Pathogens & Diseases Part 1

Learning Objectives

• Behaviour of a system in an equilibrium - what happens when there are disturbances?
• What are feedback mechanisms and how is it linked to homeostasis
• The human body as a system - its behaviour when it is healthy versus when it is diseased
• Any system is usually connected to other systems, both internally and externally
• Thinking about things as systems means looking for how every part relates to others
• The output of one part of a system can become the input to other parts.
• Such feedback can serve to control what goes on in the system as a whole & serves to keep changes within specific limits.

Homeostasis is the tendency of an organism or a cell to regulate its internal conditions, usually by a system of feedback controls, to maintain *equilibrium or stability within its internal environment, regardless of the outside changing conditions.

(*equilibrium=stay healthy)

A system of equilibrium may return to the same state of equilibrium if the disturbances it experiences are small. 

(e.g. When our body temperature increases during an exercise, we perspire and subsequently the body temperature decreases)

How this works

As temperature increases, nerves detect the increase and sends signal to brain. When the brain realises, it sends signal to sweat glands to perspire.

But large disturbances may cause it to escape that equilibrium and eventually settle into some other state of equilibrium. 

(e.g. When our body temperature increases, even though we perspire, the body temperature continues to increase.) 

^This happens during a fever.