Background: all living organisms are sensitive to the environment; this means they can detect changes in their environment these changes are known as stimuli. The parts of the body which detects the stimuli are called receptors. In animals there known as the sense organs: The nervous system collects information about changes inside or outside the body, decides how the body should respond and controls that response. Information is collected by receptor cells that are usually grouped together in sense organs, also known as receptors. Each type of receptor is sensitive to a different kind of change or stimulus.

There are five different sense organs which are mentioned below: Sense Organ Sense Stimulus Skin Touch Pressure, pain, hot/cold temperatures. Tongue Taste Chemicals in food and drink. Nose Smell Chemicals in the air. Eyes Sight Light, movement Ears Hearing Balance Sound movement. The eye is an example as it’s a receptor that detects light. The flow of the information from stimulus to response is: Stimulus ; Receptors ; (senses) ; sensory neurone information ; central nervous system (brain and spinal cord) ; motor neurone instructions; effectors (muscles and glands) ; response.

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The sense organs are connected to the rest of the nervous system which is made up of the brain, spinal cord and peripheral nerves. It is in the brain and spinal cord that information is processed and decisions are made. The brain and spinal cord together are called the central nervous system (CNS). Signals are sent through the nervous system in the form of electro-chemical impulses. There are three types of nerve cells or neurones: Sensory neurones which carry signals to the CNS Motor neurones which carry signals from the CNS controlling how we respond Relay (intermediate or connecting) neurones which connect other neurones together.

A sensory neurone: Neurones are specialised in several ways: They can be very long to carry signals from one part of the body to another. They have many branched nerve endings or dendrites to collect and pass on signals.  Many neurones are wrapped in a layer of fat and protein, the myelin sheath, which insulates cells from each other and allows the impulses to travel faster. Neurones are usually grouped together in bundles called nerves. The different parts of the nervous system may all be involved when we respond to a stimulus. The simplest type of response is a reflex.

Reflexes are rapid, automatic responses which often act to protect us in some way. For example, blinking if something gets in your eye or sneezing if you breathe in dust. The pathway that signals travel along during a reflex is called a reflex arc: Stimulus ; receptor ; sensory neurone ; spinal cord ; motor neurone ; effector ; response Example: Stand on a pin ; nerve endings ; sensory neurone ; spinal cord ; motor neurone ; leg muscles ; leg moves. Simple reflexes are usually spinal reflexes which mean that the signals are processed by the spinal cord, not the brain. This causes the spine to send a signal back to the effector.

Effectors are part of the body that respond- either muscles or glands. There are also cranial reflexes which send signals straight to the brain. Signals are also passed from one neurone to another even tough they do not touch. Between nerve endings there are small gaps called synapses, signals can be passed through synapses because when an electrical impulse reaches a synapse, chemicals called transmitter substances are released from the membrane of one nerve ending and travel across to special receptor sites on the membrane of the next nerve ending, triggering off another nerve impulse.

Signals however are not always passed across the synapses. Planning: in this experiment I will be investigating how the different factors affect the time of reaction. I will be depriving my fellow students of there sight to see how it affects there reaction time. In this experiment I decided I will drop a 50cm ruler 10cm above everyone’s right hand and see how long it takes them to catch it. The students will all try it with their sight and without their sight so I can compare the results and see how much sight affects the rate of reaction.

I will further my experiment by comparing the girls and boys results to see if gender affects the rate of a persons reaction. In total I will use 5 girls and 5 boys I will also compare those people who are left of right handed. Aim: To investigate the effect of depriving people from their senses and how this affects there reaction rate. Factors and fair test: If I am going to make this a fair test, then I will have to control these other factors like I mentioned below: The main factors which will need to be considered whilst doing the experiment are: The sex of the student.

Whether they are a girl or boy will affect there rate of reaction so I will be using the same amount of boys and girls. I will be investigating this further. There sight will affect the rate of reaction for example they can see the ruler they will be more likely to catch it. This is another factor I will be testing.  The distance between their hand and ruler will affect the rate of reaction as they will be able to catch it quicker if it was closer to ensure its affair experiment I will be measuring 10cm above the hand each time I do the experiment so the distance will be kept constant.

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