homeostatis mechanism

1. CHHAYA CHOUGULE
MODERN COLLEGE OF PHARMACY (FOR LADIES) MOSHI

2. •Homeostasis refers to the body’s ability to physiologically regulate
its inner environment to ensure its stability in response to
fluctuations in external or internal conditions.
•The liver, the pancreas, the kidneys, and the brain (hypothalamus,
the autonomic nervous system and the endocrine system) help
maintain homeostasis.
•The liver is responsible for metabolizing toxic substances and with
signaling from the pancreas maintains carbohydrate metabolism.
The liver also helps to regulate lipid metabolism and is the primary
site of cholesterol production.
•The kidneys are responsible for regulating blood water levels, re-
absorption of substances into the blood, maintenance of salt and ion
levels in the blood, regulation of blood pH, and excretion of urea and
other waste products.
• The hypothalamus is involved in the regulation of body
temperature, heart rate, blood pressure, and circadian rhythms
(which include wake/sleep cycles).

3. •Homeostasis can be influenced by either internal or existinc
conditions (instrinsic factors) or external or environmental conditions
(extrinsic factors) and is maintained by many different mechanisms.
•All homeostatic control mechanisms have at least three
interdependent components for the variable being regulated:
A sensor or receptor that detects changes in the internal or external
environment. An example is peripheral chemoreceptor's, which detect
changes in blood pH.
The integrating center or control center receives information from
the sensors and initiates the response to maintain homeostasis. The
most important example is the hypothalamus, a region of the brain that
controls everything from body temperature to heart rate, blood
pressure, satiety (fullness), and circadian rhythms (including, sleep and
wake cycles).
An effector is any organ or tissue that receives information from the
integrating center and acts to bring about the changes needed to
maintain homeostasis. One example is the kidney, which retains water if
blood pressure is too low.

4. TYPES OF FEEDBACK

5. Interactions among the elements of a homeostatic control system maintain stable
internal conditions by using positive and negative feedback mechanisms.

6. Figure: The Positive Feedback Mechanism of the Blood Clotting Cascade. Extrinsic
factors such as damage or injury activated the cleavage of zymogen proteins in the
blood clotting cascade. Activation of the zymogen, Thrombin IIa begins the
formation of the fibrin clotting network and also elicits positive feedback that
further upregulates the entire clotting cascade.

7. Figure 8.1 Homeostatic Regulation of Temperature in Humans. Core body
temperature is maintained at a normal setpoint of 37oC. If the core temperature rises
above (right hand side) or drops below (left hand side) the setpoint, internal biological
responses are initiated to return the core temperature back to the setpoint range.
Once this is achieved, negative feedback loops are initiated to down regulate the
internal biological responses so that the core temperature doesn’t overshoot the
required change.

8. Figure 8.3: Effects of Aldosterone and ADH on Kidney Function. When fluid
levels in the body are low, ADH (Vasopressin) is secreted by the pituitary gland
and Aldosterone is secreted by the adrenal glands. ADH decreases the loss of
water whereas Aldosterone increases the reabsorbtion of Na+ within the
collecting duct of the kidneys. Water is reabsorbed with the Na+ causing an
increase in fluid retention and decreased urine output.

9. Glucose Homeostasis. When blood sugar rises due to a meal (Path 1), the
pancreas senses the increase in blood glucose levels. In response, it releases
the peptide hormone, insulin. Insulin interacts with downstream target cells in
the body, including liver and muscle tissue, where it causes the uptake of
glucose from the blood stream into the cell. The excess glucose is stored as
the carbohydrate, glycogen. This returns blood glucose levels back to
normal. If it has been several hours after eating a mean, blood glucose levels
will begin to fall (Path 2). This signals liver cells to breakdown glycogen into
glucose monomers. The glucose can then be realeased back into the
bloodstream.

10. THANK YOU