Physiological Changes to Cold Temperatures

Vasoconstriction in skin

- Hypothalamus stimulates sympathetic nerves for blood vessels in skin to contract
- Decreases flow of warm blood to skin from internal organs.
- Decreases heat loss from the body surface.

Shivering

- Hypothalamus sends stimuli to parts of the brain that increase skeletal muscle tone
↳Leads to oscillating (rhythmic muscle tremors) at a rate of 10-20 per second, increases body heat production as the cells perform cell respiration as they tremor
- Controlled by hypothalamus, but we can consciously control it to stop shivering through the cerebral cortex.

Stimulates adrenal medulla via sympathetic nerves

- Increases secretion of adrenaline and noradrenaline into blood. Increases cellular metabolism
↳which increases heat production

Increases thyroxine production

- Hypothalamus causes the anterior pituitary to secrete TSH, and the thyroid gland releases thyroxine in blood
- Increases thyroxine levels, increasing metabolic rate, increasing body temperature
- Slower to have an effect, but longer-lasting