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Biology OCR AS Level > Hormones > Flashcards

Hormones Flashcards

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1
Q

The endocrine system is another system (a series of glands) , in addition to the nervous system, used for communication around the body. What are the signals used for communication between the endocrine system and target organs?

A

Hormones

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2
Q

How are hormones transported from endocrine glands to the target organs?

A

They are transported in the blood

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3
Q

Define hormones?

A

Hormones are molecules released by endocrine glands directly into the blood to carry chemical signals from the glands to a specific target organ/tissue.

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4
Q

What are the two types of hormones? Give examples

A
  • Protein hormones (e.g. insulin, adrenaline)

- Steroid hormones (e.g. oestrogen, testosterone)

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5
Q

How do protein and steroid hormones differ in function?

A

Protein hormones - insouble in the phospholipid membrane so cannot pass through. Therefore they bind to a receptor on the plasma membrane to bring about a response.
Steroid hormones - soluble in the phospholipid membrane so can enter the cell and even pass through the nuclear envelope to have a direct effect on the DNA.

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6
Q

How do steroid hormones trigger the production of a protein?

A

Steroid hormone passes through plasma membrane to enter the cytoplasm, where it binds to a specific receptor, complementary in shape to produce a receptor-steroid hormone complex, which can pass through nuclear envelope and binds to chromosomal material, to stimulate production of mRNA which codes for a protein.

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7
Q

What releases hormones into the blood?

A

Endocrine glands

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8
Q

How are endocrine glands different to other glands like exocrine glands?

A

Endocrine glands release substances directly into the blood – they have no ducts/do not use ducts.
However, exocrine glands secrete substances into ducts that transport it to the target tissue/organ without entering the blood stream.

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9
Q 
Label the following glands on the picture below:
Pituitary gland
Thyroid gland
Thymus
Adrenal glands
Ovaries 
Testes
A

PICTURE IS IN NOTES

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10
Q

What are the cells/tissue/organ receiving hormones called?

A

The target cells/tissue/organ
*For target cells, the cells can be found together in one location like epithelium of collecting duct for ADH, or the cells can be spread across various tissues for adrenaline, which results in lots of different changes across the body.

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11
Q

How do non-steroid hormones bind to target cells/tissues/organs?

A

Hormones bind to specific receptors on the plasma membrane of the target cell, which are complementary in shape to the hormone.

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12
Q

What are first messengers?

A

These are extracellular signalling molecules that bind to complementary receptors on the plasma membrane to initiate an effect inside the cell. Non-steroid hormones are an example of first messengers.

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13
Q

What are second messengers?

A

These are intracellular signalling molecules that are activated in response to the cell being exposed to an extracellular signalling molecules. They stimulate a change in the activity of a cell.

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14
Q

State the series of steps that occur when a first messenger, a non-steroid hormone, binds to a plasma membrane receptor?

A

First messenger (e.g. non-steroid hormone) binds to plasma membrane receptor. A G-protein in the membrane is activated, which in turn activates an effector molecule, usually an enzyme like adenyl cyclase, which converts ATP, an inactive molecule into an active second messenger, cyclic AMP (cAMP). The second messenger will then stimulate a change in the activity of the cell by directly acting on another protein or by initiating a cascade of enzyme activity.

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15
Q

Where are the adrenal glands located?

A

Above each kidney

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16
Q

Each gland is divided into what two regions?

A

Divided into the outer adrenal cortex and inner adrenal medulla.

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17
Q

Why are both regions of the adrenal gland, well supplied with blood vessels?

A

So that the hormones and substances (like cortisol/glucocoticoids/mineralocorticoids) produced here can easily enter the bloodstream

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18
Q

What is the structure of the adrenal cortex?

A

Has an outer capsule surrounding three distinct layers of cells:

  • Zona glomerulosa – outermost later
  • Zona fasiculata – middle layer
  • Zona reticularis – innermost layer
  • Further inwards is the adrenal medulla
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19
Q

Role of zona glomerulosa?

A

Secretes mineralocorticoids e.g. aldosterone

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20
Q

Role of zona fasiculata?

A

Secretes glucocorticoids e.g. cortisol

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21
Q

Role of zona reticularis?

A

Secretes cortisol if correct enzymes present.
If correct enzymes not present, secretes precursor molecules that are used to make sex hormones. Ovaries and testes take up the precursor molecules and synthesise the sex hormones.

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22
Q

What does mineralocorticoids do?

A

Controls + maintains conc. of Na and K in the blood = therefore involved in maintaining blood pressure.
Aldosterone controls conc. of Na and K by binding to complementary receptors on the cells lining the distal convoluted tubule + collecting ducts in the kidney. Upon binding, there is an increase Na+ reabsorption, and decrease K+ reabsorption in the DT and CD. Opposite happens if no receptor binding.

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23
Q

What does glucocorticoids do?

A

Control carbohydrate, fats and protein metabolism in liver.
In response to the stress OR low blood glucose levels, cortisol released to stimulate the production of glucose from the conversion of glycogen, fats and proteins in the liver (gluconeogenesis + glycogenolysis).

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24
Q

Which sex hormones are produced and where?

A

Testosterone in testes, Oestrogen in ovaries.

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25
Q

Role of sex hormones?

A

Help development of secondary sexual characteristics and regulate the production of gametes.

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26
Q

Where is adrenaline produced?

A

Adrenaline is produced from the adrenal medualla of the adrenal gland.

27
Q

Adrenaline is a protein hormone so communicates with target cells by binding to a receptor on the plasma membrane of the cell. Why are adrenaline receptors found in may cells/tissue in the body?

A

This is because an adrenaline has a widespread effect on our body = can cause out eyes to dilate, blood vessels to constrict, increase heart rate, and stimulate conversion of glycogen to glucose.

28
Q

State if aldosterone, cortisol and adrenaline is a steroid hormone or protein hormone?

A

Aldosterone (and all mineralocorticoids), cortisol (and all glucocorticoids) and all hormones produced in the adrenal cortex are steroid hormones.
Adrenaline is a protein hormone (it is made in the adrenal medulla)

29
Q

Hormones produced from the adrenal cortex are made from?

A

Cholesterol

30
Q

Where is pancreas located?

A

Below stomach

31
Q

What does the pancreas secrete?

A
  • Pancreatic juices containing digestive enzymes which are secreted into small intestines
  • Hormones secreted from the islets of Langerhans into the blood.
32
Q

h

A

h

33
Q

Why is the pancreas an exocrine gland?

A

It secretes pancreatic juices containing digestive enzymes into a duct = the pancreatic duct, which deliver them directly into the duodenum of the small intestine (directly).

34
Q

What cells of the pancreas are involved in the exocrine function?

A
  • The exocrine cells are grouped together in small clusters surrounding tiny tubules.
  • Each cluster is called an acinus (acini for plural).
  • The acini are grouped together to form lobules with each lobule being separated by connective tissue.
  • The cells of the acini secrete the enzymes they synthesise into the tubule at their centre which join together to form the intralobular ducts which then combine to make the pancreatic duct.
  • The pancreatic duct then carries the enzymes from each lobule to the small intestine.
35
Q

How can you identify the endocrine section (islets of Langerhans) from an exocrine section (acini) of the pancreas?

A

Using differential staining – islets of Langerhans would appear lighter than the acini.

36
Q

What does the fluid from pancreatic duct contain?

A
  • pancreatic amylase – digests amylose to maltose
  • trypsinogen – inactive protease which gets converted to trypsin when it enter the duodenum
  • lipase – digests lipids
  • sodium hydrogencarbonates (alkaline) - to neutralise acidic contents from stomach that enter the small intestines
37
Q

What cells of the pancreas are involved in the endocrine function?

A

Among the lobules of acini are group of cells called the islet of Langerhans which contain alpha and beta cells.

  • The alpha cells secrete glucagon
  • The beta cells secret insulin.
  • The islet of Langerhans are well vascularised with blood capillaries in and around them, so hormones can move directly into the blood.
38
Q

What is the normal blood glucose concentration?

A

4-6mmoldm-3

39
Q

What monitors the blood glucose concentration in an individual?

A

The alpha or beta cells in the islets of Langerhans

40
Q

Which cells of the islet of Langerhans detect an increase in blood glucose concentration and what do they do in response?

A

Beta cells detect increase in BGC, and release insulin in response.

41
Q

What are the target cells of insulin?

A

Hepatocytes, muscle cells + other cells e.g. cells in brain

42
Q

What are the steps that occur in the beta cell, to release insulin, when a high BGC is detected?

A

1) Beta cells contain both potassium and calcium ion channels in plasma membrane. In normal conditions potassium ion channels are open to allow K+ ion to diffuse out (to keep the membrane potential at the resting potential of -70mV) and calcium ion channels are closed.
2) When glucose concentration outside the cells is high (i.e. in the blood) the glucose moves into the beta cells triggering a cascade of enzyme activity occurs, (including the conversion of glucose to glucose phosphate using glucokinase) and eventually the glucose is metabolised to produce ATP.
3) The ATP is then used to close the potassium ion channels so K+ cannot diffuse out making the potential across the membrane more positive.
4) This change in membrane potential triggers calcium channels to open and calcium ions diffuse in and bind to vesicles containing insulin causing them to migrate and fuse with the membrane, to release insulin into the blood (exocytosis).

43
Q

How does the insulin trigger a response within target cells?

A

1) Insulin (first messenger) binds to receptors on the target cell’s plasma membrane, which are specific and complementary in shape to it.
2) This activates a g-protein which in turn activates the enzyme Adenyl cyclase, which converts ATP to cAMP.
3) cAMP (a secondary messenger inside the cell) in turn triggers tyrosine Kinase to phosphorylates inactive enzymes so that they become active.
4) These activated enzymes then causes vesicles carrying transporter proteins (GLUT4) to move to the plasma membrane and embed themselves.
5) Glut-4, then facilitates the diffusion of glucose into the liver cell and glycogenesis will occur. Glucose may also be converted to lipids. An increase used of glucose in respiration may also occur.

44
Q

Which cells of the islet of Langerhans detect an decrease in blood glucose concentration and what do they do in response?

A

Alpha cells detect a decrease in BGC, and release glucagon in response.

45
Q

What are the target cells of glucagon?

A

Hepatocytes, muscle cells + other cells e.g. cells in brain.

46
Q

How does glucagon trigger a response within target cells?

A

The glucagon will bind to receptors on the plasma membrane of target cells, which are specific and complementary in shape to it - first messenger response
This will activate the second messenger response which will result in glycogen being hydrolysed back into glucose (glycogenolysis) and gluconeogenesis. More fatty acids will be used in respiration
The glucose will be released back into the blood stream via GLUT 2 transporter proteins via facilitated diffusion.
*THIS IS ALL YOU NEED TO KNOW!

47
Q

What happens to the respiratory substrate used in the cells releasing glucose into the blood stream?

A

The cell will change its respiratory substrate and use fatty acids.
It could also make its own glucose (for respiration) by converting amino acids or fats into glucose (gluconeogenesis)

48
Q

What mechanism is the concentration of blood glucose controlled by?

A

Negative feedback mechanism

49
Q

What is diabetes mellitus?

A

A condition in which the blood glucose concentrations cannot be controlled effectively.

50
Q

There are two types of diabetes mellitus. What are the two types of diabetes mellitus?

A

Type 1 and Type 2

51
Q

What is type 1 diabetes?

A

An autoimmune disease, in which the body’s immune system attacks and destroys the beta cells in the islets of Langerhans. This means people with Type 1 diabetes don’t produce any insulin. This is why Type-1 diabetes is also known as insulin-dependant diabetes.

52
Q

Why is glucose found in the urine of individuals with Type 1?

A

This is because in these individuals, after eating, BGC rises and stays high, as their body is not producing insulin which triggers glycogenesis. The kidney can’t reabsorb all this glucose, so some of it is excreted in the urine.

53
Q

What is type 2 diabetes?

A

This is when the beta cells do not produce enough insulin OR when the target cells of the insulin do not respond to the insulin produced.

54
Q

Why do the target cells of people with Type 2 diabetes not respond?

A

This is because the receptors on their surface used for insulin binding, no longer work.

55
Q

What increases the risk of Type 1 diabetes?

A

Family history of diabetes

56
Q

What increase the risk of Type 2 diabetes?

A
  • Obesity
  • Lack of regular exercise
  • Diets high in sugar, particularly refined sugars
  • Being asian
  • Family History
57
Q

How is type 1 diabetes treated?

A
  • Insulin injections
  • insulin pump therapy - small device constantly pumps insulin into the blood stream through a needle which is permanently inserted under the skin
  • islet/beta cell transplantation – healthy beta cells implanted into pancreas of Type 1 diabetes individual (from deceased donor or grown from stem cells)
  • a complete pancreas transplant
  • changes in lifestyle: losing weight, exercising regularly, monitoring diet (matching carbohydrate intake and use) - MENTION THE ONES ABOVE FIRST.
58
Q

Issues with beta cell and pancreas transplants?

A
  • Issue with rejection
  • Need to take immunosuppressants
  • May need to replace beta cells every so often (as the beta cells do not undergo mitosis)
  • Demand for transplantable pancreases outweighs their availability
59
Q

How is type 2 diabetes treated?

A
  • changes in lifestyle: losing weight (where possible), exercising regularly, monitoring diet (matching carbohydrate intake and use)
  • medication which reduces amount of glucose released by liver to blood stream or medication which boosts the amount of insulin released from the pancreas
60
Q

What is the source of insulin for treating diabetes?

A
  • In past, insulin extracted from pancreas of animals which matches human insulin most closely
  • More recently, human insulin is manufactured by genetically engineered bacteria.
61
Q

Advantages of using insulin from genetically modified bacteria?

A
  • exact copy of human insulin = thus faster acting + more effective
  • less chance of developing tolerance to the insulin
  • less chance of rejection
  • less risk of infection
  • cheaper to manufacture over extraction
  • manufacturing process is more adaptable to demand
  • fewer moral and ethical reasons (no animals involved)
62
Q

When can hypoglycaemia occur?

A

Hypoglycaemia can occur when blood glucose concentration gets too low – can happen when too much insulin is injected

63
Q

When can hyperglycaemia occur?

A

Hyperglycaemia can occur when blood glucose concentration gets too high – can happen when too little insulin is injected.

Biology OCR AS Level (10 decks)

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