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Foundation of Medicine > Feedback control: Temperature and other vital signs > Flashcards

Feedback control: Temperature and other vital signs Flashcards

1
Q

What is normal pulse

A

60-100bpm

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2
Q

What is normal respiratory rate

A

12-20 breaths per minute

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3
Q

What is normal oxygen saturation

A

greater than 96%

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4
Q

What scale is used to determine consciousness

A

AVPU scale (Alert, Voice, Pain, Unresponsive)

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5
Q

What is normal capillary refill time

A

Less than 2 seconds

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6
Q

What is core body temperature definition

A

Temperature of blood and internal organs

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7
Q

What is core body temperature in degrees Celsius

A

37.8

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8
Q

How is core body temperature maintained

A

Homeostatically, within structures deep within the body

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9
Q

What happens to core body temperature when changes in the environment occur

A

Kept constant within a narrow range = Normothermia

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10
Q

What does normothermia achieve

A

-Optimum cellular function
-Optimum cellular metabolism

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11
Q

What does increasing core body temperature achieve

A

Speeds up cellular metabolism.
Overheating causes protein denaturation, nerve malfunction, convulsions (seizure) and death

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12
Q

What does decreased core body temp cause

A

Slows cellular metabolism and function which can be fatal

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13
Q

What are the ways of monitoring core body temperature

A

-Indirect estimate
-Direct estimate

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14
Q

What is indirect estimate way of measuring body temperature

A

Infrared tympanic thermometer
In eardrum
Normal range is 36-37.5 degrees

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15
Q

What temperature is considered abnormally high and whats it called

A

Greater or equal too 38 degrees
Fever is 38-40 degrees
Hyperthermia is above 40 degrees

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16
Q

What temperature is considered abnormally low and whats it called

A

below 35 degrees
Called hypothermic

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17
Q

Where to avoid when measuring core body temperature estimates

A

Avoid peripheral sites
e.g. Oral, axilla

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18
Q

Where can you measure to get a direct estimate of core body temperature

A

Rectal or oesophageal
- Slightly higher than tympanic (ear) temp.

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19
Q

What is diurnal variation in body temperature

A

Temperature varies during the day in the same individual- lowest in early morning

20
Q

What can alter normal body temperature

A

Activity
Exercise
Emotions
Exposure to extreme temps
Menstrual cycle- Higher in 2nd half of cycle from ovulation

21
Q

How do we maintain a core body temperature

A

Heat gain and loss must be in balance

22
Q

What are ways of Heat gain

A

Internal environment= Metabolic heat gain

External environment= Radiation, convection and conduction

23
Q

What are ways of heat loss

A

To external environment–=
Radiation
Conduction
Convection
Evaporation

24
Q

How do you maintain core body temperature when it decreases

A

Heat gain is increased
Heat loss is decreased

25
Q

How do you maintain core body temperature when it increased

A

Heat gain is decreased
Heat loss is increased

26
Q

What is metabolic heat

A

Oxidation of metabolic fuel derived from food in the body

27
Q

What is BMR and what does it lead too

A

Basal metabolic rate= minimum amount of energy required to sustain vital bodily functions

Leads to basic level of heat production

28
Q

What is BMR increased by and what does it increase

A

Hormones including adrenaline, noradrenaline and thyroxine

Increases muscle activity and hence metabolic heat production:
Increases shivering by increasing muscle activity which creates heat

29
Q

What is radiation and why is it relevant to the human body

A

Emission of heat energy in form of electromagnetic waves from a surface

Human body emits and absorbs radiant heat, half of heat is lost via it

30
Q

What is conduction and what does it depend upon

A

Transfer of heat between objects in contact from warmer to cooler object

Depends upon temperature gradient and thermal conductivity

31
Q

What is convection and what happens in the body

A

Transfer of heat energy by air (or water) currents helping carry heat away from the body

Air next to skin warmed by conduction making it less dense= rises whilst cooler air moves next to skin
This forced air movement increases combined effect of conduction-convection

32
Q

What is the wind chill factor

A

Forced air movement allow a greater total amount of heat to be carried away from the body in a given period of time

33
Q

What does combining convection and conduction do

A

Dissipate heat from body (disappear)

34
Q

What is evaporation

A

Water in skins surface and respiratory airway lining converted to vapour (requires energy)

35
Q

How does evaporation cool the body (example)

A

As energy required comes from the body, evaporative heat is loss therefore cools the body

-Sweating is active evaporative process controlled by sympathetic nervous system

36
Q

What is passive evaporative heat loss

A

Occurs continuously, water molecules passively diffuse from skin surface and lining of respiratory airway- NOT SUBJECTED TO PHYSIOLOGICAL CONTROL

37
Q

What control system is used to maintain core body temperature

A

Negative feedback control

38
Q

What are the sensors, control centre and effectors in temperature control

A

Sensor
- Central thermoreceptors
-Peripheral thermoreceptors

Control centre
-In hypothalamus

Effectors
- Skeletal muscles
-Skin arterioles
-Sweat glands

39
Q

What does the hypothalamus act as in temperature control

A

Acts as bodies thermostat (Maintaining set point)

40
Q

What activates posterior hypothalamic centre

A

cold

41
Q

What activates anterior hypothalamic centre

A

warmth

42
Q

Where does the hypothalamus have neural connections with

A

Limbic system and cerebral cortex

Motor neurons which control skeletal muscles

Sympathetic nervous system

43
Q

What do Effectors (skin arterioles, skeletal muscles and behavioural adaptions) do when posterior hypothalamic centre is activated by cold

A

Skin arterioles- Vasoconstriction
(Contraction reduces blood flow to skin so decreased heat loss)

Skeletal muscles- increase heat production:
Increased muscle tone
Shivering
Increased voluntary movement

Postural changes (reduce surface ares and wear warm clothing to decrease heat loss

44
Q

What do Effectors (skin arterioles, skeletal muscles and sweat glands) do when anterior hypothalamic centre is activated by warmth

A

Skin arterioles- Vasodilation
(Relaxation to increase blood flow to surface increasing heat loss)

Skeletal muscles- decrease heat production
-Decreased muscle tone
-Decreased voluntary movements

Sweat glands- Sweating
Evaporation to increase heat loss

Also wear cool clothing to increase heat loss

45
Q

How does temperature set point change in a fever greater than 38 (4 steps)

A
  1. Infection/ inflammation causes chemicals to be released from macrophages acts as endogenous pyrogen
  2. These pyrogens stimulate prostaglandins release in hypothalamus
  3. Prostaglandins act on hypothalamic thermo-regulatory centre to reset thermostat to higher temp
  4. Hypothalamus initiates mechanisms to heat the body ‘COLD RESPONSE’ shivering and vasoconstriction to meet new set point = fever
46
Q

How is hypothalamus set point restored during fever

A

Pyrogen release reduced/stopped
THEN
Prostaglandin synthesis is decreased/ stopped

‘HOT RESPONSE’then occurs to cool the body

Foundation of Medicine (23 decks)

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