Homeostasis and Negative Feedback

Homeostasis is the ability of the body to maintain a stable internal environment despite changes in the external environment.

A mechanism used to maintain homeostasis
Involves a response to a change in the body that reverses the change
Three components:
1. Sensor: detects the change in the body
2. Integrator: interprets the signal from the sensor and sends a response
3. Effector: carries out the response to reverse the change
Examples:
- Thermoregulation: when body temperature rises, sweat glands are activated to cool the body
- Blood glucose regulation: when blood glucose levels rise, insulin is released to lower levels

Maintaining a stable blood glucose level is crucial for proper bodily function
Regulation involves a negative feedback loop:
- Sensor: pancreatic cells detect changes in blood glucose levels
- Integrator: pancreatic cells interpret the signal and send a response
- Effector: insulin is released to lower blood glucose levels, or glucagon is released to raise levels
Insulin:
- Lowers blood glucose levels by facilitating glucose uptake in cells
- Stimulates glycogen synthesis in the liver
Glucagon:
- Raises blood glucose levels by stimulating glycogen breakdown in the liver
- Stimulates glucose release from stored glycogen

Maintaining a stable balance of water and electrolytes in the body
Regulation involves a negative feedback loop:
- Sensor: osmoreceptors in the hypothalamus detect changes in blood osmolality
- Integrator: hypothalamus interprets the signal and sends a response
- Effector: ADH (antidiuretic hormone) is released to regulate water reabsorption in the kidneys
ADH:
- Stimulates water reabsorption in the kidneys to decrease blood osmolality
- Inhibits water reabsorption in the kidneys to increase blood osmolality

Maintaining a stable body temperature (around 37°C) is crucial for proper bodily function
Regulation involves a negative feedback loop:
- Sensor: thermoreceptors in the hypothalamus detect changes in body temperature
- Integrator: hypothalamus interprets the signal and sends a response
- Effector: sweat glands, shivering, and vasodilation/vasoconstriction are activated to cool or warm the body
Cooling mechanisms:
- Sweating: evaporation of sweat cools the body
- Vasodilation: increased blood flow to the skin surface cools the body
Warming mechanisms:
- Shivering: muscle contraction generates heat
- Vasoconstriction: decreased blood flow to the skin surface conserves heat

Hormones play a crucial role in maintaining homeostasis
Endocrine glands produce hormones that regulate various bodily functions
Examples of hormonal regulation:
- Insulin and glucagon regulate blood glucose levels
- ADH regulates water reabsorption in the kidneys
- Thyroid hormone regulates metabolic rate
Hormonal regulation involves a negative feedback loop:
- Sensor: detects changes in the body
- Integrator: interprets the signal and sends a response
- Effector: hormone is released to reverse the change

Ability of the body to maintain a stable internal environment despite changes in the external environment

Maintaining a stable blood glucose level is crucial for proper bodily function
Regulation involves a negative feedback loop with pancreatic cells as sensors, integrators, and effectors
Insulin lowers blood glucose levels by facilitating glucose uptake in cells and stimulating glycogen synthesis in the liver
Glucagon raises blood glucose levels by stimulating glycogen breakdown in the liver and glucose release from stored glycogen

Maintaining a stable balance of water and electrolytes in the body
Regulation involves a negative feedback loop with osmoreceptors in the hypothalamus as sensors, hypothalamus as integrator, and ADH as effector
ADH stimulates water reabsorption in the kidneys to decrease blood osmolality and inhibits water reabsorption to increase blood osmolality

Maintaining a stable body temperature (around 37°C) is crucial for proper bodily function
Regulation involves a negative feedback loop with thermoreceptors in the hypothalamus as sensors, hypothalamus as integrator, and sweat glands, shivering, and vasodilation/vasoconstriction as effectors
Cooling mechanisms: sweating, vasodilation
Warming mechanisms: shivering, vasoconstriction

Hormones play a crucial role in maintaining homeostasis
Endocrine glands produce hormones that regulate various bodily functions
Examples of hormonal regulation: insulin and glucagon regulate blood glucose levels, ADH regulates water reabsorption in the kidneys, thyroid hormone regulates metabolic rate

The body maintains a constant temperature of around 37°C despite changes in environmental temperature.
Negative feedback mechanisms regulate body temperature:
- Heat loss occurs through sweating and vasodilation.
- Heat gain occurs through shivering and vasoconstriction.
The hypothalamus acts as a thermostat to regulate body temperature.

The body maintains a narrow pH range of 7.35-7.45.
Buffering systems help maintain pH balance:
- Bicarbonate-carbonic acid buffer.
- Phosphate buffer.
- Protein buffers.
The respiratory system regulates CO2 levels to maintain pH.
The renal system regulates H+ ion excretion to maintain pH.

The body maintains proper water balance through the regulation of water intake and excretion.
The hypothalamus and kidneys work together to regulate water balance.
Osmoreceptors in the hypothalamus monitor blood osmolality.
Antidiuretic hormone (ADH) and aldosterone regulate water reabsorption in the kidneys.
The thirst mechanism stimulates water intake when blood osmolality increases.

The body maintains proper osmotic balance through the regulation of solute and water levels.
The kidneys and hypothalamus work together to regulate osmotic balance.
Osmoreceptors in the hypothalamus monitor blood osmolality.
ADH regulates water reabsorption in the kidneys to maintain osmotic balance.
Sodium and potassium ion balance also play a crucial role in osmoregulation.

The body exchanges oxygen and carbon dioxide with the environment through the respiratory system.
Chemoreceptors in the carotid and aortic bodies monitor CO2 and O2 levels.
Negative feedback mechanisms regulate gas exchange:
- Increased CO2 levels stimulate increased ventilation rate.
- Decreased O2 levels stimulate increased ventilation rate.