D3.3 - thermoregulation Flashcards
What are endotherms?
Birds and mammals are endotherms; they maintain a steady internal temperature that is almost always higher than their surroundings.
How does thermoregulation occur in humans?
Humans, along with all mammals and birds are endotherms, so regulate their body temperature by homeostasis through physiological and behavioural means.
What are 2 examples of events that lower core body temperature?
- Vasodilation
- Sweating
What are 4 examples of events that raise core body temperature?
- Vasoconstriction
- Shivering
- Uncoupled respiration in brown adipose tissue
- Hair erection
How does vasodilation lower core body temperature?
1) Body is hot.
2) Hypothalamus sends impulses to the arterioles near the skin surface.
3) Smooth muscle relaxation widens their lumens = vasodilation.
4) More blood flows through the capillaries in the skin.
5) More heat is released into the surrounding air.
How does sweating lower core body temperature?
1) The hypothalamus sends impulses to initiate sweating.
2) The water in sweat evaporates, transferring heat from the skin surface, cooling the body and preventing overheating.
- Heat increases molecular motion, so hydrogen bonds between water molecules break, separating the water molecules and changing water from liquid to a vapour.
- Water has a high latent heat of vaporisation, so a lot of energy is required for evaporation of water, which makes it an effective coolant.
How does vasoconstriction raise core body temperature?
1) Body is too cold.
2) Hypothalamus sends impulses to arterioles near the skin surface.
3) Smooth muscle contraction narrows their lumens = vasoconstriction.
4) Less blood flows through capillaries in the skin.
5) Less heat is released into the surrounding air.
How does shivering raise core body temperature?
- Stimulated by the hypothalamus.
- Repeated muscle contraction requires energy through respiration, which also releases heat.
How does thyroxin raise core body temperature?
The pituitary gland releases hormones that affect the thyroid gland, causing the release of thyroxin when body temperature is too low.
What is the role of thyroxin?
- Increases metabolic rate an therefore the rate of energy release and use
- Controls the body temperature variation in a daily rhythm of 24 hours, with the temperature dropping ~0.2C during the night.
How does hair erection raise core body temperature?
- This occurs in response to the release of epinephrine (adrenaline) from the adrenal glands, which is stimulated by the hypothalamus.
- A layer of air is trapped, insulating the body from cold air.
How does uncoupled respiration in brown adipose tissue raise core body temperature?
When stimulated by the hypothalamus, brown adipose cells respire, but they do not generate ATP.
Instead, respiration and ATP are ‘uncoupled’ and the chemical energy in the respiratory substrate is solely transferred to heat.
How are brown adipose cells adapted?
Brown adipose cells contain lots of mitochondria.
- While all humans contain brown adipose tissue, infants contain a higher proportion as they have a higher surface area: volume ratio than adults, so heat is lost proportionally faster.
- Newborn infants are also unable to shiver, due to underdeveloped muscle tone.
What is the role of the peripheral thermoreceptors?
detect skin temperature, providing information about how the environment will impact the core body temperature
What is the role of the hypothalamus?
uses thermoreceptors to detect skin temperature, providing information about how the environment will impact core body temperature
How is the body temperature detected?
- peripheral thermoreceptors
- hypothalamus
(nervous system)
How is the response to body temperature co-ordinated?
Hypothamalus coordinates information from its own thermoreceptors and the peripheral thermoreceptors to initate heating or cooling mechanisms, as appropriate.
What is the role of adrenal glands?
releases adrenaline to cause hair erection
What is the role of the pituitary gland?
releases hormones that affect the thyroid gland, causing release of thyroxin when body temperature is too low
What are examples of tissue that acts as effectors of temperature change?
- muscle
- adipose
What is the role of the muscles?
shiver to generate heat
What is the role of adipose?
brown tissue that generates heat through respiration
What are the components of the endocrine system?
- Pituitary gland
- Thyroxin
- Adrenal glands
What are the components of the nervous system?
- Peripheral thermoreceptors
- Hypothalamus
- Effectors (muscle and adipose)
Which body systems are integrated in thermoregulation?
Nervous system and Endocrine system
