Biology

All living organisms must be able to detect changes in their environment and respond appropriately. Changes in the environment are called stimuli. A stimulus may be in either the external environment (outside the organism) or the internal environment (inside the organism).

A nerve impulse occurs when the resting potential across the membrane of a neurone has a sufficiently high stimulus. A stimulus is any disturbance in the external or internal environment which changes the potential difference across a membrane.

may be: chemical, thermal / electrical / change in light intensity.

the ability to respond appropritaley to stimuli, is one of the characteristic featers of life. Each organism has its own sepcific type of sensitivity that imporves its chances of survival.

In large multicellular animals such as mammals, stimuli are detected in sense organs.

Body part or cell that reacts to a stimulus in a particular way, or a cell substance in the body that produces an effect. p. ex. In a reflex the effector muscle acts before your brain is able to think.

and organs tat respond to sttimuli are called effectors.

The interconnections form circuits which enable us to control our muscles, think, remember and even sturd our own brains.

the nervous system and the endocrine system. Both involve cell signaling.

neurones, which convey information as nerve impulses (electrochemical signals)

a cell body, containing a nucles, and nerve fibres, long extensions that transmit nerve impulses rapidly from one part of the body to another.