Learning Target: Mechanisms of Homeostasis

I Can… Explain how negative feedback mechanisms help regulate and maintain a narrow range of internal conditions in the human body among a wide range of external conditions.

I Will…• List and define the components of a control system• Define feedback• Explain how negative feedback works.• Give an example of negative feedback in

the human body• Give an example of positive feedback in

the human body

Learning Target: Mechanisms of Homeostasis

KEY CONCEPT: Humans need to regulate and maintain a narrow range of internal environment conditions among a wide range of external environmental conditions in order to stay alive.

Primarily achieved by negative feedback

Learning Target: Mechanisms of Homeostasis

Why are there such narrow ranges that need to be maintained?

Remember:• Metabolism – all the chemical reaction in the body• Enzymes can be easily denatured (altered & damaged)• pH• Temperature

• Concentrations• Movement across membrane• Substances that maintain

normal cell functioning

Learning Target: Mechanisms of Homeostasis

Control System:• Sensors – receptors• Gather information• Internal Environment e.g. CO2 level in blood• External Environment e.g. _______________

• Control Centers – Brain and Spinal Cord• Evaluates / Interprets information from sensors• Determines actions to be taken

Learning Target: Mechanisms of Homeostasis

Control System:• Communication Centers – Carry messages from

control centers to targets• Nervous system• Endocrine system

• Target – Organ, tissue, or cell that will carryout action from communication center• Alters functioning in response to message• Maintains homeostasis

Learning Target: Mechanisms of Homeostasis

Feedback process:• Information sent from sensors to control center• Control center compares current conditions to ideal set

point conditions• Control center determines action based on comparison• Sends action instructions through communication

systems to target• Target carries out action• Information sent from sensors to control center• Control center compares….

Constant loop

Learning Target: Mechanisms of Homeostasis

Negative Feedback – counteracts (works against) current conditions to move back to ideal value• Reverses current condition back to normal• Primary method of maintaining homeostasis

Positive Feedback – reinforces current conditions• Increases rate of change away from ideal value• Continues until stressor is eliminated

Learning Target: Mechanisms of Homeostasis

e.g. CO2 level in blood• Person holding their breath• Sensors register ↑ CO2 levels in blood• Send information to Control Center

(Medulla Oblongata) in brainstem• Control center compares current values to ideal• Determines action and sends instructions

through communication center (motor nerves)• Diaphragm and ribcage (target) relax then

contract forcing you to take a breath.

Negative Feedback

Negative Feedback

Learning Target: Mechanisms of Homeostasis

Other common examples:• Sweating when hot • Evaporation of sweat cools down body with elevated

temperature• Shivering when cold• Heat production from muscle contractions warm cold

body temperature• Drinking a 72 oz. Big Gulp• Increase urination of excess fluids

• Eat a candy bar• Insulin produced to take care of

excess sugar in blood

Learning Target: Mechanisms of Homeostasis

e.g. Childbirth•

Positive Feedback

Learning Target: Mechanisms of Homeostasis

I Can… Explain how negative feedback mechanisms help regulate and maintain a narrow range of internal conditions in the human body among a wide range of external conditions.

I Will…• List and define the components

of a control system• Define feedback• Explain how negative feedback works.• Give an example of negative feedback in

the human body• Give an example of positive feedback in

the human body

Learning Check √:Completion of Ch. 28. 2 Study Guide WS