Thermoregulation Flashcards
What is the normal temperature for the body
the normal temperature is 36.7 oC (98.06oF)
the range is 36.3-37.1 oC
What temperatures in the body are controlled
Core
Oral
Skin
Hands and feet are not controlled and are usually sacrificed
How does the core temperature change with the circadian rhythm
temperature will flunctuate about 1 to 2 degrees over a 24 hour period with the coldest temperature being at about 6am in the morning
What measures the temperature throughout the body
Thermoreceptors found in the skin, viscera, and the brain
viscera tells the temperature of the food
How does temperature affect the body
temperature affects the enzyme activity and can change the cellular function
What receptors tell us about the environment
Cutaneous thermoreceptors
these are often bimodal and distinguish temperature and touch
they can be warm or cold sensitive
there are 10x more cold sensitive thermorecptors than warm
where does thermoreceptors send their information
to the hypothalamus specifically the Preoptic and the superoptic regions
What sets the temperature for the body
the Hypothalamus
it has the connections to control the hormonal and autonomic and behavioral changes that are part of thermoregulation
WHat are the three jobs of the hypothalamus when it comes to controlling the temperature
Determing the set point
Receiving info about current temperature
Deciding what to do based on these findings
How does set point change with enviromental factors
with sleep: the temperature in the body decreases
with excersise: The temperature increases and there fore increases its set point
what part of the hypothalamus responds to heat
Anterior hypothalamus
promotes heat loss behaviors
What part of the hypothalamus responds to cooling
Posterior hypothalamus
Heat production behaviors
What are ways the body produces heat
Autonomic nervous system (sympathetics)
Endorine: thyroxine and epinephrine
muscular activity
Non shivering thermogenesis
How is muscle activity activated via being cold
shivering:
dorsomedial posterior hypothalamus will increase motor neuron excitation
INcrease in muscular voluntary activity:
Via the cortex to make an individual jump and run
What are ways Non shivering thermogenesis occurs
Strong hormonal influence
- Thyroxin increases metabolic rate (cold is a stimulus for TRH release)
- Epinephrine
INcrease food intake to increase metabolism to produce heat
Drown adipose tissue for babies (innervated by the sympathetic nervous system)
How does brown adipose tissue work
Low efficiency hydrolysis pf ATP via the uncoupling proteins that leads to heat production
has been found that white fat does express some of these uncoupling proteins to produce heat
What are the two kinds of evaporative heat loss
insensible (respiratory)
Sweating (controlled)
Evaporative heat loss is energy that is lost as water evaporates
what is convection
form of heat loss that is the movement of molecules away from contact (air heating and rising)
what is conduction
form of heat loss that is the transfer of heat between objects in physical contact with one another
What is radiation
form of heat losss where the infrared radiation transferring heat between 2 objects not in physical contact
you and the walls of the room
significance of blood and heat loss
How much blood that is sent to the skin determines how much heat moves from the blood to the external environment
this is whay if someone is hot they become flushed so that the heat in the blood can escape through the skin
How does sweating occur and what innervates it
Innervated by sympathetic cholinergic neurons that release acetylcholine that binds to a muscarinic receptor
What is the two step process of sweating and the differences between a high and low flow rate
Step 1: Filtration of serum including the ions from the blood into the sweat gland
Step 2: as the fluid travels up to the skin surface, water and sodium are reabsorbed in the duct of the gland which creates a osmotic gradient to pull back water
Low flow rate:
-concentrated due to little wter being absorbed
high flow rate: lots of water and little sodium do to aldosterone keeping the Na+ in the body
How is a fever produced and reduced
the hypothalamus increases the set point therefore the body will increase the bodies temperature this is done by:
Hypothalamus is informed by the Immune cells that release prostagladin E2 in the presence of endotoxins
therfore the hypothalamus increases the Temperature of the set point and the body will increase its temperature through shivering and moving blood flow away from the skin
once the bug is gone, no more prostagladin to tell the Hypothalamus to increase the bodies temperature so the hypothalamus sets the temp back to normal and the body will follow with heat loss
