Week 1 PPT (Homeostasis)

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Homeostasisq
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Defined as maintenance of a relatively
stable internal environment
Homeostasis is essential for survival and
function of all cells.
Maintenance of Homeostasis
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Nervous system
•
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Controls and coordinates bodily activities that require
rapid responses.
Detects and initiates reactions to changes in external
environment and internal environment.
Endocrine system
•
Secreting glands of endocrine regulate by release of
hormones.
Control of Homeostasis
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Homeostasis is continually being
disrupted by:
•
External stimuli
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heat, cold, lack of oxygen,
pathogens, toxins
Internal stimuli
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Body temperature
Blood pressure
Concentration of water, glucose,
salts, oxygen, etc.
Physical and psychological
distresses
Stimuli Demo
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Ice Water and Heart Rate/Blood Pressure.
Homeostasis Components
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There are three main components
(players) involved when homeostasis is
disrupted by a stimuli.
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The Receptor
The Control Center
The Effector
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Receptors
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The receptor is an organ or sensor that
receives the chemical signal and
communicates to the next Component (
the control center).
•
In the case of blood sugar the liver is the
main receptor.
Homeostatic Control Systems
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The control system must be able to:
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Receives signal from the receptor. It also can
sense deviations from the norm its self.
Integrate this information with other relevant
information.
Sends a signal to the appropriate organ or
gland to make the necessary adjustment.
Generally the Brain (hypothalamus) is the
control center. However, the pancreas is its
own control center for blood sugar.
Effector
•
The effector is the component that causes
the change. It sends out the chemical to
deal with the stimulus.
•
In the case of blood sugar the pancreas
would be the effector because it sends out
the insulin.
Homeostatic Control Systems
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Feedback - refers to responses made after
change has been detected
•
Types of feedback systems
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Negative
Positive
Feedback Loops: Types
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Negative feedback loop
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original stimulus reversed (shut off)
most feedback systems in the body are
negative
Positive feedback loop
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original stimulus intensified
seen during normal childbirth
Negative Feedback Loop
Negative Feedback & Blood Pressure
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Baroreceptors in walls of
blood vessels detect an
increase in BP
Brain receives input and
signals blood vessels and
heart
Blood vessels dilate, HR
decreases
BP decreases
Positive Feed Back
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In this case the stimuli causes an increase
in the original stimulus.
Positive Feedback during Childbirth
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Stretch receptors in walls of uterus send
signals to the brain
Brain induces release of hormone
(oxytocin) into bloodstream
Uterine smooth muscle contracts more
forcefully
More stretch, more hormone, more
contraction etc.
Cycle ends with birth of the baby &
decrease in stretch
Feed Back Graphs
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To be Drawn.
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