thermoregulatory system

Question 1

thermoregulatory system

Answer 1

the ability of an organism to keep its body temperature within certain boundaries
homeotherms
- constant internal body temp regardless of external stimuli
endotherms
- generate heat internally
- maintain high basal heat production
ectotherms
- depend on external heat sources
- temp changes with environment

Question 2

internal (core) body temp

Answer 2

36.5 - 37.5 degrees celsius
optimal function 36.5 -40

Question 3

hypothermia

Answer 3

low body temp
< 35 degrees c
lowest survivable =~ 14.4 degrees c
symptoms:
- loss of motor skills
- shivering
- decrease in blood circulation and skin temperature
moderate or severe symptoms:
- confusion/ fatigue
- loss of consciousness

Question 4

hyperthermia

Answer 4

high body temp
> 38 degrees c
damage to cells > 42 degrees c
highest survivable =~46.5 degrees c
heat exhaustion
- faint or dizzy
- excessive sweating
- cool,clammy skin
- nausea or vomiting
- rapid, weak pulse
- muscle cramps
heat stroke
- throbbing headache
- no sweating
- red, hot, dry skin
- nausea or vomiting
- rapid, strong pulse
- may lose consciousness

Question 5

measuring core body temp

Answer 5

thermometer probe at an accessible site
- hypothalamus
- oesophagus
- rectum
- intestinal
- oral under tongue
- ear drum

Question 6

measuring skin temp

Answer 6

depends on:
- ambient temp
- distance from core
- skin blood flow

Question 7

law of conservation of energy

Answer 7

energy neither created nor destroyed
only transformed from one state to another
heat production
- liberate chemical energy in food we eat
- use it to resynthesize ATP
- but process is inefficient as the energy release not equal to ATP resynthesis
- release energy in form of heat
voluntary heat production
-exercise
- 70-80% EE app
involuntary heat production
- shivering
- action of hormones
-> thyroxine
-> catecholamines

Question 8

heat production during dynamic exercise

Answer 8

to contract the muscles
- chemical energy as ATP
- exothermic reaction convert to mechanical energy
- 25-30% converted to mechanical work (rest is heat)

Question 9

oxygen consumption

Answer 9

VO2 as an indicator of energy expenditure (heat production)
- 1 litre of 02 consumed produces ~ 20kJ heat
- resting vo2
-~0.25 L/min
- 0.25 x 20 = 5 kJ/ min of heat

Question 10

external heat gain

Answer 10

sky thermal radiation
solar radiation
- reflected
- air temperature and humidity
ground thermal raditaion

Question 11

specific heat capacity

Answer 11

amount of energy required to raise the temperature of a given substance by 1 degrees c
water = 4.186 kJ/kg/c
human body tissue = 3.48 kJ/ kg/c
change in thermal energy = mass x specific heat capacity x change in temp

Question 12

radiation

Answer 12

transfer of heat in the form of electromagnetic waves
~ 60% heat loss at rest at room temp

Question 13

conduction

Answer 13

heat transfer from the body to an object with direct contact
~3% heat loss at rest at room temp

Question 14

convection

Answer 14

heat transfer from one place to another by movement of fluids (air or water)
~12% heat loss at rest at room temp

Question 15

skin blood flow

Answer 15

conduction of heat to or from air or water
dependant on skin blood flow
during exercise heat dissipation by convection is reduced

Question 16

thermal gradient

Answer 16

heat transfer is always from higher to lower temps

Question 17

evaporation

Answer 17

vaporisation of sweat from water to vapour
~25% heat loss at rest and ~85% during exercise
sweat evaporation
- water to vapour
-> 1g sweat = 2.41 kJ of heat
factors effecting evaporation
- air temp (humidity) = decrease
- convection currents (wind) = increase
-skin exposure (surface) = increase

Question 18

sweating

Answer 18

sweat released from sweat glands
stimulated by sympathetic nervous system
increased SNS activity when exercising, anticipation or nervous

Question 19

quantifying sweat loss and rate

Answer 19

sweat loss (L) = change in mass + fluid intake - urine
sweat rate (L/h) = sweat loss/ time (h)
sweat rate depends on:
- body size
- absolute VO2
- aerobic fitness
- heat acclimatisation
- environment

Question 20

cold exposure: ways body loses heat

Answer 20

heat loss
- evaporation
-radiation
-conduction
-convection
evaporation (sweating) when core temperature >37 degrees c at rest ~25% and ~85% during exercise
radiation: ~60% heat loss
conduction (cold ground) : ~2% through sir conduction
- water causes more heat loss than air
convection (wind) : body loses ~12% of its heat

Question 21

methods to reduce hyperthermia during exercise

Answer 21

heat acclimation
- body temp lower at given heat
- sweat rate increases and sweat more dilute
- skin blood flow reduced more blood to muscles
- blood vol increases/ not decrease
- stroke vol maintained

Question 22

areas of body with greater heat loss

Answer 22

skull
groin
armpits
extermities

Question 23

heat exhaustion treatment

Answer 23

cooler environment
elevate feet
saline
-oral
- intravenous

Question 24

heat stroke treatment

Answer 24

rapidly cool body
-cold water
- ice bath
- wet towel
medical attention

Question 25

hyperthermia improves sprint/ power performance

Answer 25

• faster nerve conduction velocity
• improvement in muscle contractile elements
• faster metabolic rate -> Q10 effect
• increased SNS activity
  impairs endurance performance
  impairs repeated sprint ability

Question 26

Q10

Answer 26

temperature coefficient
measure of the rate of change of a biological/ chemical system as a consequence of increasing the temp by 10 degrees c

Question 27

hyperthermia: how performance impaired

Answer 27

increase core temp = increase sweat rate
decrease plasma vol
decrease blood vol
decrease venous return
decrease end diastolic vol

Question 28

hyperthermia: cardiovascular consequences

Answer 28

decrease stroke vol
increase heart rate
decrease cardiac output
decrease blood pressure
increase peripheral resistance
decrease muscle blood flow

Question 29

hyperthermia: cognitive consequences

Answer 29

impairment in
- fatigue perception increases
- scanning vigilance
-reaction time
- attention
- visual motor tracking

Question 30

hyperthermia: metabolic consequences

Answer 30

decrease VO2 MAX
increase anaerobic metabolism
increase muscle lactate

Question 31

central fatigue

Answer 31

brain stops sending out neural impulses to contract muscles

Question 32

sodium cations

Answer 32

90% of extracellular cations
pivotal role in fluid and electrolyte balance as accounts for half of osmolality of ECF
main electrolyte lost in sweat 40-50 mmol/L
replace Na+ with fluid intake

Question 33

sodium ion and body water regulation

Answer 33

sodium ion only cation to exert significant osmotic pressure
sodium ion leak into cells and pumped out against electrochemical gradient
conc Na in ECF stable
Na+ loss through urine and presipitation

Question 34

ADH

Answer 34

antidiuretic hormone
released from posterior pituitary
secretion stimulated by
- haemoconcentration
- increase plasma osmolarity
- decrease plasma volume
promotes water retention in kidney to dilute plasma

Question 35

aldosterone

Answer 35

mineralocorticoid hormone
released from adrenal cortex
secretion stimulated by:
- decrease plasma sodium
- decrease blood vol
- decrease pressure
- increase plasma potassium conc

Question 36

alcohol when dehydrated after exercise

Answer 36

increased rate of urination
lower fluid retention
reduced plasma vol

Question 37

post exercise

Answer 37

drink to replace fluid lost in sweat
include glucose for glycogen resynthesis
inclusion of Na+ aids fluid absorption in kidneys and water retention