The Reflex Arc | A-level Biology | OCR, AQA, Edexcel

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The key points covered of this video include:

1. What is a Reflex
2. The Reflex Arc
3. The Importance of Reflex Arcs

What is a Reflex

When you touch something hot you immediately draw your hand away. It is automatic and involuntary - there is no conscious thought involved and it can’t be stopped. It’s also a short lived reaction - it doesn’t last for a long time. These characteristics of the reaction make it a reflex. Reflexes are rapid responses that don’t require conscious thought.

The Reflex Arc

Reflexes are controlled by simple neurone pathways. The pathways are usually localised to the part of the body where the reflex occurs. The response starts with a receptor, which detects the stimulus to respond to. The receptor creates a signal which is passed on to a sensory neurone. The sensory neurone carries the signal into the spinal cord where it reaches a co-ordinator. A co-ordinator is an intermediate neurone that carries the signal to a motor neurone. The motor neurone brings the signal to the effector - such as a muscle.

The Importance of Reflex Arcs

Reflexes are localised to the part of the body where they occur. This means we can respond to stimuli quickly since signals don’t have to go to the brain and back. They also don’t involve many synapses - which are slow to transmit across neurones. This speed allows reflexes to be effective in protecting the body from harm. Although reflexes occur at the point of response, some signals are still sent to the brain. This allows the brain to override the response if its comprehensive decision making process deems this necessary. The simplicity of a reflex also means that it doesn’t have to be learnt, and is effective from birth.

Summary

Reflexes are rapid involuntary responses to stimuli
Reflexes start in receptors transmitted by co-ordinators and carried out by effectors
Reflexes are fast, protective, and present from birth