Homeostasis

Homeostasis

• process of maintaining a constant internal environment despite the changes in external environment

What is the internal and external environment

• internal environment is for example the tissue fluid which bathes the cells - this is regulated within narrow limits and remains close to an optimum point

• external environment is the place where the organism lives 

Exhange between internal and external environment

• living organisms have open systems where they exchange mater between the internal and external enviornments

Examples of homeostatic mechanisms

• anatomic, physiological or behavioral and are maintained by the NERVOUS SYSTEM AND ENDOCRINE SYSTEM

What constitutes the control system

• the detector

  • such as receptors - these detect changes in the external environment

• regulator/control center

  • receives information from detectors and processes and compares to a set point

  • brain, spinal cord, glands

• effectors

  • these produce a behavioral or physiological response to bring the internal environment back to a set point

  • glans and muscles

How are body conditions maintained at a set point 

• through positive and negative feedback

• feedback is a mechanism where the output is controlled in terms of the input

Negative feedback

• This is when the output is neutralized to restore the original internal equilibrium

• A response is produced to reduce initiating stimulus.which causes the response that u want to diminish.

• Feedback is determined by the control center

• the product when in excess can act as the regulator and causes the process to shut down and establish internal equilibrium

• examples include : -

→ body temperature control

→ regulating water levels via ADH

→ progesterone production inhibits fsh/lh during pregnancy

Positive feedback

-this is when the initial stimulus is intensified by the output

• process is very rare (almost goes against homeostasis)

• The system is eventually stopped by inhibitors

• examples

• Pepsinogen into active pepsin - autocatalysis

• Contractions during parturition - pressure of baby stimulates oxytocin, oxytocin causes more contractions

• Blood clotting - platelets which are activated release chemicals to activate more platelets to plug the hole

• Stimulation of a neuron - as sodium ions enter, this causes sodium channels to open hence more sodium enters