Question

Several bodily responses are described below. For each response, determine what caused the change in homeostasis.

body starts to sweat

breathing rate increases

amount of saliva produced changes

body starts to shiver

Answer 1

1) Body starts to sweat
- Cause: body temperature has risen above the hypothalamic set point (from exercise, hot environment, or fever).
- Mechanism: hypothalamic thermoregulatory center activates sympathetic cholinergic nerves to eccrine sweat glands → increased sweating for evaporative cooling to restore temperature homeostasis.

2) Breathing rate increases
- Cause: changes in blood gases/acid–base (primarily rising CO2/ falling pH; can also be low O2 or increased metabolic demand during exercise).
- Mechanism: central chemoreceptors (medulla) and peripheral chemoreceptors (carotid/aortic bodies) detect high CO2/low pH or low O2 and stimulate respiratory centers to raise ventilation until gas levels and pH return toward normal.

3) Amount of saliva produced changes
- Cause: altered autonomic input in response to stimuli (e.g., smell/taste/thought of food increases parasympathetic activity; stress/fear increases sympathetic activity).
- Mechanism: parasympathetic stimulation increases watery saliva secretion; sympathetic stimulation reduces watery secretion and tends to produce thicker, mucous-rich saliva.

4) Body starts to shiver
- Cause: body temperature has fallen below the hypothalamic set point (exposure to cold).
- Mechanism: hypothalamus triggers involuntary skeletal muscle contractions (shivering) and vasoconstriction to generate and conserve heat until core temperature is restored.