U3 Homeostasis: Thermoregulation Flashcards
Define thermoregulation
The balance of heat gain and loss to maintain a constant internal body temperature of around 37°C independent of the environmental temperature
Why does the body temperature need to remain constant at around 37°C?
- It is the optimal temperature for cellular reactions and stable cell function
- increased body temperature can cause nerve damage, structural change of proteins and death
Why is the human body usually maintained at a higher temperature than the external environment?
Because of heat produced as a result of metabolic activity
Why does exercise increase body temperature?
Exercise increases the metabolic rate and generates more heat than the body needs to keep its temperature constant
What are the two ways the body responds to deviations in temperature?
Behavioural:
- where we consciously change our behaviour
Physiological:
- where our body automatically changes its functioning without conscious control
How does heat gain/input occur?
- Heat from metabolic processes in the body
- Heat gained from surroundings by conduction and radiation
How does heat loss/output occur?
- Radiation, conduction and convection to surroundings
- Evaporation of water from skin and lungs
- Warn air breathed out
- Warm urine and feces
Define metabolic rate
The rate at which energy is released to the body by the breakdown of food
What increases the metabolic rate?
- Exercise (muscular activity)
- Stress (increased activities of autonomic nervous system)
- Body temperature (increases rate of biochemical reactions)
Define thermoreceptors
Receptors locate din the skin or hypothalamus that detect changes in temperature
What are the two types of thermoreceptors?
Peripheral thermoreceptors
- located in skin and some mucus membranes
- detect temperature changes in external environment
- sends information to hypothalamus
Central thermoreceptors
- located in hypothalamus
- detect the temperature of the internal environment
Distinguish between cold receptors and heat receptors
Cold receptors
- thermoreceptors stimulated by temperatures lower than normal
- when stimulated, the hypothalamus receives the information and initiates heat conservation and heat production mechanisms
Heat receptors
- thermoreceptors stimulated by temperatures higher than normal
- when stimulated, the hypothalamus receives the information and initiates heat production and heat loss mechanisms
What are the ways that body temperature is regulated?
- Skin
- Blood vessels
- Sweating
- Shivering
Why is the skin important in regulating body temperature?
The skin has a large surface area and its located between the internal and external environments
How can heat be lost/gained by the skin?
Conduction:
- transfer of heat by direct movement between particles
Convection:
- transfer of heat by movement of liquid or gas
Radiation:
- transfer of heat by infrared radiation emitted by objects
Evaporation:
- process of a liquid forming a gas, which absorbs heat energy
How do blood vessels regulate body temperature?
- Blood vessels located in the dermis of the sin carry heat from the core of the body to the skin
- The diameter of the surface arterioles is controlled by autonomic nerves
Vasodilation
- an increase in the diameter of the surface arterioles
- increases the blood flow through surface arterioles
- more blood is transported to the capillaries in the skin
- rate of heat loss increases
Vasoconstriction
- a decrease in the diameter of the surface arterioles
- decreases the blood flow through surface arterioles
- less blood is transported to the capillaries in the skin
- rate of heat loss decreases
How does sweating regulate body temperature?
- Occurs when body heat must be lost and surface blood vessels are at maximum dilation
- Sweating: the active secretion of fluid by the sweat glands to the skin surface
- Evaporation of sweat from the skin surface has a cooling effect as the heat is removed from the skin when liquid sweat change into vapour
- Cooling of the skin results in the cooling of the blood flowing through the skin
How does shivering regulate body temperature?
- Shivering: rhythmic muscle tremors that increase body heat production
- As no work is being done, heat produced by the muscles is released as heat
What occurs to decrease heat loss in cold conditions?
- Vasoconstriction of blood vessels in the skin
- Decreased sweating
- Conscious behaviour: putting on a jumper, curling into a ball
What occurs to increase heat production in cold conditions?
- Increased shivering
- Increased metabolic rate
- Increased voluntary physical activity
What occurs to increase heat loss in hot conditions?
- Vasodilation of blood vessels in the skin
- Increased sweating
- Conscious behaviour: removing clothes, turning on a fan
What occurs to decrease heat production in hot conditions?
- Decreased metabolic rate
- Decreased voluntary physical activity
Distinguish between heat exhaustion and heat stroke (4 dot points each)
Heat exhaustion
- Occurs in high temperature and normal humidity
- Involves increased sweating, evaporation and cooling
- There is no change in core body temperature
- Is not fatal
Heat stroke
- Occurs in high temperature and high humidity
- Involves increased sweating, but no evaporation and therefore no cooling
- The core body temperature increases
- Can be fatal
Hypothermia
- Occurs when a person’s core body temperature falls below 33°C
- The metabolic rate is decreased
- The amount of heat the body produced is decreased
- There is greater heat loss to the environment than heat gain
