Homeostasis

definition of homeostasis

the body’s maintenance of a stable internal environment and requires most of our metabolic energy

how does the body maintain homeostasis

through a number of self-regulating control systems or homeostatic mechanisms

name the four components that the mechanisms maintaining homeostasis share

1. change (stimuli) occurs constantly in and around the cells of living systems. A change is anything that requires a cell to react, such as change in temperature, pressure of chemical composition inside or surrounding the cell

2. receptors - detect the change (stimuli) and alert the proper control centre to counteract it, returning the cell and the overall system to a balanced state

3. control centre - includes a set point which tells what a particular value should (temperature around 36 degrees). the control centre receives impulses from its remote receptors and sends commands to the effector to counteract the change in environment

4. effectors - the physical change agents like muscles, glands, and fluids of the body - work horses of homeostasis. effectors act on impulses form its specific command centre eliciting responses that counteract the change and returning the internal and external cell environment to a balanced state

negative feedback

• controls many conditions in the body like temperature, CO2 and blood pH levels, osmoregulation etc

positive feedback

• a response that causes the body to become UNSTABLE

positive feedback example

• child birth

• the cycle is started when the head of the fetus comes in contact with the cervix

• this contacts causes the release of the hormones oxytocin which intensifies and speeds up contractions

• the contractions increases causes more oxytocin to be released and the cycle repeats until the baby is born

• the birthing ends the release of oxytocin and ends the positive feedback

negative feedback example

• blood pressure regulation

• blood pressure needs to remain high enough to pump blood to all parts of the body, but not too high to cause damage

• barorectptors detect the pressure of the blood going through the arteries

• if pressure is too high or low, a chemical signal is sent to the pressure control center in the brain via the glossopharyngeal nerve

• the brain then sends a chemical signal (effector) to adjust the rate of pumping

• if blood pressure is low the heart rate increases which increases blood output which increases blood pressure

• once the set point is reached, the stimulus for increased heart rate decreases

• also if blood pressure is too high the heart rate decreases till set point is reached