What are the parts and function of a negative feedback system giving examples.

Question

This discussion involves homeostasis, the negative feedback system, the parts of the feedback loop, how they interact to maintain homeostasis. It is very important that a student knows the names of the parts (anatomy,) but it is also important to know how they function (physiology) to restore homeostasis.

Answer 1

The negative feedback system responds to changes environmental stimuli and helps to maintain balance in the body (homeostasis). This video highlights two common examples of how this system works.

Answer 2

Homeostasis means balance in the environmental conditions of the body. The survival of our body cells is dependent on the precise regulation of the chemical composition of their surrounding extracellular fluid. This is a dynamic condition (constantly changing) due to a variety of factors like exercise, eating, drinking, fasting, environmental temperature changes, etc. The human body uses two feedback systems to help regulate homeostasis, the negative and positive feedback systems. You can think of a negative feedback system like a heating and cooling system in a building. We set up a comfortable upper temperature value, say 73 degrees F. We determine a comfortable low temperature value, say 67. These “threshold” values act as monitoring points not to be exceeded. If the ambient temperature goes above 73 degrees, a sensor called a thermostat registers this fact. It sends a signal to the air conditioner which releases cold air into the room dropping the temperature back into the zone between 67 and 73. This trips the thermostat to turn off the air conditioner once the rooms temp is below 73 degrees. Conversely, if the temperature drops below 67 degrees, the thermostat sends a signal to the furnace to switch on the heater. Hot air then restores the rooms temperature to “within normal limits.” So, in terms of the human body, the controlled condition of blood pressure is monitored by a sensory receptor (baroreceptors) every couple of seconds which sends a sensory message (input) to the brain (control center.) The brain evaluates the message which could be pressure is too high, within normal limits, or pressure is too low. A corrective message (output) is sent to smooth muscle and cardiac muscle to correct the problem. In the case of high blood pressure, dilation of the smooth muscle in the arteries and slowing the contractions of the heart muscle reduces blood pressure.