Co-ordination & Response Flashcards
All 17 cards in this deck
Which two organs make up the central nervous system (CNS)?
The brain and the spinal cord.
In a sensory neurone, what is the name of the part that carries the impulse from the receptor towards the cell body?
The dendron.
(The axon carries impulses away from the cell body.)What is the function of the myelin sheath around the axon of a neurone?
It insulates the axon and speeds up transmission of the electrical impulse.
What is a synapse?
A gap between two neurones.
What are the steps in transmitting an impulse across a synapse?
e.g. from a relay neurone to a motor neurone in a reflex arc- The electrical impulse arriving triggers the release of a chemical (neurotransmitter) — released by the relay neurone
- The neurotransmitter diffuses across the synapse and binds to receptors on the next neurone — the motor neurone
- A new electrical impulse is triggered in the next neurone — the motor neurone
Why is transmission across a synapse slower than transmission along an axon?
The neurotransmitter has to diffuse across the gap, which is slower than an electrical impulse travelling along an axon.
True or false? An impulse can cross a synapse in either direction.
False. Transmission is one-directional: only one neurone releases neurotransmitter and only the next neurone has the receptors for it.
What are the steps of a reflex arc, from stimulus to response?
e.g. touching a hot object and pulling your hand away- A receptor detects the stimulus — heat receptor in the skin
- A sensory neurone transmits the impulse to a relay neurone in the spinal cord (CNS), then to a motor neurone
- The motor neurone transmits the impulse to the effector, which produces the response — arm muscle contracts and the hand is pulled away
What is the role of sensory neurones?
They transmit electrical impulses from receptors (sense organs) to the CNS (brain, spinal cord or relay neurone).
In which type of neurone is the cell body found part-way along the neurone, on a side branch between a long dendron and an axon?
The sensory neurone.
True or false? A relay neurone has a long axon that carries impulses from the CNS to an effector.
False. That describes a motor neurone; a relay neurone is short and connects neurones within the CNS.
Why is a reflex action faster than a voluntary response?
The impulse bypasses the conscious parts of the brain, passing through the spinal cord with fewer neurones and synapses.
What does it mean to say a reflex action is involuntary?
It is automatic — the response happens without conscious thought.
What is a receptor?
A group of cells that detects a stimulus (a change in the environment), e.g. light receptors in the eye.
What are the two types of effector, and how does each respond?
Muscles, which contract, and glands, which secrete hormones.
Why are reflexes useful?
They protect the body: the response is fast and needs no conscious thought, so there is less chance of injury.
What is a reflex arc?
The pathway that impulses take in a reflex, from the receptor to the effector.