The human body includes mechanisms called homeostatic mechanisms that help regulate the body. This includes organs, glands, tissues and cells. The adjusting of these enables the body to constantly be stable.
The main mechanisms of homeostasis are body temperature, body fluid composition, blood sugar, gas concentrations, and blood pressure.
Homeostasis is the ability of an organism to maintain a constant and stable internal environment against disturbances from the outside. (The physiological consistency of the body despite external fluctuations.) All complex multicellular organisms maintain a stable internal environment using their organ systems. I have chosen to write about body temperature. The control of body temperature is called thermoregulation. A normal body temperature is around 37ºC. This is the temperature at which enzymes work best. The thermoregulatory center in the brain has receptors to monitor the temperature of the blood flowing through it. Receptors in the skin send impulses to the center about skin temperature.
The thermoregulation mechanism is significant to the organism as it regulates the body temperature around a certain value at a set point. This is important so that the organism doesn’t overheat or freeze. Two types of heat regulation that the body uses are endothermic and ectothermic. Endothermic regulation is where an organism can maintain their own core temperature and ectothermic regulation is where it gains the temperature of its surrounding environment.
Organisms that regulate their own temperature detect the temperature by receptors in the skin and hypothalamus in the brain. Then, nerve impulses are sent when there is a temperature change. This brings change depending on whether it is hot or cold, signaling to the muscles and glands.
Homeostasis of body temperature involves many types of effector systems including physiological and behavioural all controlled by the set-point of temperature sensing nerve cells in the hypothalamus (the thermometer).
Some effector systems the body can do to combat high and low body temperature are:
Vasodilation and vasoconstriction
Vasodilation is when the hypothalamus in the brain sends impulses to blood vessels dilate, decreasing blood pressure and increasing the flow of blood to the surface tissues under the skin meaning heat is lost. The opposite of this is vasoconstriction which reduces the blood flow to the surface tissues under the skin. This is caused by the hypothalamus sending impulses to blood vessels supplying the capillaries in the skin to contract. Vasodilation helps the body to lose heat, while vasoconstriction helps to keep heat within the body.
Sweating
Perspiration, also known as sweating, is the production of fluids secreted by the sweat glands in the skin of mammals. When the body temperature is too high, the skin produces sweat, which evaporates from the surface of the skin. As it evaporates, it takes heat energy from the body. More water and salts, in the form of ions, are lost by sweating when it is hot. These have to be replaced by taking drinks and food.
Shivering
Shivering produces heat by expending energy as the skeletal muscles contract and relax rapidly.
Pilorelaxation and piloerection
Pilorelaxation is when the hairs on your skin flatten. This means that less air is trapped next to the skin. Piloerection is when muscles at bottom of hairs contract, causing hairs to stand on end and traps an insulating layer of air. This reduces heat loss.
Behavioural response
This is controlled by the cerebral cortex in the brain. In hot weather the organism has a lower respiration, so less heat is created. In humans, the behavioral response also triggers us to open windows to increase airflow to cool ourselves down and in cold weather, by putting on a jumper so less heat escapes from the body.
Hormones
In hot weather, less thyroxine is produced and so the metabolic rate lowers. In cold weather, adrenaline is released which increases metabolic rate. If it is very cold, more thyroxine is produced, increasing the metabolic rate.
Environmental influences that result in a breakdown of the control system may be:
- external influences such as extreme environment conditions, disease or infection, drugs or toxins.
- internal influences such as genetic conditions or metabolic disorders.
Homeostasis is the maintenance of constancy of the internal environment where the `internal environment’ is the intercellular fluid also known as tissue fluid.
When an organism differs from a set point or normal temperature, the corrective mechanism is triggered.
When a change in an entity brings about the opposite effect this is known as a negative feedback mechanism. The negative feedback system is by far the most common found in the human body. The main idea is that the stimulus from one part of the body produces a response that will stop or reduce the original stimulus. Negative feedback is a reaction that causes a decrease in function.
Sometimes the corrective mechanism leading to negative feedback breaks down with the result that a deviation from the normal temperature initiates further deviation. This is known as positive feedback.
Positive feedback is rare in the human body. It forms a looped system that changes the body from its original position. Normally one part of the body enhances another parts effect which can cause an escalation of the condition. This can be bad as it’s not controlled that well. The end result is a further increase or further decrease.
Homeostasis must necessarily involve fluctuations, small though these may be. Only by deviating from the normal can the mechanism be brought into play.
The feedback system must have:
- Receptors (or sensors) capable of detecting the change;
- A control mechanism capable of initiating the appropriate corrective measure;
- Effectors which can carry out these corrective measures.