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A level Biology > 5.4 hormonal communication > Flashcards

5.4 hormonal communication Flashcards

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1
Q

define endocrine system

A

a communication system using hormones as signalling molecules released into the bloodstream

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2
Q

define hormones

A

molecules that are released by endocrine glands directly into the blood that at as messengers carrying a signal from the endocrine gland to a specific target organ or tissue

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3
Q

define target cells

A

cells that posses a specific receptor on their plasma membrane and the shape of the receptor is complementary to the hormone molecules

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4
Q

what are the 2 different types of hormones

A

protein
steroid

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5
Q

Describe the difference between steroid and protein hormones

A

Proteins are not soluble in the phospholipid bilayer and do not enter the cell so they need to bind to the plasma membrane and release a second messenger inside the cell

steroid hormones however, can pass through the plasma membrane and enter the cell and nucleus and have a direct effect on the DNA

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6
Q

what are endocrine glands

A

ductless glands that consist of groups of cells that manufacture and release hormones directly into the blood capillaries running through the gland

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7
Q

define exocrine glands

A

consist of groups of cells surrounding a small duct which they secrete their product into which the leads to the site for example the salivary glands

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8
Q

what are non-steroid hormones also known as

A

first messengers

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9
Q

Describe the action of non-steroid hormones and the activation of the second messenger

A

Non-steroid hormones(except insulin) have this pathway

The hormone binds to the receptor on the plasma membrane, causing the activation of a G protein which in turn activates the effector - adenyl cyclase- which converts ATP into cAMP which is the second messenger and acts directly on another protein such as an ion channel

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10
Q

what is the adrenal cortex

A

the outer layer of the adrenal gland

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11
Q

what is the adrenal gland

A

one of a pair of gland lying above the kidneys which release adrenaline and a number of other hormones known as corticoids

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12
Q

What is the adrenal medulla

A

the inner layer of the adrenal gland

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13
Q

What is the name of the outermost layer of the adrenal cortex

A

zona glomerulosa

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14
Q

what is the name of the middle layer of the adrenal cortex

A

zona fasciculata

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15
Q

what is the name of the inner most layer of the adrenal cortex

A

zona reticularis

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16
Q

what are the names of the layers in the adrenal cortex from out in

A

zona glomerulosa
zona fasciculata
zona glomerulosa

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17
Q

What is the function of the zona glomerulosa

A

secretes mineralocoricoids such as aldosterone which acts on absorption of sodium and decreasing absorption of potassium ions, therefore increasing water retention and blood pressure

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18
Q

What is the function of the zona fasciculata

A

secretes glucocorticoids such as cortisol which control metabolism of carbohydrates, fats and proteins in the liver and is also released in response to stress

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19
Q

what is the role of the zona reticularis

A

also secretes precursor molecules and cortisol however if the correct enzymes are not present for the release of cortisol they release precursor androgens into the blood which are taken up by the testes and ovaries and converted into sex hormones

20
Q

what kind of hormones does the adrenal cortex and medulla release

A

the medulla releases protein hormones such as adrenaline and noradrenaline whereas the adrenal cortex releases steroid hormones

21
Q

Describe the action of steroid hormones

A

The steroid hormone passes through the plasma membrane of the cell and binds with a specific receptor in the cytoplasm

the receptor-steroid hormone complex enters the nucleus of the target cell and binds to another specific receptor on the chromosomal material

the binding stimulates the production of messenger RNA molecules which code for the production of proteins

22
Q

what hormones does the adrenal medulla release

A

adrenaline and noradrenaline

23
Q

what are the effects of adrenaline on the body

A

causing body hair to stand erect
increasing heart rate
dilating the pupils
increasing mental awareness
inhibiting the action of the gut

24
Q

describe the pancreas

A

they are a small organ below the stomach with both endocrine and exocrine functions

25
Q

what are the two main secretions of the pancreas

A

pancreatic juice containing enzymes which are secreted into the small intestine

hormones which are secreted from the islets of Langerhan into the blood

26
Q

where are the exocrine cells found in the pancreas

A

they are in small groups surrounding tiny tubules and each group is called an acinus or acini plural

27
Q

Describe the exocrine function of the pancreas

A

the cells of the acini secrete the enzymes they produce into the tubule at the centre of the group
the tubules then join to form intralobular ducts that eventually combine to form the pancreatic duct that carries the pancreatic fluid into the first part of the small intestine

28
Q

Describe the contents of the pancreatic fluid

A

pancreatic amylase
lipase
trypsinogen

29
Q

Explain why trypsinogen is in pancreatic fluid and not trypsin

A

because trypsinogen is an inactive form of trypsin and it is so that the pancreatic duct is not broken down by the protease enzyme

30
Q

describe the structure and function of the endocrine system of the pancreas

A

dispersed in small patches along the acini are the islets of Langerhan
The islets of Langerhan contain alpha cells which secrete glucagon and beta cells which secrete insulin

31
Q

describe the release of insulin from the beta cells

A

the plasma membrane of the beta cells contain both calcium and potassium ion channels

The potassium ion channels are open normally and the calcium ion channels are normally closed allowing the potassium ions to diffuse out and the potential difference inside the cell is at around-70mV

When glucose concentration is high the glucose moves into the cell and is quickly used to produce ATP using the enzyme glucokinase

The extra ATP causes the potassium ion channels to close so they no longer diffuse out and so the potential difference inside the cell becomes more negative

This causes calcium ion voltage gated channels to open and calcium ions diffuse in and cause vesicles with insulin to fuse with the plasma membrane and diffuse out releasing insulin by exocytosis

32
Q

What is the name of the enzyme used in metabolism of glucose to make ATP

A

glucokinase

33
Q

what is the normal blood concentration of glucose

A

4-6 mmol/dm3

34
Q

define hypoglycaemia

A

when the blood glucose is too low for a long period of time

35
Q

Define hypergylcaemia

A

When blood glucose remains too high for a long period of time

36
Q

What happens if blood glucose concentration changes

A

A high blood glucose concentration is detected by the beta cells in the islets of Langerhan and insulin is released and a low blood glucose concentration is detected by the alpha cells and glucagon is released

37
Q

Describe the effects of insulin on the cell

A

more glucose enters the cell
glucose is converted into glycogen for storage - glycogenesis

more glucose is converted into fats

more glucose is used in respiration

38
Q

What are the effects of glucagon on a cell

A

glycogen is converted into glucose glycogenolysis
more fatty acids are used in respiration
amino acids and fats are converted into additional glucose by gluconeogenesis

39
Q

Describe how insulin acts on a cell as a first messenger

A

when insulin binds to the insulin receptor on the plasma membrane it activates the enzyme tyrosine kinase which associated with the receptor on the inside of the plasma membrane

Tyrosine kinase causes phosphorylation of inactive enzymes in the cell leading to vesicles containing glucose transporter proteins fusing and imbedding them in the plasma membrane
then extra glucose enters the cell and can be converted to glycogen and fats etc.

40
Q

define diabetes mellitus

A

a condition in which blood glucose concentration cannot be controlled effectively

41
Q

define stem cells

A

unspecialised cells that have the potential to develop into any type of cell

42
Q

describe type 1 diabetes

A

insulin-dependant diabetes and usually starts in childhood thought to be as a result of autoimmune attack where the beta cells are destroyed

no longer able to synthesise sufficient insulin and cannot store excess glucose as glycogen

43
Q

describe type 2 diabetes

A

non-insulin dependant as they can produce insulin but not enough and responsiveness to insulin declines

caused by lack of exercise obesity a high sugar diet

44
Q

What are the treatments for type 1 diabetes

A

insulin injections
insulin pump therapy
islet transplantation
pancreas transplant
using stem cells to grow new islets of langerhan

45
Q

How would you treat type 2 diabetes

A

changes in lifestyle

46
Q

what is the source of insulin for treating diabetes

A

used to be extracted from the pancreas of animals such as pigs however more recently it is from bacteria that have undergone genetic modification

47
Q

What are the advantages of using GM bacteria as a source of insulin and not animal insulin

A

exact copy of human insulin so it is faster acting
less chance of developing tolerance
less chance of rejection
lower risk of infection
cheaper to manufacture
less moral objections

A level Biology (25 decks)

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