Lecture 8.5 Thermoregulation

Question 1

What is extreme cold temp?

Answer 1

< 96 F

Question 2

What temp can we reach when exercising?

Answer 2

104F

Question 3

What temperature is higher when measured?

Answer 3

Rectal, which is about 1F higher.

Question 4

How do we gain heat?

Answer 4

basal rate (metabolism)
activity (muscle activity/shivering)
Thyroxine/testosterone/GH (hormones)
EPOC (sympathetic stimulation/excess post-exercise oxygen consumption)
Dietary stimulation

Question 5

How do we lose heat?

Answer 5

Radiation
Convection
Conduction
Evaporation

Question 6

What organ has the worst heat conduction?

Answer 6

Skin, only 1/3 as fast.

Question 7

Where does blood flow in the skin happen mainly in?

Answer 7

Arteriovenous anastomosis

Question 8

How much blood flow does our skin use?

Answer 8

0-30% of our entire CO.

Question 9

What controls heat transfer via the skin?

Answer 9

Sympathetic NS, which controls vasoconstriction.

Question 10

Define radiation.

Answer 10

Infrared heat rays that we emit. (EM waves)

Responsible for 60% of heat loss!!!! (MOST)

Question 11

Define conduction.

Answer 11

Physical contact with objects.

Responsible for 3% of heat loss (LEAST)

INCLUDES:

Physical contact with air (15% of heat loss)

Question 12

Define convection.

Answer 12

An extension of conduction.

It is us conducting our heat to the air currents around us, which then carry that heat away.

15% of heat loss normally.

Wind increases loss.

Water is 20x more effective than air at conduction, so we lose heat rapidly in water.

Question 13

Define evaporation.

Answer 13

Water heating up on the body’s surface and absorbing heat before it evaporates.

22% of heat loss.

Note:
At high air temps, it is the only means of losing body heat!!!!

Question 14

What regulates sweating?

Answer 14

ANS, either by electrical stimulation or excess heat.

Question 15

What innervates sweat glands?

Answer 15

Cholinergic fibers, but also from adrenal epi and NE.

Question 16

What are the components of sweat glands?

Answer 16

The gland at the deep part, touching the nerve directly and makes the sweat. It is also coiled.

The duct, which leads to the pore in the epidermis.

Pore, which is the opening.

Question 17

What is sweat similar to?

Answer 17

Plasma without proteins

Question 18

What is contained in sweat when we are slow sweating? Fast sweating?

Answer 18

Slow sweating:
NaCl is FULLY REABSORBED in the duct.
High in urea, lactic acid, and potassium ions.

Fast sweating:
NaCl is 1/2 reabsorbed.

Note: If a person is losing excessive salt in their sweat, they are known as unacclimatized.

Question 19

What is acclimatization?

Answer 19

Adapting to the environment.

Question 20

How much do we sweat normally vs in hot weather?

Answer 20

1L/hr in normal.

2-3L/hr in extended hot weather 1-6 weeks.
However, heat loss increases by 10x.

Question 21

What happens to someone who is acclimatized to hot weather?

Answer 21

Increased sweating.
Increased heat loss.

Decreased sodium lost in sweat
Increased aldosterone.

Question 22

What regulates our body temperature?

Answer 22

Hypothalamus

Question 23

If we are cold, what does our body do?

Answer 23

Shiver
Piloerection
Skin vasoconstriction
Increased thermogenesis

Question 24

What are the 3 ways we can increase thermogenesis?

Answer 24

Shivering
Sympathetic excitation (uncoupling of oxidation and phosphorylation)

Thyroxine secretion

Question 25

If we are hot, what does our body do?

Answer 25

Vasodilate skin blood vessels

Sweat

Decrease thermogenesis (depressed shivering and depressed chemical thermogenesis)

Question 26

Do we have more cold or warm receptors?

Answer 26

Cold (10x) more

Question 27

Where are the deep cold receptors found in our body?

Answer 27

Spinal cord
Abdominal viscera
Around the great veins

Question 28

What is fever?

Answer 28

A body temperature greater than normal range.

Question 29

What causes fever?

Answer 29

Abnormalities in the brain
Toxic substances affect the hypothalamus

Question 30

What are pyrogens?

Answer 30

Things that cause fever.

Question 31

What are the pyrogens?

Answer 31

Proteins
Breakdown products of proteins
Lipopolysaccharide toxins released from bacterial cell membranes

Question 32

What is the main cytokine involved in fever?

Answer 32

IL-1

Question 33

Why is aspirin an antipyretic?

Answer 33

It inhibits the formation of prostaglandins, which are pyrogens.

Question 34

Why do we feel chills and flushed when we have a fever?

Answer 34

Our body feels cold because it is trying to reach the new higher set point.