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OCR Biology Paper 1 > 5.4 - Hormonal Communication > Flashcards

5.4 - Hormonal Communication Flashcards

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1
Q

Define hormone

A
  • Chemical messenger that triggers response in target cells
  • Sends information about changes in environment around body
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2
Q

Define endocrine gland

A
  • Group of specialised cells
  • Secrete hormones into bloodstream
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3
Q

Define endocrine system

A

Series of endocrine glands around the body

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4
Q

Describe the difference between an endocrine gland and an exocrine gland

A
  • Endocrine gland secretes hormones directly into bloodstream
  • Exocrine gland secretes chemicals through ducts into organs
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5
Q

Where is insulin secreted from and what is its function?

A
  • Insulin is secreted from the beta cells of the pancreas.
  • It decreases blood glucose concentration.
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6
Q

Where is glucagon secreted from and what is its function?

A
  • Glucagon is secreted from the alpha cells of the pancreas.
  • It increases blood glucose concentration.
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7
Q

Where is adrenaline secreted from and what is its function?

A
  • Adrenaline is secreted from the adrenal medulla.
  • Adrenaline increases heart and breathing rate, and raises blood glucose level.
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8
Q

Where is ADH secreted from and what is its function?

A
  • ADH is secreted from the pituitary gland.
  • It increases water reabsorption in the kidneys.
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9
Q

Describe how hormones travel around the body to target cells

A
  • Secreted into blood stream by endocrine gland
  • Travel in blood plasma to target cell
  • Bind to specific receptors on target cell
  • Trigger target cells to produce response
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10
Q

Describe how steroid hormones trigger an effect in target cells

A
  • Lipid soluble
  • Diffuse through phospholipid bilayer
  • Bind to steroid hormone receptors inside cell
  • e.g. in cytoplasm, in nucleus
  • Hormone-receptor complex forms
  • Acts as transcription factor
  • Facilitates or inhibits transcription of specific gene
  • e.g. oestrogen
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11
Q

Describe how non-steroid hormones trigger an effect in target cells

A
  • Hydrophilic so cannot pass through phospholipid bilayer
  • Bind to specific receptors on cell surface membrane of target cell
  • Triggers cascade reaction mediated by secondary messengers
  • e.g. adrenaline
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12
Q

Where are the adrenal glands located?

A

On top of each kidney

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13
Q

Describe the structure of the adrenal glands

A

Medulla
- Inner region of gland
- Produces adrenaline, noradrenaline

Cortex
- Outer region of gland
- Produces cortisol, aldosterone

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14
Q

How is the production of hormones in the adrenal cortex controlled?

A

By hormones released from pituitary gland

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15
Q

Outline the three main types of hormone produced by the adrenal cortex

A

Glucocorticoids
- e.g. cortisol - helps regulate metabolism and blood pressure
- e.g. corticosterone - regulates immune response

Mineralocorticoids
- e.g. aldosterone - controls blood pressure

Androgens
- Male and female sex hormones

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16
Q

Outline the hormones secreted by the adrenal medulla

A

Adrenaline
- Increases heart rate
- Raises blood glucose concentration

Noradrenaline
- Works with adrenaline in response to stress
- Increases heart rate, widens pupil, widens air passages

Both released when sympathetic nervous system is stimulated

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17
Q

Outline the main roles of the pancreas

A
  • Produces and secretes enzymes for digestion
  • Produces hormones to control blood glucose concentrations
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18
Q

Which endocrine tissue is responsible for producing and secreting insulin and glucagon?

A

Islets of Langerhans

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19
Q

Which cells in the islets of Langerhans produce glucagon?

A

Alpha (⍺) cells

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20
Q

Which cells in the islets of Langerhans produce insulin?

A

Beta (β) cells

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21
Q

What is the role of the pancreatic acini?

A
  • Acts as exocrine glandular tissue
  • Produces digestive enzymes and pancreatic juice
  • Enzymes and pancreatic juice secreted into ducts
  • Travel through ducts to small intestine
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22
Q

Explain how the pancreas acts as both an endocrine and exocrine gland

A

Endocrine
- Produces insulin and glucagon hormones
- ⍺ cells secrete glucagon
- β cells secrete insulin
- Hormones secreted directly into bloodstream

Exocrine
- Produces enzymes for digestion (amylase, protease, lipase)
- Releases enzymes via a duct into the small intestine

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23
Q

Define glycogenolysis

A
  • Glycogen stored in liver and muscle cells broken down into glucose
  • Glucose released into blood stream
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24
Q

Define gluconeogenesis

A
  • Production of glucose from non-carbohydrate sources
  • e.g. from glycerol and amino acids in the liver
25
Q

Outline how blood glucose concentration can be increased

A
  • Diet - eating carbohydrate-rich food
  • Glycogenolysis
  • Gluconeogenesis
26
Q

Define glycogenesis

A
  • Production of glycogen from glucose
  • Glycogen stored in liver
27
Q

Outline how blood glucose concentration can be decreased

A
  • Respiration - glucose used to produce ATP
  • Glycogenesis
28
Q

Describe the effect of insulin on other cells

A
  • All cells (except red blood cells) have receptors for insulin on cell surface membrane
  • Binding of insulin to receptor causes change in tertiary structure of glucose protein channels
  • Channels open so more glucose enters cell
  • Insulin activates enzymes that convert glucose to glycogen
29
Q

Explain how insulin lowers blood glucose levels once secreted

A
  • Causes glucose channel proteins to open - Increases rate of absorption of glucose by cells
  • Increases respiratory rate
  • Increases rate of glycogenesis in liver
  • Increases rate of glucose to fat conversion
  • Inhibits release of glucagon from ⍺ cells
30
Q

Where is insulin broken down?

A

Liver

31
Q

When is most insulin secreted?

A

Soon after eating

32
Q

What happens when high blood glucose concentration returns to normal?

A
  • Detected by β cells in pancreas
  • Secretion of insulin reduced
  • Example of negative feedback
33
Q

Describe the effect of glucagon on other cells

A
  • Produced by alpha cells in pancreas
  • If blood glucose concentration too low, ⍺ cells in islet of Langerhans detect fall and secrete
    glucagon into bloodstream
  • Only liver and fat cells have receptors for glucagon on cell surface membrane
  • Binding of glucagon to receptor causes cascade of reactions inside liver and fat cells
34
Q

Explain how glucagon raises blood glucose levels once secreted

A
  • Promotes glycogenolysis - Liver breaks down glycogen into glucose
  • Reduces amount of glucose absorbed by liver cells
  • Increases gluconeogenesis - Increases conversion of amino acids and glycerol into glucose - Takes place in liver
  • Inhibits release of insulin from β cells
35
Q

What happens when low blood glucose concentration returns to normal?

A
  • Detected by ⍺ cells in pancreas
  • Secretion of glucagon reduced
  • Example of negative feedback
36
Q

Describe how negative feedback is used to control blood glucose concentration

A
  • β cells and ⍺ cells detect change in blood glucose concentration

If higher glucose concentration, β cells release insulin
- Causes increased uptake of glucose by effector cells
- Glucose converted to glycogen via glycogenesis
- Use of glucose in respiration increased
- Blood glucose concentration falls, less insulin released

If lower glucose concentration ⍺ cells release glucagon
- Causes increased conversion of glycogen to glucose via glycogenolysis
- Increased conversion of amino acids and lipids to glucose via gluconeogenesis
- Glucose leaves cells by facilitated diffusion through glucose channels
- Blood glucose concentration increases, less glucagon released

37
Q

Explain the mechanism by which insulin is released from β cells

A

When blood glucose concentration increases:
- Glucose moves into cell through glucose transporter protein
- Glucose metabolised inside mitochondria
- Produces ATP (via aerobic respiration)
- ATP binds to ATP-sensitive potassium channels
- Causes potassium channels to close
- K+ ions cannot diffuse out of cell
- Potential difference falls
- Depolarisation occurs
- Depolarisation causes voltage-gated calcium channels to open
- Ca2+ ions enter cell
- Cause vesicles to release insulin by exocytosis

38
Q

Explain how insulin is stored in β cells when blood glucose concentration is normal

A

Normal blood glucose concentration:
- Potassium channel in plasma membrane of β cells are open
- K+ ions diffuse out of cell
- Resting potential of -70mV maintained
- Insulin stored within vesicles

39
Q

Explain why β cells continue to secrete insulin even when there is no further glucose intake

A
  • Continues to be secreted as long as blood glucose concentration remains high
  • Sufficient ATP still present and so K+ channels remain closed
  • Exocytosis still being triggered by Ca2+
40
Q

What is diabetes?

A

Inability to control blood glucose levels properly

41
Q

What are the two types of diabetes?

A
  • Type I - early-onset
  • Type II - late-onset
42
Q

Describe the cause of Type 1 diabetes

A
  • Immune system destroys beta cells of pancreas
  • Insulin no longer secreted
  • Can be hereditary or triggered by environmental factor (e.g. infection, cancer)
43
Q

Describe the treatment of Type 1 diabetes

A
  • Regular insulin injections
  • Blood glucose levels monitored
44
Q

Define hyperglycaemic

A

Blood glucose concentration too high

45
Q

Define hypoglycaemic

A

Blood glucose concentration too low

46
Q

Why is careful monitoring of blood glucose concentration necessary with Type I diabetes?

A
  • Blood glucose concentration varies throughout the day
  • e.g. increased exercise will cause blood glucose concentration to decrease
  • Knowing exact blood glucose concentration ensures correct dose of insulin given
  • If too low a dose they will remain hyperglycaemic
  • Can result in death if left untreated
  • If too high a dose they can become hypoglycaemic
  • Can result in a coma/unconsciousness
47
Q

Describe the cause of Type II diabetes

A
  • Insulin continues to be produced
  • Target cells in liver are unable to respond to insulin
48
Q

Describe the treatment of Type II diabetes

A

Careful control of diet

49
Q

List features that would increase a person’s risk of developing Type II diabetes

A
  • Obesity
  • Sedentary lifestyle
  • High intake of sugar
  • Genetic predisposition
  • Increasing age
  • High blood pressure
50
Q

List the symptoms of Type II diabetes

A
  • Decreasing responsiveness to insulin
  • High blood glucose
  • Glucose in urine
  • Loss of weight / tiredness
  • Increased production of urine
  • Dehydration and thirst
51
Q

Explain the dietary advice that should be given to a patient who has developed Type II diabetes

A
  • Regulate diet/total calorie intake and exercise
  • Ensures a balanced energy budget
  • Low fat diet
  • Avoid weight gain
  • Consume complex carbohydrates
  • Ensure gradual release of glucose into blood
  • Eat regular small meals
  • Ensure a steady supply of glucose
  • Do not go for long periods without meals
  • Avoid large drop in blood glucose
  • Consume foods with low glycemic index
  • Avoid abrupt changes in blood glucose
52
Q

How was insulin originally obtained for medical use?

A

From pancreas of slaughtered pigs and cows

53
Q

How is insulin produced today?

A

Genetic modification of bacteria

54
Q

Why is insulin from genetically modified bacteria more effective than pig/cow insulin?

A
  • Bacteria produce human insulin
  • Cow/pig insulin may have different structure
  • Receptors for insulin in human not fully complementary to pig/cow insulin
55
Q

State the advantages of treating Type I diabetes by using insulin that has been produced by
genetically modified bacteria rather than insulin that has been extracted from pigs

A
  • Plentiful and dependable supply
  • Cheap to manufacture
  • Not cruel to pigs
  • No religious objections
  • Reliable quality
  • Human insulin produced so no allergic reaction
56
Q

What type of stem cells are required for stem cell therapy of Type I diabetes?

A

Totipotent stem cells

57
Q

Where are totipotent stem cells extracted from?

A
  • Human embryos
  • From infertility treatments or terminated pregnancies
58
Q

Why is stem cell therapy still not widely used?

A
  • Technology still being developed
  • Ethical concerns over use of embryos
  • Unknown whether uncontrolled cell growth could occur
  • Causing tumour formation

OCR Biology Paper 1 (20 decks)

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