VirtualPhysiologist.com
Metabolism
Glycolysis is the metabolic breakdown of
sugar, thus releasing energy in the form of
ATP (adenosine triphosphate, a
neurotransmitter and the major energy
source within cells that drive muscle
contraction and protein synthesis)
How does the metabolic system work?
Our bodies are complex, powerful machines.
All machines need energy to do work. Every
single cell in our body serves some function,
and each cell needs this energy in order to
fulfill their unique function. How we utilize
this energy is through our metabolism; it is
how we take the energy from the food we eat
(and drink) and convert it into energy that our
bodies can use. The main source of energy in
the human body is glucose.
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Major players in the human metabolic
system include:
The gastrointestinal tract is a long, hollow
tube with specialized sections that each serve
different functions. It begins at the mouth
and ends at the anus. The mouth manually
breaks down food, the stomach begins to
digest and chemically break down food, the
small intestine finishes digesting and begins
absorbing food, and the large intestine
absorbs the final nutrients, water, and sends
the waste to the anus for excretion.
The pancreas provides the enzymes needed
for the GI tract to digest different
macronutrients. The pancreas also produces
several essential hormones, two of which are
glucagon and insulin. Glucagon is released
when our blood sugars are low (when we are
fasting). It tells our bodies that we need
energy, and begins breaking down fat, muscle,
and glycogen (the short-term storage form of
glucose) to use for energy. Insulin is the
opposite; it is produced when we are in a fed
state. It tells our bodies that we are full, and
to store the excess glucose (as glycogen or
fat).
The liver is a multifunctional organ. It stores
and breaks down glucose (in glycogen or
triglyceride form), produces bile (the fluid
needed to absorb cholesterol), produces and
breaks down proteins, manages the
cholesterol, triglycerides and lipoproteins
(transporters of fat) found in our blood,
detoxifies, and stores several vitamins,
among many other functions.
The gallbladder stores and excretes the bile
that was produced in the liver. Bile is
essential to digest and absorb fats.
The thyroid produces T3 and T4, the
hormones that affect the rate of our
metabolism.
The cardiovascular system delivers blood
(with nutrients) to all of the cells in our body.
The heart pumps the blood, the veins and
arteries are the highways that deliver the
blood throughout the body, and the
capillaries disperse the blood to each
individual cell.
The hypothalamus receives the hormonal
signals that alarm us when we are hungry or
full. Leptin tells us that we are full and speeds
up our metabolic rate. Ghrelin tells us that we
are hungry and prompts us to eat; it also
slows down our metabolic rate.
When any of these major players are not
working harmoniously, our metabolic health
is affected. Non-alcoholic fatty liver disease,
high LDL levels, plaque formation in the
arteries, and insulin blockage of the leptin
pathway are all examples of metabolic
disharmony.