HUMAN PHYSIOLOGY

Objectives:1. Define homeostasis2. Describe mechanisms used by the

human body to maintain balance3. Identify how the body uses these

mechanisms

HOMEOSTASIS

• Tendency towards a relatively stable state or equilibrium (balance)

• Examples: • Body Temperature 98.6 F• Blood has a neutral pH = 7

Mechanisms Use to Maintain Homeostasis

1. Electro-chemical signals quick messages transferred by the nervous system

2. Negative feedback mechanisms long term responses often carried out by hormones

3. Lock and Key controls transmission of messages based on a shape configuration at the cellular level

Negative Feedback Mechanisms

• Any change from the normal range of function is opposed or resisted

• Two responses that work in opposition• Examples:

• Blood pressure• Temperature• Respiration rate• Blood glucose levels

Negative Feedbackand Blood

Sugar

Lock and Key Model

• Molecules have a shape that only fits specific receptors

• Ex. Square peg only fits into square hole• Enzymes chemical proteins in the body that

assist or speed up chemical reactions (catalyst)

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html

Communication• Cells communicate with one another by releasing

chemicals.• Chemicals bind to receptors on the surface of

other cells• The blood stream carries the chemicals to where

they are needed• When the lock and key is formed, the message

has been sent

http://www.youtube.com/watch?v=U6uHotlXvPo

Determining “Self” from Invaders

• Your bodies immune (defense) system needs to be able to determine what is “self” and what is an invader

• It uses the lock and key method to determine invaders from self

http://www.youtube.com/watch?v=cL9KY_ECzfo

Using Lock and Key Model in Therapies

• Scientists create drugs that mimic (look like) messenger molecules• These messenger molecules may activate

the response• Or the molecule may fit, but not

perfectly, so the hole is blocked and the message CANNOT be sent