Thermoregulation

What is thermogreulation?

Regulation of the body internal temperature, allowing humans to control body temperature relatively independent of external factors. This allows humans to live and survive in a wide range of climates.

What are the two general ways of controlling temperature?

1. Changes metabolism (Ineternal mechanisms)
2. Changes to heat transfer (transfer of heat with the external environment)

What si conduction?

Conduction: The transfer of heat from 2 objects touching (one cooler than the other)
Solid --> Solid
-Laying on hot concrete to gain heat

What is convection?

Convection: When air makes contact with an object, becoming warm, then moving away taking the heat with it. The faster the rate of air flow - the quicker heat is lost.
Transfer of heat via moving liquids or gases
-Cold wind makes you lose heat

What is radiation?

Radiation: Where heat is emitted and transferred to another object without physical contact.
Heat is transferred without contract
-You gain heat from the sun by it radiating heat
-You lose heat by radiation from your skin

What is evaporation?

Evaporation: The conversion of a liquid to a gas during which heat is used (and therefore lost) to facilitate the transition. This is the cooling effect that occurs from sweating on the skin.
Liquid particles with high energy from a gas. The change of state requires energy and leaves remaining particles with less energy and therefore cooler
-Body cools down when swat is evaporated

WHat are the thermoreceptors?

•Peripheral - located in skin and detect changes in external environment
•Internal - located in hypothalamus and detect changes in internal environment
The hypothalamus (the modulator) receive nerve impulses from either the peripheral or internal thermoreceptorsW

How is hot and cold detected?

Peripheral themoreceptors is separated into hot and cold
•Cold - detect the stimulus of reduction in temperature
•Hot - detect the stimulus of increase in temperature

What are the behavioural response to control heat exchange?

-Putting clothes on/ off: Changes amount of convection (Transfer of heat via moving liquids or gases) and radiation (where heat is emitted and transferred to another object without physical contact.)
-Huddling/curling in balll: Reduces surface area to minimize heat loss through radiation (the emission of infrared heat waves without direct contact) and conserves heat through conduction by increasing physical contact with warm surfaces or other organisms.
-Movement within environment: Moving into shade or into breeze has potential to increase or reduce all four methods of heat transfer (e.g. moving away from the sun to avoid radiation)
-Food/ drink: Gain/ lose heat via conduction (The transfer of heat from 2 objects touching)

What is the negative feedback for behavioural responses?

Stimulus: Decrease in external temperature in the environment
Receptor: Peripheral cold thermoreceptors located on the skin detect drop in temperature
Modulator: The hypothalamus receives a nerve impulse which travel along sensory neurons from the thermoreceptors. Hypothalamus sends a signal to the frontal lobe in the erebral cortex (controls voluntary movement)
Effector: Frontal lobe sends a nerve impulse by motor neurons to the somatic nervous system division to skeletal muscles
Response: Behavioral action carried out by skeletal muscles to reduce heat loss.

What are behavioural response to control metabolism?

-Movement of body: Increase/ decrease in physical activity to icnrease/ decrease cellular respiration and heat productionWh

What are the physiological response to control heat exchange?

-Vasoconstriction/ Vasodilation: Of blood vessels in the skin to increase/ decrease heat loss from the blood by convection (Transfer of heat via moving liquids or gases) and radiation (heat is transferred without contract)
-Sweating: Increase heat loss by evaporation ( conversion of a liquid to a gas during which heat is used (and therefore lost) to facilitate the transition)
-Depth of breathing increases: Under sympathetic stimulation. Often then individual begins respiring through an open mouth rather than nasal passageways, increases evaporative losses through the lungs
-Goose bumps: Arrector pili muscles trap a layer of warm air, reducing heat loss by radiation (heat is transferred without contract) and convection (Transfer of heat via moving liquids or gases)

What is the negative feedbackloop for vasoconstriction?

-Stimulus: Body's internal temperature decreases
-Receptor: Internal cold thermoreceptors in the hypothalamus detect a drop in internal body temperature (decrease in the blood)
Cold peripheral thermoreceptors located in skin and detect changes in external environment and send a sensory nerve impulse to the hypothalamus
-Modulator: Hypothalamus.
Hypothalamus sends a motor nerve impulse through the autonomic nervous system to smooth muscles
-Effector: Smooth muscles in peripheral arterioles in the skin.
-Response: Constriction of smooth muscles of the arterioles of the skin reduces blood flow to the skin (narrowing of blood vessels).
Less blood is transported to the capillaries in the skin and the rate of heat loss decreases
This reduces heat loss and helps increase the body temperature
-Feedback: Internal temperature rises back to set point.

What is the negative feedback loop for vasodilation?

-Stimulus: Body's internal temperature increases
-Receptor: Internal hot thermoreceptors in the hypothalamus detect an increase in internal body temperature (increase in the blood)
Peripheral hot thermoreceptors located in skin and detect changes in external environment and send sensory information to hypotahalamus
-Modulator: Hypothalamus. It sends a motor nerve impulse through the autonomic nervous system (involuntary response) to the smooth muslces in the arteriole walls
-Effector: Smooth muscles in peripheral arterioles in the skin.
-Response: Smooth muscles relax causing blood vessles to widen.
This Increases blood flow to the skin causing surface temperature to rise and a greater heat loss through radiation and convection
-Feedback: Internal temperature reduces back to set point.

What is the negative feedback loop for sweating?

Stimulus: Environmental temperatures are high (above usually above 28 degrees Celsius)
Receptors: Peripheral hot thermoreceptors located in the skin send a sensory nerve impulse to the hypothalamus
Modulator: Hypothalamus sends a motor nerve impulse to the autonomic nervous system to affect sweat glands
Effector: Sweat glands
Response: Sweat glands increase secretion of sweat.
As sweat evaporates from the skin surface, it increase heat loss from the body, cooling it down
For water to evaporate, heat is required to change the water molecules from liquid to gas. This heat is obtained from the skin resulting in a decrease in body temperature
Feedback: Prevents internal body temperature from rising (and causes them to decrease)

What is the negative feedback loop for depth of breathing?

Stimulus: Internal body temperature increase due to external heat or physical activity (increases cellular respiration and therefore heat production)
Receptors: Internal hot thermoreceptors in the hypothalamus detect a increase in blood temperature
Peripheral hot thermoreceptors in the skin which send a sensory nerve impulse to the hypothalamus
Modulator: Hypothalamus sends a signal to the respiratory centre in the medulla oblongata of the brain stem, which then send it to respiratory muscles
Effector: Respiratory muscles (diaphrgm, intercostal muscles)
Response: Respiratory muslces contract more forcefully and frequently to increase the depth and rate of breathing. Individuals begin breathing through mouth rather than nasal passage increasing evaporative losses through the lungs
Feedback: Evaporative heat loss helps reduce internal body temperature back to set point.

What is the negative feedback loop for goosebumps

-Stimulus :Body's internal temperature decreases
-Receptor: Internal thermoreceptors in the hypothalamus detect a drop in internal temperature (decrease in blood temperature). Cold peripheral thermoreceptors in the skin detect a decrease in external temperature
-Modulator: Hypothalamus receives signals from thermoreceptors. Sends motor nerve impulses via the autonomic nervous system to effectors in the arrector pili muscles
-Effector: Arrector pili muscles attached to hair follicles in the skin
-Response: Arrector pili muscles contract, causing goosebumps (hairs stand upright)Traps a thin layer of insulating air close to the skin, reducing heat loss to the environment
-Feedback: Reduced heat loss helps body temperature return toward the set point

What are physiological response to control metabolism?

-Shivering: Increases heat produced through muscle activity (rhythymic contractions of skeletal muscles increase MUSLCE activity which increase metabolic rate and icnrease heat production)
-Thyroxine: Long term response icnrease s levels of thyroxine in colder environments and therefore heat production (and vice versa)
-Adrenaline and noradrenaline: Short term response in severe cold. Increases metabolism and therefore increase heat production (hypothermia)

What is the negative feedback for shivering?

Stimulus: Decrease in internal body temperature
Receptor: Internal cold thermoreceptors located in hypothalamus detect a decrease in blood temperature
Modulator: Hypothalamus sends a nerve impulse through a somatic MOTOR nerve to the skeletal muscle
Effector: Skeletal muslces
Response: Skeletal muscles undergo rhythymic muscle tremors, (rapid contraction and relaxation of muscles) producing heat by the muscles.

What is the negative feebdack for thyroxine

Stimulus: Decrease in internal body temperature
Receptor: Internal cold thermoreceptors located in hypothalamus detetc the decrease in blood temperature
Modulator: Hypothalamus sends secreting factors through the local capillary network through the hypothalamic-hypothseal portal system, to cause the anterior pituitary gland to secrete thyroid-stimulating hormones
Effector: Thyroid-stinmulating hiomrones effect the thyroid gland
Response: Thyroid gland begins to release thyroxine into the blood.
Thyroxine caue all body cells to increase metabolic rate which increases cellular respiration which causes an increase in heat production.
This increases body temperature.

What is the negative feedback for adrenaline and noradrenaline?

Stimulus: Decrease in internal body temperature
Receptor: Cold thermoreceptors in the hypothalamus detect the decrease in body temperature (decreas ein blood temperature)
Peripheral cold thermoreceptors in the skin detect changes in the external environment and send a sensory nerve impulse to the hypothalamus
Modulator: Hypothalamus sends an autoomic, sympathetic nerve impulse to adrenal medulla
Effector: Adrenal medulla secretes adrenaline and noradrenaline into bloodstream
Response: Adrenaline and noradrenaline effect most tissues and increase metabolic rate. This therefore increases cellular respiration and produces more heat.
This helps to maintain internal body temperature in conditions where there is rapid heat loss