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Unit 1 - Reflexes
If your hand touches a hot object the reflex response is to move it away very quickly!

Unit 1 - Reflexes

The nervous system allows an organism to react to its surroundings and coordinate its behaviour, improving its chances of survival. This GCSE Biology quiz takes a closer look at reflexes - the most primitive, yet fundamental, automatic response mechanism.

Our reflexes allow us to take action without thinking, but how? Well, the mechanism works like this - in a reflex reaction, a stimulus is received by receptors and an automatic, rapid response is generated by the central nervous system without the involvement of the brain. In situations where there is a danger to the body, reflex actions can save precious fractions of a second.

This is achieved through what is termed a reflex arc. A reflex arc begins with a receptor. This passes a signal to a sensory neuron that connects to the spinal cord. In the spinal cord, a relay neuron sends the signal directly to a motor neuron. The motor neuron connects to an effector which is generally a muscle so that the body can respond. The relay neuron also sends a signal to the brain so that you are aware of what is happening.

The first cell in the reflex is which type of neuron?
These detect stimuli
What is the correct order of the reflex arc?
Motor - relay - sensory
Sensory - motor - relay
Sensory - relay - motor
Relay - sensory - motor
The brain is not involved, although the relay neuron does send a message to the brain so that the animal is aware of what is happening
The last cell in the reflex is which type of neuron?
Also called an effector as it makes the body do something
What is the name for the connection between two nerve cells?
The nerve impulse is usually transmitted from neuron to neuron by a chemical
If the effector is a gland, what would the response be?
A release of blood
The release of a hormone
A muscle contraction
A muscle expansion
Glands are part of the endocrine system and are where hormones are produced
A reflex arc consists of a chain of which type of cells?
Nerve cells are called neurons (sometimes spelt with an 'e' as neurones)
Your hand touches a hot object. What is the reflex response?
To grab hold of the object
To throw the object
To move the hand away swiftly
To think about what to do
Reflexes are very fast and do not involve thinking. This protects the organism from dangers such as a hot object
Which of the following is not true of reflexes?
Faster than hormonal responses
Brain not involved
Act for a short time
Brain involved
Although there is a connection to the brain, the nerve impulses that cause the reflex pass only through the central nervous system. Going through the brain would slow things down
The synapse between the sensory and relay neurones is within which part of the body?
The brain
The heart
The spinal cord
The muscles
The bundle of neurons in the spinal cord is referred to as the central nervous system
Which of the following is an example of an effector?
The heart
The liver
The kidneys
The muscles
Effectors are the output organs for reflexes and they include both muscles and glands
You can find more about this topic by visiting BBC Bitesize - Coordination and control - The nervous system

Author:  Donna Maria Davidson

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