U1 - Homeostasis & Feedback Loops

homeostasis

body's maintenance of a stable internal environment despite changes in the external environment

sickness (illness, disease)

whenever the body is NOT in homeostasis

feedback loops

aka homeostatic mechanisms

these monitor aspects of the internal environment and correct any changes

have 6 main parts:

receptors & stimuli; control center & set point; effectors & responses

receptors

provide information about *stimuli*

typically cells of some sort

stimulus

any change in the internal environment of the body

control centers

tells what a particular value should be according to its appropriate *set point*

will typically be the brain in most scenarios

set point

in regards to a certain level of something within the body, it refers to the best concentration/value/level of that something within the body

feedback loops attempt to keep the body near the ________

effectors

elicit *responses*

typically a muscle or a gland

responses

the actions the body takes to correct a change in the internal environment

negative feedback loop

most common form of feedback loop

moves variable back towards the middle/set point

takes on a sin/cos-shaped graph; will oscillate around the set point, indicating a normal range of values

positive feedback loop

uncommon form of a feedback loop

moves variable away from the middle/set point

takes on a J-shaped curve (exponential growth)

they DO NOT stop on their own - outside influence must disrupt the loop

ex. childbirth, production of chemicals to clot blood

time limitations

a characteristic of positive feedback loops that states that positive feedback loops are done typically for a process that must be completed within a short timeframe

intensification of stress

a characteristic of positive feedback loops that states that they intensify the initial stimuli/imbalance instead of reduce them like in negative feedback loops