9 - Fever Flashcards
Why must humans maintain a stable body temperature within a narrow range?
Metabolic processes are dependent on temperatures being kept within that range
Name the condition where the body temperature is too high.
Hyperthermia
Name the condition where the body temperature is too low.
Hypothermia
Why is temperature different at surfaces of the body than at its core?
Surfaces exchange heat with the environment
How is body temperature kept relatively stable?
Circulation of blood
What is the normal range for core temperature?
36.2 to 37.4 deg C
Time of day and point in the ___ cycle cause temperature to fluctuate.
Menstrual
Why does the temperature on the forehead tend to be lower than the core body temperature?
Environmental temperature cools it down
Of the following, list the 2 most accurate areas to measure core body temperature: armpit, mouth, rectum, vagina.
- Rectum
2. Vagina
Of the following, list the 2 least accurate areas to measure core body temperature: armpit, mouth, rectum, vagina.
- Mouth
2. Armpit
Order the following areas from most to least accurate for measurement of core body temperature.
- Ear
- Mouth + Armpit
- Rectum + Vagina
- Rectum + Vagina
- Ear
- Mouth + Armpit
Symptoms of hyperthermia manifest primarily in the ___ nervous system.
Central
Symptoms of hypothermia manifest primarily in the ___ nervous system.
Central
The main effect of hypothermia is a slowing down of metabolism. What are some signs and symptoms that would be indicative of a dangerously slow metabolism?
- Low heart rate
- Weak pulse
- Slurred speech
- Sluggishness
- Clumsiness
- Memory loss
- Unconsciousness
The main effect of hyperthermia is a speeding up of metabolism. What are some signs and symptoms that would be indicative of a dangerously fast metabolism?
- Cramps
- Nausea
- Vomiting
- Headache
- Dizziness
- Fainting
- Coma
Compare the effect of hyperthermia and hypothermia on metabolic rate.
Hyperthermia: increases metabolic rate
Hypothermia: decreases metabolic rate
Hyperthermia ___ metabolic rate.
Increases
Hypothermia ___ metabolic rate.
Decreases
Body temperature above ___ deg C can be very dangerous.
40
Body temperature below ___ deg C can be fatal.
28
What is the typical age for a febrile convulsion?
6 months to 5 years
A child has a febrile convulsion. When you see them, they are not fully alert. What are the first two things you should do?
- Put the child in the recovery position
2. Maintain their vital signs
A child presents with a febrile convulsion. List 4 illnesses that need to be excluded.
- Meningitis
- Septicemia
- UTI
- Chest infection
What type of parasite causes malaria?
Plasmodium
How does malaria induce pallor?
Causes the blood vessels to constrict
What stain would identify malaria in a blood film?
Giemsa
Abnormal body temperature is dangerous both for its own effects and for the mechanisms by which the body tries to ___ it.
Control
Why are you more likely to feel cold sitting next to a window with no curtains?
Body loses heat via radiation to a nearby cold surface
Abnormal body temperature mainly affects which system?
CNS (central nervous system)
Describe why some surgeries are performed after cooling the body temperature.
Lower body temperature ->
Lower metabolic rate ->
Reduced oxygen requirements ->
Body parts less vulnerable to lack of oxygen
The core temperature depends on the balance between heat lost and heat ___.
Gained
How does exercise increase body heat?
Raises metabolic rate
Why do you feel hotter after eating a meal?
Increased metabolic rate raises core body temperature
List 2 involuntary physiological mechanisms for increasing body heat.
- Shivering
2. Activation of brown adipose tissue
What are the 4 processes by which body heat can be lost?
- Convection
- Conduction
- Radiation
- Evaporation
Why do convection, conduction, and radiation only reduce body heat when the environment is cooler than the body?
Heat must SHIFT from the body to the environment
Which form of heat loss can occur even when the environment is hotter than the body?
Evaporation (via sweat)
Air is a ___ conductor.
Poor
List 2 ways that clothes keep the body warm. (Hint: both related to air.)
- Trap air, which is a good insulator
2. Reduce convective loss
In which condition would air, which a good insulator, actually reduce body heat?
When it is flowing (e.g., wind chill)
What is conduction (re: body heat)?
When body heat shifts to a cooler object via direct physical contact
What is radiation (re: body heat)?
When body heat shifts to a cooler object via EMR waves
What is convection (re: body heat)?
When body heat is lost via air movement
Which unit measures the insulating properties of clothes?
Tog
Water is a ___ conductor.
Good
List 2 situations where the body would lose heat via conduction.
- Immersed in cold WATER (e.g., Jack from Titanic)
2. Lying on a cold SURFACE (e.g, drunk person lying in a ditch)
Why would wearing a scarf and toque prevent convective heat loss?
Warm air rises
What percentage of body heat do babies lose from the head?
80%
How would long, flowy clothes keep the body cool?
Promote convective heat loss (i.e., warm air rises from the top and is replaced by cool air coming in from the bottom, creating a fan-like effect)
What is the major mechanism for loss of body heat in adults?
Radiation (accounts for 60-70% of heat loss)
List 3 variables that determine the rate at which heat radiates from the outermost surface of the body to surrounding surfaces.
- Temperature difference
- Distance
- Color
What is latent heat?
The heat needed to convert liquid water to vapour
The body loses heat when sweat ___.
Evaporates
How do aluminum space blankets keep the body warm?
REFLECT heat back onto the body surface
Water evaporates CONSTANTLY from the skin surface and ___ tract.
Respiratory
Water evaporates CONSTANTLY from the skin surface and respiratory tract. This is known as ___ evaporation.
Insensible
What is the thermo-neutral temperature?
Environmental temperature at which core body temperature does not change
List 2 variables that affect the thermo-neutral temperature.
- Body’s heat production
2. Amount of insulation (i.e., how hard it is to lose heat)
Hard exercise will ___ the thermo-neutral temperature.
Decrease
Heavy clothing will ___ the thermo-neutral temperature.
Decrease
Our bodies adjust heat loss and gain to make the environment that we’re in ___.
Thermo-neutral
Compare blood flow to the skin in cold and warm conditions.
Cold: reduced
Warm: increased
Brown adipose tissue generates heat by uncoupling which cellular process?
Oxidative phosphorylation
The activation of brown adipose tissue is driven by the ___ nervous system.
Sympathetic
Compare the amplitude and frequency of muscle contractions during shivering.
Amplitude: low
Frequency: high
Why are UTIs more common in women than in men?
The opening of the female urethra is CLOSER to the anal canal, which is a common source for bacteria causing UTIs
What is atrophic vaginitis?
Thinning and drying of vaginal tissue due to lack of estrogen
Why are UTIs more common in older men than younger men?
Aging might lead to PROSTATE ENLARGEMENT, which impedes bladder emptying and causes bacteria to fester
Why are UTIs more common in older women than younger women?
Menopause causes thinning and drying of tissue around the urethra (i.e., atrophic vaginitis), thus the tissue cannot repel bacteria as well
What are the 2 most common tests for UTIs?
- Dipstick
2. Urine sample
What is the most common bacteria causing UTIs?
E. coli
In sweat glands, acini produce secretions and ducts remove the solute, leaving water. Why does profuse sweat taste saltier?
The more you sweat, the less salt is recovered by sweat ducts
List 2 complications of excessive sweating.
- Dehydration
2. Salt deprivation
What part of the brain regulates body temperature?
Hypothalamus
Which type of cells in the hypothalamus detect core body temperature by monitoring blood temperature?
Nerve cells
What is the set point?
A desired value determined by the hypothalamus (picture: thermostat)
How does DNP cause hyperthermia?
Leads to an uncontrolled increase in metabolism
A ___ is a temperature above the normal range, resulting from an increase in the set point.
Fever
List 2 non-pathological triggers that alter the set point.
- Circadian rhythm
2. Menstrual cycle
Core body temperature ___ at night.
Decreases
Core body temperature ___ during the luteal phase (2nd half) of the menstrual cycle.
Increases
What is a pyrogen?
A fever-inducing agent
Pyrexia is a synonym for ___.
Fever
What is the term for a substance travelling in the blood stream that elevates the set point for body temperature?
Pyrogen
Which body system produces endogenous pyrogens?
Immune system
Cytokines are ___ pyrogens.
Endogenous
What produces exogenous pyrogens?
Pathogens
Although pathogens are exogenous pyrogens, they almost always act by stimulating ___ pyrogens.
Endogenous
All pyrogens lead to the production of ___, which act on the hypothalamus.
Prostaglandins
Anti-pyrexic drugs (e.g., acetaminophen) ___ prostaglandin production.
Inhibit
How do anti-pyrexic drugs (e.g., acetaminophen) inhibit prostaglandin production?
Act on COX enzymes
Which enzymes produce prostaglandins?
COX enzymes
In broad terms, which physiological process generates most body heat?
Metabolism
The following describes how a fever is induced. Pyrogen enters bloodstream -> Stimulation of \_\_\_ -> Increased set point in hypothalamus -> Body temperature rises
The following describes how a fever is induced. Pyrogen enters bloodstream -> Stimulation of PROSTAGLANDINS -> Increased set point in hypothalamus -> Body temperature rises
Which medical condition arises from an adversely high body temperature?
Heat stroke
Why would a fever cause you to shiver despite a raised body temperature?
Raised set point causes your body to act as if you are cold
Pyrogens are often produced in waves. Describe how this would induce sweating during a fever.
Pyrogen concentration falls ->
Set point reduced ->
Body acts as if temperature is too high ->
Sweating to increase heat loss
Why would you suddenly feel hot when a fever breaks?
Pyrogen concentration in the blood falls, lowering the set point
List 2 effects of exercise on insulin.
- More rapid absorption
2. Increased effectiveness
How does exercise reduce the demand on pancreatic beta cells?
Stimulates non-insulin dependent glucose uptake into muscle