Homeostasis Chapter 1 Mr. Knowles Anatomy and Physiology Liberty Senior High School.
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Transcript of Homeostasis Chapter 1 Mr. Knowles Anatomy and Physiology Liberty Senior High School.
Homeostasis• “Homeo”- same.• “-stasis”- standing or
status.• To maintain a relatively
constant internal environment.
• External environment has many variables-temp., pH, amount of energy, etc.
What is a stimulus and a response?
• Stimulus- an environmental change that signals the body in some way.
• Response- the change in cellular activity the body makes in order to maintain homeostasis.
Homeostasis is a Balancing Act!
• Chemical reactions within cells work most effectively within a certain range of conditions (temp., pH, salt, energy).
• Organ systems work together to maintain this stable internal environment.
Homeostatic Regulation• Two Mechanisms:
1. Autoregulation- activities of a cell, tissue or organ change automatically when faced with environmental variation.
Ex. Cells in a certain tissue need more O2. Cellsrelease chemicalsdilate (open) blood vessels nearbylocal cells receive more O2 . Only localized changes.
Homeostatic Regulation• Two Mechanisms:
2. Extrinsic Regulation-activities of several systems, such as the nervous and endocrine, work together to adjust or change the internal environment.
Ex. Touching a hot stove nervous system respondsprocesses informationmuscle contraction .
Ex. Endocrine system releases chemical messengers (hormones) affect many systems for a long period, last for hours, days.
Homeostasis Has Three Parts• Receptor- a sensor that is sensitive to a
particular environmental change or stimulus.• Control Center- receives and process the
information supplied by the receptor.• Effector- a cell or organ that responds to the
commands of the control center and whose activity opposes or enhances the original stimulus.
Two Types of Feedback1. Negative Feedback- when the
effector(s) activated by the control center oppose or eliminate stimulus. Most common feedback system; thermoregulation, salt, energy, pH, etc.
Homeostasis and Negative Feedback
• It is range in which there is a set point.
• The set point is not a fixed value.
• The set point is dynamic and can change for the time of day or the individual.
The Second Kind of Feedback
2. Positive Feedback- initial stimulus produces a response that exaggerates or enhances its effects. Less common.Ex. Labor contractions, Blood clotting
Homeostasis is a Balancing Act!
• Organ systems work together to keep within the range around the set point.
• The systems are interdependent.
• All are necessary for survival.
Show Me an Example of Homeostasis!
The New Living Body-Homeostasis, 1995, VT 574.1
HOM
Push Here for Another Example