1.3- Body Temperature Regulation

Question 1

What are the 5 main way to have heat production?

Answer 1

Basal metabolism 
Thermic effect of food
Exercise 
Shivering 
BAT (brown adipose tissue)

Question 2

What are the 4 primary ways of heat loss

Answer 2

Radiation
Conduction
Convection (needs medium: air or water)
Evaporation

Question 3

Why elevate internal temperature?

Answer 3

Decrease bacterial growth
Increase lymphocyte proliferation
Neutrophil extravasation

Question 4

Does it change outcomes to undertake antipyretic medicines

Answer 4

Usually no

Question 5

What are some microbial that elevate temperature?

Answer 5

Viruses, bacteria, fungi

Question 6

What are some non microbial antigens that elevate temperature?

Answer 6

Antigens (rejection of foreign particle)
Inflammatory agents (asbestosis, turpentine)
Plant lectins (ricin, mistletoe, phytohemagglutinin)
Host derived (inflammatory bile acids, urate crystals, complement fragments)

Question 7

What are the 4 primary pyrogenic cytokines?

Answer 7

IL-1 beta
IL-6
TNF α
Interferon α

Question 8

How do these substance cause a fever?

Answer 8

These can signal through the blood brain barrier through the endothelial cells that cause an increase in prostaglandins which cause a fever. It could go through perivascular macrophages also associated with the blood brain barrier to increase the amount of prostaglandins through a mechanism through the astrocytes involving Rank or Rank L that increase prostaglandin synthesis. Peripheral macrophages (lungs, liver) can increase prostaglandin synthesis, these prostaglandins may be able to directly signal the brain.

Question 9

What are prostaglandins?

Answer 9

Group of lipids made at site of tissue damage or infection that are involved in dealing with injury and illness. Control inflammation blood clots, induce labor

Question 10

What are the circumventricular organs?

Answer 10

Subfornical organ
Median eminence
Posterior pituitary
Pineal gland
ONLT (organum vasculosum of lamina terminalis)
Area postrema
There are all areas in which the blood barrier is leakier

Question 11

Which areas do we focus on for fever?

Answer 11

Subfornical organ and OVLT as they’re close to the hypothalamus where the signal reaches to cause a fever

Question 12

How does the signal get across the blood brain barrier?

Answer 12

Endothelial cells in the blood brain barrier form very tight junctions which repel most substances, gases can cross and some solutes.
Astrocyte layer forms tight junctions around endothelial layer often times known as foot like projections providing support & regulation
Capillary is what will be transferring prostaglandin signal.

Question 13

Where are these EP3 receptors located?

Answer 13

Anterior and preoptic areas:
Heat responses, sweating
Cold responses, shivering

PGE2 molecules stimulate EP3 receptors in preoptic anterior hypothalamic neurons and these will induce fever response

Question 14

What are some causes of hyperthermia

Answer 14

Drug induced hyperthermia (substance that increases metabolic rate-amphetamines, cocaine)
Neuroleptic malignant syndrome (antipsychotic drugs)
Serotonin syndrome (drug induced through serotonin uptake inhibitors)
Malignant hyperthermia usually in response to anesthetic
Endocrinopathy (eg. In thyroid hormone)
CNS damage or stroke

Question 15

What are the ways in which body temperature normally changes?

Answer 15

Low in early morning (36.5)
High in late afternoon (37.5)
Usually a temperature change in menstrual cycle, low in follicular phase and high in luteal phase ~0.3 degrees

Question 16

What are the 6 common way in medicine that measure temperature?

Answer 16

1. Axilla
   Strength: easy to use
   Weakness: skin temperature influences, accuracy, need time 3-5 min
2. Blood
   Strength: accuracy
   Weakness: invasive, need an in dwelling catheter
3. Esophageal
   Strength: accuracy, except for swallowed food/water
   Weakness: feels invasive, need secured esophagus
4. Oral
   Strength: non invasive, ease of use
   Weakness: low temp readings and ventilation issues
5. Rectal
   Strength: stable temp & longer recordings
6. Tympanic membrane
   Strength: stable temp, ease of use
   Weakness: lower temp readings, can be affected by face temperature

Question 17

Discuss the categorization of fever

Answer 17

Take into account female reproductive age and what phase of their menstrual cycle they are in

Any temperature above normal value after accounting for the normal temperature rhythms and condition is categorized-fever
Normal 36.5-37.5
Low grade fever 37.8-38.3
High grade fever 39.4-40
Hyperexia 41 is a dangerous condition which can even involve some neurological damage