https://www.youtube.com/watch?v=CLv3SkF_Eag
 refers to the ability of an organism or
environment to maintain stability in
spite of changes. The human body is
full of examples of homeostasis.
Homeostasis
happens in all
Kingdoms:
Archaebacteria,
Eubacteria, Protista,
Fungi,
Plantae, and
Animalia
The Human Body
Humans require
many systems for
digestion,
respiration,
reproduction,
circulation,
excretion,
movement,
coordination, &
immunity
The components of the human
body, from cells, to tissues to
organs to organ systems, interact
to maintain homeostasis.
 The maintenance of a constant environment in the
body.
 Achieved by many different internal controlled
mechanisms that detect deviations and make
corrective actions.
 Your body has mechanisms to keep the cells in a constant
environment OR Dynamic Equilibrium
Homeostatic Loop:
EXAMPLE
Feedback Mechanisms
In order to maintain
homeostasis, the body
uses feedback loops
There are two types:
1. Negative Feedback
2. Positive Feedback
Feedback Mechanism
NEGATIVE FEEDBACK LOOP
POSITIVE FEEDBACK LOOP
(DECREASES EFFECTS)
(INCREASES EFFECTS)
Stimulus produces a response which reduces
the original stimulus. (used for homeostasis)
Most are in this category
◦ Examples:
◦ Sweating (reduces being hot)
◦ Shivering (reduces being cold)
◦ Blood Sugar (reduces sugar in
blood)
◦ Stomata's and guard cells in plants
(reduce water loss in transpiration)
Stimulus produces a response which
increases the stimulus.
Examples:
◦ Drug addicts (needs more drugs)
◦ Apple ripening (ethylene is
increased)
◦ Hormone produced to speed up
contractions in childbirth (increases
faster childbirth)
Negative Feedback
Mechanism
Stimulus
1. Initial Hormone is
Released
2. Stimulates 2nd
Hormone to release
3. Inhibits further
release of initial
hormone
Increase in Body Temperature
Positive Feedback
Mechanism
Stimulus
1. Initial hormone is
released
2. Stimulates 2nd
hormone to release
3. Inhibits further
release of initial
hormone
The release of oxytocin to intensify the
contractions that take place during childbirth.[
Difference Between
Negative and Positive Feedback Loops
Negative feedback: the response is
moved to the target set point
Example: Thermostat turns on the A/C
when the house get too hot.
1.
Glucose (Blood sugar regulation)
2.
Stomata in plants and guard cells in plants;
regulates transpiration
Positive feedback: the response is
moved away from the target set point
Example: Speakers, sound going into
microphone is processed to produce a
magnified response sound coming out of
the speakers.
1.
Childbirth (Labor)
2.
Breastfeeding
3.
Blood Pressure
3.
Drug Addiction
4.
Hunger
4.
Fruit Ripening
5.
Temperature Regulation
6.
pH Balance
Worksheet