Feedback Control: Temperature and other vital signs

Question 1

What is core body temperature?

Answer 1

The core body temperature is the temperature of the blood and internal organs

Question 2

What is normothermia?

Answer 2

The optimum temperature for cellular activity and metabolism. Core body temperature is kept at this temperature by negative feedback control.

Question 3

At what temperatures are fevers, hypothermia and hyperthermia classified?

Answer 3

Fever- 38-40 degrees
Hyperthermia- above 40 degrees
Hypothermia- below 35 degrees

Question 4

What do you use to obtain an indirect core body temperature estimate?

Answer 4

Infrared tympanic (ear drum) thermometer or infrared forehead strips

Question 5

What do you use to obtain a direct core body temperature estimate?

Answer 5

Rectal or oesophageal thermometer

Question 6

What is diurnal variation?

Answer 6

The variation of body temperature throughout the day. For example, the CBT is at its lowest in morning and highest in evening.

Question 7

How does the body lose heat?

Answer 7

• radiation
• conduction
• convection
• evaporation

Question 8

How does the body gain heat?

Answer 8

• Metabolic heat gain
• radiation
• some convection and conduction
• muscle activity

Question 9

What is the basal metabolic rate?

Answer 9

The minimum amount of energy required to sustain vital body functions which leads to heat production

Question 10

What are the sensors in the maintenance of CBT?

Answer 10

Thermoreceptors

Question 11

What are the two types of thermoreceptors?

Answer 11

• Central Thermoreceptors (found in hypothalamus, abdominal organs)
• Peripheral thermoreceptors (found in skin)

Question 12

What is the control centre of the maintenance of CBT?

Answer 12

Hypothalamus

Question 13

What part of the hypothalamus is activated by cold?

Answer 13

Posterior hypothalamic centre

Question 14

What part of the hypothalamus is activated by warmth?

Answer 14

Anterior hypothalamic centre

Question 15

What are the effectors in the maintenance of the CBT?

Answer 15

• Skeletal muscles
• Skin arterioles
• Sweat glands

Question 16

What happens in the cold response?

Answer 16

• Vasoconstriction
• Skeletal muscles- Increase shivering, muscle tone and voluntary movement
• Other behavioural adaptations e.g. postural change and warm clothing

Question 17

What happens in the hot response?

Answer 17

• Vasodilation
• Sweating (evaporation of sweat) by sympathetic
• Skeletal muscles- Decrease muscle tone and voluntary movement
• Other behavioural adaptations e.g. cool clothing

Question 18

What is the pathway of a fever?

Answer 18

•infection or inflammation occurs
Chemicals (cytokines) released from macrophages act as an endogenous pyrogen
• Endogenous pyrogen stimulate the release of prostaglandins in the hypothalamus
• The prostaglandins act on the hypothalamic thermo-regulatory centre to “reset” the thermostat at a higher temperature
• The hypothalamus initiate mechanisms to heat the body “cold response” to raise the body temperature to the new set point
•The body temperature increases to reach the new set point resulting in “fever”

Question 19

After a fever, how is the hypothalamic set point restored?

Answer 19

If the pyrogen release is reduced/stopped or the prostaglandins synthesis is decreased/ceased. The hypothalamus then initiates mechanisms to cool the body “hot response” to reduce the body temperature to the normal hypothalamic set point.