Principles (Coordination)

Electrically

Chemically

Histamine

Prostaglandins

Tropism

 

 

Introduction

 

Effectors in the body such as muscles and glands may get their signals to contract or secrete substances in two ways: electrically by nerve impulses or chemically by hormones.

 

Nerve cells have electrical impulses pass along them which results in their secretion of a neurotransmitter onto the target cells which respond quickly, locally and in a short-lived way.

 

Hormones on the other hand circulate in the bloodstream, reaching distant target cells and exerting a long-lasting but slow effect.

 

 

Above is a synapse and below you can see an example of the interaction between multiple hormones across a big distance (brain- and ovary-secreted hormones exerting both local and…