Homeostasis and Feedback Loops

Definitions Homeostasis –balance in the body Stimulus- something in the environment that causes a change (can be internal) Response – action of organism as a result of stimulus Feedback mechanisms/loops – processes by which the body maintains levels

1) receptor (nerve) recognizes stimulus Steps 1) receptor (nerve) recognizes stimulus

2)sensory neuron transmits a message from the receptor, to a control center

3)message is carried to a control center (brain), message is interpreted, and the correct ordered

4) Motor neuron carries message from control center to effector organ dictating response

Effector organ 5) Effector organ receives message and conducts the response

Afferent vs. Efferent pathway Afferent pathway = message to the brain Efferent pathway = message from the brain

Positive Feedback Loop Body responds by increasing stimulus stimulus Ie. Oxytocin in childbirth - chemical increases rate of contractions until the child is born

Graph of Positive Feedback X-axis is time Y-axis is hormone secreted

Negative Feedback loops Body’s response counters the change Tries to maintain a median Ie. Blood glucose, temp, blood O2/CO2 levels