Lecture 8: Control of Body Temp

Question 1

Ectotherms: or

Answer 1

Poikilotherms: species that do not regulate their internal body temperature
–reptiles, amphibians and most fish

Question 2

Endotherms: or

Answer 2

homotherms: species that regulate internal body temperature

- - examples; mammals and birds

Question 3

homotherms have a relatively ___ core body temp

Answer 3

stable, about 37 degrees in humans

Question 4

are there fluctuations in core temp?

Answer 4

YES

• -minimum in early morning, max in afternoon
• –also fluctuations linked to menstrual cycle (peak of ovulation about 0.5 degrees C increase)

Question 5

key components of the system which controls core temperature

Answer 5

• thermal sensors
• Thermosensory afferent pathways
• integration system
• efferent pathway
• thermal effectors –> generate heat or dissipate heat

Question 6

temp control =

Answer 6

negative feedback loop

Question 7

when the body gets too hot:

Answer 7

• Brain notices increase
• 1. blood vessels dilating
• 2. sweating
• blood temp decreases

Question 8

when the body gets too cold

Answer 8

• brain notices decrease
• 1.blood vessels constrict
• 2. no sweating
• 3. activation of brown fat
• blood temp increases

Question 9

consequences of deviations in body temperature: 40-44 degrees c

Answer 9

-Heat stroke with multiple organ failure and brain lesions

Question 10

consequences of deviations in body temperature: 38-40 degrees c

Answer 10

Hyperthermia ( as a result of fever or exercise)

Question 11

consequences of deviations in body temperature: 36-38 degrees c

Answer 11

normal range

Question 12

consequences of deviations in body temperature: 34-36degrees c

Answer 12

mild hypothermia

Question 13

consequences of deviations in body temperature: 30-34 degrees c

Answer 13

impairment of temperature regulation

Question 14

consequences of deviations in body temperature: 27-29 degrees C

Answer 14

cardiac fibrillation

Question 15

normal cellular metabolism generates –>

Answer 15

heat

Question 16

amount of heat generated by normal cellular metabolism depends on

Answer 16

the rate of energy consumption, by extension is linked to oxygen consumption

Question 17

Respiratory Quotient: what is it

Answer 17

gives an indication of the type of fuel being utilised by the body

Question 18

Respiratory Quotient: equation

Answer 18

CO2 eliminated / O2 consumed

–> varies depending on fuel source

Question 19

resting metabolic rate is the =

Answer 19

energy consumption necessary for the basal functions of resting cells

Question 20

the resting metabolic rate dissipates energy equivalent to ____ as heat

Answer 20

85 watt bulb

Question 21

the active metabolic rate dissipates energy equivalent to ____ as heat; what happens when heat is not removed from the body??

Answer 21

1000 watt bulb

–core temperature would increase by 1C about every ten minutes (limiting duration of exercise)

Question 22

heat balance basic equation

Answer 22

storage of heat = Heat production - Heat losses

Question 23

heat production =

Answer 23

Metabolism - Work done on the environment

Question 24

heat losses =

Answer 24

radiative heat loss + convective heat loss + evaporative heat loss

Question 25

Transfer of heat around the body and away from the body:

Answer 25

heat is carried from active tissues to the body core, to prevent body overheating the heat must be transferred away from core to the skin

• main route = Convection
• minor route = conduction

Question 26

heat loss from skin:

Answer 26

• evaporation
• radiation
• convection

Question 27

convection stable/variable?

Answer 27

variable; depends on blood flow to skin

Question 28

conduction stable/variable?

Answer 28

relatively constant; depends on conductive properties of subcutaneous fat

Question 29

radiation heat transfer depends on :

Answer 29

Temperature gradient between the skin and object, surface area available and transfer co-efficient
Becomes noticeable at extremes – sunbathing – next to a fire, outside on a cold night.

Question 30

conduction:

Answer 30

transfer of heat by touching an object of different temperature e.g. ice pack, lying on hot sand

Question 31

convection:

Answer 31

when air or water carried heat between the body and the environment.
Influenced by: temperature gradient and also movement of air/water over the body
– wind = chill

Question 32

2 types of evaporation:

Answer 32

sensible (sweating) and insensible (loss of water by breathing)
– linked to SA available and water pressure gradient between skin and environment

Question 33

thermo-sensors:

Answer 33

sensors in the skin and temperature-sensitive neutrons in the hypothalamus

Question 34

central sensors:

Answer 34

excellent for monitoring core temperature, but can’t track environment.

Question 35

Peripheral- skin thermoreceptor 2 classes:

Answer 35

Warmth: linked to activation of TRPV1-4 –> 30-48 degrees C

Cold: linked to activation of TRPM8 –> 15-42 degrees C

Provide information about ambient temperature and blood perfusing the skin

Question 36

TRPV1-4 & TRPM8 :

Answer 36

CATion channels, temperature sensitive

Question 37

what shivers =

Answer 37

skeletal muscles

Question 38

warmth-sensitive neurones have an ___ affect on heat genesis pathway

Answer 38

inhibitory effect

inhibit generation of heat

Question 39

warmth sensitive neutrons detect

Answer 39

core temperature

Question 40

skeletal muscle shiver and Brown adipose tissue (BAT) stimulation =

Answer 40

heat

Question 41

stimulation of warmth sensitive neurons =

Answer 41

inhibition of pathway, leading to vasodilation and sweating! inhibits shiver and BAT command

Question 42

what stimulated Warmth-sensitive neurons

Answer 42

warm and cold skin thermoreceptors