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Biology > Homeostasis- Control of Blood Glucose Concentration > Flashcards

Homeostasis- Control of Blood Glucose Concentration Flashcards

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1
Q

Why must blood glucose concentration be carefully controlled?

A

Because all cells need a constant energy supply to work

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2
Q

How is blood glucose concentration monitored?

A

By cells in the pancreas

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3
Q

When does blood glucose concentration rise?

A

After eating food containing carbohydrate

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4
Q

When does blood glucose concentration fall?

A

After exercise, as more glucose is used in respiration to release energy

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5
Q

How is blood glucose concentration controlled?

A

By insulin and glucagon

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6
Q

How is insulin secreted?

A

By Beta cells in the islets of Langerhans in the pancreas

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7
Q

How is glucagon secreted?

A

By Alpha cells in the islets of Langerhans in the pancreas

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8
Q

What does insulin do?

A

Lowers blood glucose concentration when it’s too high

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9
Q

How does insulin lower blood glucose concentration?

A
  1. Insulin binds to specific receptors on cell membranes of liver cells and muscle cells
  2. Increases permeability of muscle cell membranes to glucose so cells take up more glucose- involves increasing number of channel proteins in cell membranes
  3. Also activates enzymes in liver and muscle cells that convert glucose into glycogen
  4. Cells are able to store glycogen in cytoplasm as an energy store
  5. Glycogenesis= forming glycogen from glucose
  6. Insulin also increases rate of respiration of glucose
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10
Q

What does glucagon do?

A

Raises blood glucose concentration when it’s too low

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11
Q

How does glucagon raise blood glucose concentration?

A
  1. Glucagon binds to specific receptors on cell membranes of liver cells
  2. Activates enzymes in liver cells that break down glycogen into glucose
  3. Glycogenolysis= breaking down glycogen
  4. Also activates enzymes involved in formation of glucose from glycerol and amino acids
  5. Gluconeogenesis= forming glucose from non-carbohydrates
  6. Glucagon decreases rate of respiration of glucose
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12
Q

What is glycogenesis?

A

Process of forming glycogen from glucose

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13
Q

What is glycogenolysis?

A

Breaking down glycogen

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14
Q

What is gluconeogenesis?

A

Forming glucose from non-carbohydrates

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15
Q

Why are responses produced by hormones slower than those produced by nervous impulses?

A

Because hormones travel in the blood

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16
Q

Why do effects from hormones last longer?

A

They are not broken down as neurotransmitters are

17
Q

How do negative feedback mechanisms work when they detect a rise in blood glucose concentration?

A
  1. Pancreas detects blood glucose concentration is too high
  2. Beta cells secrete insulin and alpha cells stop secreting glucagon
  3. Insulin binds to receptors on liver and muscle cells
  4. Cells take up more glucose, glycogenesis is activated, cells respire more glucose
  5. Less glucose in the blood —> return to normal blood glucose concentration
18
Q

How do negative feedback mechanisms work when they detect a fall in blood glucose levels?

A
  1. Pancreas detects blood glucose concentration is too low
  2. Alpha cells secrete glucagon and beta cells stop secreting insulin
  3. Glucagon binds to receptors on liver cells
  4. Glycogenolysis is activated, gluconeogenesis is activated, cells respire less glucose
  5. Cells release glucose into the blood —> return to normal blood glucose concentration
19
Q

What is GLUT4?

A

A glucose transporter- a channel protein in skeletal and cardiac muscle cells

20
Q

When is GLUT4 stored in vesicles in the cytoplasm of cells?

A

When insulin levels are low

21
Q

When is the movement of GLUT4 to the membrane triggered?

A

When insulin binds to receptors on the cell-surface membrane

22
Q

How is glucose transported into the cell?

A

Through the GLUT4 protein by facilitated diffusion

23
Q

What is adrenaline?

A

A hormone secreted from your adrenal glands

24
Q

When is adrenaline secreted?

A

When there’s a low concentration of glucose in your blood, when your stressed and when your exercising

25
Q

What does adrenaline do when it binds to receptors in the cell membrane of liver cells?

A

It activates glycogenolysis and inhibits glycogenesis

26
Q

How does adrenaline increase glucose concentration?

A

Activates glucagon secretion and inhibits insulin secretion

27
Q

How does adrenaline get the body ready for action?

A

By making more glucose available for muscles to respire

28
Q

How do adrenaline and glucagon act via a secondary messenger?

A
  1. Receptors for adrenaline and glucagon have specific tertiary structures that make them complementary in shape to their respective hormones- adrenaline and glucagon bind to their receptors and activate an enzyme called adenylate cyclase (adenylyl cyclase)
  2. Activated adenylate cyclase converts ATP into a chemical signal (second messenger)
  3. Second messenger called cyclic AMP (cAMP)
  4. cAMP activates enzyme called protein kinase A. Protein kinase A activates a cascade (chain of reactions) that breaks down glycogen into glucose (glycogenolysis)
29
Q

What is type I diabetes?

A

Immune system attacks beta cells in islets of Langerhans so they can’t produce any insulin

30
Q

What is the cause of type I diabetes?

A

Unknown for sure, genetic predisposition, may be caused by a viral infection

31
Q

What is hyperglycaemia?

A

Blood glucose level rises and stays high after eating

32
Q

How is type I diabetes treated?

A

Insulin therapy- regular insulin injections throughout the day or an insulin pump to continuously deliver insulin

33
Q

What is hypoglycaemia?

A

A dangerous drop in blood glucose levels

34
Q

What can help avoid a sudden rise in glucose?

A

Eating regularly and controlling simple carbohydrate intake

35
Q

What are risk factors in type II diabetes?

A

Obesity, family history, lack of exercise, age, poor diet

36
Q

What is type II diabetes?

A

When beta cells don’t produce enough insulin or don’t respond properly to insulin

37
Q

Why don’t cells respond properly to insulin in someone with type II diabetes?

A

Insulin receptors on their membranes don’t work properly so cells don’t take up enough glucose

38
Q

How can type II diabetes be treated?

A

By eating a healthy, balanced diet, losing weight and regular exercise

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