Homeostasis

Learning goals . . .To explain the process of maintaining

homeostasis through feedback loops and their components.

You will show your understanding by . . .Presenting an explanation (diagramatic,

written or kinesthetic) of thermoregulation

When things work...

Honda COG Commercial

Homeostasis (pg. 334 – 341)homeostasis – constant physiological adjustments of

the body, which maintain a relatively stable internal, fluid environment in response to external environment changes

also known as dynamic equilibrium

What happens to your body when you exercise?

body temperature increases

O2 levels being used up

increased cellular metabolism

evaporation of sweat to cool off

heart rate increases to increase blood flow

pancreas signals breaking down of biomolecules

Where did the term come from?

What happens when you exercise?

Homeostatic ControlThree main components:1. A monitor – senses state of system

2. A coordinating centre – receives incoming info about system and decides what the next steps should be

3. regulator – carries out the appropriate next step to keep system at homeostasis; receives signals from coordinating centre.

Q: What are the mechanism(s) in place that respond to a change in our environment?

A: Feedback Loops

Feedback loops

Positive feedback - a mechanism by which an output is enhanced

Example: Contractions in childbirth: contractions stimulate oxytocin which stimulates more muscle contractions

Feedback Systemspositive feedback (feed-forward) system

progesterone decrease

uterus endocrine system

oxytocin

increased contractions

Negative Feedback Mechanisms by which an output is

diminished• Any change from normal range of function

is resisted in negative feedback.

• The change initiates responses that bring the function of the organ back to its normal range.

• Negative feedback loops require a Receptor, A Control Center, and Effectors.

Blood Pressure Example• Blood vessels have receptors which can

measure the resistance of blood flow against vessel walls

• The brain (control center) receives info about change in body’s internal conditions, sends out signals via nerves

• Effectors - the muscles, organs, and other structures that receive signals from the control center and respond to correct the deviation.

Feedback Systemsnegative feedback system

blood pressure drops

brain nerve pathwayblood pressure rises

heart rate increases

arteries constrict

ThermoregulationText pg. 338 - 341

Assignment:Explain the control of body temperature

in terms of a feedback mechanism (positive or negative)

Be prepared to present your answer

Weird Body QuirksBrain freeze“Ice cream headaches”

happen when something cold touches nerves in the roof of the mouth, triggering blood vessels in the front of your head to constrict -- producing pain. Try this quick pain relief trick: Press your tongue to the roof of your mouth to warm it up.

Charley Horse

These startling spasms and tightening in leg muscles can last a few seconds, even several minutes. While the cramps have no exact cause, dehydration, muscle overuse, and a lack of certain nutrients -- like potassium and calcium -- can be culprits. Walk around to relieve the pain, or shake your leg and stretch the muscle.