|
Homeostasis:
2.
The
negative feedback mechanism involving the hormone insulin for controlling the concentration of blood glucose
Doc Brown's Biology exam study revision notes
Sub-index of notes on homeostasis:
Blood sugar level
control, insulin, diabetes
(2) The
negative feedback mechanism for controlling the concentration of blood glucose
How
does the body control blood sugar level ?
For glucose level read 'the blood concentration of the
sugar glucose' C6H12O6
The pancreas is always checking on the
concentration of glucose in the blood that flows through it.
(a) If your glucose level in the blood is too
high the 1st hormone insulin is secreted by the pancreas.
After a meal the glucose concentration in the
blood rises and insulin causes it to move into the cells in the body for
respiration.
BUT, the insulin also causes cells in liver and
muscle to convert some of the glucose into glycogen - an chemical energy
store.
So, prompted by the pancreas detecting a high
level of blood sugar, the insulin secreted promotes cellular uptake of
glucose for respiration AND the formation of glycogen.
If the glucose concentration is too high, the
pancreas secretes insulin.
Therefore, the conversion of glucose to
glycogen, reduces the glucose concentration in the blood.
When the glucose level reduces, insulin is
no longer secreted by the pancreas and the conversion of glucose to glycogen
stops and the blood glucose level is stabilised.
(b) If the pancreas detects your blood glucose level is too low the 2nd
hormone glucagon is secreted by the pancreas into the bloodstream.
Glucagon makes the liver and muscle cells convert glycogen
into glucose and transported to where it is needed.So the blood level of glucose increases
- it needs to if you are engaged in vigorous exercise!
When the glucose concentration reaches an
appropriate level, secretion of either insulin or glucagon stops and so does the
interconversion of glycogen and glucose, thus stabilising the glucose level.
Note:
(i) Don't mix up or misspell the hormone
glucagon and the
'energy store'
glycogen !
(ii) Insulin hormone reduces glucose level
and glucagon hormone increases glucose level.
(iii) When two effectors or substances work in
opposite ways to restore something in the body to normal, they
are said to be antagonistic.
The two hormones insulin and glucagon are
working antagonistically because they have opposite effects,
but both effects are trying to return the glucose level to normal.
The
control of blood sugar levels is described below in terms of a
'homeostasis mechanism' - a 'negative feedback mechanism' using both a
tabular and graphical representation of the process.
|
The homeostasis negative
feedback system for glucose level control
|
|
(a) The homeostasis negative feedback system for too high a
glucose level - insulin is added |
(b) The homeostasis negative feedback system for too low a
glucose level - glucagon added |
| 1. The
pancreas detects the blood sugar level is too high. |
1. The
pancreas detects the blood sugar level is too low. |
| 2. Insulin is
secreted by the pancreas to mix with the excess glucose. |
2. Glucagon
is secreted by the pancreas. |
| 3. The excess
glucose is now moved from the blood into liver and muscle cells -
triggered by the insulin. |
3. There is
too little glucose but there is glycogen stored in the liver |
| 4. The
glucose level is now reduced to the appropriate level. |
4. The
secreted glucagon triggers the breakdown of glycogen into glucose
sugar - using the liver's energy store. |
| 5. Overall the
secreted insulin makes the liver turn the excess glucose into
glycogen - effectively a store of chemical potential energy for future use. |
5. Overall the
glucose level is increased in the blood to meet the respiration
demands of the body. |
| This
is all automatically done by the organism's complex control
systems and enables the organism e.g. your body, to maintain as near
as possible the 'ideal' glucose level for healthy life!
BUT it all depends on insulin production - and
there may be diabetic problems - read on |
A simplified graphical representation of controlling
the concentration of glucose in blood.
Both the hormones insulin and glucagon are made and
secreted from the pancreas.
Keywords, phrases and learning objectives for this part on the insulin negative
feedback mechanism to control blood sugar level
In terms of homeostasis be able to describe and
explain the negative feedback mechanism involving the hormone
insulin, which is secreted from pancreas, and controls the
concentration of glucose (for respiration) in the blood stream. Be
able to interpret the body's response (insulin feedback mechanism)
from a diagram if the glucose level in the blood becomes too high or
too low.
WHAT NEXT?
TOP OF PAGE
INDEX
of biology notes on
homeostasis: Control of blood sugar level - insulin and diabetes
INDEX of all my BIOLOGY NOTES
BIG website, try using the [SEARCH
BOX], maybe quicker than the many indexes!
Basic Science Quizzes for
UK KS3 science students aged ~12-14, ~US grades 6-8
Biology * Chemistry
* Physics for UK
GCSE level students aged ~14-16, ~US grades 9-10
Advanced Level Chemistry
for pre-university age ~16-18 ~US grades 11-12, K12 Honors
Find your GCSE/IGCSE
science course for more help links to all science revision notes
email doc
brown - comments - query?
Use your
mobile phone or ipad etc. in 'landscape' mode?
SITEMAP Website content © Dr
Phil Brown 2000+. All copyrights reserved on Doc Brown's biology revision notes, images,
quizzes, worksheets etc. Copying of website material is NOT
permitted. Exam revision summaries and references to science course specifications
are unofficial.
Using SEARCH some initial results may be ad links you
can ignore - look for docbrown
|
