Body_Temp_2021

Homeostasis

  • Homeostasis refers to the body's ability to maintain a stable internal environment despite changes in external conditions.

Body Temperature

  • The regulation of internal body temperature is crucial for optimum conditions for enzyme-catalysed reactions.

Normal Internal Body Temperature

  • Normal Body Temperature: 37°C.

  • Consequences of Temperature Changes:

    • Above 37°C:

      • Enzymes denature (lose structure and function).

      • Metabolic pathways are blocked.

    • Below 37°C:

      • Metabolism slows.

      • Can affect brain function.

Methods of Heat Loss and Gain

Radiation

  • Heat transfer through infrared electromagnetic rays.

  • Body radiates heat; loses heat if the surrounding temperature is lower than body temperature.

  • About 60% of total heat loss in a nude person occurs via radiation.

Conduction

  • Heat exchange between objects in direct contact.

  • Minimal heat loss from contact with solid objects (3%).

  • Larger heat loss occurs through conduction to air.

Convection

  • Heat removal through air currents.

  • Heat must be conducted to air first, increasing removal ceiling.

  • 12% of body heat is lost via this method; wind increases heat loss significantly.

Evaporation

  • Water evaporates from skin/lungs, even without sweating (approx. 600 ml/day).

  • Sweating is a key regulated heat loss method.

  • Heat loss occurs primarily through evaporation when other methods are ineffective.

  • Humidity decreases evaporation efficiency.

Other Losses

  • Small heat loss through urine and faeces.

Body Temperature Control

  • Hypothalamus: Contains Thermoregulatory Centre that monitors blood temperature.

    • Acts as a thermostat set to 37°C.

    • Receives input from skin thermoreceptors.

Feedback Systems

  • Feedback System: Cycle of monitoring and evaluation affecting body conditions.

Basic Components

  1. Receptor: Sensors that respond to changes (stimuli).

  2. Control Centre: Sets range of values, evaluates inputs, and sends outputs.

  3. Effector: Receives output from control centre and produces response.

Response to High Body Temperature

  • Detection: Thermoreceptors in hypothalamus respond to high body temperature.

  • Responses:

    • Vasodilation: Blood vessels widen, increasing blood flow toward skin surface.

    • Sweating: Heat energy converts sweat into vapor, cooling the body.

Response to Low Body Temperature

  • Detected by thermoreceptors in the hypothalamus.

  • Responses:

    • Vasoconstriction: Blood vessels constrict, reducing blood flow to skin.

    • Decreased sweating.

    • Shivering: Muscle contractions generate heat.

Keeping Warm

  • Piloerection: Hair muscles contract to insulate by trapping a layer of warm air.

  • Not very effective in humans; creates goosebumps instead.

Voluntary Responses

  • Human behavior adapts to temperature changes:

    • Cold: Add clothing, seek heat sources, exercise.

    • Hot: Remove layers, hydrate with cold drinks, reduce physical activity.

Heat-Related Conditions

Heat Stroke

  • Occurs when cooling mechanisms fail, leading to very high body temperature.

  • Can cause unconsciousness and potentially death if untreated.

Heat Exhaustion

  • Results from dehydration due to extreme sweating and exercise.

  • Decreased blood volume can lead to collapse from low blood pressure.