Feedback Control: Temperature and Vital Signs

Question 1

what are all the vital signs?

Answer 1

pulse (60-100)

blood pressure (120/80)

resp. rate (12-20)

oxygen saturation (96%+)

temperature (37degrees)

consciousness (AVPU)

capillary refill time (<2 seconds)

Question 2

what is meant by core body temperature

Answer 2

the temp. of blood and internal organs (37.8 degrees Celsius)

Question 3

what is meant by normothermia

Answer 3

the optimum for cellular function and metabolism

*very important to maintain body temperature in a narrow range ie overheating would lead to proteins denaturing and decreased wouldn’t be enough for metabolic activities and cellular functions to be carried out

Question 4

what is normal tympanic temperature

Answer 4

36 - 37.5 degrees

Question 5

what is the temperature of a fever

Answer 5

38 - 40 degrees

Abnormal

Question 6

what is the temperature of hyperthermia

Answer 6

40 + degrees

Abnormal

Question 7

when would hyperthermia be considered

Answer 7

<35 degrees Celsius

Question 8

what sites should be avoided when finding out core body temperature

Answer 8

peripheral sites ie sublingual/oral/axilla

Question 9

where would you examine to find out a direct estimate of core body temperature?

Answer 9

rectal or oesophageal

Question 10

when does body temperate vary

Answer 10

> in each individual - ie everyones normals are different
usually lower in the morning and higher in the evening - diurnal variation
may be altered by exercise, activity, emotions or exposures to certain temperatures
varies during the menstrual cycle - ie higher in the 2nd half of the cycle (from the time of ovulation)

Question 11

how does our body gain heat

Answer 11

internally from metabolic heat game

externally from radiation

Question 12

how do our bodies lose heat

Answer 12

externally from radiation conduction convection and evaporation

Question 13

what is the BMR

Answer 13

basal metabolic rate : it is the minimum amount of energy required to sustain vital body functions

• it also leads to a basic level of heat production
• the BMR can be increased by hormones such as adrenaline, noradrenaline and thyroxine

Question 14

other than the BMR what’s another way of gaining heat

Answer 14

muscle activity/shivering

Question 15

where are the central thermoreceptors in the negative feedback control mechanism for temperature?

Answer 15

in the hypothalamus, abdominal organs

Question 16

where are the peripheral thermoreceptors

Answer 16

in the skin

Question 17

what are the effectors in this negative feedback system

Answer 17

• skeletal muscles
• skin arterioles
• sweat glands

Question 18

where is the temperature control centre

Answer 18

hypothalamus

Question 19

what are the two centres of the hypothalamus, and what stimuli activates each one?

Answer 19

there is the posterior and anterior hypothalamic centre

posterior is activated by the cold

anterior is activated by the warm

Question 20

what are the neural connections associated with the hypothalamus

Answer 20

• limbic system
• cerebral cortex
• motor neurons
• sympathetic nervous system

Question 21

what is the posterior hypothalamic centre response when activated by cold?

Answer 21

vasoconstriction (skin arterioles)
increased muscle tone and shivering (skeletal muscles)
postural changes and warm clothing (behavioural adaptations)

Question 22

what is the anterior hypothalamic centre response

Answer 22

vasodilation

sweating

decreased muscle tone, decreased
voluntary movement

cool clothing

Question 23

how does the set point of body temperature change in fever?

Answer 23

-if we have infection of inflammation this leads to the release of endogenous pyrogens ie interleukins (from macrophages)
-these pyrogens then stimulate the release of prostaglandins in the hypothalamus and this then resets the temperature set point in the hypothalamus to be higher
-this then activates the ‘cold response’ (the set point is now higher but core body temperature will be the same)
this then results in increased heat production and decreased heat loss
(which raises body temp)
= fever

Question 24

how would the hypothalamic temperature set point be restored to normal?

Answer 24

if the body manages to fight the cause of pyrogen release ie the cessation of pyrogen release / antipyretics

or

if prostaglandin synthesis is decreased / ceased

Question 25

how does the hypothalamus restore the set point back to normal ?

Answer 25

the hypothalamus initiates mechanisms to cool the body ie ‘hot response’ to reduce the body temperature to the normal set point

ie feeling sweaty and hot after feeling shivery and cold is a good thing