HOMEOSTASIS
DEFINITION:
Homeostasis can be defined as the process by which living organisms regulate their internal
environment to maintain a stable and constant condition despite the external changes.
Importance
a) For the survival and proper functioning of living organisms
b) Internal conditions remain within a range(stability).
Components of Homeostasis are:
• Set point: This is the value or range for a particular variable. E.g of set point for body temperature is
36°c to 38°c.
• Receptors(sensors): They detect deviations from the set point and send information to a control
centre. Examples include thermoreceptors that sense change in temperature.
•Control centre: It processes the information received from receptors and sends signals to the effectors.
The hypothalamus in the brain often serves as the control centre for various homeostatic processes.
•Effectors: They carry out the necessary actions to return the system to it's set point. This can include
organs, tissues or cells that make changes in the body's physiological state.
Examples of Homeostasis
1. Blood Glucose Regulation
Set point: Around 90 mg/dL
Sensors: Pancreatic cells
Control Centre: Pancreas
Effectors: Liver, adipose tissue, muscle cells
Process: When blood glucose levels rise after eating, the pancreas detects this change and releases
insulin. Insulin facilitates the uptake of glucose into cells, lowering blood glucose levels. When blood
glucose levels drop, the pancreas releases glucagon, which prompts the liver to release stored glucose
into the bloodstream.
2. Osmoregulation
Set point: Proper balance of water and electrolytes
, Sensors: Osmoreceptors in the hypothalamus
Control Centre: Hypothalamus and kidneys
Effectors: Kidneys, sweat glands, thirst mechanism
Process If the body becomes dehydrated, Osmoreceptors in the hypothalamus detect the high
concentration of solutes in the blood. The hypothalamus then releases Antidiuretic hormone (ADH),
signalling the kidneys to reabsorb more water. This reduces urine output and conserves water. If there is
excess water, ADH release is suppressed, leading to increased urine output.
3. Thermoregulation
Set point: Approximately 37°C(98.6°F)
Sensors: Thermoreceptors in the skin and hypothalamus
Control Centre: Hypothalamus
Effectors: Sweat glands, muscles and blood vessels
Process: If body temperature rises, thermoreceptors in the skin and hypothalamus detect the change.
The hypothalamus (control Centre) triggers effectors such as sweat glands to increase perspiration and
blood vessels to dilate, allowing heat to dissipate (be lost or used up). Conversely, if body temperature
drops, the hypothalamus induces shivering and vasoconstriction to conserve heat.
NORMAL HOMEOSTATIC MECHANISMS
a) Positive Feedback Loops:
The positive feedback loop is less common but essential in certain situations, positive feedback amplifies
changes rather than reducing them. An example is the release of oxytocin during childbirth. Oxytocin
cause contractions, which push the baby towards the birth canal. This pressure causes more oxytocin to
be released, increasing contractions until the baby is born.
b) Negative Feedback Loops:
The negative feedback loop is the primary mechanism for maintaining homeostasis. In negative
feedback loop, a change in a variable triggers a response that counteracts the initial change. For
example, when blood glucose levels rise, insulin secretion is increased to lower glucose levels, and once
the levels are back to normal, insulin secretion decreases.
c) Feedforward Mechanism:
Feedforward Mechanisms are anticipatory responses that help maintain homeostasis by preparing the
body for a change in a physiological variable before it actually occurs. Unlike feedback mechanisms,
which respond to changes after they happen. Feedforward Mechanisms act proactively, based on
DEFINITION:
Homeostasis can be defined as the process by which living organisms regulate their internal
environment to maintain a stable and constant condition despite the external changes.
Importance
a) For the survival and proper functioning of living organisms
b) Internal conditions remain within a range(stability).
Components of Homeostasis are:
• Set point: This is the value or range for a particular variable. E.g of set point for body temperature is
36°c to 38°c.
• Receptors(sensors): They detect deviations from the set point and send information to a control
centre. Examples include thermoreceptors that sense change in temperature.
•Control centre: It processes the information received from receptors and sends signals to the effectors.
The hypothalamus in the brain often serves as the control centre for various homeostatic processes.
•Effectors: They carry out the necessary actions to return the system to it's set point. This can include
organs, tissues or cells that make changes in the body's physiological state.
Examples of Homeostasis
1. Blood Glucose Regulation
Set point: Around 90 mg/dL
Sensors: Pancreatic cells
Control Centre: Pancreas
Effectors: Liver, adipose tissue, muscle cells
Process: When blood glucose levels rise after eating, the pancreas detects this change and releases
insulin. Insulin facilitates the uptake of glucose into cells, lowering blood glucose levels. When blood
glucose levels drop, the pancreas releases glucagon, which prompts the liver to release stored glucose
into the bloodstream.
2. Osmoregulation
Set point: Proper balance of water and electrolytes
, Sensors: Osmoreceptors in the hypothalamus
Control Centre: Hypothalamus and kidneys
Effectors: Kidneys, sweat glands, thirst mechanism
Process If the body becomes dehydrated, Osmoreceptors in the hypothalamus detect the high
concentration of solutes in the blood. The hypothalamus then releases Antidiuretic hormone (ADH),
signalling the kidneys to reabsorb more water. This reduces urine output and conserves water. If there is
excess water, ADH release is suppressed, leading to increased urine output.
3. Thermoregulation
Set point: Approximately 37°C(98.6°F)
Sensors: Thermoreceptors in the skin and hypothalamus
Control Centre: Hypothalamus
Effectors: Sweat glands, muscles and blood vessels
Process: If body temperature rises, thermoreceptors in the skin and hypothalamus detect the change.
The hypothalamus (control Centre) triggers effectors such as sweat glands to increase perspiration and
blood vessels to dilate, allowing heat to dissipate (be lost or used up). Conversely, if body temperature
drops, the hypothalamus induces shivering and vasoconstriction to conserve heat.
NORMAL HOMEOSTATIC MECHANISMS
a) Positive Feedback Loops:
The positive feedback loop is less common but essential in certain situations, positive feedback amplifies
changes rather than reducing them. An example is the release of oxytocin during childbirth. Oxytocin
cause contractions, which push the baby towards the birth canal. This pressure causes more oxytocin to
be released, increasing contractions until the baby is born.
b) Negative Feedback Loops:
The negative feedback loop is the primary mechanism for maintaining homeostasis. In negative
feedback loop, a change in a variable triggers a response that counteracts the initial change. For
example, when blood glucose levels rise, insulin secretion is increased to lower glucose levels, and once
the levels are back to normal, insulin secretion decreases.
c) Feedforward Mechanism:
Feedforward Mechanisms are anticipatory responses that help maintain homeostasis by preparing the
body for a change in a physiological variable before it actually occurs. Unlike feedback mechanisms,
which respond to changes after they happen. Feedforward Mechanisms act proactively, based on
