The Nervous System Flashcards
What does the nervous system allow the body to do?
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.
What is a neurone?
A neurone is a nerve cell that consists of a cell body with thin fibres stretching out from it. The fibres carry electrical impulses.
What are receptors?
Receptors are groups of specialised cells. They can detect changes in the environment, which are called stimuli, and turn them into electrical impulses.
Where are receptors located?
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.
What is skin sensitive to?
Touch, pressure, pain and temperature.
What is the tongue sensitive to?
Chemicals in food.
What is the nose sensitive to?
Chemicals in the air,
What are eyes sensitive to?
Light.
What are ears sensitive to?
Sound and position of the head.
What happens when a receptor is stimulated?
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.
What is an effector?
An effector is any part of the body that produces a response.
What 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.
What do sensory neurones do?
Sensory neurones carry signals from receptors to the spinal cord and brain.
What do relay neurones do?
Relay neurones carry messages from one part of the CNS to another
What do motor neurones do?
Motor neurones carry signals from the CNS to effectors.
What is the axon?
The fibre that carries electrical impulses from the cell body to the dendrites is called the axon.
What is the dendron?
The fibre that carries electrical impulses t the cell body is called the dendron.
What is the myelin sheath?
The myelin sheath is the fatty layer surrounding the axon.
What is the similarity between a motor and a sensory neurone?
They both have a cell body and fine branches called dendrites.
What is the difference between a motor and a sensory neurone?
Motor neruones have very long axons, where as sensory neurones have short ones.
What is a synapse?
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.
What is a reflex action?
When a receptor is stimulated, it sends a signal to the central nervous system, where the brain co-ordinates the response. But sometimes a very quick response is needed, one that does not need the involvement of the brain. This is a reflex action.
What happens in a reflex action?
Receptor detects a stimulus - change in the environment, sensory neurone sends signal to relay neurone, motor neurone sends signal to effector
and the effector produces a response.
What happens in bright lights to our eyes?
- Radial muscles of the iris relax.
- Circular muscles of the iris contract.
- Less light enters the eye through the contracted pupil.
