Lecture 13: Temperature Regulation

Question 1

list the factors that determine heat production

Answer 1

BMR
muscle activity
thyroxin
norepinephrine and epinephrine
increased cellular chemical activity
extra metabolism

Question 2

list the factors that determine rate of heat loss

Answer 2

how rapidly heat ca be conducted from body core to skin

how rapidly heat can be transferred from skin to surroundings

Question 3

list the mechanisms that increase body temperature

Answer 3

skin vasoconstriction
piloerection
increase of thermogenesis

Question 4

list the mechanisms of heat loss from skin surface

Answer 4

radiation
conduction
convection

Question 5

Define radiation

Answer 5

refers to thermal energy transferred to objects I the external environment

Question 6

Define conduction

Answer 6

transfer of energy from one body to another when they are in close contact

Question 7

Define convection

Answer 7

heat is transferred between two objects by air or water

Question 8

Define evaporation

Answer 8

heat is dissipated by the use of thermal energy to cause a change from fluid to gas

Question 9

Define chemical thermogenesis

Answer 9

increased in rate of cellular metabolism due to sympathetic stimulation

Question 10

Compare concentrations of constituents of sweat when flow of precursor through the duct is low (slight stimulation of glands) versus rapid (strong stimulation).

Answer 10

When they sweat glands are stimulated only slightly, the precursor fluid passes through the duct slowly causes ion concentrations to be relatively high
When they are strongly stimulated, the fluid passes so quickly that the ion concentrations will be low

Question 11

What effect does aldosterone have on sweat composition?

Answer 11

Increased secretion of aldosterone results from a slight decrease in sodium chloride concentration which allows acclimatization

Question 12

Describe how the anterior pre optic area controls body temperature

Answer 12

Anterior pre-optic area contains large numbers of heat sensitive neurons. These neurons function as temperature sensors for controlling body temperature. They increase their firing rate in response to body temperature.

Question 13

Describe how the pre optic area controls body temperature

Answer 13

When the pre optic area is heated, skin all over the body immediately breaks out into a profuse sweat. This response is an immediate reaction to cause the body to lose heat, allowing the body to return to normal temp.

Question 14

Where is the primary motor area for shivering located; what is its relationship with the anterior hypothalamic preoptic area; under what conditions is this area activated?

Answer 14

Dorsomedial portion of the posterior hypothalamus
Normally inhibited by signals from heat center in anterior hypothalamic preoptic area
Excited by cold signals from skin and spinal cord

Question 15

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

Answer 15

Increase in rate of cellular metabolism due to sympathetic stimulation
Uncouples oxidative phosphorylation
Degree of thermogenesis is directly related to amount of brown fat

Question 16

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

Answer 16

When the body temperature above the usual range of normal
Pyrogens released from toxic bacteria or those released from degenerating body tissues cause fever during disease conditions
When the set point of the hypothalamic temperature regulating center becomes higher than normal, all mechanisms for raising the body temperature are brought into play
Pyrogens can directly act on the hypothalamic temperature regulating center to increase its set point

Question 17

Explain how the following affect fever: IL-1, prostaglandins, and aspirin.

Answer 17

IL-1 and prostaglandins increase set point temperature
Aspirin decreases set point temperature by inhibiting cyclooxygenase which results in decrease in production of prostaglandins