3 - Thermoregulation Flashcards
What two temperatures do not change much with their exposure to the environment?
Core temperature
Oral temperature
What two temperatures change a lot with body temperature and the environmental temperature?
Hand and feet temperature
Core temperature has a circadian rhythm to it. It varies 1-2 degrees over a 24 hour period. It is lowest at _______ and highest at ________.
6 AM
Early evening
A controlled variable, in this case the core temperature, is measured by _________ that are found in the skin, viscera, and brain. The different locations of these tell the brain about different temperatures that could potentially be a threat to the core temperature.
Thermoreceptors
Cutaneous thermoreceptors are important because they tell us about _________ conditions. They are often ________, meaning they can detect temperature and touch sensitivity. They also may be cold or warm sensitive (10x as many cold sensitive receptors).
Environmental
Bimodal
What would you have thermoreceptors in your gut?
They don’t just sense the core temperature, but also threats to the maintenance of the core temperature. Food ingested may change the body temperature, and the receptors will tell the hypothalamus about these threats.
The hypothalamus is the site for thermal regulation, specifically its _______ and _______ regions.
Pre-optic
Superoptic
Neuron cells bodies in the hypothalamus are sensitive to changes in temperature (in Pre-optic and Superoptic regions). There are 3x as many (COLD/WARM) sensitive neurons, and all the neurons relay their information to other areas of the hypothalamus.
Warm
The core temperature is measured by thermoreceptors, which send signals back to the “controller”, in this case the __________.
Hypothalamus
The hypothalamus has the connections to control the _________, _________, and _________ changes that are part of thermoregulation.
Hormonal
Autonomic
Behavioral
The hypothalamus has three functions as the controller for body temperature, which are…
1) Determining set point (for core temp.)
2) Receiving info about current temperature
3) “Deciding” what to do
The hypothalamus has a ________ for core temperature, that is decided by the brain.
Set-point
Set-point can be changed depending on the circumstances. With sleep, temperature (INCREASES/DECREASES) so this results in a (INCREASE/DECREASE) in set-point.
Decreases
Decrease
Set-point can be changed depending on the circumstances. With exercise, temperature (INCREASES/DECREASES) so this results in a (INCREASE/DECREASE) in set-point.
Increases
Increase
***Temp can increase as high as 40 degrees Celsius with exercise
What part of the hypothalamus deals with response to heat and heat loss behaviors?
Anterior hypothalamus
What part of the hypothalamus deals with response to cooling and heat production behaviors?
Posterior hypothalamus
________ tissue is a great insulator. Its thermal conductance is about 1/5 that of skin, muscle, etc. But in babies, the high surface area in proportion to their size means they lose _______ better than adults.
Adipose
Heat
***This is why babies are so chunky, it’s a thermoregulatory mechanism to keep them warmer.
Core temperature is measured by thermoreceptors, which signal to the hypothalamus (which adjusts set-point). The hypothalamus will then induce ______ ______ or ______ _______ depending on the situation. This will result in a change to the core temperature.
Heat loss
Heat production
What are the mechanisms of heat production?
- ANS (especially sympathetic)
- Endocrine (Thyroxine and Epinephrine)
- Muscular Activity
- Non-shivering Thermogenesis
What are the two forms of muscular activity to induce heat production?
1) Shivering
2) Increase voluntary activity
For shivering (muscular activity) in heat production, the signal begins in the ________ _______ hypothalamus and sends axons down the Spinal Cord to increase _________ excitation.
Dorsomedial Posterior
Motoneuron
To increase voluntary activity (muscular activity) in heat production, it is done via the _______. Examples are jumping, running, gas station bounce, etc.
Cortex
Non-shivering thermogenesis in heat production has three mechanisms, which are…
1) Strong hormonal influence (Thryoxine and Epinephrine)
2) Increased food intake leads to increase in metabolism
3) Brown adipose tissue (babies and animals)
The hormonal influence in non-shivering thermogenesis is from ________ and ________. ________ increases the metabolic rate because cold is a stimulus for TRH release, which affects blood glucose levels and energy metabolism.
Thyroxine
Epinephrine
Thyroxine
Brown adipose tissue uses _________ innervation for initiation.
Adrenergic
Brown adipose tissue has low efficiency hydrolysis of ______ via uncoupling proteins that lead to more heat production than otherwise.
ATP
Brown fat is innervated by __________ fibers, as well as circulating ________.
Sympathetic
Epinephrine
Brown adipose tissue is critical in _______.
Infants
This type of heat loss occurs when energy (heat) is lost as water evaporates.
Evaporative heat loss
What are the two kinds of evaporative heat loss?
1) Insensible (respiratory) – i.e., dogs panting
2) Sweating (controlled)
This type of heat loss is from the movement of molecules away from contact (air heating and rising).
Convection
This type of heat loss is from the transfer of heat between objects in physical contact with one another.
Conduction
This type of heat loss is the transfer of heat between 2 objects not in physical contact (i.e., between you and the walls).
Radiation (Infrared Radiation)
How much blood that is sent to the skin determines how much heat moves from the blood to the external environment. If we are cold, then (MORE/LESS) blood is sent to the skin so we lose (MORE/LESS) heat. If we are hot, then (MORE/LESS) blood is sent to the skin so we lose (MORE/LESS) heat.
Less
Less
More
More
***When cold, less blood is sent to skin so that makes you pale. When hot, more blood is sent to skin so that makes you flush/red!
If we have a decreased core temperature, that means the set-point temperature is lower than the body temperature. What needs to happen to try to raise the core temperature?
Increase heat production – via shivering and non-shivering thermogenesis
Decrease heat loss – blood moves away from the skin and decrease EHL (evaporated heat loss)
This is a controlled increase in body temperature due to an infection.
Fever
During a fever, the ________ increases because the body temperature is doing what the hypothalamus directs it to do.
Set-point
During a fever, the “bug” will secrete ________ and the immune cells that have been activated will release _______. Together, these activate _________ which is what sends signals to the hypothalamus to increase the set-point temperature. At this point, the body temperature is lower than the set-point temperature, which is why we initially shiver and have the chills when we get sick (works the same way as trying to keep from losing heat).
Endotoxins
Cytokines
Prostaglandin E2
During a fever, eventually the “bug” is vanquished, so no more endotoxins are being released and there is no more activation of the immune system to release cytokines. In the absence of these, the hypothalamus instructs the set-point to return to normal. At this point, the body temperature is (MORE/LESS) than the set-point temperature.
More
When the body temperature is more than the set-point temperature when a fever breaks, this induces what to happen?
Decrease heat production – Apathy/Inertia and Anorexia
Increase heat loss – Conduction/Convection, EHL (sweat), Insensible heat loss (panting)
***This is why you get really hot and sweaty once a fever breaks!
Anaerobic and Aerobic mechanisms in the body at all times are producing _______. We have to do something with it.
Heat
A _______ gland has a coiled region surrounded by lots of blood vessels nearby. It has a duct leading to the skin where water will pool and evaporate.
Sweat
***Major way to lose heat!
In the first stage of sweating, there is sympathetic _________ innervation at the coiled region. _________ is the NT, binding to a _________ receptor.
Cholinergic
ACh
Muscarinic
***This is sympathetic (even though it doesn’t release norepinephrine) because anatomically they follow the pattern (i.e., comes from thoracic and lumbar regions, goes to sympathetic chain, etc.)
The sympathetic innervation to the sweat gland causes _________ of the nearby blood vessels, which causes the filtration of serum including the ions (Na, Cl) into the sweat gland.
Vasodilation
As the fluid travels up the duct (from sweat gland) to the skin surface, its composition is modified. ________ is reabsorbed from the duct back into the blood, and ________ follows it due to the osmotic gradient created.
Sodium
Water
***How much a person sweats determines how much sodium and water is reabsorbed.
How much a person sweats determines how much sodium and water is reabsorbed. If I’m only a little hot, there is a low flow rate so sweat is concentrated. There is a little water on the skin surface because (MORE/LESS) water is reabsorbed. (HIGH/LOW) amounts of sodium are also reabsorbed (but not as much as water).
More
High
How much a person sweats determines how much sodium and water is reabsorbed. If I’m very hot, there is a high flow rate and lots of water is released. This means there is less time to reabsorb sodium or water, so you make a lot of sweat that is _______.
Salty
When it’s hot in the summer and you’re constantly outside, your body has to make a change so you’re not losing so much sodium all the time from sweating. _________ will decrease your loss of sodium but won’t take back the water. This is a mechanism called _________.
Aldosterone
Acclimation
