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
Stimulus
Effector
Activity occurs
Which enhances OR
Opposes the 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