Homeostasis and feedback The Human Body

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Homeostasis and feedbackThe Human Body

• An IRSC Live Virtual Lesson
• By Diana Lenartiene, Ed. S.

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Definition of Homeostasis
The biological definition of homeostasis is the
tendency of an organism or cell to regulate its
internal environment and maintain equilibrium,
usually by a system of feedback controls, so as
to stabilize health and functioning. Generally,
the body is in homeostasis when its needs are
met and its functioning properly.
http//anatomyandphysiologyi.com/homeostasis-posit
ivenegative-feedback-mechanisms/
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Every organ in the body contributes to
homeostasis. A complex set of chemical, thermal,
and neural factors interact in complex ways, both
helping and hindering the body while it works to
maintain homeostasis.
http//anatomyandphysiologyi.com/homeostasis-posit
ivenegative-feedback-mechanisms/
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Homeostatic control To maintain homeostasis,
communication within the body is essential. The
image below is an example of how a homeostatic
control system works. Here is a brief
explanation Stimulus- produces a change to a
variable (the factor being regulated). Receptor-
detects the change. The receptor monitors the
environment and responds to change
(stimuli). Input- information travels along the
(afferent) pathway to the control center. The
control center determines the appropriate
response and course of action. Output-
information sent from the control center travels
down the (efferent) pathway to the
effector. Response- a response from the effector
balances out the original stimulus to maintain
homeostasis.
http//anatomyandphysiologyi.com/homeostasis-posit
ivenegative-feedback-mechanisms/
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Think of it as an extremely complex balancing
act. Heres a diagram of the process.
http//anatomyandphysiologyi.com/homeostasis-posit
ivenegative-feedback-mechanisms/
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We will now view a video Explaining homeostasis
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Afferent pathways- carry nerve impulses into the
central nervous system. For instance, if you felt
scorching heat on your hand, the message would
travel through afferent pathways to your central
nervous system. Efferent pathways- carry nerve
impulses away from the central nervous system to
effectors (muscles, glands). The feeling of heat
would travel through an afferent pathway to the
central nervous system. It would then interact
with the effector and travel down the efferent
pathway, eventually making the person remove
their hand from the scorching heat.
http//anatomyandphysiologyi.com/homeostasis-posit
ivenegative-feedback-mechanisms/
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Negative feedback mechanisms Almost all
homeostatic control mechanisms are negative
feedback mechanisms. These mechanisms change the
variable back to its original state or ideal
value. A good example of a negative feedback
mechanism is a home thermostat (heating system).
The thermostat contains the receptor
(thermometer) and control center. If the heating
system is set at 70 degrees Fahrenheit, the heat
(effector) is turned on if the temperature drops
below 70 degrees Fahrenheit. After the heater
heats the house to 70 degrees Fahrenheit, it
shuts off effectively maintaining the ideal
temperature.
http//anatomyandphysiologyi.com/homeostasis-posit
ivenegative-feedback-mechanisms/
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Stimulus and response flowchart of feedback
http//www.opencurriculum.org/5385/homeostasis-and
-regulation-in-the-human-body/
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The control of blood sugar (glucose) by insulin
is another good example of a negative feedback
mechanism. When blood sugar rises, receptors in
the body sense a change . In turn, the control
center (pancreas) secretes insulin into the blood
effectively lowering blood sugar levels. Once
blood sugar levels reach homeostasis, the
pancreas stops releasing insulin. These are just
two examples of negative feedback mechanisms
within our body, there are 100s, can you think
of a few more?
http//anatomyandphysiologyi.com/homeostasis-posit
ivenegative-feedback-mechanisms/
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Positive feedback mechanismsA positive feedback
mechanism is the exact opposite of a negative
feedback mechanism. With negative feedback, the
output reduces the original effect of the
stimulus. In a positive feedback system, the
output enhances the original stimulus. A good
example of a positive feedback system is child
birth. During labor, a hormone called oxytocin
is released that intensifies and speeds up
contractions. The increase in contractions causes
more oxytocin to be released and the cycle goes
on until the baby is born. The birth ends the
release of oxytocin and ends the positive
feedback mechanism.
http//anatomyandphysiologyi.com/homeostasis-posit
ivenegative-feedback-mechanisms/
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Another good example of a positive feedback
mechanism is blood clotting. Once a vessel is
damaged, platelets start to cling to the injured
site and release chemicals that attract more
platelets. The platelets continue to pile up and
release chemicals until a clot is formed. Just
remember that positive feedback mechanisms
enhance the original stimulus and negative
feedback mechanisms inhibit it.
http//anatomyandphysiologyi.com/homeostasis-posit
ivenegative-feedback-mechanisms/
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Compare negative and Positive feedback
Negative Feedback Positive Feedback
1.Resist change in the body and bring back the original state.For example when you are exposed to cold your body temperature drops and your body make changes to bring it back to the body temperature. 2. In this feedback loop, the values remain with in a range. For example blood sugar is maintained at 100mg/ml. If blood sugar level goes up te control center pancreas steps in and produce insulin hormone, which helps to pump sugar into cells.Once the sugar levels reach normal pancreas stops secreting insulin. 3. Common in the body  4. This feedback loop is initiated by a stimulus that disturbs the homeostasis of a body system.For e.g. Eating sugar disrupts the glucose balance in the blood and triggers the Negative feedback loop of insulin. 1. Reinforce change in the body that results in a positive out come. For example when a pregnant mother is ready to deliver the bab, the hormone oxytocin levels shoots up causing stronger uterine contractions. 2. Values goes out of range 3. Very uncommon  4. Positive feedback loop is also triggered by a stimulus and
http//biochemhelp.com/define-homeostasis-what-is-
the-difference-between-negative-and-positive-feedb
ack-systems.html
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Table 1 Types of Homeostatic Regulation in the
Body
Homeostatic Processes Hormones and Other Messengers Tissues, Organs and Organ Systems Involved
Osmoregulation (also known as excretions) Excess water, salts, and urea expelled from body Antidiuretic hormone (ADH), aldosterone, angiotensin II, carbon dioxide Kidneys, urinary bladder, ureters, urethra (urinary system), pituitary gland (endocrine system), lungs (respiratory system)
Thermoregulation Sweating, shivering, dilation/constriction of blood vessels at skin surface, insulation by adipose tissue, breakdown of adipose tissue to produce heat Nerve Impulses Skeletal muscle (muscular system), nerves (nervous system), blood vessels (cardiovascular system), skin and adipose tissue (integumentary system), hypothalamus (endocrine system)
Chemical Regulation (including glucoregulation) Release of insulin and glucagon into the blood in response to rising and falling blood glucose levels, respectively increase in breathing rate in response to increases carbon dioxide levels in the blood, and release of carbon dioxide into exhaled air from lungs, secretion of erythropoietin by kidneys to stimulate formation of red blood cells Insulin, glucagon, cortisol, carbon dioxide, nerve impulses, erythropoietin (EPO) Pancreas (endocrine system), liver (digestive system) adrenal glands (endocrine system) lungs (respiratory system), brain (nervous system), kidneys (urinary system)
http//www.opencurriculum.org/5385/homeostasis-and
-regulation-in-the-human-body/
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We will now view a video on Homeostasis and
feedback
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What we have learned

• Homeostasis is from the Greek and means staying
  the same.
• Homeostasis has internal and external stimuli
  which effect it and cause the body to give
  negative or positive feedback.
• Negative feedback is more common than positive
  feedback
• A feedback loop is the set of stimulus and
  response activities related to a specific
  situation. We studied several examples.
• Prolonged exposure to negative feedback can cause
  disease or death. This is why Homeostasis is so
  important to the human body.

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• Thank you for viewing this presentation.
• Diana Lenartiene, IRSC ABE Instructor