Homeostasis and Negative Feedback Mechanism

len Alfred Ajibola - Thu, 21st March, 2019 @ 13:55

Topics in Biology

Food web explained with examples Biology Scheme of Work, SS1, First Term Biology Scheme of Work, SS1, 2nd Term Biology Scheme of Work, SS1, 3rd Term Seminal Vesicles and Bulbourethral Glands as Male Accessory Sex Organs Male Reproductive System: Scrotum and its contents Brain: Introduction to the Human Brain Forebrain: Lobes of the Cerebrum and their Functions Cerebellum: Parts and Functions of the Cerebellum Midbrain: Division and Functions of the Midbrain Negative Feedback Mechanism in Homeostasis Arterial Disorders: Characteristics and Causes of Arterial Disorders Types of Desert and their Characteristics Characteristics of Tropical Rainforest Swamp Forest: What are Swamp Forests? Characteristics of Swamp Forests Savanna: Savanna and Grassland explained Savanna - Types of Savanna Tropical Savanna and Temperate Savanna with their Characteristics Introduction to Biomes: What is a Biome?

Academic Questions in Biology

Please check out our Test Your Knowledge page to see all Questions and Answers

The final organisms in a food chain are best referred to as _____.

  • A. saprophytes

  • B. parasites

  • C. commensals

  • D. decomposers

  • E. tertiary consumers

  • F. quatenary consumers

Which of the following is a category of long bones?

  • A. Stunted long bones
  • B. Reduced long bones
  • C. Giant long bones
  • D. Bended long bones
  • E. Curved long bones
  • F. Elongated long bones

The end product of photosynthesis is _____.

  • A. O2
  • B. C​​​​​​2​​​​C5OH
  • C. H2​​​​​O
  • D. CO2
  • E. C6H12O6
  • F. C2H5COOH

The above diagram illustrates a _____.

  • A. Food Chain
  • B. Food Web
  • C. Food Pyramid
  • D. Food Link
  • E. Food Hub
  • F. Food zone

The living cells that makes up cartilages are called _____.

  • A. osteocytes
  • B. osteoblasts
  • C. osteoclasts
  • D. chondroblasts
  • E. chrondocytes
  • F. Osteoprogenitor cells

Which of the following statement is incorrect with regards to chitin?

  • A. Ecdysis is a term associated with chitin
  • B. It is a skeletal material
  • C. It is a type of skeleton
  • D. It is present outside the organism
  • E. It does not grow when the organism grows
  • It is present in ants

Which of the following is NOT a function of the human skeleton?

  • A. Gives Shape
  • B. Provides Protection
  • C. Aids in Locomotion
  • D. Supports Movement
  • E. Assists in Inhalation and Exahalation
  • F. None of the above
  • G. All of the above

Organisms that manufacture their own food through the help of sunlight or chemicals are best referred to as _____.

  • A. autotrophs
  • B. chemosynthetic
  • C. photosynthentic
  • D. chemoautotrophs
  • E. photoautotrophs
  • F. chemoautotrophs

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What is Homeostasis?

Have you ever wondered why on a sunny day you drink a lot of water and tend to produce lesser urine? On the contrary, think about how likely you will produce more urine on a cold day and drink less water too. This is so because some processes are constantly ongoing inside your body and they are necessary for your survival.

Please read on the Basic Characteristics of Life here.

Now, let's imagine that someone has a fever. His or Her temperature will be abnormally high as a result of the fever. The person may sweat abnormally or even urinate abnormally. On your part, you will suspect that some processes are not working right inside the person.

Please read on Vectors of Diseases here.

Medically speaking, for a person to be physiologically healthy, the conditions and processes in his or her body must be carefully and properly controlled. This internal control is what homeostasis entails.

Homeostasis can be defined as the regulation and maintenance of a constant (or nearly constant) internal environment.

Understanding Internal Environment

Recall that your environment is everything that surrounds you; for instance air, water, phone, shoes and anything around you right now. This concept of environment is your external environment.

In physiology, we have another concept of environment called the internal environment; and it is this environment that the bodily homeostatic organs constantly regulate to it's best optimum conditions.

Now let's think of it this way; if for instance; the external environment is very dirty and unhealthy (from lack of regulation, cleanliness and healthy living), children will suffer from illnesses and diseases like cholera, typhoid and dysentery. This is true because the respective causative organisms (of such diseases) will find their way into the child's body systems and invariably, the environment inside their body (internal environment).

Please read on Microorganisms causing Food, Water and Air Borne Diseases here.

As living organisms, human beings are composed of trillions of cells. These cells aren't just stacked upon one another (like a pack of cards); instead, they are separated by a fluid filled space.

ICF and ECF - Len Academy
The above diagram illustrates the various fluids seen within and around the cell

The fluid filled space present outside all the cells of any multi-cellular organism is termed as the Extracellular fluid or ECF.

Note: The Blood Plasma (found inside the blood vessels; that is "arteries, veins and capillaries") is a component of the ECF because they are present outside the body cells. The same is true for the interstitial fluid which is also another component of the ECF.

Please read on various Disorders of the Artery here.

The ECF accounts for about 35% (one-third) of the Total Body Water (TBW) in healthy adults.

Please read on Immunization here.

Similarly, inside each of the cells is another kind of fluid called the Intracellular Fluid or ICF.

The ICF comprises of the cytoplasm of each cell's organelle which contains water, proteins and electrolytes.

About 65% (two-third) of the Total Body Water is ICF. For this reason, the volume of ICF is greater than that of ECF with regards to the Total Body Water (TBW).

The Total Body Water (TBW) accounts for about 65% of the body weight of an average man. (This value will vary with age, for instance children will have a higher percentage value while that of the aged will be lesser).

The above fact on TBW affirms that: "humans are composed more of water (liquid) than solids".

You can read on some amazing facts in Biology here.

The two compartment accounting for the Total Body Water are the ICF and ECF; and these presents the internal environment.

It is these internal environments that are regulated via homeostasis.

You can read on the Red Blood Cells and Hemoglobin here.

Note: The concentration of substances within the internal environment must be at a very narrow range, else, the organism becomes sick and may eventually die. Most of the medical drugs function by restoring the internal environment to it's normal composition.

You can read on Types and Functions of Drugs here.


Systems Coordinating Homeostasis

In humans, homeostasis is achieved through two systems; these are:

  1. Nervous System: It comprises of the brain and spinal cord.
    Please read on the Uniqueness of Man (The Brain).

  2. Endocrine System: It has every thing to do with hormones. The pituitary gland is often referred to as the master endocrine gland; that is, it regulates the homeostatic functions of other endocrine glands.

For now, think of endocrine glands as the producers of hormones.

These two systems coordinates all homeostatic processes by regulating the respective homeostatic organs in the body.

Homeostatic Organs

Below are some homeostatic organs alongside a summary of their homeostatic functions:

  • Hypothalamus: Regulates body temperature, sleep, appetite and thirst.

  • Kidney: Regulates water, salts and electrolyte via urine formation.

  • Skin: Regulates water, salts and electrolyte via sweat formation.

  • Liver: Regulates the storage of glucose, storage of blood, production of bile, breakdown of proteins, cleansing of the body and much more.

  • Pancreas: Regulates blood glucose and glycogen.

  • Lungs: Regulates oxygen and carbon(IV)oxide intake through breathing.

The diagram below shows the various homeostatic organs and their locations.

Endocrine Glands - Len Academy

Note: The nervous and endocrine systems regulate the above homeostatic organs through a mechanism called the negative feedback mechanism.

Please read more on Negative Feedback Mechanism in Homeostasis here.

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Alfred Ajibola is a Medical Biochemist, a passionate Academician with over 7 years of experience, a Versatile Writer, a Web Developer, a Cisco Certified Network Associate and a Cisco CyberOps Associate.

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All voluntary and concious activity of right handed people are controlled from the left part or hemisphere of the brain

A snail can actually sleep for 3 years 😁

An adult human being is composed of about 60% water. In fact, a newly born baby is composed of about 80% of water. This will drop to 65% after a year and finally to about 60% as the child ages

Without saliva, food can never be enjoyed. Food becomes tasteless since saliva is needed to dissolve the chemicals present in food onto the tongue’s taste buds.

Saliva also contains an enzyme called salivary amylase or "ptyalin" which helps to digest cooked starch to maltose. Maltose is a double sugar or disaccharide. Please read on sugars here


For a thing to be considered Living, it must possess all the Basic Characteristics of Life. These include:

  1. Movement

  2. Respiration

  3. Nutrition

  4. Irritability or Sensitivity

  5. Growth

  6. Excretion

  7. Reproduction

  8. Death

  9. Adaptation

  10. Competition

Please read the explanations on all the Basic Characteristics of Life here

During strenuous exercises like sprinting or 🏃 running, your body may actually work in the shortage of oxygen. During this time, your body owes oxygen (called oxygen debt) and it must be replenished or repayed after the exercise is stopped. This is why you breathe excess of oxygen after you stopped the exercise.

This is the concept of anaerobic respiration

A food Chain is a diagram that shows the relationship between plants and animals within a habitat on the basis of how they rely on each other for food.

Note: Habitat is a place where an organism live. It is of three types:

  • Terrestrial (Land)
  • Aquatic (Water)
  • Arboreal (🌲 Treetops)

You can read on Food Chain here

The term Biology originated from two Greek words. They are:

  • Bios: means life. 
  • Logos: means knowledge or to study.

Biology can therefore be defined is the study of life

Anything that has life is generally considered as a living organism (or organism) 🌱🐐🐓. All living organisms must be able to carry the following activities:

  1. Movement
  2. Respiration
  3. Nutrition
  4. Irritability or Sensitivity
  5. Growth
  6. Excretion
  7. Reproduction
  8. Death
  9. Adaptation
  10. Competition

The above listed points are often regarded as the basic characteristics of life. You can memorize them using the acronym (MR. NIGER DAC).

You can read on the introduction to Biology and the basic characteristics of life here

The gas used in the manufacture of food by plants is Carbon dioxide or Carbon(IV)oxide or CO2. 

Plants manufacture food through a process called photosynthesis. Please read on photosynthesis here

Note: Plants are the only orgnisms that take away CO2 from the atmosphere