Definition of Homeostasis
Homeostasis refers to the capability of living systems to keep a constant as well as homogeneous internal environment in order for the systems to function normally.
- It is the desire to find balance in the face of various environmental as well as natural influences.
- Homeostasis produces a dynamic equilibrium wherein continual changes occur while steady circumstances are maintained.
- The body’s numerous internal variables (such as body temperature, pH, ion concentration, as well as blood sugar level) are regulated by homeostasis.
A range of regulatory mechanisms are used to combat both external and internal factors that induce changes in the body.
- Individual organs or the entire body can indeed manage homeostasis.
What keeps Homeostasis under control?
Maintaining Homeostasis/Homeostasis Mechanisms
The regulation of homeostasis relies on a sophisticated system that uses individual units to operate in a certain order to maintain a certain variable at a steady level. All homeostasis mechanisms are made up of four distinct units:
- Stimulus is something which causes changes in the system including the variable.
- Stimulus denotes that the variable has deviated from its typical range, hence commencing the homeostasis process.
- An instance is when the body temperature rises above 37°C because of many of reasons. The rise in temperature of the body shows that the upper range of body temperature has been surpassed.
- Homeostasis relies on sensors and receptors to monitor and respond to changes inside the body.
- Sensor detects changes in the system and delivers the data to the control unit.
- Nerve cells, as well as receptors such as thermoreceptors and mechanoreceptors, are included in sensors/receptors.
- Control unit
- When the information is supplied to the control unit, it compares the modified value to its usual value.
- If the value differs from the typical value, the control centre stimulates the effectors in response to the stimuli.
- A control unit is the thermoregulatory unit inside the hypothalamus of the brain, which regulates body temperature.
- Muscles, glands, organs, and other similar structures which are activated by the control unit’s signal are examples of effectors.
- An effector is a target on which the control unit acts to return a variable’s value to normal.
- The effector basically opposes the stimulus in order to neutralise its effect.
- In the case of thermoregulation, sweat glands are effectors which are activated by the thermoregulatory unit to make sweat in order to return the temperature of the body to its normal state.
A feedback loop is just a biological system which aids in the maintenance of homeostasis by producing results which either enhance (positive feedback) or inhibit (negative feedback).
When there is a change in a system, an alarm is triggered, which causes the feedback loop to start. The output either supports or hinders the modification.
The system possesses two distinct feedback loops that help to maintain homeostasis:
- Negative feedback loop
- The majority of homeostatic processes are sustained via negative feedback loops.
- To stabilise the system, negative feedback loops create an output which tries to reduce the influence of the stimulus.
- These loops tend to oppose as well as act against the stimulus which may have activated the system.
- Negative feedback loops are activated in two ways;
- In the very first situation, activation happens when the value of a variable (such as temperature of the body) exceeds its normal value and must be reduced.
- Activation occurs in the other instances when the variable‘s value goes below its normal value and have to be regained.
- Creation of RBCs by the kidneys in response to a lower quantity of oxygen in the body is an example of a negative feedback loop.
- Negative feedback loops can exist in nature, like in the carbon cycle, which is balanced dependent on the concentration of carbon emissions.
- Positive feedback loop
- Certain biological as well as natural systems may use positive feedback loops, where the output of the loop tries to strengthen the effect of the stimulus.
- Positive feedback loop is commonly seen in processes which must be completed rapidly.
- As a result, positive feedback loops tries to progress the process towards completion instead of equilibrium.
- The child birth process is an example of a positive feedback loop inside the body. As the baby’s head presses against the cervix, the neurons in that region are activated. This encourages the brain to transmit signals to produce oxytocin, which increases uterine contractions and puts more pressure on the cervix, facilitating birth.
- Positive feedback loops, such as negative feedback loops, can be seen in nature all through the ripening of fruits on trees. When one fruit ripens, it emits ethylene gas, which causes the fruits surrounding it to ripen as well.
Different Types of Homeostatic Regulation in the Body
A range of homeostatic regulation mechanisms operate in the human body to balance chemical or physical elements. There are three types of homeostatic control in the body in particular, which are:
- Thermoregulation is the process which occurs inside the body which is responsible for regulating the body’s core temperature.
- Thermoregulation is based on a negative feedback loop wherein the temperature of body is returned to normal after it has been boosted or dropped above its usual range.
- Sweating as well as dilation of blood vessels counterbalance increased temperature of body, whereas contraction of blood vessels and breakdown of adipose tissue to produce heat prevent lowered temperature of body.
- The process of thermoregulation is maintained by organs like the skin as well as adipose tissue of the integumentary system, as well as the hypothalamus of the brain.
- Osmoregulation is the act of keeping a constant osmotic pressure within the body by adjusting fluid and salt contents.
- Excess water, ions, as well as other compounds such as urea are eliminated from the body during this process to preserve osmotic balance.
- A typical example of Osmoregulation process is the elimination of surplus water as well as ions from the circulation as urine in order to preserve blood osmotic pressure.
- Rennin-angiotensin system as well as other hormones such as antidiuretic hormones operate as messengers for the body’s electrolytic control system.
- Chemical regulation
- Chemical regulation is the method of producing hormones to regulate the concentrations of chemicals in the body such as glucose and carbon dioxide.
- In order for blood sugar levels to return to normal, the concentration of hormones like insulin rises all through this process.
- A similar pattern can be seen in the respiratory system, in which the rate of breathing increases as the carbon dioxide concentration rises.
(a) Acid-Base Homeostasis
- Acid-base homeostasis refers to the process of regulating the pH of intracellular and extracellular fluids inside the body.
- Normal physiology requires a pH balance of fluids inside the body.
- To avoid fluctuations in the pH of fluids, a number of chemical buffers are available in diverse parts of the body.
- Blood plasma is another example of acid-base balance, since excess carbonic acid is broken down into hydrogen ions and bicarbonate ions.
- If the blood pH is low, hydrogen ions are released into urine, increasing the pH, while if the blood pH is high, bicarbonate ions are released into urine, decreasing the pH.
(b) Homeostasis of Glucose
- The process of preserving a desirable level of glucose inside the blood through the opposing as well as balanced action of insulin and glucagon hormones is known as glucose homeostasis.
- The level of glucose in the blood is critical for maintaining the body’s normal functioning.
- When the quantity of glucose in the blood declines as a result of fasting for an extended period of time, glucagon converts the conserved glycogen into glucose to regain homeostasis.
- Likewise, whenever blood glucose levels rise, insulin converts glucose into glycogen to restore the balance.
(c) Calcium homeostasis
- The process of balancing calcium levels in the body is referred to as calcium homeostasis.
- The skeletal system is essential for calcium homeostasis. Moreover, calcitonin, vitamin D, and parathyroid hormone are needed.
- If blood calcium levels are low, the parathyroid hormone (PTH) drives osteoclastic activity, which promotes bone demineralization and calcium ion release into the blood.
- PTH also increases absorption of calcium inside the kidneys, so balancing calcium levels in the blood.
- If blood calcium levels are excessively high, the thyroid hormone secretes calcitonin, which inhibits osteoclastic activity while promoting bone absorption.
- Likewise, the hormone inhibits calcium absorption by the kidneys, so conserving calcium levels.
(d) Fluid Homeostasis
- Fluid homeostasis is the process of maintaining consistent concentrations of water and electrolytes in different physiological fluids.
- The reasoning underlying this concept is that in order for the body’s fluid level to be balanced, the amount of water shed by the body must match the amount of water absorbed.
- Röder, P. V., Wu, B., Liu, Y., & Han, W. (2016). Pancreatic regulation of glucose homeostasis. Experimental & molecular medicine, 48(3), e219. https://doi.org/10.1038/emm.2016.6
- Zhang, L., Ai, Y., & Tsung, A. (2016). Clinical application: Restoration of immune homeostasis by autophagy as a potential therapeutic target in sepsis. Experimental and therapeutic medicine, 11(4), 1159–1167. https://doi.org/10.3892/etm.2016.3071
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