Biology Communication

Communication

• all living organisms need to detect stimuli and respond to them.
• A stimulus is a change in the environment that causes a response.
• Environment-. external e.g change in air temperature. 

internal e.g. change in CO2 concentration in blood.

• response is a change in physiology or behaviour. e.g. stimulus e.g fear Response e.g increase in heartbeat (touch/movement) Venus flytrap stimulus=hair response=eat fly

• plants and animals are multicellular. specialisation means that different parts of the organism have to communicate with each other.

• cells communicate by secreting chemicals in to the surrounding medium(tissue fluid) which will react with receptors and become chemical signals for short distances.

• there are four ways cells can communicate:

1). paracrine system:cells which release chemicals in to tissue fluid (short distances) e.g. histamines in damaged cells + allergen.

2). endocrine system: cells which release chemicals hormones go in to tissue fluid  and into blood to target cells. (long)

3). nerve system: specialised cells/neurons info travels as nervous impluses and at end chemicals released e.g. nurotransmitter acet

4). neurosecrition: some nerve cells which secrete chemicals into blood e.g. ADH (made in peturity gland target kidney).

Homostatis

• the maintanence of a constant internal enviroment despite changes
• temeperature has to remain constant (77…