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Chapter 22
Metabolism & Energy Balance
70
Physiology
Undergraduate 3
11/30/2015

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Term
2 hypothalamic centers on which behavioral regulation of food intake is based
Definition
1. feeding center (tonically active)
2. satiety center (stops food intake by inhibiting the feeding center)
Term
What tissue secretes adipocytokines (chemical signals that influence food intake & satiety)?
Definition
adipose tissue
Term
glucostatic theory
Definition
glucose metabolism by hypothalamic centers regulates food intake
Term
lipostatic theory
Definition
a signal from the body's fat stores to the brain modulates eating behavior so that the body maintains a particular weight
Term
leptin
Definition
a protein hormone synthesized in adipocytes that provides evidence for the lipostatic theory; discovered in 1994
Term
neuropeptide Y (NPY)
Definition
a brain neurotransmitter that seems to be the stimulus for food intake
Term
ghrelin
Definition
a peptide secreted by the stomach during fasting & increases hunger when infused into human subjects
Term
equation for total body energy
Definition
total body energy = energy stored + energy intake - energy output
Term
equation for energy output
Definition
energy output = work + heat
Term
3 types of work that contribute to energy output
Definition
1. transport work (moves molecules from one side of a membrane to the other)
2. mechanical work (uses intracellular fibers & filaments to create movement)
3. chemical work (used for growth, maintenance, & storage of information & energy)
Term
What is the most direct way to measure the energy content of food?
Definition
direct calorimetry
Term
kilocalorie
Definition
the amount of heat needed to raise the temperature of 1 liter of water by 1 degree C
Term
metabolic rate
Definition
an individual's energy expenditure; measuring this is more complex than figuring the caloric content of ingested food
Term
oxygen consumption
Definition
the rate at which the body consumes oxygen as it metabolizes nutrients; the most common method for estimating metabolic rate
Term
Is measuring oxygen consumption an example of direct calorimetry or indirect calorimetry?
Definition
indirect
Term
respiratory quotient (RQ) / respiratory exchange ratio (RER)
Definition
the ratio of CO2 produced to O2 consumed
Term
equation for metabolic rate (in kcal/day)
Definition
metabolic rate = L O2 consumed/day X kcal metabolized/L O2
Term
basal metabolic rate (BMR)
Definition
an individual's lowest metabolic rate
Term
resting metabolic rate (RMR)
Definition
metabolic rate after a 12-hour fast in a person who is awake but resting; used because measuring the BMR of a sleeping person is difficult
Term
6 factors that affect metabolic rate in humans
Definition
1. age & sex
2. amount of lean muscle mass
3. activity level
4. diet
5. hormones
6. genetics
Term
diet-induced thermogenesis
Definition
the phenomenon where resting metabolic rate increases after a meal
Term
metabolism
Definition
the sum of all chemical reactions in the body
Term
3 things that the reactions making up metabolic pathways do
Definition
1. extract energy from nutrients
2. use energy for work
3. store excess energy so that it can be used later
Term
anabolic pathways
Definition
metabolic pathways that synthesize large molecules from smaller ones
Term
catabolic pathways
Definition
metabolic pathways that break large molecules into smaller ones
Term
fed state / absorptive state
Definition
the period of time following a meal, when the products of digestion are being absorbed, used, & stored
Term
fasted state / postabsorptive state
Definition
once nutrients from a recent meal are no longer in the bloodstream & available for use by the tissues
Term
3 things that biomolecules we ingest are destined for
Definition
1. energy
2. synthesis
3. storage
Term
nutrient pools
Definition
nutrients that are available for immediate use
Term
glycogenesis
Definition
the synthesis of glycogen from glucose
Term
lipogenesis
Definition
when additional excess glucose (due to limited glycogen stores) is converted to fat
Term
glycogenolysis
Definition
when the body converts glycogen to glucose if plasma glucose concentrations decrease
Term
gluconeogenesis
Definition
when amino acids can be converted into glucose if glucose intake is low
Term
lipoprotein lipase
Definition
an enzyme bound to the capillary endothelium of muscles & adipose tissue that converts the triglycerides to free fatty acids & glycerol when the lipid complexes begin to circulate through the blood
Term
7 steps of fat synthesis: transport & fate of dietary fats
Definition
1. bile salts help break down dietary fats into components that can be absorbed
2. intestinal epithelial cells assemble absorbed cholesterol, lipoproteins, & lipid complexes into chylomicrons
3. chylomicrons are transported to the blood via the lymphatic vessels
4. lipoprotein lipase converts triglycerides into free fatty acids & glycerol
5. adipose cells reassemble the fatty acids & glycerol into triglycerides for storage
6. chylomicron remnants & HDL-C enter the liver for further processing, creating lipoprotein complexes such as LDL & VLDL
7. LDL-C is transported via the blood to most of the cells, where the cholesterol is used for synthesis
Term
3 steps of fat synthesis: triglyceride & cholesterol synthesis from glucose
Definition
1. glycerol can be made from glucose through glycolysis
2. fatty acids are made when 2-carbon acyl units from acetyl CoA are linked together
3. one glycerol plus 3 fatty acids make a triglyceride
Term
deamination
Definition
the removal of the amino group from the amino acids
Term
4 parts of fasted state metabolism
Definition
1. liver glycogen becomes glucose
2. adipose lipids become free fatty acids & glycerol that enter blood
3. muscle glycogen can be used for energy
4. brain can use only glucose & ketones for energy
Term
urea
Definition
what the liver converts ammonia & ammonium ions into because they are toxic
Term
lipolysis
Definition
when the fasted-state body needs to use stored energy so lipases break down triglycerides into glycerol & fatty acids
Term
4 steps of lipolysis
Definition
1. lipases digest triglycerides into glycerol & 3 fatty acids
2. glycerol becomes a glycolysis substrate
3. beta-oxidation chops 2-carbon acyl units off the fatty acids
4. acyl units become acetyl CoA & can be used in the citric acid cycle
Term
What do excess acyl units become if fatty acid breakdown produces acetyl CoA faster than the citric acid cycle can metabolize it?
Definition
ketone bodies
Term
islets of Langerhans
Definition
small clusters of cells scattered throughout the body of the pancreas; described by Paul Langerhans in 1869
Term
2 things that beta cells produce

*beta cells are a type of islet cells (75%)*
Definition
1. insulin
2. amylin (a peptide)
Term
alpha cells
Definition
the type of islet cells that secrete glucagon; make up 20% of islet cells
Term
D cells
Definition
the type of islet cells that secrete somatostatin
Term
5 factors that influence insulin secretion
Definition
1. increased plasma glucose
2. increased plasma amino acids
3. feedforward effects of GI hormones
4. parasympathetic activity
5. sympathetic activity
Term
insulin-receptor substrates
Definition
proteins that are phosphorylated by activated by insulin receptors
Term
5 steps in insulin's cellular mechanism of action
Definition
1. insulin binds to tyrosine kinase receptor
2. receptor phosphorylates insulin-receptor substrates
3. second messenger pathways alter protein synthesis & existing proteins
4. membrane transport is modified
5. cell metabolism is changed
Term
4 ways insulin lowers plasma glucose
Definition
1. insulin increases glucose transport into most insulin-sensitive cells
2. insulin enhances cellular utilization & storage of glucose
3. insulin enhance utilization of amino acids
4. insulin promotes fat synthesis
Term
What is the most common pathology of the pancreatic endocrine system?
Definition
diabetes mellitus
Term
osmotic diuresis
Definition
the loss of water in the urine due to unreabsorbed solutes
Term
insulin resistance
Definition
the common hallmark of type 2 diabetes; the delayed response to an ingested glucose load seen in the 2-hour oral glucose tolerance test
Term
amylin
Definition
a peptide hormone that is co-secreted with insulin
Term
homeothermic
Definition
bodies that regulate internal temperature within a relatively narrow range
Term
conductive heat gain
Definition
the transfer of heat between objects that are in contact with each other; ex) the skin & a heating pad or the skin & hot water
Term
conductive heat loss
Definition
the loss of body heat to a cooler object that is touching the body; ex) an icepack or a cold stone bench
Term
How must of heat lost from a person at rest in a normal room is accounted for by radiant heat loss?
Definition
nearly half
Term
convective heat loss
Definition
the process in which heat is carried away by warm air rising from the body's surface; enhances radiant & conductive heat loss
Term
evaporative heat loss
Definition
takes place as water evaporates at the skin's surface & in the respiratory tract
Term
2 places where thermoreceptors are located
Definition
1. peripherally in the skin
2. centrally in the anterior hypothalamus
Term
What type of neurons mediate active cutaneous vasodilation?
Definition
sympathetic ACh neurons
Term
shivering thermogenesis
Definition
the body uses shivering to generate heat
Term
nonshivering thermogenesis
Definition
metabolic heat production by means other than shivering
Term
pyrogens
Definition
chemicals released by various immunocytes in response to toxins from bacteria & other pathogens
Term
hyperthermia
Definition
a condition in which body temperature rises to abnormally high values; ex) heat exhaustion & heat stroke
Term
heat exhaustion
Definition
severe dehydration & core body temperatures of 37.5-39 degrees C
Term
heat stroke
Definition
a more severe form of hyperthermia with higher core body temperatures
Term
malignant hyperthermia
Definition
body temperature becomes abnormally elevated due to genetics
Term
hypothermia
Definition
a condition in which body temperature falls abnormally low
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