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Exercise & Environment > Cardiovascular and respiratory control: fundamental temperature regulation > Flashcards

Cardiovascular and respiratory control: fundamental temperature regulation Flashcards

1
Q

core body temperature

A

temperature of the body around the main organ

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2
Q

what temperature is maintained within a narrow range

A

core body temperature. Will remain stable despite changes in atmospheric pressure

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3
Q

what temperature is not maintained within a narrow range

A

skin temperature

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4
Q

normal core body temp range

A

36-37.5 degrees C

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5
Q

how accurate are oral temperature readings

A

~0.5 lower than rectal measures

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6
Q

Hyperthermia

A

40 degrees or above

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7
Q

Hypothermia

A

35 degrees of below

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8
Q

what causes natural changes in body temerature

A

circadian rhythm & menstrual cycle

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9
Q

methods of measuring core temperature

A 
Oral 
Aural
rectal
oesophageal
GI tract
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10
Q

pros and cons of oral core temp measure

A

simple and non invasive but can underestimate

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11
Q

pros and cons of aural core temp measure

A

fast, can be uncomfortable and underestimate

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12
Q

pros and cons of rectal core temp measure

A

continuous, slow, close to Tc

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13
Q

pros and cons of oesophageal core temp measure

A

continues, slow, close to Tc but can be affected by food and drink

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14
Q

pros and cons of GI tract core temp measure

A

temperature pill radio transmitter, continuous varies along GI tract and has to be retrieved

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15
Q

what physiological process generates heat

A

metabolism

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16
Q

what % of energy production is lost as heat

A

75% lost as heat energy

energy used for skeletal muscle contraction only produces 25% work

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17
Q

modes of heat transfer

A

radiation
convection
conduction
evaporation

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18
Q

what is radiation

A

infrared wavelength, lower than those of visible spectrum

heat you feel if you stand infrot of a fire

19
Q

what is convectional heat

A
  • gravitationally induced heat transport
  • driven by expansion of air or fluid on heating
  • hot air expanded has lower density and so will rise above the cold dense air
  • in forced convection, strong air or liquid flow can increase heat loss markedly
20
Q

what is conduction heat

A

little heat is lost by conduction normally, as still air in clothing is a poor conductor!

  • thermal conductivity of water is 25 times that of air
  • cold water immersion at 10 degrees can lead to death in 2 hours
21
Q

Evaporation

A

water evaporates insensibly from skin and lungs throughout the day and this heat loss cannot be controlled for purposes of temperature regulation.

  • evaporation of water needs 2400kj of energy
  • daily insensible water loss is ~800ml and accounts for 20W
  • sweating can increase heat loss to about 20 times with BMR and a loss of up to 3l/hour
22
Q

Normal negative feedback in thermoregulation

A
  • thermoreceptors monitor temperature
  • information passed onto hypothalamus
  • hypothalamus compares information to set point of 37
  • hypothalamus can send signals to effects of body to initiate corrective mechanisms to maintain set point
23
Q

erros & delays in thermoregulation feedback loop

A
  • alterations to set point
  • inaccurate sensitivity in effectors and receptors
  • limits with which beyond they do not work
  • gain errors, effectors do too much
  • delays in signal from receptor or control to effector
24
Q

where is the hypothalamus

A

walls of the 3rd ventricle just above the pituitary glad

25
Q

areas of the hypothalamus for thermoregulation

A
  • preoptic area contains cells which respond to local change in temperature
  • posterior area contains cells which respond to distant change in temperature, this looks like central controller
26
Q

what area of hypothalamus responds to local change in temperature

A

preoptic area.

mostly respond to warming

27
Q

which are of hypothalamus responds to distant change in temperature

A

posterior responds to distant change in temperature like skin
this looks like central controller

28
Q

central controller of thermoregualtin

A

posterior of hypothalamus

29
Q

outline thermoregulation of skin

A
  • blood flow redistribution
  • skin deep thermoregulation
  • counter current exchange mechanism
  • muscle tone
  • horripilation
  • sweat
  • set point setting
30
Q

how does blood flow redistribution play a role in thermoregulation

A

CO increases with exercise intensity and blood flow redistributed, with skeletal muscle recieving most
but skin blood flow also increases for thermoregulation as heat is lost from blood running near skins surface

31
Q

Skin deep thermoregulation

A
  • superficial veins are present in one apical areas of the body
  • blood flow in the skin can rage from barely zero to more than 30% of cardiac output
  • skin receptors adapt markedly
32
Q

arteriovenous anastomosis

A

precapillary communications between the arteries and veins that open when the body reaches a high temperature, and enable the body to cool itself

33
Q

countercurrent exchange mechanism in thermoregulation

A
  • arteries transport warm blood deep in the arms and legs
  • deep veins are position alongside arteries
  • in the cold, blood returns through deep veins and heat is transferred from the arteries to the veins
  • heat is conserved via counter current exchange mechanism
  • in the heat, the deep veins constrict more and blood flows to the superficial veins so heat loss at skins surface
34
Q

muscle’s role in thermoregulation

A

skeletal muscle tone will increase when core temp falls

  • when tone rises above critical level, shivering begins
  • cold signals from skin and spinal chord activate shivering
  • signals from pre-optic region inhibit shivering
  • maximum shivering can raise heat production 5-fold
35
Q

what activates shivering

A

cold signals from skin and spinal cord

36
Q

what inhibits shivering

A

signals from pre-optic

37
Q

non shivering thermeogenesis

A

occurs via brown adipose tissue

  • brown fat can generate large amounts of heat
  • oxidative phosphorylating in BAT is mainly uncoupled because of UCP1
  • when cells stimulated by sympathetic fevers, mitochondria produce lots of heat and little to no ATP
38
Q

Horripilation in thermoregulation

A

Fur and feathers are important for animals, as they trap air for great heat.
Humans just get goose pimples

39
Q

sweat glands in thermoregulation

A
  • primary protein-free secretion formed by the glandular portion
  • water and salt are reabsorbed while passing through the duct, depending on rate of sweating
  • low sweating rates, sweat is rich in urea, lacatate and K as most of the salt and water is reabsorbed
  • in high sweating rates, more salt is reabsorbed that water and sweat is more dilute
40
Q

set point temperature in thermoregulation

A

skin temp alters the set point and can anticipate the change in core temperature

  • as skin temp increases, sweater will start at a lower hypothalamus temp = reduced set point
  • as skin temp decreases, sweating will start at a higher hypothalamic temperature = set point is raised
  • when the skin is warm, shivering will start at a lower core temperature = set point reduced
  • when skin is cold, shivering will start at a higher core temperature = set point is raised
41
Q

when skin is cold, set point is

A

raised

42
Q

when skin is warm, set point is

A

lowered

43
Q

TZ

A

thermoneutral zone

44
Q

what is TZ

A

Range of ambient temperatures in which humans employ vasomotor control alone to maintain a constant core body temperature e.g no shivering or sweating occurs

tends to be 25-30 degrees but we constantly shift the TZ by altering clothing and room temperature

Exercise & Environment (14 decks)

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