Homeostasis
is a characteristic of a system that regulates its internal environment and
tends to maintain a stable, relatively constant condition of properties.
Stimulus: Produce a change to a variable.
Receptor: Detects the change .The
receptor monitor the environment and responds to change.
Input: Information travels along the
afferent pathway (carry nerve impulses into the central nervous system) to the
control centre. The control centre determines the appropriate response and
course of action.
Output: Information sent from the
control centre travels through the efferent pathway (carry nerve impulses from
the central nervous system to effectors) to the effector.
Response: A response from the effector
balance out the original stimulus to maintain homeostasis.
A group
of receptors and effectors communicating with their control centre forms a
feedback system that can regulate a controlled condition in the body’s internal
environment. In a feedback system, the response of the system “feedback”
information to change the controlled condition in some way, either negating it
(negative feedback) or enhancing it (positive feedback).
Negative Feedback Mechanism:
Negative
feedback is a type of regulation in biological systems in which the end product
of a process in turn reduces the stimulus of that same process.
Example:
Regulating Blood Sugar
Every
time we eat, a negative feedback mechanism controls the level of sugar in our
blood. The main sugar found in our blood is glucose. After taking something, our
body absorbs the glucose from our bloodstream and deposits it into the blood.
This increases the concentration of glucose and stimulates pancreas to release
a chemical called insulin. Insulin is a cellular signalling molecule which
tells muscle and liver cells to uptake glucose. Liver cells store the excess
glucose as glycogen, a chain of glucoses used as a storage product. Muscle
cells can store the glucose or use it to make ATP and contract. As this process
happens, glucose concentrations are depleted in the blood. Glucose was the main
signal for the pancreas to produce insulin. Without it, the pancreas stops
producing insulin and the cells stop taking up glucose. Thus, glucose levels
are maintained in a specific range and the rest of the body has access to
glucose consistently. The negative feedback mechanism in this system is seen
specifically in how high glucose levels lead to the pathway turning on, which
leads to a product meant to lower the glucose level. When glucose becomes too
low, the pathway shuts off.
Positive feedback
mechanism:
A
positive feedback mechanism is the exact opposite of a negative feedback
mechanism. In a positive feedback system, the output enhances the original
stimulus.
Example:
child birth
During
labor, a hormone called oxytocin is released that intensifies and speeds up
contractions. The increase in contractions causes more oxytocin to be released
and the cycle goes on until the baby is born. The birth ends the release of
oxytocin and ends the positive feedback mechanism.
