Overview
This lecture explains how the body maintains its core temperature through thermoregulation, focusing on the roles of the hypothalamus, smooth muscle, and skeletal muscle in response to hot and cold environments.
Thermoregulation Overview
- Thermoregulation is the process by which the body maintains its core temperature.
- The skin senses temperature changes and sends signals to the brain.
- The hypothalamus in the brain regulates responses to both heat and cold.
Brain Regions in Thermoregulation
- The anterior hypothalamus activates when it's hot, triggering cooling mechanisms.
- The posterior hypothalamus responds to cold, activating warming mechanisms.
Muscle Roles in Temperature Regulation
- Two main muscle types involved: smooth muscle (in arterioles) and skeletal muscle (voluntary muscles).
- Smooth muscle in arterioles controls heat exchange by constricting or dilating blood vessels.
- Skeletal muscle helps warm the body by shivering when cold.
Response to Heat
- In hot conditions, smooth muscle in arteriole walls relaxes, causing vasodilation (blood vessel widening).
- Vasodilation increases blood flow to the skin, allowing more heat to escape the body.
- Skeletal muscle does not contribute to cooling during heat.
Response to Cold
- In cold conditions, smooth muscle contracts, causing vasoconstriction (narrowing of blood vessels).
- Vasoconstriction reduces blood flow to the skin, keeping heat near the body core.
- Skeletal muscle contracts involuntarily (shivering) to generate additional heat via ATP breakdown.
Key Terms & Definitions
- Thermoregulation — Regulation of body temperature by physiological mechanisms.
- Hypothalamus — Brain region that controls thermoregulation.
- Anterior Hypothalamus — Front part activated during heat to promote cooling.
- Posterior Hypothalamus — Back part activated during cold to promote warming.
- Smooth Muscle — Muscle in arteriole walls that regulates blood flow and heat loss.
- Skeletal Muscle — Muscle attached to skeleton, used in shivering to produce heat.
- Vasodilation — Widening of blood vessels to increase heat loss.
- Vasoconstriction — Narrowing of blood vessels to conserve heat.
- Shivering — Involuntary skeletal muscle contractions that produce heat in cold environments.
- Exothermic Reaction — Chemical reaction that releases heat, such as ATP breakdown in shivering.
Action Items / Next Steps
- Review the structure and function of hypothalamus regions.
- Study how muscle types contribute to body temperature regulation.
- Prepare for questions on mechanisms of vasodilation and vasoconstriction.