Homeostasis introduction + negative loop examples

Part 2: Homeostasis

LO:

• Define and describe homeostasis.

Principles of physiological control:

 Homeostasis is the principle of maintaining ‘dynamic constancy’ of the internal environment.
 Coined by Walter Cannon
 Essential for normal functioning of cells
 Different homeostatic mechanisms control different physiological parameters.


It is maintaining a stable
They need a constant
condition internally
environment to function
regardless of what is
normally to produce the
happening externally.
outputs.


Homeostasis:

The endocrine system (hormones) and nervous system (electrical impulses) regulate homeostasis.

– Hormones = “to excite”

Components of a homeostatic control mechanism include:

Detector (aka receptors) – Monitors some physiological variable.

Effector – Able to bring back variable to set point after deviation.

Integrating center – ensures that the response of effector is appropriate to deviation detected

Control is achieved via feedback loops, most commonly negative feedback loops.

Deviation in physiological parameters results in a response in opposite direction to return the
parameter to the original value, e.g., control of blood [glucose], body temperature, etc.




Blood cells Glucagon
Gluco cells Insulin
se


Gluc Cellular uptake
ose & utilization of
glucose


We have 2 main branches in terms of homeostasis control in the body:

1. The endocrine system (hormones) - Release of hormones from glands