Interdependency of cells

The cells in multicellular organisms do not work independently of each other. In animals for example, muscle cells in the legs depend on red blood cells in the blood to supply them with oxygen and neurons in the brain to make them contract.

To ensure that all the cells in a multicellular organism function correctly for the survival of an organism, the cells need systems for communication with each other.

The nervous system

Nervous systems

The building blocks of the nervous system are neurons (nerve cells). Neurons are specialised to allow rapid communication between cells in different parts of the body by transmitting electrical impulses.

There are three types of neurons:

  • sensory neurons
  • inter neurons
  • motor neurons

Some neurons are specialised to allow them to detect changes in environmental factors such as light, sound and temperature. These neurons are found in sense organs.

The central nervous system (CNS) is composed of all the neurons that make up the brain and spinal cord.

A human body showing the central nervous system which is the area encompassing the brain and spinal chord.

The function of the Central Nervous System (CNS) is:

  • To process sensory information. The CNS receives electrical impulses from sensory neurons connected to the sense organs.
  • To coordinate the body's response. The CNS transmits electrical impulses, along motor neurons, to glands and muscles.

Muscles produce rapid responses by contracting. Glands produce responses more slowly by releasing chemicals.