Download File - Mr. Shanks` Class

BLOOD
GLUCOSE
CONTROL
Blood glucose control
1. The goal is to maintain the level of glucose within a narrow range.
If there is too little blood glucose, the body cells will not be
able to get enough in and so will be low in energy
If there is too much blood glucose, the body cells will not be able to
get enough in and so will be low in energy
2. Hormones
The hormones insulin and glucagon are the major controllers
The hormones epinephrine and nor-epinephrine plus
glucocorticoids are also involved in control at a minor level
INSULIN
in feedback loops
Liver converts glucose to glycogen
regulators
Body cell uptakes more glucose
coordinator
Beta cells in Islets of
Langerhans release INSULIN
result
Blood sugar drops
sensor
Hypothalamus detects high
blood glucose
high
Blood glucose
Blood glucose
low
sensor
Hypothalamus detects low
blood sugar
Blood sugar rises
results
Alpha cells in the Islets of
Langerhans secrete GLUCAGON
coordinator
regulator
Liver converts
glycogen to glucose
Insulin
increases
fat
storage
Glucagon
increases
fat release
Insulin action
glucose
insulin
insulin
receptor
active
ATP
cAMP
glucose uptake
Insulin action
1. Stimulates glucose uptake into cells thus reducing blood glucose
insulin
insulin
receptor
glucose
active
ATP
cAMP
glucose uptake
Now, skip ahead to “Insulin Actions”
2. Stimulates protein synthesis by increasing amino acid
transport
3. Inhibits liver gluconeogenesis (ie the production of
glucose from non-carbohydrate sources like protein
and fats
4. Inhibits lipid breakdown
5. Inhibits glycogen breakdown and
stimulates glycogen synthesis
CONSEQUENCES OF A LACK OF INSULIN
Hyperglycemia – glucose can’t get into cells and the osmotic
effect of glucose leads to damage to eyes & kidneys
Muscle protein is broken down to release amino acids which are
used to make glucose, leads to muscle wasting
Fats are broken down to convert lipids to glucose [lipolysis]
Diabetic ketoacidosis – breakdown in fat cells leads to
production of free fatty acids and ketone bodies. Can lead to
coma and death
5. Diabetes –
Type I Diabetes
the loss of blood glucose homeostasis
a. person fails to make sufficient insulin
b. Insulin must be added to the system
test
kit
Type II Diabetes
a. The pancreas produces insulin but
body cells do not react to it
b. The body then produces more insulin
c. Eventually the beta cells wear out
and no more insulin is made
d. To prevent this, a person must change
their diet
Diabetic diet control
1. Avoid foods high in sugar
2. Eat complex carbohydrates
3. Eat food high in fibre
4. Keep diet low in fat
5. Eat more, smaller meals
6. Bedtime snacks high in protein
7. Exercise daily
8. Keep caffeine intake low
9. Keep alcohol intake low
6. Short term changes in blood sugar
a. Blood glucose is regulated over time by insulin &
glucagon but sometimes the body needs a sudden
burst of glucose
b. These responses are called stress responses and they
elevate blood glucose only, there is no hormone to
lower blood glucose in these responses
c. Because this is not a feedback loop, stress can continue
and problems will result [pg 389 Table 2]
d. Stress responses [next slide]
Stress sensed by brain
Short-term
Hypothalamus responds
Spinal chord
nerves stimulate
Adrenal gland
medulla
Epinephrine &
norepinephrine
released
Glycogen  glucose
Long term
Pituitary gland releases
ACTH to stimulate
Adrenal gland
cortex
Glucocorticoids
released
Amino acids  glucose
Fats  fatty acids
Fatty acids  glucose
Blood glucose increased
Blood glucose increased
The glycemic index (GI)
a numerical system of measuring how much of a rise in
circulating blood sugar a carbohydrate triggers
the higher the number, the greater the blood sugar
response.
food type
GI
roasted peanuts
14
milk chocolate
49
skim milk
31
white rice
98
french fries
75
baked potato
85
potato chips
54
dates
fresh pineapple
103
61
Patterns of blood sugar
over time for non diabetics & diabetics
Blood glucose over time for different conditions.
B
L
O
O
D
C
G
L
U
C
O
S
E
B
A
D
0
1
2
3
4
5
TIME
A- Normal response because blood glucose stays within a narrow range
B. Type II Diabetic response because blood glucose does respond to hormones, but is slow to do so
C. Type I Diabetic response / no insulin because blood glucose is falling very slowly
D. Type I Diabetic response / Insulin at 2.5 because blood glucose does fall after 2.5
The Hunger
Hormone:
GHRELIN
Ghrelin Discovery
Ghrelin was first described in 1999.
They chose the name ghrelin because
"ghre" is the Proto-Indo-European root of
the word "grow," as ghrelin also
stimulates the pituitary gland to release
growth hormone.
Ghrelin
Cells in the stomach secrete ghrelin.
The hormone ghrelin
stimulates appetite
Insulin and leptin suppress
appetite
The rise in blood sugar following a meal causes an
increase in insulin.
The rise in insulin depresses ghrelin and so the
desire to eat more is reduced.
People with lower insulin levels suppress ghrelin
less and so are hungrier more often.
Fluctuations in blood ghrelin levels.
Fat cells secrete leptin which decreases ghrelin
levels.
Basically having extra body
fat signals the body to
accumulate less extra fat.
Eating the same amount of calories of fat as of
carbohydrate results in less suppression of ghrelin.
This means that a diet high in fat leaves you hungrier!
Not all carbohydrates are equal at suppressing ghrelin.
Drinks sweetened with fructose
suppress ghrelin 50% as much as
those sweetened with glucose.
People who drink fructose drinks
are more likely to choose fatty
foods to accompany them and
ghrelin may be involved in this.
When people diet, their
ghrelin levels rise as the
body tries to replace
lost calories.
I’ve found this great new
dieting technique that really
works
Surprisingly, people with naturally high blood levels
of ghrelin tend to be slimmer than those with lower
levels.
People who are obese tend
to have less responsive
ghrelin levels, so that eating
does not reduce their desire
to eat more.
More
ghrelin
please
A lack of sleep has been shown to alter people’s
eating habits.
Just two nights of getting only 4 hours of sleep
increased ghrelin levels by almost 30%.
Researchers are working on drugs to reduce ghrelin
levels as possible ‘diet pills’.
Maybe people just have to realize that they are not all
the same height so they have to accept that they will not
all be the same weight!