Regulation of Body Temperature

Question 1

What is the bodies core temperature? And how is it maintained?

Answer 1

37.8

maintained homeostatically

Question 2

What is normothermia?

Answer 2

normal core body temperature which is optimum for cellular metabolism and function

Question 3

What is core temperature?

Answer 3

The temp of structures deep within the body

Question 4

What does increased body temperature do? What happens if the body overheats?

Answer 4

increase body temp - speeds up cellular metabolism

Overheating - causes protein denaturation, nerve malfunction, convulsions and death

Question 5

Describe tympanic temperature and the normal range?

Answer 5

Ear drum

Normal - 35.5-37.5

Question 6

Describe rectal temperature and normal range?

Answer 6

rectal
normal - 36.7-37.5
most accurate measurement

Question 7

How does normal body temperature differ in individuals?

Answer 7

Varies during the day, lowest temp in the morning
Altered by activity, emotions exercise
Varies during menstruation

Question 8

How do you maintain core body temperature at a constant temp?

Answer 8

Heat gain and heat loss must be in balance

Question 9

What are the different methods of heat gain?

Answer 9

Internal - metabolic heat

External - Radiation, Convection, Conduction

Question 10

What are the different methods of heat loss?

Answer 10

External - convection, conduction, radiation and evaporation

Question 11

What is basal metabolic rate?

Answer 11

minimum amount of energy required to sustain vital body functions
It leads to a basic level of heat production

Question 12

How can the BMR be increased?

Answer 12

By hormones, such as adrenaline, noradrenaline and thryoxine

Question 13

How can metabolic heat be increased?

Answer 13

BMR
Muscle activity
Shivering - via muscle activity

Question 14

Describe heat exchange with the external environment - RADIATION?

Answer 14

Radiation - emission of heat energy in the form of electromagnetic waves from a surface
The human body both emits and absorbs radiant heat
Had the body’s heat loss is through raditation

Question 15

Describe heat exchange with the external environment - CONDUCTION?

Answer 15

Conduction - transfer of heat between objects in contact (towel on human)
Heat moves from warmer to cooler
Small percentage total heat exchange takes place through conduction

Question 16

Describe heat exchange with the external environment - CONVECTION?

Answer 16

Convection - Transfer of heat energy by air (or water) currents that help to carry heat away from the body.
Combines with conduction

Question 17

Describe the wind chill factor in terms of convection?

Answer 17

Forced air movement allow a greater total amount of heat to be carried away from the body in a given period of time

Question 18

Describe heat exchange with the external environment - EVAPORATION?

Answer 18

Energy is required o convert water in skins surface to lining of the respiratory airways into vapour

This energy comes from the body resulting in evaporative heat loss and hence cooling of the body

Question 19

What are the 2 different types of evaporation?

Answer 19

Passive - water molecules continuously passively diffuse from the surface of the skin and the linings of the respiratory airways

Active - sweating controlled by the sympathetic nervous system

Question 20

How does the human body maintain its core temperature at a set point?

Answer 20

By homeostatic mechanisms involving negative feedback control

Question 21

Describe the basic negative feedback control?

Answer 21

Sensor –> control centre –> effector(s)–> sensor

Question 22

What are the sensors in temperature control?

Answer 22

Central thermoreceptors 
(in hypothalmus, abdominal organs, elsewhere)
Peripheral thermoreceptors (in skin)

Question 23

What is the control centre in temperature control?

Answer 23

Hypothalamus (anterior and posterior)

Question 24

What are the effectors in temperature control?

Answer 24

Skeletal muscles - shiver
Skin arterioles - vasoconstriction - conserve heat, less blood
Sweat glands - sweating

Question 25

What are the neural inputs to the hypothalamus?

Answer 25

the negative feedback receptors for temperature regulation

Question 26

What does the hypothalamus act as?

Answer 26

The body's thermostat (maintains the temp at a set point)

Question 27

Describe what the anterior and posterior hypothalamus do?

Answer 27

Anterior - activated by warmth | Posterior - activated by cold

Question 28

Describe what the posterior hypothalamus would do in response to cold?

Answer 28

Vasoconstriction (contraction of the arterioles’ smooth muscles) - blood flow to the skin surface is reduced - heat conservation (Decreased heat loss) ``` Increased muscle tone Shivering Increased voluntary Movement (behavioural) (increased heat production) ``` Postural changes (reduce exposed surface area) Warm clothing (decreased heat loss)

Question 29

Describe what happens during 'fever'

Answer 29

Chemicals released from macrophages (certain type of phagocytic white blood cells) in response to infection or inflammation act as an endogenous pyrogen Endogenous pyrogen (e.g. interleukins) 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” (e.g. shivering and skin vasoconstriction) to raise the body temperature to the new set point The body temperature increases to reach the new set point resulting in “fever”

Question 30

When would the hypothalamic set point would be restored to normal after fever?

Answer 30

if the pyrogen release is reduced/stopped or the prostaglandins synthesis is decreased/ceased

Question 31

What would the hypothalamus then initiate to reduce the body temperature to the normal hypothalamic set point?

Answer 31

mechanisms to cool the body “hot response” (e.g. sweating and skin vasodilatation)

Question 32

What happens if the temperature set point is raised to a new higher level?

Answer 32

Fever (38-40 degrees)

Question 33

What is hyperthermia?

Answer 33

Extreme uncontrolled increase in body temperature (elevation of body temperature beyond accepted range due to failure of heat regulating mechanisms. Above 40 degrees

Question 34

What is hypothermia?

Answer 34

Drop in body temperature below that required for cellular metabolism. Temperature at or below 35°C