Video Transcript
A blood sample was collected from a
healthy man two hours after eating. What are the results most likely to
show? (A) An increase in glucagon
secretion. (B) An increase in glucose levels
in the blood sample. (C) A decrease in insulin
secretion. Or (D) all of the answers are
correct.
This question asks us about a blood
sample that is taken from a healthy male two hours after he consumes a meal. Let’s review what usually happens
to the concentrations of glucagon, glucose, and insulin in the blood after ingesting
a meal to answer this question correctly.
Humans obtain their nutrition by
consuming food. An essential nutrient that we
require in this food is carbohydrate. Carbohydrates are broken down in
the digestive system into smaller sugars, such as glucose. Glucose is an essential molecule in
humans as it is used in cellular respiration, which is how the body’s cells release
energy for various vital cellular processes.
After consuming a meal, the levels
of glucose in the blood will begin to rise within the first and second hours, as
large carbohydrates in our food are broken down into glucose. And this glucose is subsequently
absorbed into the bloodstream. While glucose is essential for
cellular respiration to release energy, when glucose levels are too high, this can
damage body tissues and be more harmful than beneficial.
In order to counteract high blood
glucose levels, an organ called the pancreas usually secretes a hormone called
insulin around two hours after a meal is consumed. This delay in insulin secretion
occurs because the food needs to be broken down and absorbed into the bloodstream
before the body can detect that the levels are too high. Ultimately, insulin will help to
lower blood glucose levels. For example, insulin stimulates the
body cells to take up more glucose from the blood and store it as glycogen. As insulin will increase in the
blood a short while after a meal, not decrease, we can deduce that answer option (C)
is incorrect.
If a person does not eat for an
extended time, for example, during periods of fasting, their blood glucose levels
will become low, which causes the pancreas to release a different hormone called
glucagon. This hormone will help to raise
blood glucose levels back to an optimal, healthy range, partly by stimulating the
breakdown of glycogen stores in cells and releasing this free glucose that is
produced into the bloodstream. As glucagon will only be secreted
if blood glucose levels fall below a healthy range, and not following a meal, we can
deduce that answer (A) is incorrect.
We know that following a meal blood
glucose levels will rise as large carbohydrates are broken down in the digestive
system. So we have found the correct
answer. A blood sample collected from a
healthy person two hours after eating is most likely to show (B): an increase in
glucose levels in the blood sample.
