A level Biology exam revision resources written by A level Examiners


A simple reflex is movement of a body part in response to stimulus. It is a rapid, innate automatic response to a stimulus and involves only a few neurones and synapses. We looked at the nerve pathway involved in a reflex in Nervous Communication - Reflex Arc  click to make the link, and that helps explain why they are quick and the response does not vary. Watch out for synoptic questions on reflexes.

Reflexes can be linked together to produce more complicated behaviours. A common example of this is breast-feeding in humans.

There are several reflexes involved in the sequence.

Reflex Behaviour

Rooting reflex (baby) Also called nipple-seeking behaviour. When the breast touches the baby it will turn its head with its mouth open until it finds the nipple.

Mouth opening reflex When the nipple touches the lips of the mouth of the baby, its mouth opens.

Sucking reflex (baby) When the baby attaches to the nipple it begins to suck.

Let-down reflex (mother) The stimulation of the nipples by the baby sucking, causes the reflex release of the hormone oxytocin. This hormone triggers smooth muscle contraction in the mammary glands, causing the release of milk.

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