Fast signals. Lasting signals.

The nervous system sends electrical impulses along neurons and chemical signals across synapses. Responses can be rapid and localised. Reflex pathways can act before conscious processing.

The endocrine system releases hormones into the blood. Responses tend to be slower and longer-lasting, and only target cells with suitable receptors respond. Both systems coordinate homeostasis rather than acting in isolation.

INTERACTIVE MODEL

Coordinating a response

Nervous route: electrical impulse then synaptic signalSignal routeNervousNervousEndocrine

Explore: Select a signalling route and compare travel time and duration.

\text{stimulus}\to\text{receptor}\to\text{coordinator}\to\text{effector}

WORKED EXAMPLE

A hand touches a hot surface.

Sensory neurons carry a signal to the spinal cord.
A reflex pathway activates muscle rapidly to withdraw the hand.

Assumed knowledge

Cells and receptors.

Learning checkpoints & source

YOUR LEARNING CHECKPOINT

Compare nervous and endocrine signalling.
Trace a reflex or hormonal pathway.

QCAA Biology · Unit 2 · Homeostasis ↗

READY TO TRY IT?

Fast signals. Lasting signals.

Coordinating a response

A hand touches a hot surface.

Put the idea to work.