Bellringer:

Today 9/17

• Bellringer• Summer Assignments• Homeostasis Notes• Homeostasis Worksheet & Activity

Remember: I need WebQuests shared with me!sparkinson@rsd6.org

Maintaining Life

• Necessary Life functions– Internal things you need your body to do

• Survival Needs– External things you need for your body

Homeostasis (pg 8-12)

• The ability of the body to maintain a relatively constant internal environment, regardless of environmental changes

Components of Homeostasis:

1. Variable– Regulated factor or event

2. Receptor– Structure to monitor situation

3. Control Center– Structure that determines “set point”

4. Effector– Carries out response

Example:Homeostasis of Breathing Rate

How it works:

• As you accumulate CO2 in your bloodstream, acidity of your blood increases

• Receptors in your carotid and aorta sense this, signal to medulla

• Medulla signals to diaphragm intercostal muscles- Breathing rate is now increased!

• CO2 concentration lessened- acidity decreased

Afferent vs. Efferent Pathways

• Afferent Pathway– Signal from receptor to control center

–Approach control center

• Efferent Pathway– Signal from control center to effector

–Exit control center

Negative Feedback Mechanism

• Most homeostatic control mechanisms are negative

• Prevent sudden, severe changes in the body

• Causes the variable to change in a way OPPOSITE the initial change

• Nervous System and Endocrine system

Positive Feedback Mechanisms

• Causes the variable to change in the SAME direction as the original change– ONE DIRECTION– AKA cascades

Positive Feedback Mechanisms (cont)

• Result is a greater change from set point

• Typically activate events that are self-perpetuating

• Usually not related to maintenance of homeostasis

Homeostatic Imbalance?

• DISEASE!– Examples• Fever• Hypertension• Hashimoto’s disease• Graves disease• Kidney Malfunction• Diarrhea

In class…

• Find an example of a way the human body maintains homeostasis (text book will help!)

• Identify the components

• What type of mechanism is it?

• What can happen if there is an imbalance of this homeostasis?