Bell Ringer…

1. Put the following in order, from smallest to largest: organ, molecule, organelle, atom, organ system, tissue, organism, and cell

2. How might a health-care professional provide the basic requirements of life to an unconscious patient

3. Which characteristics of life does an automobile have? Why is a car not considered alive?

Homeostasis and System Integration

Interactions between organ systems

Organ systems are interdependent, interconnected, and packed together in a

relatively small space

Remember, a change in one level of organization can/will cause changes at all

levels

Due to this, the body has homeostatic regulation

Homeostasis:

• refers to the existence of a stable internal environment

• a variety of physiological mechanisms act to prevent potentially dangerous changes in the environment inside the body

• survive, every living organism MUST maintain homeostasis

Homeostatic regulation: adjustments in physiological system that preserve homeostasis

Homeostatic regulation involves:

• a receptor sensitive to a particular environmental change (stimulus)

• a control center (aka: integration center) which receives and processes the information from the receptor

• an effector, which responds to the commands of the control center and whose activity opposes or enhances the stimulus

Stimulus

Receptor

Control Center

Effector

Activity occursWhich enhances OROpposes the stimulus

Stimulus

Positive feedback:

• when the initial stimulus produces a response that reinforces the stimulus

• it is important in driving a potentially dangerous or stressful process to completion in a very rapid manner

Bell Ringer….

1. What is homeostasis?

2. Compare and contrast receptor and effector

3. What is another name for the control center

4. During a positive feedback mechanism, what happens to the stimulus?

Negative feedback:

• when the initial stimulus produces a response the opposes the stimulus

• usually ignore minor variations because they maintain a “ normal range” or “set point” rather than a fixed value

• each person has their own individual homeostatic set points, therefore it is impractical to define “normal” homeostatic conditions very precisely

• physiological values are reported either as averages or as a range that includes 95% or more of the sample population

When homeostatic regulation fails, organ systems begin to malfunction and the

individual experiences the symptoms of illness.

Review…

• What is homeostasis?

• What is the difference between negative feedback and positive feedback?

• What are the parts of homeostasis regulation?

Review of Homeostasis…

• When we begin to become dehydrated, we usually become thirsty, which causes us to drink fluids. On the basis of what you now know about control systems, decide whether the thirst sensation is part of a negative or positive feedback control system and defend your choice

More review of homeostasis…

• When a person is diagnosed as diabetic, they no longer produce the proper amount of insulin need by the body. This is due to a break down in homeostasis.

• Explain how homeostasis works with keeping our insulin levels ~ 90mg/100mL when the level becomes too high

• The organs involved in this process are:– Pancreas – releases insulin into the blood– Liver – takes up glucose and stores it– Brain – decides what to do

On Your Own…

• Describe a homeostatic mechanism that helps regulate blood pressure