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B5 B) The Nervous System
B5 B) The Nervous System
We have cells in our body called receptors that detect stimuli (changes in the environment). Our bodies respond to stimuli by taking appropriate actions; the actions that the body takes are known as the response. For example, if a ball was flying towards my face, I would probably move out of the way or raise my hands to block the ball from hitting my face. In this example, the stimulus (the change in the environment) is the ball that is travelling towards my face. My response is me moving out of the way/ raising my hands to block the ball.
It is the receptors that are responsible for detecting the stimuli, which is the change in the envioronment. We have many different receptors in our bodies. Here are some of the receptors in the body:
These receptors send electrical impulses along neurones to coordination centres. The coordination centres process the information and send messages to effectors that bring about a response. There are two different types of effectors and they cause a response in different ways. One type of effector is a muscle, which brings about a response by contracting. The other type of effector is a gland, which brings about a response by secreting a hormone (a chemical).
The flow diagram below shows what happens from a stimulus to a response.
It is the receptors that are responsible for detecting the stimuli, which is the change in the envioronment. We have many different receptors in our bodies. Here are some of the receptors in the body:
- Eyes – detects light
- Ears – detects sound and balance
- Skin – detects temperature and touch/ pressure
- Tongue – detects chemicals
These receptors send electrical impulses along neurones to coordination centres. The coordination centres process the information and send messages to effectors that bring about a response. There are two different types of effectors and they cause a response in different ways. One type of effector is a muscle, which brings about a response by contracting. The other type of effector is a gland, which brings about a response by secreting a hormone (a chemical).
The flow diagram below shows what happens from a stimulus to a response.
Within Coordination
The nervous system is responsible for coordinating responses. The nervous system is made up of a few different parts. Here are the parts:
We can now add some more detail to the coordination part of the earlier flow diagram. The stimulus is detected by a receptor. The receptor sends an electrical impulse along a sensory neurone to the CNS. The CNS then decides on the appropriate action to take. An electrical impulse is then sent along a relay neurone in the CNS to a motor neurone. The electrical impulse travels along a motor neurone from the CNS to the effector. The effector then produces a response. The more detailed flow diagram is shown below.
The nervous system is responsible for coordinating responses. The nervous system is made up of a few different parts. Here are the parts:
- Receptors – these detect a change in stimuli.
- Sensory neurones – these are neurones that take electrical impulses from receptors to the central nervous system (CNS).
- Central Nervous System (CNS) – the CNS is the brain and spinal cord in vertebrates (animals with backbones). The CNS is the coordination centre – it receives electrical impulses from the sensory neurones and coordinates the appropriate response. The CNS contains another type of neurone called relay neurones. Relay neurones take electrical impulses from sensory neurones to motor neurones.
- Motor Neurones – these take electrical impulses from the CNS to the effectors.
- Effectors – these are muscles and glands that respond to electrical impulses. The effectors bring about a response.
We can now add some more detail to the coordination part of the earlier flow diagram. The stimulus is detected by a receptor. The receptor sends an electrical impulse along a sensory neurone to the CNS. The CNS then decides on the appropriate action to take. An electrical impulse is then sent along a relay neurone in the CNS to a motor neurone. The electrical impulse travels along a motor neurone from the CNS to the effector. The effector then produces a response. The more detailed flow diagram is shown below.
Example of Touching Something Hot
Let’s now have a look at an example of me touching something that is hot with my hand (a hot frying pan). The stimulus for this example would be the hot frying pan. The receptor would be the skin cells on my hand, which would realise that the plate is hot. These receptors on my hand will send electrical impulses along sensory neurones to the CNS. The CNS will then decide on the appropriate response. An electrical impulse is then sent along a relay neurone to a motor neurone within the CNS. The electrical impulse then travels along a motor neurone from the CNS to the effector, which will be the bicep. The bicep (effector) will contract after receiving the electrical impulse from the motor neurone; the contracting of my bicep will pull my arm/ hand away from the hot frying pan (the response).
Let’s now have a look at an example of me touching something that is hot with my hand (a hot frying pan). The stimulus for this example would be the hot frying pan. The receptor would be the skin cells on my hand, which would realise that the plate is hot. These receptors on my hand will send electrical impulses along sensory neurones to the CNS. The CNS will then decide on the appropriate response. An electrical impulse is then sent along a relay neurone to a motor neurone within the CNS. The electrical impulse then travels along a motor neurone from the CNS to the effector, which will be the bicep. The bicep (effector) will contract after receiving the electrical impulse from the motor neurone; the contracting of my bicep will pull my arm/ hand away from the hot frying pan (the response).