B&G UNIT 4.- THE INTERACTION FUNCTION

We have mechanisms which perceive changes in order to interact with the external environment and with our own body. Our organism adapts and responds to those changes.

A stimulus is a change in our internal or external environment, which we perceive thanks to internal and external receptors.

There are two systems that process that information:

• The nervous system: the responses it produces are transmitted by nervous impulses. Nerve coordination generates a quick response.
• The endocrine system: this system is formed by glands that secretes hormones. Hormones are chemical mesengers circulating in the blood. They coordinate the internal organs. This system of coordination generates a slow and lasting response.

Then, some organs (the effectors), carry out the response to the order received from the coordination organ. The effectors can be muscles and glands (a gland is an organ that secrets a certain substance).

We have many different sense organs:

• The organ of smell: the pituatory gland in the nose.
• The organ of touch: there are different receptor cells in the skin which detect stimuli.
• The organ of taste: the taste buds on the tongue.
• The organ of hearing and balance: the ears sense sound vibrations, and it has also receptor cells which detect our position and movement.
• The organ of sight: the eyes sense light that enters through the pupil.

NERVOUS COORDINATION

Nervous coordination is realised by the nervous system, that sends information through the neurons by means of nervous impulses. The nervous system receives information from the receptors, processes and coordinates it and elaborates responses that effectors execute.

There are two main parts:

• The central nervous system (CNS): receives information from all over the body, it interprets this information and uses it to control the body's system. It is formed by the brain and the spinal cord.
• The peripheral nervous system (PNS): connects the sense organs to the central nervous system, and the central nervous system to the effectors.

EFFECTORS

The locomotor system allows the human being to move and to interact with the environment. This system is composed of two systems: the human skeleton and the muscular system. Other types of effectors are glands.

ENDOCRINE COORDINATION

Endocrine coordination is a mechanism which regulates the actions of many of the body's organs, in a slow but prolongued manner. It is carried out by the endocrine system, which is composed of a series of endocrine glands that produce and secrete hormones.

HEALTH AND INTERACTION FUNCTION

• To avoid many illnesses related to the eyes, it is advisable to avoid intense light and contact with irritants, and to prevent those related to hearing, you should avoid excessively noisy surroundings.
• To favour a healthy nervous system, you need to avoid stress and addictions, and take precautions to avoid, or at least reduce, the damage caused by accidents.
• Following a healthy diet, avoiding alcohol and doing physical exercise are habits which favour a healthy endocrine system.
• Moderate physical exercise, a balanced diet and other healthy behaviour keep the musculoskeletal system in good condition.