Lecture 13

Question 1

What do the following factors determine?

BMR

Muscle activity

Thyroxin

Norepinephrine and epinephrine

Increased cellular chemical activity

Extra metabolism for digestion, absorption, and food storage

Answer 1

The heat rate of heat production

Question 2

State the 2 factors the determine the rate of heat loss

Answer 2

How rapidly heat can be conducted from body core to the skin

How rapidly heat can be transferred from the skin to the surroundings

Question 3

State the 3 mechanisms that raise body temperature

Answer 3

Shivering

Metabolic Pathways

Thyroxin secretion

Question 4

Describe the following terms and then state what is common among them.

Radiation:

Conduction:

Convection:

Answer 4

Radiation: loss of heat in the form of heat rays (this occurs from all objects that are NOT at absolute zero, so pretty much everything)
(If temperature of the body is greater than the ambient temperature, more heat is radiated from the body than to the body)

Conduction: kinetic energy of the molecules of the skin is transferred to the air if the air is colder than the skin

Convection: removal of heat from the body by convection air currents

These are all methods through which heat is lost from the skin

Question 5

What effect does aldosterone have on sweat composition?

Answer 5

Aldosterone stimulates Na+ resorption from sweat, urine, and the GI tract

Therefore, aldosterone reduces the level of Na+ that is present in sweat

Question 6

Describe the anterior pre-optic and pre-optic areas of the hypothalamus and their role in controlling body temperature.

Answer 6

Anterior pre-optic area of the hypothalamus: inhibits the shivering portion of the brain (the dorsomedial portion of the posterior hypothalamus)

Pre-optic area of the hypothalamus: (sometimes referred to at the “heat dissipation center of the brain”) basically just monitors the thermal receptors throughout the body and tries to maintain it’s “set point”

Question 7

What is the primary motor area for shivering? what is it’s relationship with the anterior hypothalamic preoptic area? Under what conditions is this area activated?

Answer 7

The dorsomedial portion of the posterior hypothalamus

The dorsomedial portion of the posterior hypothalamus is normally inhibited by signals from the anterior hypothalamic preoptic area
(However, this inhibition does NOT occur when shivering is being orchestrated by the dorsomedial portion of the posterior hypothalamus)

activated under the conditions of: receiving cold signals from the skin and spinal cord

Question 8

Define chemical thermogenesis and explain how it is related to epinephrine/norepinephrine and brown fat.

Answer 8

Chemical thermogenesis: an increase in the rate of cellular metabolism due to sympathetic stimulation (or norepinephrine in the blood)

The degree of thermogenesis that occurs is directly related to the amount of brown fat that is present in the person

Question 9

Define “fever” and explain how pyrogens relate to the hypothalamic thermostat set point. (4 secretions)

Answer 9

Fever: body temperature above the usual range of normal body temp

Pyrogens increase the set point temp by increasing production of interleukin-1, TNF, IL-6, and INF in phagocytic cells

Question 10

Explain how the following affect fever:

IL-1 and prostaglandins

aspirin

Answer 10

IL-1, and prostaglandins increase the set point temp

Aspirin decreases the set-point temp by inhibiting cyclooxygenase which results in the decrease in production of prostaglandins