different lighting conditions.

1. A naughty bee stings fingers

2. Stimulation of pain receptor

3. Message travels along the sensory neurone.

4. Message is passed along a relay neurone

5. Message travels along a motor neurone

6. When message reaches an effector to contracts to move arm away from the bee.

This 1-6 action happens in seconds without you even thinking about it.

" focusing the eye" is a reflex action.

Light receptors detect an object, and a message is sent to the brain along a sensory neurone.

The brain automatically works out if the object is in focus if the object is blurry it sends a message to the cillary muscles, that control the thickness of the lens.

To look at Distant objects:

The cillary muscles relax and lens is thin

To look at near objects:

The cillary muscles contract and the lens is thickened

Hormones are chemical messengers

They are produced in endocrine glands. They are released directly into the blood,which then carries them on to different places.But only affect particular cells in particuar places. The affected cells are called target cells, they have the right receptors to respond to the hormone.

Insulin- helps control the blood sugar levels. Its produced in the pancreas.

Oestrogen and Progesterone- These hormones help control the menstrual cycle.

If the blood sugar levels are too high insulin is added

If the blood sugar levels are too low insulin is NOT added.

Diabetes- the pancreas stops making enough insulin

Insulin is made using genetically enginereered bacteria from humans.

First line of defence is to stop pathogens enterin the body. Like

The skin, Mucus, Cilla, Lysozyme (tears).

Second Line of defence is non-specific white blood cells (nswbc)

- anything that passes the first line of defence the body should detect and the white blood cells called Phagocytes should pick it up!

- the nswbc engulf microbes and digest them.

Third line of defence is specific white blood cells

- White blood cells called lymphocytes attack specific microbes

-These cells detect microbes around them and generate antibodies to attack the new microbe. The body then becomes immune to this microbe because it will remember the antibodie that it produced and may use it again.

Transmission of microorganisms can happen in diffeferent ways:-

By direct contact

-During childbirth

-Droplet infection

-Sexual contact

-Touch

By indirect contact

Vector-borne (by another living thing)

Vehicle borne

- food, water or objects (eg surgical instraments.)

Tuberculosis is caused by a bacterium and can be passed on from droplet infection.

Tb in the uk is incresing

Tb can be pervented and treated..

by having a vaccination called a BCG vaccination. The injection can prevent TB in up to 80% of those who are given the vaccine.

Developing new drugs to combat the disease is expensive

Drugs can be Beneficial or Harmful, legal or illegal.

Drugs can effect you behaviour by affecting your nervous system. Interferring with the signals your body sends.

Sedatives and Stimlulants have different effects on the nervous system

Sedative- alcohol, barbiturates, solvents. Slows down responses by decreasing the speed of which the information passes through the synapse.Poor judgement of distance.

Stimulants- Nicotine, Ecstacy, Caffine- Increase the activity of the brain by speeding up the messages passed across the synapse this maks you more awake and alert.

Solvents affect the lungs and neurones. They are useful chemical which can often be missused as a drug. They are seditives which slow down the messages between the synapses ( causing a lot of damage as well)

Pain killers- Ibuprofen, Paracetamol and Aspirin are common household pain killers although there are much strong painkillers like morphine and cannabis. Cannabis is now illeagal and is only avalaible by precription.

Opiates include Opium, morphine and codenine- they're all found in the opium poppy!

Electric current is a flow of electrons round a circuit

Electrons are negetivly cahrged particles.

Voltage is a driving force that drives the particles around the circuit.

Resistance is something in the circuit that slows the flow down.

Increasing the Voltage- More current will flow

Increse resistance- Less current will flow.

Ac changes direction(mains) whilst Dc (battery and solar cells) doesnt.

Rotating a magnet in a coil of wire induces a voltage. This is called electromagnetic induction.

As you turn the magnet the magnetic field through the coil changes- this change in the magnetic field creates a voltage and so a current flows in the opposite direction.

4 things affect the size of the induced voltage

1. The strength of the magnet

2.The area of the coil

3. the number of turns on the coil

4. The Speed of movement

Power stations burn stuff to produce steam to turn a turbine that spins the magnet inside a coil of wire producing a voltage that make the electrons flow around the circuit.

LDR have lower reistance in Bright light

a thermistor is a temperature dependent resisor and have low resistance in warmer conditions.

Camera controls depend on varying resistance using a LDR.

Batteries are either dry cell or rechargable

Dry cell are usulally Zinc carbon or alkaline, but there are loads of different types.

Rechargable batteries

Battery Capacity is measured in amp hours

15 amp hours could supply a 5 amp current for 3 hours or a 3amp current for 5 hours.

Earth wires and fuses can protect you from Elecrric shocks

If a large current passes through the live wire and touches the metal ccasing. It travels back down the earth wire and melts the fuse which then insulates the metal case from eletric shocks.

Residual current circuit breakers

This detects a change in current if someone is electricued the live current is reduced and the circuit breaker detects this and stops the power supply.