What is Homeostasis
⦿ Walter Cannon coined the term ‘Homeostasis’ to describe how the human body regulates its internal environment at normal and constant level.
⦿ The word Homeostasis (homeo- = “same, resembling”, stasis = “standing still or state”) refers the ability of living organism or a cell to maintain its internal environment and keep it at an equilibrium.
⦿ The common variables such as temperature, pH of body fluids and water, sugar level, blood pressure, hormones, respiratory gases, nutrition etc. are constantly monitored and balanced by body’s homeostasis
⦿ Normal level of such variables in the body is collectively referred to a set point. In other words, the set point is the normal physiological value or range of values necessary for body functions.
⦿ The homeostatic control center regulates the set points of variables for optimum function of the body and life processes.
For example, our body has the set point of 70-100 mg/dl for blood glucose and the 37̊ °C (98.6 °F) for body temperature at which our healthy body works the best
⦿ Homeostasis is regulated by the four components of the homeostatic control mechanism:- These are:-
Stimulus (variables)
Receptors or sensor.
Control center.
Effectors.
⦿ Stimulus: Stimulus is an internal and external variable that causes chang in a set point in the body and requires a cell to react.
Such variables stimulate the homeostatic control system through receptors.
⦿ Sensor or sensory receptors: Sensors are specialized chemical structures in organs which detect the change in the set points of variables.
Receptors send information to the control center to counteract.
For example, beta cells of the pancreas detect the abnormal sugar level in the body, receptors in certain arteries detect the change in blood pressure and sensory nerve cells monitor change in the body temperature etc.
Receptors produce a signal and send impulse to the central center for action
⦿ Control center: The control centers are located in the brain which monitor the normal range of variable in the body and act to maintain homeostatic conditions.
As soon as the control center receives sensory impulses from the receptors, it sends instructions to the effector to counteract the change in the environment.
For example, hypothalamus, a small region in the brain, is the thermoregulatory center of the body as it regulates the body temperature and maintains at 37 °C.
When the body temperature alters, it receives information from sensory receptor and sends signal to the effectors to stabilise the body temperature at set point 37 °C.
⦿ Effectors: The cells, tissues or organs that respond to the instructions received from the control center serve as the effectors. After receiving the specific signal, effectors reverse the change to normal value and maintain homeostasis.
These regulatory mechanisms are termed as feedback mechanism.
For example, sweat glands work as effectors by releasing sweat to lower body temperature in the body; and hepatocytes of the liver release glucose to increase blood glucose levels.
