Thermoregulation, BMR, Basic Nutrition Flashcards
Average core temp is between:
98F (36.7C) and 98.6F(37C) orally can range from 97-99.5
Skin temperature:
rises and falls with temperature of surroundings and structures lying beneath it
We consider someone febrile at:
100.4 F or 38C
104 F or 40C is getting dangerous
Sites used for core measurement:
rectal, oral, vaginal, bladder, tympanic
how we measure surface measurement:
axillary, skin of forehead, non-contact IR devices
Thermoregulation basics: body temp is controlled by:
balancing heat production against heat loss
heat production>heat loss=rise in body temp
heat loss>heat production=decrease in body temp
Homeostatic receptors are:
sensors that monitor environment and respond to changes
control center in homeostasis determines:
set point which is the range at which variable is maintained
the effector in homeostasis:
means for the control center’s response(output) to the stimulus
Heat production is a by-product of:
metabolism
extra rate of metabolism caused by:
muscle activity (shivering)
thyroxine
effects of epinephrine, norepinephrine, and sympathetic stimulation of cells
increased chemical activity in the cells themselves
metabolism needed for digestion, absorption, and storage of foods
Most heat is produced in deep organs at ____, and skeletal muscles during_____
rest, exercise
heat is transferred to the skin where it is lost to the air and other surroundings; the rate at which heat is lost depends primarily on:
- how rapidly heat can be conducted from where it is primarily produced to the skin
- how rapidly heat can be transferred from the skin to the surroundings
Insulation:
skin and especially the subcutaneous tissues act together as a heat insulator
fat conducts heat only 1/3 as readily as other tissues
in the cold, minimal amounts of blood flow from the heated internal organs to the skin=effective means of maintaining normal internal core temp
heat transfer to skin..
blood vessels distributed profusely throughout the skin
rate of blood flow into skin venous plexus can vary from barely above 0 to as great as 30% of cardiac output
Low rate of skin flow occurs in ____ temps, and _____ heat conduction and _____heat is lost
colder, decreases, less
high rate of skin flow occurs in _____, ________ heat conduction, and _____ heat is lost
warmer, increases, more
four types of heat loss from skin surface
radiation
conduction
convection
evaporation
- Radiation is:
2. When temp of body>temp of surroundings:
- the loss of heat in form of infrared heat rays (all objects not at absolute zero temp radiate such rays, including the walls and objects around us)
- a naked person will lose about 60% of total heat by radiation at normal room temp - a greater quantity of heat is radiated from the body than is radiated to the body
- Conduction is:
2. once the temp of the air adjacent to the skin=temp of skin…
- the direct loss of heat via kinetics or the energy of molecular motion..transfer of heat through physical contact
- no further loss of heat occurs via conduction to air
conduction to objects only accounts for 3% where as conduction to air about 15% in conduction with convection
Convection:
aka the wind chill process; the removal of heat from the body by air currents
wind removes layer of air immediately adjacent to the skin and replaces it by new air much more rapidly
What would happen with the air convection process when one wears clothes?
normal clothing decreases heat loss by 1/2
arctic-type clothing decreases heat loss to as little as 1/6th
with regard to conduction and convection with water, each unit of water adjacent to the skin can absorb far greater quantities of heat than air can therefore…
the rate of heat loss to water is usually many times greater than the rate of heat loss to air
- Evaporation is:
- Evaporation _______ be controlled for purposes of temp regulation
- Loss of heat via evaporation of sweat can be controlled by __________
- the loss of heat when water evaporates from body surface
can occur even when person is not sweating=insensible loss when unable to detect sweat-occurs at a rate of about 600-700 mL/day - cannot
- regulating rate of sweating
Heat loss with sweating is controlled by what nervous system?
sympathetic
two types of sweat glands
Eccrine: innervated by somatic nervous system via Ach
Apocrine: regulated by androgens
- If skin temp>temp of surroundings, heat can be lost by _________
- once temp of surroundings > skin temp, the body then gains heat by both _______
- under these conditions, the only means by which the body can rid itself of heat is by ______
- radiation and conduction, sometimes convection
- radiation and conduction
- evaporation
Organ systems responsible for heat loss and how:
skin: vasodilation and perspiration
cardiovascular: increased cardiac output to compensate for peripheral vasodilation with increased volumes of blood to periphery
respiratory: some degree of evaporation
Temperature is regulated by:
the hypothalamus
Thermostatic detection occurs in the hypothalmic area of the brain as well as in the:
skin and deep body tissues
Heat sensitive cells function
signals sent to skin to induce sweating
vasodilation of skin vessels
decrease in heat production (inhibition of shivering and chemical thermogenesis)
cold sensitive cells:
what is piloerection?
Piloerection-brings hairs in upright position as in goose bumps
vasoconstriction of skin vessels
increase in heat production (shivering, thyroxine secretion)
Hyperthermia is a:
state of unusually high core body temp
Predisposing factors of hyperthermia include age and health of the pt. Patients with type 1 DM can become hyperthermic more easily because _______
of the damage to their autonomic nervous system
Medications that can be a predisposing factors for hyperthermia are:
diuretics-dehydration
beta blockers-can cause vasodilation through blockade of alpha-adrenergic receptors
psychotropics-can affect CNS regulation
other factors that predispose pt to hyperthermia:
level of acclimation: adjust to environment change
length and intensity of exposure
environmental factors like humidity and wind
Heat cramps:
usually caused by:
treated with:
painful, easily treated, acclimation occurs like muscle soreness
-painful contractions of larger muscle groups during or shortly after strenuous exercise in the heat
-caused by replacement of water without adequate salt resulting in a low sodium state in the muscles
-treated with cooling measures, fluids, electrolyte replacement, oral or IV
no changes in mental status or fever
Heat exhaustion:
caused by:
Symptoms:
Treated with:
serious but no organ damage, mild hyperprexia ( elevation of core temperature)
Caused by salt or water depletion in the face of heat stress
Symptoms include mild hyperprexia, nausea, vomiting, lightheadedness, dehydration with minimal altered mental status; leads rapidly to heat stroke if not rapidly reversed
Treated with cooling measures and IV normal saline-further electrolyte replacement guided by serum electrolyte levels