Chapters
In this article, we will discuss homeostasis and the importance of homeostasis in mammals. We will also explain the principles of homeostasis in terms of internal and external stimuli, receptors, coordination systems (nervous system and endocrine system), effectors (muscles and glands), and negative feedback. In the end, we will discuss that urea is produced in the liver from the deamination of excess amino acids. So, let us get started.
Organisms have various control systems which allow them to function properly and efficiently. These systems ensure that the internal environment of the organisms remains relatively consistent. We can define hemostasis as:
The process of maintaining consistent internal body conditions is referred to as hemostasis
Importance of Homeostasis?
Homeostasis is a critical process for organisms because it ensures that organisms maintain optimal conditions for enzyme action and cell function. Organisms have sensory cells that can detect information about internal and external conditions of the body. Homeostasis controls the following physiological factors in mammals.
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- Core body temperature
- Metabolic waste like carbon dioxide and urea
- Glucose concentration in the blood
- Water potential of the blood
- pH of blood
- The concentration of the respiratory gases such as oxygen and carbon dioxide in the blood
In mammals, homeostasis depends on two different coordination systems to transfer information between various body parts. These systems are:
- Nervous system: The information is transferred as electrical impulses that move along neurons
- Endocrine system: The information is transferred as chemical messengers known as hormones that move in the blood
Negative Feedback
To maintain homeostatic balance, the majority of the homeostatic control mechanisms in organisms employ negative feedback. Homeostatic balance refers to keeping certain physiological factors like blood glucose concentration within certain boundaries.
The control loop of the negative feedback includes:
- A sensor or receptor: For detecting a stimulus that is involved with a physiological factor or condition
- A coordination system (endocrine and nervous system): For transmitting information between various body parts
- An effector (glands and muscles): For carrying out a response.
The results of a negative feedback loop include:
- Continuous monitoring of the factor or stimulus
- If a factor increases, the body responds to make the factor decrease
- If a factor decreases, the body responds to increase the factor
In the next section of the article, we will discuss the principles of homeostasis in terms of internal and external stimuli, receptors, coordination systems (nervous system and endocrine system), effectors (muscles and glands), and negative feedback.
Coordinating Homeostatic Mechanisms
Homeostatic mechanisms allow the organisms to keep the conditions inside their body relatively constant. Three main homeostatic mechanisms are:
- Thermoregulation: It involves the control of body temperature
- Osmoregulation: It involves the control of the water potential of fluids in the body
- The control of glucose concentration in the blood
The above-mentioned homeostatic mechanisms in mammals need information to be transmitted between various body parts. The two coordination systems in mammals that do this are:
- The nervous system
- The endocrine system
The Nervous System
The nervous system in humans contains:
- The central nervous system (CNS): It includes the brain and the spinal cord
- The peripheral nervous system (PNS): It includes all nerves in the body
The nervous system allows us to comprehend our surroundings, respond to them, and coordinate and regulate the functions of the body. The information is sent through the nervous system as nerve impulses which are electrical signals that travel along the nerve cells referred to as neurons. A bundle of neurons is called a nerve. Neurons coordinate the activities of the sensory receptors like those present in the eye, decision-making centres in the central nervous system, and effectors like glands and muscles.
The Endocrine System
Hormones
A hormone refers to a chemical substance that is produced by an endocrine gland and is carried by the blood. They are chemicals that transfer information from one part of the body to another and trigger a change. Hormones change the activity of one or more target organs.
Hormones are employed to control functions that do not require quick responses. The endocrine glands that produce hormones in animals are collectively referred to as the endocrine system.
Glands
A gland refers to a group of cells that produces and releases one or more substances. They do so by a process called secretion
Endocrine glands entail a proper blood supply because when they make hormones, they require them to enter the bloodstream, especially the blood plasma as soon as possible. When they enter the bloodstream, they move around the body to the target organs to trigger a response. Hormones are only able to affect cells with receptors that the hormone can bind to. These cells will receptors are either present on the cell surface membrane or inside the cells. To make an effect, the receptors must be complementary to hormones.
In the next section of the article, we will discuss that urea is produced in the liver from the deamination of excess amino acids.
Production of Urea
- Several metabolic reactions take place inside our bodies which produce waste products
- It is critical to remove these waste products through a process known as excretion
- Several excretory products are created in humans. The two main waste products are urea and carbon dioxide. These two waste products are formed in relatively greater quantities than other waste products.
Urea
- Formed due to surplus amino acids, the waste product “urea” is produced in the liver
- If we eat more protein than needed, then our body cannot store the surplus proteins. However, the proteins contain amino acids which can still provide the needed energy
- The amino group is eliminated from each amino acid to make this energy accessible by a process known as deamination.
- Deamination involves:
- The removal of an amino group (-NH2) of amino acid along with an extra hydrogen atom
- Their combination results in the formation of ammonia (NH3)
- The keto acid left can enter the Krebs cycle so that it can be respired, transformed into glucose, or converted into fat/glycogen for storage
- Ammonia is a highly soluble and toxic compound that is a result of a deamination process. If it is allowed to build up in the blood, it can be quite damaging:
- It dissolves in the blood to create alkaline ammonium hydroxide which disrupts the pH of the blood
- It can affect the reactions of the cell metabolism like respiration
- It meddles with the cell signalling processes
- It is prevented by converting ammonia to urea because urea is less soluble and toxic than ammonia
- The combination of ammonia with carbon dioxide generates urea
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