Pain reflex arcs as an example of involuntary responses with skeletal muscle as the effector
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Question
What is a reflex?
Answer
A **fast, automatic response** to a stimulus that needs **no conscious thought**.
Question
What is a reflex arc?
Answer
The fixed nerve pathway a reflex follows: **stimulus -> receptor -> sensory neuron -> relay neuron (CNS) -> motor neuron -> effector -> response**.
Question
Why are reflexes so fast?
Answer
The signal takes a **short cut through the spinal cord** instead of travelling to the brain and back.
Question
What does a receptor do in a reflex arc?
Answer
It **detects the stimulus** and starts a nerve impulse (e.g. a sensory nerve ending in the skin).
Question
What is the effector in a reflex arc?
Answer
A **muscle or gland** that carries out the response (e.g. a muscle that contracts).
Question
In a pain reflex, what is the receptor?
Answer
A **sensory nerve ending** in the skin.
Question
In a pain reflex, what is the effector?
Answer
A **muscle** that contracts to pull the body part away.
Question
Where are the synapses in a reflex arc located?
Answer
**Inside the CNS** — in the grey matter of the **spinal cord**.
Question
Which neuron carries the impulse INTO the CNS?
Answer
The **sensory neuron** (S = sending in).
Question
Which neuron carries the impulse OUT of the CNS?
Answer
The **motor neuron** (M = moving out).
Question
What does a mechanoreceptor detect?
Answer
**Touch, pressure, texture, stretch or vibration.**
Question
What does a thermoreceptor detect?
Answer
**Temperature** (heat and cold).
Question
What does a chemoreceptor detect?
Answer
**Chemicals** — this is how **taste and smell** work.
Question
What does a photoreceptor detect?
Answer
**Light** (e.g. the brightness of light entering the eye).
Question
In the pupil reflex, what is the effector and what does it do?
Answer
The **iris muscles** — they **contract to make the pupil smaller**, reducing the light entering the eye.
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Topic 3.6 hub
Integration of body systems
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