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Body Temperature and
Metabolism
Body Temperature
Normal human temperature range is 96.5-99.5F
(36-38C)
Temperature variances in the very young
(difficulty maintaining normal temp) and very
old may not be well tolerated
In 24 hr period, temp fluctuates 1 to 2 degrees F
Heat Production
Cell respiration, which produces energy from
food, also produces heat
Hormones (thyroxine), stress (release of
epinephrine), organs (muscles/tone, liver), food
intake, and fever are factors that affect body heat
production
Thyroid Affect on
Metabolism
Heat Loss
Through Skin:
Radiation - heat transfer to cooler objects not
touching skin (room temp)
Conduction - heat loss to cooler air or objects
touching skin (clothing)
Convection - air currents move warmer air away
from skin (use of fan)
Sweating - evaporation to cool, but can cause
dehydration
Skin Temperature
Regulation
Arterioles in dermis constrict or dilate ti decrease
or increase blood flow.
Warm environment = vasodilation, increase
blood flow to body surface, promoting heat loss
Cool environment = vasoconstriction, decreases
blood flow, decreasing heat loss
Respiratory - Evaporation of water from warmth
of respiratory mucosa causes heat loss
Body Temperature
Regulation
Hypothalamus - responsible for regulation of
body temperature (the “thermostat” of the body)
Balances body temperature through heat
production and loss to keep set temperature
Heat Conservation
Vasoconstriction in skin shunts blood away from
the body surface
More heat is kept in the body’s core
More heat can be produced by increased muscle
tone, which is called shivering
Fever
Fever is an abnormally high body temperature,
may be accompany infection, physical trauma,
cancer, or CNS damage
Pyrogens - substances that may cause a fever,
include bacteria, foreign protein and chemicals
released during inflammation
Endogenous pyrogens “generated from within”,
raises setting of the hypothalamic thermostat
Fever
Benefits include inhibiting the metabolism of
pathogens, shortening the duration of infection
When body temperature raises above 106F, the
hypothalamus loses its ability to regulate temperature
Protein in cells (enzymes) are damaged by high
temperatures
Antipyretics lower fever by affecting the hypothalamic
thermostat
Metabolism
All reactions that take place in the body
Anabolism-synthesis/formation, the bonding
together of smaller molecules to form larger ones
Anabolism reactions require energy, usually in
the form of ATP
Catabolism - decomposition, the breaking of
larger bonds to form smaller molecules, releasing
energy
Cell Respiration
Glucose + O2 results in CO2 + H2O + ATP + Heat
The purpose of the reaction is to produce ATP
The lungs provide O2 for the process and also
eliminate CO2 through exhalation
Energy (heat) gives us a body temperature
Glycolysis
Enzymes for the reaction of glycolysis are located in the
cytoplasm of cells
Oxygen is not required for glycolysis (anaerobic)
Begins the process of destabilizing glucose to begin the
breakdown process
No oxygen results in lactic acid release which causes
muscle fatigue
When oxygen present, pyruvic acid goes to Kreb cycle
Kreb Cycle
Enzymes for Kreb cycle located in mitochondria
This is an aerobic process requiring oxygen
Kreb Cycle
Cell Respiration
Cytochrome Transport
System
Cytochromes are proteins that contain either
iron or copper, found in the mitochondria
Pairs of hydrogen that once belonged to glucose
are brought to cytochromes by carrier molecules
NAD and FAD
Most of the ATP produced in cell respiration
comes from this stage
Proteins and Fats
Glucose is preferred energy source, proteins and
fats also are an alternative energy source
Proteins are made up of amino acids
Excess amino acids are deaminated in the liver,
removing the amino group
The remaining portion is converted to a molecule
that can then move into the Kreb cycle
Ketones
Amino acids and fatty acids can be converted by
the liver to ketones
Ketones are used slowly in cell respiration
Ketosis develops when ketones become the
primary energy source
Energy in Nutrients
Calories- “c” amount of energy needed to raise
temperature of 1 gram of water 1 degree celsius
Kilocalorie- “C” or kcal, is 1000 times the amount
of energy listed above (represents calorie counts
on food labels
One gram of carbs= 4 kcal
One gram of fat= 9 kcal
One gram of alcohol= 7 kcal
Metabolism Regulating
Hormones (pg 434)
Synthesis of Foods
3 food types used in anabolic reactions to
synthesize necessary materials for cells
Glucose - used to build pentose sugars, used for
production of chromosomes, stored as excess in
liver and muscle (glycogen)
Amino Acids-used in synthesis of proteins
(myoglobin, WBC’s, albumin). Excess contribute
to glycogen storage
Fatty Acids/Glycerol-fats stored as triglycerides in
adipose tissue. Phospholipids essential in cell
membranes (essential FA=diet, Cholesterol=liver)
Metabolic Rate
The amount of heat production as a result of
metabolism
Kcal are units used to measure energy expended
by the body
Energy required for merely living is BMR,
affected by: exercise, age, body type, sex, stress,
food intake, and climate
BMI