The control of glucose concentration in the blood. - PowerPoint Presentation

Slide1

The control of glucose concentration in the blood.

Slide2

Hormones

Hormones are produced

by

endocrine

glands.

Endocrine glands secrete hormones

directly into the

bloodstream.

Hormones travel

in the

plasma of the blood until

they arrive at their

target organ or cell

.

Slide3

Target cells have protein receptors on their cell surfaces that are complementary to the hormone.

Hormones can be effective in very low concentrations and often have widespread and long-lasting effects.

Slide4

Slide5

The pancreas and liver are involved in controlling blood glucose level

Slide6

Slide7

The

P

ancreas

The pancreas is both:

an

exocrine gland,

releasing enzymes into the pancreatic duct

an

endocrine gland

secreting hormones from the islets of Langerhans directly into the blood.

Protease, amylase, lipase

Insulin, glucagon

Slide8

Slide9

Islet of Langerhans

Slide10

There are two types of cells in the Islets of Langerhans

α cells – are larger and produce the hormone

glucagon. They also detect a fall in blood glucose level.

β cells – are smaller and produce the hormone

insulin. They also detect a rise in blood glucose level.

Slide11

The Liver

Glycogenesis

Glycogenolysis

Gluconeogenesis

Slide12

Some hints

Gluco

/

glyco

= glucose

Glycogen = glycogen (!)

Neo = new

Lysis = splitting

Genesis = birth/origin

Therefore:

Glycogen – o – lysis = splitting of glycogen

Gluco

-neo-genesis = formation of new glucose

Slide13

Why is glucose needed? Why control the level?

Glucose is needed by all body cells for respiration therefore glucose levels need to be relatively constant.

If the level falls too low, cells will be deprived of energy and die

Slide14

Brain cells are especially sensitive to glucose levels as they can only respire glucose.

If levels are too high the water potential of the blood falls and creates osmotic problems and dehydration

The normal blood glucose concentration in humans is between 82-110mg/

dL

.

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Blood glucose comes from three sources

Directly from the diet in the form of glucose and from the breakdown of other carbohydrates such as starch, maltose, lactose and sucrose.

From the conversion of stored glycogen (in the liver and muscles) to glucose –

glycogenolysis

.

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From gluconeogenesis

, which is the production of new glucose, i.e. glucose from sources other than carbohydrates. E.g. the liver can make glucose from glycerol and amino acids.

Slide17

When you eat carbohydrates…

Your blood glucose level increases.

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The increase in blood glucose is detected by

β

cells in the pancreas

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The beta cells are found in the islets of Langerhans and they release insulin

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Insulin

Insulin circulates in the blood stream and attaches to the cell membranes of liver, muscle and fat-storing cells, it causes…..

The rate of respiration in cells to increase

The conversion of glucose to glycogen which is stored in the liver and muscles-

glycogenesis

. Insulin activates the

enzymes

that convert glucose to glycogen.

The conversion of glucose to fat

Slide21

Causes intracellular enzymes that convert glucose to glycogen and fat to become more active.

These speed up the synthesis of proteins and lipids. Although glucose is the main substance for respiration, some cells also respire components of proteins (i.e. amino acids) and lipids (i.e. glycerol). If fewer of these are available then cells use more glucose and take up more from the blood.

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Overall….

-increased absorption of glucose into cells, especially muscle cells

-increased respiratory rate of cells

-increased conversion of glucose to glycogen (glycogenesis)

-increased conversion of glucose to fat

=reduced glucose levels in the blood

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A decrease in the concentration of glucose in the blood is detected by

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α – cells in the islets of Langerhans

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α – cells in the islets of Langerhans secrete glucagon into the blood

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Only cells of the liver have receptors for glucagon

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Glucagon activates the enzymes that

convert

glycogen to glucose in the liver

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It also increases the conversion of amino acids and glycerol into glucose

Slide29

The role of adrenaline in regulating blood glucose level

Slide30

Adrenaline activates enzymes that causes the breakdown of glycogen to glucose in the liver

Adrenaline also inactivates the enzymes that synthesise glycogen from glucose

Slide31

Summary question answers