Post by Na9er on Oct 17, 2012 15:27:23 GMT -5
The Nervous System allows the body to respond, through effectors, to changes in the environment detected by receptors. The process involves neurones and is usually coordinated by the brain. A reflex action is an extra-rapid response to a stimulus, this process also involves the nervous system but it bypasses the brain.
Receptors and effectors
Receptors are groups of specialized cells. They can detect changes in the environment, which are called stimuli, and turn them into electrical impulses. Receptors are often located in the sense organs, such as the ear, eye and skin. Each organ has receptors sensitive to particular kinds of stimulus.
The central nervous system (CNS) in humans consists of the brain and spinal cord. When a receptor is stimulated, it sends a signal along the nerve cells neurones to the brain. The brain then co-ordinates the response.
Effectors
An effector is any part of the body that produces the response. Here are some examples of effectors:
Neurones
Neurones are nerve cells. They carry information as tiny electrical signals. There are three different types of neurones, each with a slightly different function:
The axon is surrounded by a fatty layer known as the myelin sheath. This helps to protect the neurone and allow impulses to travel faster.
Synapses
Where two neurones meet, there is a tiny gap called a synapse. Signals cross this gap using chemicals released by a neurone. The chemical diffuses across the gap makes the next neurone transmit an electrical signal.
1. An electrical impulse travels along an axon.
2. This triggers the nerve-ending of a neuron to release chemical messengers called neurotransmitters.
3. These chemicals diffuse across the synapse (the gap) and bind with receptor molecules on the membrane of the next neuron.
4. The receptor molecules on the second neuron bind only to the specific chemicals released from the first neuron. This stimulates the second neuron to transmit the electrical impulse.
Receptors and effectors
Receptors are groups of specialized cells. They can detect changes in the environment, which are called stimuli, and turn them into electrical impulses. Receptors are often located in the sense organs, such as the ear, eye and skin. Each organ has receptors sensitive to particular kinds of stimulus.
The central nervous system (CNS) in humans consists of the brain and spinal cord. When a receptor is stimulated, it sends a signal along the nerve cells neurones to the brain. The brain then co-ordinates the response.
Effectors
An effector is any part of the body that produces the response. Here are some examples of effectors:
- A muscle contracting to move the arm
- A muscle squeezing saliva from the salivary gland
- A gland releasing a hormone into the blood.
Neurones
Neurones are nerve cells. They carry information as tiny electrical signals. There are three different types of neurones, each with a slightly different function:
- Sensory neurones carry signals from receptors to the spinal cord and brain.
- Relay neurones carry messages from one part of the CNS to another.
- Motor neurones carry signals from the CNS to effectors.
The axon is surrounded by a fatty layer known as the myelin sheath. This helps to protect the neurone and allow impulses to travel faster.
Synapses
Where two neurones meet, there is a tiny gap called a synapse. Signals cross this gap using chemicals released by a neurone. The chemical diffuses across the gap makes the next neurone transmit an electrical signal.
1. An electrical impulse travels along an axon.
2. This triggers the nerve-ending of a neuron to release chemical messengers called neurotransmitters.
3. These chemicals diffuse across the synapse (the gap) and bind with receptor molecules on the membrane of the next neuron.
4. The receptor molecules on the second neuron bind only to the specific chemicals released from the first neuron. This stimulates the second neuron to transmit the electrical impulse.