THERMOREGULATION AND PYREXIA

Question 1

At what temperature does denaturing start to occur?

Answer 1

45 degrees

Question 2

At what temperature does the brain stop functioning?

Answer 2

below 35 degrees and above 40 degrees

Question 3

how does body temperature vary?

Answer 3

it varies all over the body, with the peripheries being cooler than the trunk
it also varies over the day, with temp reaching a Max at about 6pm
gender- ovulation causes a 0.5 increase in temperature

Question 4

what’s the most accurate way of measuring body temperature?

Answer 4

rectal temperatures

Question 5

where can you find thermoreceptors?

Answer 5

skin, liver, and skeletal muscles, and hypothalamus,

Question 6

what are the 2 types of thermoreceptors? which is more common?

Answer 6

hot (C fibres) and cold receptors (A delta fibres)

cold receptors are 3.5 times more common than hot receptors

Question 7

which structure coordinates temperature?

Answer 7

the anterior hypothalamus

Question 8

what is normal body temperature?

Answer 8

37 degrees

Question 9

why do the elderly feel the cold more?

Answer 9

Our circulation decreases as we age due to the walls of our blood vessels naturally losing their elasticity. When blood moves slower through our bodies, our extremities are colder and get cold faster.
we also get a thinning fat layer under the surface of the skin so insulation slowly decreases

Question 10

what are some heat production methods that the body uses?

Answer 10

shivering
brown fat
vasoconstriction
contracting erector pili
increased catecholamine production

Question 11

what are some methods of heat loss that the body uses?

Answer 11

vasodilation
conduction
convection
sweating
exhaling 
bodily fluid excretion e.g. diarrhoea

Question 12

why is shivering only a short term method for heat production?

Answer 12

because its so metabolically expensive - uses a lot of oxygen

Question 13

what is brown fat?

Answer 13

adipose tissue that is rich in mitochondria

Question 14

how does brown fat produce heat

Answer 14

through thermogenesis - it metabolises very inefficiently, producing a lot of heat

Question 15

what is paradoxical vasodilation?

Answer 15

at very cold temperatures, our blood vessels dilate, they bathe our poor, vulnerable skin in nice, warm blood arriving from our warm innards

Question 16

how does erector pili contraction help conserve heat?

Answer 16

it makes the hairs stand on end which creates a pocket of air which acts as insulation

Question 17

how does increased catecholamines helps generate heat?

Answer 17

increased catecholamines causes a generalised increased metabolic rate which produces heat as a by-product

Question 18

what controls metabolic rate?

Answer 18

thyroxine

Question 19

why, if a patient is hypothyroid, do they have a higher risk of hypothermia?

Answer 19

because less thyroxine = metabolic rate slows down = less heat produced as a by-product

Question 20

what is conduction?

Answer 20

heat loss through physical contact with an object

Question 21

what is convection?

Answer 21

heat loss through the movement of air or water molecules across the skin

Question 22

what is a normal amount to sweat a day?

Answer 22

0.5-2 liters an hour during physical activity

Question 23

describe the movement of sweat from the gland to the surface of the skin?

Answer 23

sweat glands filter plasma, leaving the proteins and taking the electrolytes. It concentrates this ultra filtrate and as it moves up the duct, closer to the skin, sodium is absorbed back and urea remains. when the fluid comes out at the skin, the sodium content has reduced and the urea is highly concentrated

Question 24

why does sweat smell?

Answer 24

bacteria on the skin break down acids contained in the sweat produced by apocrine glands
the by-products of the bacteria produce the smell

Question 25

How do we define hypothermia?

Answer 25

a core temperature of less than 35 degrees | very severe hypothermia is less than 28 degrees

Question 26

what are clinical features of hypothermia?

Answer 26

confusion, coma, cardiovascular collapse, slow shallow breathing, slurred speech, shivering

Question 27

how do we manage hypothermia in a hospital?

Answer 27

warming with air and IV fluids | consider cardio-pulmonary bypass machine if severe hypothermia

Question 28

how do we define hyperthermia?

Answer 28

a core temperature above 38 degrees

Question 29

when does hyperthermia become severe?

Answer 29

over 40 degrees

Question 30

what are clinical features of hyperthermia?

Answer 30

confusion, seizures, coma, cardiovascular collapse, sweating, exhaustion, flushed red skin, muscle cramps, headaches, nausea

Question 31

what are some causes of pyrexia?

Answer 31

``` infections blood transfusions inflammation malignancies hypothalamic insults ```

Question 32

outline the physiology of pyrexia?

Answer 32

immune cells detect th presence of a pathogen -> inflammatory cytokines are released which can be pyrogenic -> induces synthesis of PGE2 -> acts on thermoregulatory neurones of hypothalamus to raise body temp set point -> body produces heat

Question 33

what are some pyrogenic cytokines?

Answer 33

IL6 Il1 and TNF

Question 34

what are some drugs and their targets for pyrexia?

Answer 34

steroids - target phospholipaseA2 | NSAIDs target COX1 and COX2

Question 35

what's useful about a fever?

Answer 35

it slows down the growth of pathogens and boosts the immune response

Question 36

In which clinical situations can pyrexia be bad?

Answer 36

head injury | post cardiac arrest

Question 37

how do we treat pyrexia?

Answer 37

paracetamol NSAIDs, sponging/ice packs in small amounts, exposure, fans, cardio-pulmonary bypass if severe