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A2 Biology > Hormonal Communication > Flashcards

Hormonal Communication Flashcards

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1
Q

What is a hormone?

A

Molecules that are released by endocrine glands directly into the blood, acting as messengers, carrying a signal from the endocrine gland to a specific target organ or tissues.

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2
Q

What are the two types of hormone?

A
  • Protein and peptide hormones

- Steroid hormones

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3
Q

Name 3 examples of Protein hormones

A
  • Adrenaline
  • Insulin
  • Glucagon
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4
Q

Name 2 examples of Steroid hormones

A
  • Oestrogen

- Testosterone

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5
Q

How do Protein hormones act?

A

They’re not soluble in the phospholipid membrane so don’t enter the cell. They need to bind to the cell surface membrane and release a second messenger inside the cell.

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6
Q

How to Steroid hormones act?

A

They can pass through the membrane and enter the cell and the nucleus, to have a direct effect on the DNA in the nucleus.

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7
Q

Why are endocrine glands described as ductless?

A

They consist of groups of cells that manufacture and release the hormone directly into the blood in capillaries running through the gland.

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8
Q

Cells that receive an endocrine signal are called what?

A

Target Cells

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9
Q

Name a place that target cells are grouped together in a target tissue

A

Eg. Epithelium of the collecting ducts

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10
Q

What must the target cells of non-steroid hormones posses?

A

A specific receptor on their plasma membrane that is complementary to the shape of the signalling molecule (hormone).

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11
Q

What does the necessity of a complementary surface receptor enable hormones to do?

A

Hormones can be carried in the blood without affecting cells that do not posses the correct specific receptor.

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12
Q

Which hormones are known as first messengers?

A

Non-steroid hormones

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13
Q

What does a first messenger usually stimulate?

A

Stimulate the release of another signalling molecule inside the cell, a secondary messenger.

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14
Q

What does a second messenger stimulate?

A

Stimulates a change in the activity of the cell?

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15
Q

Give an example of a common effector molecule in a cell

A

Adenyl Cyclase

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16
Q

Outline the process of activation of a secondary messenger

A
  1. G-protein activated when the hormone binds to the receptor
  2. G-protein activates an effector molecule (usually an enzyme that converts an inactive molecule in to the active secondary messenger)
  3. 2nd messenger could cat directly another protein/initiate cascade of enzyme-controlled reactions that alter activity of the cell.
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17
Q

What are two difference between Endocrine and Exocrine glands?

A

Endocrine glands release hormones, exocrine do not.

Exocrine glands have ducts, Endocrine are ductless

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18
Q

Name two differences between the first and second messengers.

A
  • First messengers are signalling molecules outside the cell where as secondary are INSIDE the cell
  • First’s stimulate release of ANOTHER signalling molecule whereas seconds stimulate a change in activity of the cell
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19
Q

Why can Steroid hormones enter the cell?

A

Because they are soluble in the phospholipid membrane unlike Protein hormones.

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20
Q

What are the Adrenal glands?

A

A pair of endocrine glands that lye above the kidneys, which release adrenaline and other hormones called corticoids.

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21
Q

What is the name of the inner layer of the Medulla?

A

The Adrenal Medulla

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22
Q

What are the three layers of the Adrenal Cortex?

A
  • Zona Glomerulosa (outermost layer)
  • Zona fasciculata (middle layer)
  • Zona reticularis (innermost layer)
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23
Q

What is the function of the outer layer of the adrenal cortex? (the zona glomerulosa)

A

It secretes mineralocorticoids

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24
Q

What is the function of the middle layer of the adrenal cortex? (the zona fasciculata)

A

It secretes glucocorticoids

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25
Q

What is the function of the innermost layer of the adrenal cortex? (the zona reticularis)

A

Secretes precursor molecules that are used to make sex hormones

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26
Q

Where is the adrenal medulla found?

A

At the centre of the adrenal glands

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27
Q

What does the adrenal medulla secrete?

A

Adrenaline and Nonadrenaline

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28
Q

What molecule is used by the adrenal cortex to produce a range of hormones?

A

Cholesterol

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29
Q

What can hormones from the adrenal glands do?

A

They’re steroid based so can enter cell by dissolving into the cell surface membrane. They enter the nucleus and have a direct impact on the DNA to cause PROTEIN SYNTHESIS

30
Q

What happens with the adrenal gland hormones once inside the cell?

A
  • The receptor-steroid hormone complex enters nucleus of target cell and binds to another specific receptor on the chromosomal material.
  • Binding stimulates production of messenger RNA molecules which code for the structure of proteins
31
Q

Name the 3 hormones secreted from the adrenal cortex

A
  • Mineralocorticoids
  • Glucocorticoids
  • Cortisol
32
Q

Give 2 functions of Mineralocorticoids

A
  • Help control Na and K concentrations in the blood,
  • As a result they help maintain blood pressure by increasing absorption of Na, decreasing K, increasing water retention so increasing blood pressure
33
Q

What is the function of Glucocorticoids?

A

They help control the metabolism of carbohydrates, fats, and proteins in the liver.

34
Q

What is the function of Cortisol?

A
  • Secretes precursor molecules that are used to make sex hormones
  • (they help regulate the production of gametes.)
35
Q

What type of molecule is adrenaline and from what is it derived?

A
  • A polar molecule

- From the AA Tyrosine

36
Q

Why can’t adrenaline enter cells through the plasma membrane like a steroid hormone?

A

It derives from an amino acid meaning it is a non-steroid hormone.

37
Q

Why are the effects of adrenaline widespread?

A

Many cells and tissues have adrenaline receptors?

38
Q

Name 4 effects of adrenaline on the body

A
  • Relaxing smooth muscles in the bronchioles
  • Increasing heart rate
  • Pupils dilate
  • Stimulating conversion of glycogen to glucose
39
Q

Describe the process of the action of a steroid hormone

A
  1. Steroid hormone passes through cell membrane
  2. Steroid hormone binds with a specific receptor in the cytoplasm
  3. Receptor-steroid hormone complex enters nucleus of target cell and binds to another specific receptor on the chromosomal material
  4. Binding stimulates production of mRNA molecules
40
Q

What’s the difference between the hormones released by the adrenal cortex and the hormones released by the medulla?

A

Adrenal cortex hormones = Steroid based

Medulla hormones = Protein based/ non steroid

41
Q

Why does adrenaline cause an increase in blood glucose levels?

A

It has the effect of stimulating the conversion of glycogen into glucose so glucose levels will quickly increase

42
Q

What are the two main secretions of the pancreas?

A
  • Pancreatic juices, containing enzymes which are secreted into the small intestine
  • Hormones, that are secreted from the islets of Langerhaans into the blood.
43
Q

What do most cells in the pancreas synthesise and release?

A

Digestive enzymes

44
Q

The exocrine cells are in small groups surrounding tiny tubules, what is the name of each group of cells?

A

Acinus

45
Q

What substance do the cells of the Acini secrete?

A

The enzymes they synthesise, into the tubule at the centre of the group

46
Q

The tubules from the Acini join to form what?

A

Intralobular ducts that eventually combine to make up the pancreatic duct.

47
Q

What does the pancreatic duct do?

A

It carries the fluid containing the enzymes into the first part of the small intestine.

48
Q

What 3 enzymes does the fluid from the pancreatic duct contain?

A
  • Amylase (pancreatic) = a carbohydrate which digests amylase to maltose
  • Trypsinogen
  • Lipase = Digests lipid molecules
49
Q

What two types of cells do the islets of Langerhaans contain?

A

The Alpha and Beta cells that make up the endocrine tissues in the pancreas

50
Q

What substances do Alpha and Beta cells secrete?

A 
Alpha = Glucagon
Beta = Insulin
51
Q

What effect does the release of insulin from the islets of langerhaans produce?

A

Blood glucose concentration reduces

52
Q

Outline how Insulin is released from the Beta cells

A
  • Cell membrane has Na+ and K+ channels
  • The K+ channels are usually open, so K+ ions flow out
  • When blood glucose conc. high, glucose moves into cell
  • The glucose is metabolised to produce ATP
  • The extra ATP closes the K+ ion channels
  • Accumulation of K+ ions alters P.D across membrane (Inside becomes less negative)
  • Change in P.D opens up the Sodium channels
  • Calcium ions cause vesicles of insulin to fuse with cell membrane, releasing insulin by EXOCYTOSIS
53
Q

If a persons blood glucose concentration remains too low for long periods of time, the person is considered to be what?

A

Hypoglycaemic

54
Q

What is the main problem caused by Hypoglycaemia?

A

Inadequate delivery of glucose to the body tissues and in particular the brain

55
Q

Which cells constantly monitor the concentration of glucose?

A

The cells in the Islets of Langerhaans

56
Q

How do the Islets of Langerhans respond to a change in the blood glucose concentration?

A

By releasing the relevant hormone

  • Insulin if the blood glucose is high
  • Glucagon if blood glucose is too low
57
Q

What happens if blood glucose drops too low?

A

Beta cells respond by secreting insulin into the blood

58
Q

Outline the process of human insulin’s effect on a cell

A
  • Human Insulin is a small protein so can’t pass through the cell surface membrane
  • Insulin binds to the insulin receptor, activating the enzyme Tyrosine Kinase
  • TK causes phosphorylation of inactive enzymes in the cell
59
Q

Name 4 effects that Insulin has on the cell

A
  • More transporter proteins specific to glucose are placed near the cell membrane
  • More glucose enters the cell
  • Glucose in cell converted to glycogen for storage (Glycogenesis)
  • More glucose is converted to fats
60
Q

What cells detect if blood glucose drops too low, and what do they do?

A

Alpha cells in the Islets of Langerhans, which then secrete the hormone Glucagon

61
Q

What are the target cells of glucagon?

A

Hepatocytes (liver cells)

62
Q

What happens when blood passes the liver cells?

A
  • Glucagon binds to the receptors
  • This stimulates a G protein
  • The G protein activates the adenyl cyclase inside each cell
  • Adenyl Cyclase converts ATP into cAMP
  • This activates a series of enzyme-controlled reactions in the cell
63
Q

Name 3 effects of glucagon in the cell

A
  • Glycogen converted to glucose (glycogenolysis)
  • More fatty acids used in respiration
  • AAs and fats converted into additional glucose
64
Q

The concentration of blood glucose is controlled by a negative feedback mechanism involving what two hormones?

A

Insulin and Glucagon

65
Q

What is the term for the blood glucose concentration dropping too low?

A

Hypoglycaemic

66
Q

What is the term for the blood glucose concentration rising high?

A

Hyperglycaemic

67
Q

Diabetes is thought to be the result of what?

A

The result of an autoimmune response in which the body’s immune system attacks and destroys the beta cells

68
Q

What happens to excess glucose in a healthy person?

A

It’s converted into glycogen in the liver and muscles

69
Q

What can a person with diabetes not do?

A

They’re no longer able to synthesise sufficient insulin and cannot store excess glucose as glycogen.

70
Q

Name 2 factors that bring on an earlier onset of type 2 diabetes

A
  • Obesity/Lack of regular exercise

- Being Afro-caribbean or Asian origin

71
Q

Name 3 alternatives to insulin injections to treat type 1 diabetes

A
  • Insulin pump therapy
  • Islet cell transplantation
  • Complete pancreas transplant
72
Q

Insulin is now produced from genetically modified bacteria rather than pig insulin. Name two advantages of this

A
  • Less chance of rejection due to an immune response

- lower risk of infection

A2 Biology (13 decks)

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