Homeostasis what you must know for HSC Biology

Homeostasis, the self-regulatory process by which biological systems tend to maintain stability while adapting to optimal conditions for survival. Life goes on when homeostasis is successful. Failure to do so will result in disaster or death. The stability achieved is actually a dynamic equilibrium in which constant changes occur, but relatively uniform conditions prevail.


Systems in dynamic equilibrium tend to reach a steady state, a state of equilibrium that resists changing external forces. When such a system is disturbed, built-in regulators react to deviations to establish a new equilibrium. Such processes require feedback control. All processes of functional integration and coordination, whether mediated by electrical circuits or by the nervous and endocrine systems, are examples of homeostatic regulation.

A well-known example of homeostatic regulation in mechanical systems is the operation of a room temperature controller or thermostat. At the heart of a thermostat is a bimetallic strip that opens and closes an electrical circuit in response to temperature changes. When the room cools down, the circuit is closed, the furnace works and the temperature rises. At the set value, the circuit is interrupted, the oven stops, and the temperature drops. Biological systems are more complex and have very crude controllers to match such mechanical devices. However, the purpose of these two systems of his is the same. That is, to keep the activity within a given range, whether controlling the thickness of the rolled steel or controlling the pressure in the circulatory system.

Body temperature homeostasis

Body temperature control is a good example of homeostasis in a living system. A normal human body temperature is around 37°C, but factors such as exposure, hormones, metabolic rate, and illnesses that cause excessive heat or cold can affect this number. Thermoregulation is controlled by an area in the brain called the hypothalamus. Body temperature feedback is sent through the nervous system to the brain for compensatory regulation of respiratory rate, blood glucose levels, and metabolic rate. The circulatory system also plays an important role.
Its baroreceptors (baroreceptors in blood vessels that respond to stretch) relay blood pressure information to the brain and transport hormones secreted by the hypothalamus and thyroid gland. These act to regulate the body’s metabolism. Heat loss in humans is facilitated by activity that causes more blood to circulate near the surface of the skin, sweating, and decreased heat exchange mechanisms.

It is important to emphasize that when the system is functioning properly, the homeostatic response is inevitable and automatic, and steady state or homeostasis can be maintained by many systems working together. For example, flushing is one of the body’s automatic reactions to heat. However, this will result in a reduction in body temperature and the individual will return to normal.

The negative feedback loop through which all of this is mediated will allow the organism to return to normal body temperature.

from learn-biology.com

Blood glucose homeostasis

Blood glucose – or sugar content of blood – is another significant consideration for humans. When blood glucose levels can’t be properly regulated, this can lead to diseases such as diabetes.

How insulin works: When a person ingests carbohydrates from food, the body converts them into glucose. It is a monosaccharide that acts as an essential energy source. But the body doesn’t consume all the glucose at once. Instead, it is converted into a storage molecule called glycogen and stored in the liver and muscles. When the body needs energy, glucagon converts glycogen into glucose in the liver. Enters the bloodstream from the liver. In the pancreas, different types of islet cells release insulin and glucagon. Beta cells release insulin and alpha cells release glucagon. How Insulin Works The body’s cells need glucose for energy, and insulin ensures that the glucose is taken up by the cells. Insulin Trusted Source binds to insulin receptors on cells throughout the body, opening the cells to allow glucose entry. Low insulin levels are constantly circulating throughout the body. Elevated insulin levels tell the liver that a person’s blood sugar is also high, and the liver absorbs glucose and turns it into glycogen. and bring a person’s blood sugar levels back to normal.

How Glucagon Works: The liver stores glucose to fuel cells during periods of hypoglycemia. Skipping meals or not eating enough can lower your blood sugar. The liver stores glucose to keep blood sugar levels constant between meals and sleep. When a person’s blood sugar drops, pancreatic cells secrete glucagon, stimulating her processes of gluconeogenesis and glycogenolysis. The liver uses these processes to supply or stimulate the production of glucose. During glycogenolysis, glucagon directs the liver to convert glycogen into glucose, making it more readily available in the bloodstream. produce glucose from Gluconeogenesis also occurs in the kidney and other organs. When the body’s glucose levels rise, insulin causes glucose to enter the cells.

From bio.libretexts.org

Insulin and glucagon work in cycles. Glucagon interacts with the liver to raise blood sugar levels, whereas insulin lowers blood sugar levels by helping cells use glucose. However, insulin and glucagon keep blood sugar levels in a healthy range overall. When the body does not absorb or convert enough glucose, blood sugar levels remain high. Insulin provides cells with glucose for energy by lowering the body’s blood sugar levels and helping cells absorb glucose. Glucagon is released from the pancreas when blood sugar levels are too low. Glucagon directs the liver to release stored glucose, increasing blood sugar levels in the body.

Hyperglycemia occurs due to high blood sugar levels. Sustained high levels can cause long-term damage throughout the body.

Hypoglycemia occurs due to low blood sugar. Symptoms include fainting, dizziness, and can be life-threatening.


Question 1.

True or false:

A living system with a dysfunctional homeostasis system has a non-infectious disease

Question 2.

Explain the fundamental components of a negative feedback loop [4 marks]

Question 3.

Compare and contrast body temperature homeostasis and blood sugar homeostasis.


  1. True

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