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
Heat stroke characteristics:
results from:
symptoms that can arise:
-critical organ damage, sign. mortality, elevated body temp, usually >105f, 40.5C
-results when the body’s thermoregulatory mechanisms are overwhelmed by the heat stress; body temp rises markedly with eventual multisystem organ failure-like kidneys shutting down
-in severe cases, pt may become confused and/or agitated
tachycardia and tachypnea with hypotension-shock symptoms
Exertional Heatstroke
occurs in younger, physically fit with normal thermoregulatory systems
frequently not dehydrated and may be wet with perspiration
sign. elevated body temp due to stress
Classic Heatstroke
occurs in older or debilitated exposed passively to sign. thermal stress over hours or days
- ability to respond can be compromised by CV disease, drugs, alcohol
- usually perspiring for sign. time and profoundly dehydrated
Treatment of heatstroke:
ABCs cooling measures to lower the pts temp to < 101F/38.3 within an hour prevent shivering keep pt NPO IV NS fluid boluses oxygen cardiac monitoring anticipate seizures! treat with valium
Hypothermia defined as:
core temp. of less than 35c/95f
mild, moderate, severe
-mostly seen in cold climates but can develop without exposure to extreme environmental conditions
age groups at risk for hypothermia
elderly lose their ability to sense cold
neonates have large surface-to-volume ratio
both groups have limited ability to increase heat production and conserve body heat
individuals with an altered sensorium like alcohol, drugs, trauma
pathophysiology of hypothermia:
heat generated by:
heat preserved by:
heat is generated by cellular metabolism (heart and liver)
loss occurs through the skin and lungs via: evaporation, radiation, conduction, convection
heat preserved by: peripheral vasoconstriction, shivering, nonshivering thermogenesis=increase in metabolic rate from thyroid and adrenal glands
Mild hypothermia presentation:
tachypnea, tachycardia, hyperventilation
ataxia, dysarthria(trouble speaking), impaired judgement
shivering
cold diuresis=increased urinination due to increased blood pressure (look at slide)
Presentation of moderate hypothermia
sinus bradycardia, decreased cardiac output, hypoventilation, afib, junctional bradycardia, other arrhythmias
CNS depression, hyporeflexia
decreased renal blood flow and loss of shivering
paradoxical undressing
presentation of severe hypothermia
pulmonary edema, oliguria(no urine produced), areflexia, coma, hypotension, bradycardia, ventricular dysrhythmias, asystole
diagnosis of hypothermia
must use low reading electronic thermometer
labs to identify potential complications:
electrolytes, hematocrit, coagulation studies, ABGs, EKG: elevation of the J point or J or Osborne wave
Management of hypothermia
ABCs initiation of rewarming: passive external rewarming active external rewarming: combination of warm blankets, radiant heat, warm baths or forced warm air active internal rewarming
why do you have to be careful in rewarming pt in hypothermic conditions?
risk is core temperature after-drop which occurs when trunk and extremities warmed simultaneously
warm trunk 1st and minimize use of peripheral muscles!
active internal rewarming
can be used alone or with active external rewarming
pleural and peritoneal irrigation with warm saline
hemodialysis and cardiopulmonary bypass
warm humidified oxygen
warm IV fluids and bladder or GI irrigation with warm saline may be used
treatment of hypothermia induced dysrhythmias
hypothermic heart is very sensitive to movement so rough handling of the pt can precipitate dysrhythmias
afib and flutter usually resolve with rewarming
can not manage vfib or asystole until core temp is brought up to 86-90f/30-32.2c
metabolic rate and what it is estimated by:
metabolic rate is the energy expenditure per unit time (calories per hour)
estimated by food consumption, energy released as heat, oxygen used in metabolic processes
factors that influence metabolic rate:
exercise
food intake
shivering
anxiety
Basal metabolic rate defined as:
-the minimal rate of energy expenditure per unit time by endothermic animals at rest
-also the energy output of the body to perform essential metabolic functions
body’s idling speed-the minimal waking rate of internal energy expenditure
BMR assessed by:
direct calorimetry-measured rate of heat production
indirect calorimetry-measured oxygen consumption
factors that influence BMR:
food intake
thyroid hormone
activity level
age
energy definition:
calorie:
the capacity to do work
-calorie is the amount of heat energy necessary to raise the temperature of 1 gram of water 1 degree centigrade
nutritional calorie is 1000 calories or the kilocalorie
Neutral energy balance occurs:
positive energy balance occurs:
negative energy balance occurs:
- when input and out match
- when intake exceeds output..energy is stored as glycogen or fat
- when output exceeds intake..energy stores are depleted
food intake is controlled by the:
hypothalamus (partially)
feeding centers: lateral hypothalamus
satiety centers: ventromedial hypothalamus
factors that affect food intake:
pre gastric factors: appearance of food, taste/odor of food, learned preferences and aversions, psych factors
gi and postabsorptive factors
long-term controls-results from complex integration of hormonal, neural, metabolic signals
Protein degradation:
the splitting of proteins by hydrolysis of the peptide bonds with formation of smaller polypeptides
fat synthesis:
creation of fatty acids from acetyl co A and malinyl-coA precursors through action of enzymes called fatty synthesis
fat breakdown:
process in which fatty acids are broken down into their metabolites, in the end generating acetyl-coA
Anabolism
requires energy(ATP) an anabolic reaction is one than involves creating large molecules out of smaller molecules -when body makes fat out of extra nutrients you eat
catabolism:
produces energy
a catabolic reaction is one that breaks down large molecules to produce energy like in digestion
the pancreas produces 2 _______ hormones to control blood sugar:
antagonistic
insulin and glucagon
insulin is produced by what cells and what is it action on blood sugar:
beta cells in islets of langerhans facilitates glucose entry in cells stimulates glycogenesis inhibits glycogenlysis inhibits gluconeogenesis
insulins action on fat:
increases transport into adipose cells
promotes protein synthesis
inhibits protein degradation
insulin action on protein:
promotes uptake of amino acids by muscle and other tissue
promotes protein synthesis
inhibits protein degradation
control of insulin secretion is _____ feedback based on:
negative
serum glucose and amino acids, GI hormones, parasympathetic activity like when you eat a meal..the presence of glucose, amino acids, or fatty acids stimulates the pancreas to secrete insulin
Glucagon is secreted by ______ and function:
pancreatic alpha cells
glucagon raises blood glucose levels by stimulating the liver to metabolize glycogen into glucose molecules and to release glucose into the blood
glucagon promotes/stimulates what processes:
promotes glycogenolysis
stimulates gluconeogenesis
promotes fat breakdown
epinephrine, cortisol, and growth hormone do what to blood AA and muscle protein?
all increase glucose and fatty acids
cortisol increases blood amino acids and decreases muscle protein
GH decreases blood AA and increases muscle protein
metabolism definition:
nutrients are used by all cells to:
- organized process though which nutrients like proteins, fats, and carbs are broken down, transformed or otherwise converted into cell energy
- synthesize large quantities of ATP
ADP is converted to ATP by :
the energy gained from the oxidation of carbohydrates, proteins, fats; ATP is then consumed by various reactions necessary to cell function
Calorie or kilocalorie=
1000 small calories which is the energy required to raise the temp of 1 kg of water by 1 degree celsius
final products of carbohydrate digestion are:
glucose (80%)
fructose and galactose
after absorption from the intestines fructose and galactose are converted to _____, in the _______
glucose, liver
the liver stores glucose as glycogen by what process?
glycogenesis-glucose molecules are added to chains of glycogen for storage
What is released when quick energy is needed and acts on the liver and skeletal muscle?
epinephrine
what stimulates gluconeogenesis?
what is gluconeogenesis?
serum glucagon levels
synthesis of glucose from noncarbohydrate precursors
carbohydrate metabolism is the breakdown of:
breakdown of starches and sugars into smaller units to be used for energy..glycogen storage
in fat metabolism, almost all the fats in the diet are absorbed into the intestinal lymph via _________.
what do these empty into?
chylomicrons empty into the juncture of the jugular and subclavian veins
they are removed from the blood in the adipose tissue and liver by lipoprotein lipase
when carbs are down, lack of _______, reduces the rate of glucose use and increases fat metabolism
insulin
epi, norepi, corticotropin, glucocorticoids and growth hormone activate _____?
what hormone can cause rapid mobilization of fat?
- hormone sensitive triglyceride lipase
2. thyroid hormone
protein metabolism is when:
proteins are broken down into amino acids in the GI tract and absorbed into the blood
-most of the AA in the blood enter the cells and form new proteins but a pool of free AA exists in the blood as well as plasma proteins
there is constant equilibrium between the cell proteins, free AA, and plasma proteins
when cells have reached limit of stored proteins…….
excess AA are degraded in the liver and used for energy or stored as fat or glycogen
growth hormone _______ synthesis of cellular proteins and _______ glucose release and uses fatty acids for energy
increases, decreases
glucorticoids ______ proteins in the tissue
decrease
testosterone _____ protein in the tissue
increases
BMI is a measurement of what?
body fat based on height and weight ratio
applies to ages 18-65
BMI is a persons weight in kg divided by the square of height in meters
healthy BMI
overweight BMI
Extremely obese
18-24
25-29
>39
recommended daily allowances (RDA)
purpose?
define the intakes that meet the nutrient need of almost all healthy persons in a specific age and sex group
purpose is to advise clinicians and the general public about the level of vitamin and nutrient intake necessary to prevent disease
