Negative feedback loop

A control loop that pushes a variable back toward normal and then stops

Positive feedback loop

A control loop that amplifies the change, pushing farther from normal until something else stops it

Homeostasis

Keeping the body's internal conditions steady despite outside changes

Set point

The normal value the body tries to stay near (like 98.6 F)

Stimulus

The event or change that knocks the system off its normal state

Receptor

The sensor that detects the change and sends a signal

Control center

The decision maker that reads the signal and picks the fix (like a thermostat)

Effector

The part that actually carries out the fix

Response

The action that pushes the system back to normal

Thermoreceptors

Temperature sensors in the skin and brain

Hypothalamus

The brain's thermostat that decides how to handle heat or cold

Vasodilation

Blood vessels widening so more warm blood reaches the skin

Vasoconstriction

Blood vessels narrowing to keep warm blood away from the skin

Platelets

Tiny blood cells that stick to exposed collagen and start a clot