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Homeostasis > Hormones and Control of Blood-Glucose Concentration > Flashcards

Hormones and Control of Blood-Glucose Concentration Flashcards

1
Q

What is Homeostasis ?

A

In mammals involves a physiological control system that maintain the internal environment within restricted limits.

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2
Q

What is positive feedback ?

A

a change from the normal level is detected and triggers a response which accentuates the change and takes it further from the norm.

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3
Q

Give 3 examples of Negative Feedback

A

Temperature and pH
Heart Rate
Blood-glucose concentration

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4
Q

What is negative feedback ?

A

a change from normal level is detected and triggers a response which opposes or reverses the change in order to restore the normal level.

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5
Q

Why must temperature and pH be controlled ?

A

Enzymes and proteins are sensitive to changes in temperature and pH.
changes could reduce the efficiency of enzymes or denature them.

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6
Q

Why must water potential of blood be controlled ?

A

changes in water potential could cause cells to shrink or expand due to water entering or leaving by osmosis.

could cause cells to burst.

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7
Q

Why must blood glucose concentration be controlled

A

a constant blood glucose concentration is needed to maintain a constant water potential

a reliable source of glucose is needed by the cells for respiration.

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8
Q

What is glycogenesis ?

A

making glycogen from glucose/
involves activation of enzymes in the liver and muscle that convert glucose to glycogen via a condensation reaction.

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9
Q

What is glycogenolysis ?

A

Hydrolysis of glycogen to glucose.

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10
Q

What is gluconeogenesis ?

A

conversion of non-carbohydrate molecules to glucose.

making glucose from other sources such as amino acids, fatty acids, glycerol.

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11
Q

What are three sources of Blood Glucose ?

A

absorption from the gut following digestion of carbohydrates in the diet.

Glycogenolysis

Gluconeogenesis.

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12
Q

Why is it bad if blood glucose levels fall too low ?

A

cells will be deprived of energy and die.

brain cells can only respire glucose.

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13
Q

why is it bad if blood glucose levels rise too high

A

If the concentration of glucose in the blood rises too high, it lowers the water potential of the blood and can cause cells to lose water.
Resulting in dehydration.

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14
Q

Which hormone does alpha cells secrete ?

A

GLUCAGON

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15
Q

Which hormone does beta cells secrete ?

A

INSULIN

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16
Q

Where are alpha and beta cells found ?

A

ISLETS OF LANGERHANS IN THE PANCREAS

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17
Q

How does insulin increase the uptake of glucose from the blood by facilitated diffusion ?

A

Insulin binds to specific receptors on the membranes of target cells.

This stimulates them to add more glucose transporter proteins to their cell surface membrane which increases the permeability of the cells to glucose.
(vesicles fuse with the cell membrane)

As a result, the rate of facilitated diffusion increases

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18
Q

what are the target cells of insulin ?

A

liver cells
muscle cells
adipose cells

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19
Q

What is the response to an increase in plasma glucose concentration ?

A

Increase blood glucose concentration detected by beta cells.

stimulate increased secretion of insulin from beta cells.

more insulin binds to receptors on liver, muscle, adipose cells
causes more glucose transporter proteins to become active and move to the plasma membrane.

insulin increases the permeability of liver/ muscle cells to glucose.
Glucose moves by facilitated diffusion into cells down a concentration gradient.

Insulin activates enzymes in liver and muscle cells to convert glucose to glycogen-glycogenesis

insulin activates enzymes in adipose tissue to convert glucose to fat
raises rate of respiration of cells using more glucose.

20
Q

how is insulin production stimulated in beta cells ?

A

the plasma membranes of the beta cells have protein carriers which transports glucose into the cells by facilitated diffusion. This stimulates vesicles of insulin to move to the membrane and release insulin into the capillaries.

21
Q

which hormone increases blood glucose levels ?

A

GLUCAGON

22
Q

which hormone decreases blood glucose levels ?

A

INSULIN

23
Q

Insulin causes an increase in the number of glucose carrier molecules in the cell membranes of muscle and adipose cells. How does this lower blood glucose levels

A

The rate of uptake of glucose from the blood by facilitated diffusion is greatly increased.

23
Q

Insulin causes activation of enzymes in the liver and muscle that convert glucose (phosphate) to glycogen. How does this lower blood glucose level ?

A

Maintains a steep diffusion gradient between the blood and the cells so increases the rate of uptake.

24
Q

Insulin causes activation of enzymes in adipose tissue to convert glucose to fat. How does this lower blood glucose level ?

A

Maintains a steep diffusion gradient between the blood and the cells so increases the rate of uptake.

25
Q

How does glucagon raise blood glucose levels ?

A

Glucagon causes activation of enzymes in the liver that break down stored glycogen into glucose (Glycogenolysis)

Activation of enzymes in the liver that convert other substances e,,g glycerol, amino acids into glucose (Gluconeogenesis)

This raises levels as Glucose is released from the liver into the bloodstream.

26
Q

Which type of cells does Glucagon effect ?

A

liver cells

27
Q

What is the response to a fall in plasma glucose concentration ?

A

decrease in plasma glucose concentration detected by hypothalamus.
secretion of glucagon from alpha cells.
Binds to specific receptors on cell surface membrane of liver/muscle cells
activation of adenyl cyclase in liver
converts ATP to CAMP
CAMP activates protein kinase A
hydrolysis of glycogen to glucose in liver cells
also activates enzymes for gluconeogenesis
leads to formation of glucose from non-carbohydrate molecules
facilitated diffusion of glucose out of liver cells.

28
Q

What is the name of the model that Glucagon and Adrenaline use ?

A

The Second Messenger Model

29
Q

What is Adrenaline ?

A

a Hormone which raises blood glucose levels in times of stress

30
Q

Explain how Adrenaline works by the Second Messenger Model.

A

Adrenaline binds to specific receptors on the cell surface membrane of the target cell to form a hormone-receptor complex.
A protein changes on the inside of the membrane.
The hormone-receptor complex activates an enzyme on the inside of the membrane called adenylyl cyclase.
This converts ATP into CAMP by removing 2 phosphate groups.
cAMP acts as a second messenger.
Binds to protein kinase enzyme-
Protein Kinase changes shape and is activated
Glycogen is hydrolysed to glucose
Therefore blood glucose concentration increases.

31
Q

What is type 1 diabetes ?

A

Auto-immune disease resulting in no production of insulin.

32
Q

Who has type 1 diabetes ?

A

begins in childhood

33
Q

What is the cause of type 1 diabetes ?

A

the body’s T-cells attack and destroy the beta cells so there is a shortage of insulin.

34
Q

What are the effects and symptoms of type 1 diabetes ?

A

Blood glucose concentration rises to very high levels after a meal- can affect the brain and lead to a coma or death
Kidneys cannot absorb all the glucose, so glucose appears in the urine.
Glucose in urine results in less water being reabsorbed so urinate frequently and feel thirsty.
Tiredness and weight loss

35
Q

What is the treatment of type 1 diabetes ?

A

Blood glucose levels monitored with Biosensors
injections of insulin- is a protein so cannot be taken by mouth as would be digested
Carbohydrate intake and exercise also need to be carefully managed.

36
Q

What can happen if a diabetic takes too much insulin ?

A

This could lower the blood glucose levels too much, resulting in unconsciousness.

37
Q

What is type 2 diabetes ?

A

Disease caused by a lack of responsiveness in cells to insulin

38
Q

What are the two different causes of type 2 diabetes ?

A

Glycoprotein receptors in the body, especially in the liver and fat storage tissue, lose their responsiveness to insulin.
May also be due to an inadequate supply of insulin from the pancreas.

39
Q

Who tends to have type 2 diabetes ?

A

tends to occur in over 40s but becoming more common in obese adolescents.

40
Q

what are the effects and symptoms of type 2 diabetes ?

A

Tiredness, blurred vision and sugar in the urine are possible symptoms.
symptoms develop slowly and may go unnoticed.

41
Q

What is the treatment of type 2 diabetes ?

A

Regulate the intake of carbohydrate in the diet- avoid sugary food or forms of starch that rapidly increase blood glucose concentration
Fat content of the diet needs to be kept low
Exercise is also needed to improve the body’s sugar metabolism.
Drugs may be needed to stimulate insulin production.
Insulin injections may be necessary.

42
Q

After glucagon is secreted from alpha cells it is broken down in a matter of minutes what is the advantage of this ?

A

It prevents glucagon from having a prolonged effect; [1 mark]
So blood glucose concentration does not increase too much / too high; [1 mark]

43
Q

Explain why it is advantageous for adrenaline to be amplified through a second messenger

A

Each molecule of hormone (adrenalin) can produce many molecules of cAMP; [1 mark]
And these in turn activate large numbers of enzymes; [1 mark]
This means that (blood) glucose concentration is raised very quickly; [1 mark]

44
Q
A

Homeostasis (2 decks)

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