Cardiovascular and respiratory control: fundamental temperature regulation

Question 1

core body temperature

Answer 1

temperature of the body around the main organ

Question 2

what temperature is maintained within a narrow range

Answer 2

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

Question 3

what temperature is not maintained within a narrow range

Answer 3

skin temperature

Question 4

normal core body temp range

Answer 4

36-37.5 degrees C

Question 5

how accurate are oral temperature readings

Answer 5

~0.5 lower than rectal measures

Question 6

Hyperthermia

Answer 6

40 degrees or above

Question 7

Hypothermia

Answer 7

35 degrees of below

Question 8

what causes natural changes in body temerature

Answer 8

circadian rhythm & menstrual cycle

Question 9

methods of measuring core temperature

Answer 9

Oral 
Aural
rectal
oesophageal
GI tract

Question 10

pros and cons of oral core temp measure

Answer 10

simple and non invasive but can underestimate

Question 11

pros and cons of aural core temp measure

Answer 11

fast, can be uncomfortable and underestimate

Question 12

pros and cons of rectal core temp measure

Answer 12

continuous, slow, close to Tc

Question 13

pros and cons of oesophageal core temp measure

Answer 13

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

Question 14

pros and cons of GI tract core temp measure

Answer 14

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

Question 15

what physiological process generates heat

Answer 15

metabolism

Question 16

what % of energy production is lost as heat

Answer 16

75% lost as heat energy

energy used for skeletal muscle contraction only produces 25% work

Question 17

modes of heat transfer

Answer 17

radiation
convection
conduction
evaporation

Question 18

what is radiation

Answer 18

infrared wavelength, lower than those of visible spectrum

heat you feel if you stand infrot of a fire

Question 19

what is convectional heat

Answer 19

• 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

Question 20

what is conduction heat

Answer 20

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

Question 21

Evaporation

Answer 21

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

Question 22

Normal negative feedback in thermoregulation

Answer 22

• 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

Question 23

erros & delays in thermoregulation feedback loop

Answer 23

• 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

Question 24

where is the hypothalamus

Answer 24

walls of the 3rd ventricle just above the pituitary glad

Question 25

areas of the hypothalamus for thermoregulation

Answer 25

- 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

Question 26

what area of hypothalamus responds to local change in temperature

Answer 26

preoptic area. | mostly respond to warming

Question 27

which are of hypothalamus responds to distant change in temperature

Answer 27

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

Question 28

central controller of thermoregualtin

Answer 28

posterior of hypothalamus

Question 29

outline thermoregulation of skin

Answer 29

- blood flow redistribution - skin deep thermoregulation - counter current exchange mechanism - muscle tone - horripilation - sweat - set point setting

Question 30

how does blood flow redistribution play a role in thermoregulation

Answer 30

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

Question 31

Skin deep thermoregulation

Answer 31

- 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

Question 32

arteriovenous anastomosis

Answer 32

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

Question 33

countercurrent exchange mechanism in thermoregulation

Answer 33

- 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

Question 34

muscle's role in thermoregulation

Answer 34

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

Question 35

what activates shivering

Answer 35

cold signals from skin and spinal cord

Question 36

what inhibits shivering

Answer 36

signals from pre-optic

Question 37

non shivering thermeogenesis

Answer 37

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

Question 38

Horripilation in thermoregulation

Answer 38

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

Question 39

sweat glands in thermoregulation

Answer 39

- 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

Question 40

set point temperature in thermoregulation

Answer 40

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

Question 41

when skin is cold, set point is

Answer 41

raised

Question 42

when skin is warm, set point is

Answer 42

lowered

Question 43

TZ

Answer 43

thermoneutral zone

Question 44

what is TZ

Answer 44

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