A&P Homeostasis Key Terms

Stimulus

Produces a change in the variable from the norm range

Sensor (Receptor)

Detects change by sensing the imbalance from the normal set point range. Sensory nerves or endocrine glands act as sensors. transmit that information to the control center by way of an afferent signal

Control Center

Receives input from the sensor and decides a response. Transmit that message to an effector by way of an efferent signal.

Effector (Muscles/Organs/Glands)

Receives input from the control center and carries out a specific action

Response

restores balance (negative feedback) or amplifies change (positive feedback)

What happens when blood sugar is low?

Alpha cells in the pancreas release glucagon → liver converts glycogen to glucose → blood sugar rises.

What happens when blood sugar is high?

Beta cells release insulin → cells take up glucose & store it as glycogen → blood sugar lowers.

What happens when body temperature drops?

Hypothalamus triggers shivering and vasoconstriction → body temperature increases.

What happens when body temperature rises?

Hypothalamus triggers sweating and vasodilation → body cools down.

What happens when water levels are low?

ADH released → kidneys reabsorb water → body retains water → normal balance restored.

What happens when water levels are high?

ADH secretion stops → kidneys excrete more water → blood solute levels normalize.

What happens when blood calcium is low?

PTH released → bones release calcium → kidneys retain calcium → calcium level rises.

What happens when blood calcium is high?

Calcitonin released → calcium stored in bones → blood calcium lowers.

What happens when blood pressure is low?

Baroreceptors signal medulla → heart beats faster, vessels constrict → BP increases.

What happens when blood pressure is high?

Baroreceptors signal medulla → heart slows, vessels dilate → BP decreases.

What type of feedback is blood clotting?

Positive feedback — platelets attract more platelets until clot seals wound.

What feedback controls childbirth contractions?

Positive feedback — oxytocin causes stronger contractions until baby is born.

How is fever an example of feedback?

Positive feedback — pyrogens raise set point; body warms to kill pathogens.

What feedback controls lactation?

Positive feedback — suckling triggers oxytocin → milk release → more suckling → more milk.

How is ovulation regulated by feedback?

Positive feedback — rising estrogen triggers LH surge → egg released.