5.1.4 - Hormonal communication Flashcards
(87 cards)
1
Q
What is diabetes mellitus?
A
A condition in which the body is no longer able to produce enough insulin to control its blood glucose concentration.
2
Q
What is hypERglycaemia?
A
Where blood glucose concentrations remain high for longer than normal periods, which can lead to organ damage.
3
Q
What is hypOglycaemia?
A
Abnormally low levels of glucose in the blood. Results in inadequate delivery of glucose to the body tissues and is particularly damaging to brain
4
Q
When can blood glucose concentration become too high?
A
- after a meal rich in sugars and other carbs
5
Q
When can blood glucose concentration become too low?
A
- after exercise
- after fasting
6
Q
What are other terms for type 1 diabetes?
A
- insulin-dependent diabetes
- juvenile-onset diabetes
7
Q
What is type 1 diabetes thought to be caused by?
A
EITHER:
- an autoimmune response in which the body’s immune system attacks and destroys the beta cells in the islets of Langerhans.
- a viral attack
8
Q
In a healthy person, what happens to glucose?
A
- glucose is absorbed into blood.
- any excess is converted to glycogen in liver and muscles.
- this glycogen = used to release glucose when blood glucose concentration FALLS.
9
Q
Describe the effect type 1 has on insulin.
A
- they are no longer able to make enough/any insulin
- cannot store excess glucose as glycogen.
> EXCESS glucose in blood is not removed quickly, leaving a prolonged period of high concentration.
> when the blood glucose FALLS, there is NO store of glycogen that can be used to release glucose.
∴ blood glucose concentration falls TOO LOW. (a ‘hypo’)
10
Q
How is type 1 usually treated?
A
By using insulin injections.
- the blood glucose conc. must be monitored and the correct dose of insulin administered to keep glucose conc. stable.
11
Q
Give 3 other types of type 1 treatment.
A
> insulin pump therapy: a small device constantly pumps insulin (at a controlled rate) into the bloodstream through a needle that is permanently inserted under the skin.
> islet cell transplantation - healthy beta cells from the pancreas of a deceased donor are implanted into the pancreas of someone with type 1.
> a complete pancreas transplant.
12
Q
What has recent research shown about the use of stem cells in treating type 1 diabetes?
A
- may be possible to treat T1 diabetes using stem cells to grown NEW ISLETS OF LANGERHANS in the pancreas.
- stem cells are not yet differentiated and can be induced to develop into a variety of cell types.
13
Q
Where are the most common sources of stem cells?
A
- in the bone marrow and in the placenta
14
Q
What have scientists discovered about the pancreas of adult mice?
A
- scientists have found precursor cells in the pancreas of adult mice.
- can develop into a variety of cell types and may be true stem cells!
- if similar cells can be found in human pancreas then they could be used to produce new beta cells in patients with T1 diabetes.
= patient free from daily insulin injections.
15
Q
What is another term for type 2 diabetes?
A
non-insulin-dependent diabetes
16
Q
What happens in type 2 diabetes?
A
- beta cells do not produce enough insulin or the body’s cells don’t respond properly to insulin.
- as people age, their responsiveness to insulin declines.
> because the specific receptors on the surface of the liver and muscle cells become less responsive and the cells lose their ability to respond to the insulin in the blood.
17
Q
In …….. diabetes, the blood glucose concentration is almost permanently ……………..
What effect does this have on the organs?
A
> type 2
raised
- high blood glucose concentration can damage the major organs and circulation.
18
Q
What factors can lead to T2 diabetes? (5 factors)
A
- obesity
- lack of regular exercise
- a diet high in sugars, particularly refined sugars
- being of Asian or Afro-Caribbean origin
- family history
19
Q
How is T2 diabetes usually treated?
A
- usually treated by changes in lifestyle.
- weight loss
- more exercise
- monitoring their diet (matching carb intake and use)
- may also take medication that reduces amount of glucose liver releases to the bloodstream or that boosts the amount of insulin released from the pancreas.
20
Q
In severe T2 cases what might the treatment include?
A
Treatment may include insulin injections or the use of other drugs that slow down the absorption of glucose from digestive system.
21
Q
Recently, insulin that has been produced by Escherichia coli bacteria has undergone genetic modification to manufacture human insulin.
State the advantages.
A
- it is an exact copy of human insulin, therefore it is faster acting and more effective
- less chance of developing tolerance to the insulin
- less chance of rejection due to an immune response
- lower risk of infection
- cheaper to manufacture the insulin than to extract it from animals
- manufacturing process = more adaptable to demand
- some = less likely to have moral objections to using the insulin produced from bacteria than to using that extracted from animals.
22
Q
What is the endocrine system?
What does it consist of.
A
A communication system using hormones as signalling molecules.
- uses the blood circulatory system to transport its signals.
> Consists of ENDOCRINE GLANDS and HORMONES.
23
Q
What are hormones?
A
‘Chemical messengers’ (proteins or steroids) that are released by endocrine glands directly into the blood.
- carry a signal from the endocrine gland to a specific target organ or tissue.
- hormone transported throughout body.
24
Q
What are endocrine glands?
A
Endocrine glands are groups of cells specialised to secrete hormones.
- secrete hormones directly into the blood in capillaries running through gland.
- they are ductless
Example: pancreas secretes insulin.
25
What are the two types of hormone?
> protein and peptide hormones, and derivatives of amino acids (e.g. adrenaline, insulin, and glucagon)
> steroid hormones (e.g. oestrogen and testosterone)
26
Explain the way in which protein hormones work. (hint: phospholipid membrane)
- not soluble in the phospholipid membrane
- do not enter cell
- protein hormones must bind to cell surface membrane and release a second messenger inside the cell.
27
Explain the way in which steroid hormones work? (hint: phospholipid membrane)
- can pass through phospholipid membrane
- do enter cell & nucleus
- have a direct effect on the DNA in the nucleus.
28
What are exocrine glands?
Exocrine glands do not release hormones.
29
Hormones are released directly into the blood from ................... glands.
Endocrine
30
What do the endocrine glands consist of?
They are ductless glands - consist of groups of cells that make
- they release the hormone directly into blood in capillaries running through gland.
31
How are glands stimulated?
- can be stimulated by a change in conc. of a specific substance (sometimes another hormone).
- can also be stimulated by electrical impulses
32
How many tissues do hormones have an effect on and why?
They are transported all around body BUT
- only have an effect in one type of tissue
- as always have a specific function
33
What are target cells and what are what are target tissues?
Each hormone will only bind to specific receptors for that hormone, found in the membranes of some cells = target cells.
Tissue that contains target cells is called a target tissue.
34
Describe how non-steroid hormones use target cells.
target cells must possess a specific receptor on their plasma membrane that is complimentary in shape to the shape of the signalling molecule (hormone).
- hormone binds to receptor & initiates changes in cell
35
How can a hormone be carried in blood without affecting every cell?
Every cell does not possess the correct specific receptor.
- only those specific target cells that possess the correct receptor will respond to the hormone.
36
Give another term for non-steroid hormones.
First messengers.
37
What are first messengers?
Signalling molecules outside the cell that bind to cell surface membrane and initiate an effect inside cell.
38
What do first messengers usually cause?
First messengers usually cause the release of another signalling molecule in the cell = second messenger.
- second messenger stimulates a change in the activity of the cell.
- they activate a chain of reactions inside cell.
39
What type of glands are adrenal glands?
Endocrine glands.
40
Describe the basic structure of an adrenal gland.
What are they supplied with that helps their function?
Each adrenal gland is divided into the outer adrenal cortex and the inner adrenal medulla.
- both regions = well supplied with blood vessels & produce hormones which are secreted directly into blood vessels.
41
The adrenal cortex is made up of three distinct layers of cells:
zona glomerulosa - outermost layer, which secretes mineralocorticoids e.g. aldosterone
zona fasciculata - middle layer, secretes glucocorticoids e.g. cortisol
zona reticularis - innermost layer, thought to secrete precursor molecules used to make sex hormones.
42
Where is the adrenal medulla found in the adrenal gland?
Found at the centre of adrenal gland.
| - secretes adrenaline & noradrenaline.
43
What substance does the adrenal cortex use to produce a range of hormones?
Cholesterol.
44
The adrenal cortex produces what kind of hormones? How do these hormones enter the cell?
Steroid based hormones.
- able to enter cells directly by dissolving into the cell surface membrane.
- the steroid hormones enter the nucleus and have a direct effect on the DNA to cause protein synthesis
45
Outline the action of steroid hormones.
1. Steroid hormone passes through cell membrane of target cell.
2. Steroid hormone binds with a specific receptor (with a complementary shape) 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 messenger RNA (mRNA) molecules, which code for production of proteins.
46
Describe the role of mineralocorticoids (e.g. aldosterone) secreted by the zona glomerulosa
- mineralocorticoids help to control concs. of sodium & potassium in blood.
∴ they contribute to maintaining blood pressure.
47
Describe the way in which aldosterone acts on cells.
- acts on cells of the distal tubules and collecting ducts in kidney
- increases absorption of Na+ ions
- decreases absorption of K+ ions
- increased water retention
∴ increases blood pressure.
48
Describe the role of glucocorticoids (e.g. cortisol) secreted by the zona fasciculata.
To help control the metabolism of carbs, fats & proteins in the liver.
49
What is the role of cortisol?
- released in response to stress or as a result of a low blood glucose conc.
- stimulates production of glucose from stored compounds (esp. glycogen, fats & proteins) in liver.
50
Where else might cortisol be released by?
- may also be released by zona reticularis
HOWEVER
- it correct enzymes aren’t present for release of cortisol, then ZR releases precursor androgens into blood.
- these are taken up by ovaries or tested & concerted to se hormones.
- sex hormones help development of secondary sexual characteristics & regulate production of gametes.
51
What does the adrenal medulla secrete?
- catecholamine hormones (modified amino acids) e.g. it secretes ADRENALINE and NORADRENALINE when you’re stressed.
52
What type of molecule is adrenaline and what is it derived from?
- it is a polar molecule derived from the amino acid tyrosine.
53
How is adrenaline different from other steroid hormones?
- adrenaline can’t enter cells through plasma membrane
- must be detected by specialised receptors on the plasma membrane of the target cells.
- MANY cells & tissues have adrenaline receptors.
∴ effects of adrenaline are widespread
54
What is the role of adrenaline?
To prepare body for activity.
| - adrenaline and noradrenaline are secreted when you’re stressed.
55
What effects does adrenaline have on the body?
- relaxing smooth muscle in the bronchioles
- increasing stroke volume of heart
- increasing heart rate
- causing general vasoconstriction to raise blood pressure
- stimulating conversion of glycogen to glucose
- dilating the pupils
- increasing mental awareness
- inhibiting the action of the gut
- causing body hair to stand erect.
56
What is the pancreas and where is it found?
A small organ lying below the stomach.
57
Why is the pancreas unusual?
- unusual because it has both exocrine and endocrine functions.
58
Give the two main secretions of the pancreas.
- pancreatic juices containing enzymes which are secreted into the small intestines
- hormones which are secreted for the islets of Langerhans into blood
59
What do most cells in the pancreas do? What type of function is this.
- most cells in the pancreas synthesise and release digestive enzymes.
This is the EXOCRINE function of the pancreas.
60
How are the exocrine cells organised in the pancreas?
The exocrine cells are in small groups surrounding tiny tubules.
61
What are acini and how are they arranged?
- each group of exocrine cells is called acinus (plural acini)
- the acini are grouped together into small lobules separated by connective tissue.
62
What do the acini secrete and what happens to the secretions?
- the cells of the acini secrete the enzymes they synthesise into the tubule at the centre of the group.
- the tubules from the acini join to form intralobular ducts that combine to make up the pancreatic duct.
- the pancreatic duct carries fluid containing enzymes into first part of small intestine (duodenum)
63
What does the fluid from the pancreatic duct contain?
1) pancreatic amylase - a carbohydrase which digests amylose to maltose
2) trypsinogen - an inactive protease which will be converted to the active form of trypsin when it enters the duodenum
3) lipase - which digests lipid molecules
4) the fluid also contains sodium hydrogencarbonate - makes it alkaline.
> helps to neutralise contents of digestive system that have just left acidic environment of stomach.
64
What are the islets of Langerhans and where are they found?
- they are areas of the pancreas that contain endocrine tissue
- dispersed in small patches among lobules of acini & found in clusters around blood capillaries
65
What do the islets of Langerhans secrete?
- secrete hormones directly into blood
66
What types of cell are islets of Langerhans made up of?
- alpha cells that secrete glucagon
- beta cells that secrete insulin
> they make up the endocrine tissue in the pancreas.
67
What happens to the blood glucose concentration when insulin is secreted from the beta cells?
- it brings about effects that REDUCE the blood glucose concentration
68
Why is insulin released when the blood glucose conc. is too high?
because insulin will reduce the blood glucose conc.
69
What happens to insulin secretion if the blood glucose conc. drops too low?
Insulin secretion decreases/stops.
70
Give the 8 steps of the mechanism of insulin secretion from the BETA cells.
1. The cell membranes of the beta cells contain calcium ion channels and potassium ion channels.
2. Potassium ion channels = normally open.
Potassium ions diffuse out of cell
∴ the inside of cell = more negative
- at rest: potential difference across cell membrane is approx -70mV
3. When glucose concentrations outside cell are high (high b glucose conc.) = glucose molecules moves into cell.
4. Glucose is quickly metabolised to produce ATP.
> this involves the enzyme glucokinase
5. Extra ATP causes potassium channels to close
6. Potassium can no longer diffuse out & this alters potential difference across cell membrane
∴ becomes LESS negative inside
7. Change in potential difference opens the calcium ion channels.
8. Calcium ions enter cell & cause the vesicles of insulin to fuse with the cell membrane, releasing insulin by exocytosis.
71
What is the normal blood concentration of glucose?
- between 4&6 mmol dm-3
OR
- 9mg 100cm-3
72
What happens if a person’s blood glucose concentration is allowed to drop below 4mmol dm-3 for long periods?
The person is said to be hypoglycaemic.
73
Why is hypoglycaemia dangerous?
- causes an inadequate delivery of glucose to body tissues & brain.
MILD hypoglycaemia = tiredness & irritability
SEVERE hypoglycaemia = impairment of brain function & confusion, could lead to seizures, unconsciousness & even death.
74
What happens if a person’s blood glucose concentration remains above 7mmol dm-3 for long periods?
The person is said to be hypERglycaemic
75
Why is hypERglycaemia dangerous?
- permanently high blood glucose concentrations can lead to significant organ damage
- a blood glucose conc. that is consistently higher than 7mmol dm-3 = used as diagnosis for diabetes mellitus
76
What cells in the pancreas monitor the conc. of glucose in blood?
The islets of Langerhans
77
How do the islets of Langerhans respond if the glucose conc. rises or falls below the acceptable limit?
- the alpha and beta cells in the IOL detect the change.
Blood glucose too high = insulin released
Blood glucose too low = glucagon released
78
What cells detect a high blood glucose conc. & What happens when insulin is secreted into the blood?
Beta cells in the IOL detect the raised conc.
- beta cells secrete insulin into blood
- it travels throughout body in circulatory system.
- target cells are LIVER cells, MUSCLE cells & other body cells inc. those in brain.
79
What happens when insulin reaches the target cells?
- the target cells have specific receptors for insulin.
> when insulin binds to the receptor which activates enzyme TYROSINE KINASE = associated with the receptor on inside of membrane.
> TYROSINE KINASE: causes phosphorylation of inactive enzymes in the cell.
- this activates the enzymes leading to a cascade of enzyme-controlled reactions inside cell.
80
List the several effects that insulin has on cells.
- more transporter proteins specific to glucose are place into cell surface membrane (achieved by causing vesicles containing these transporter proteins to fuse with membrane)
- more glucose enters cell (permeability of cell membrane has increased)
- glucose in cell is converted to glycogen for storage (glycogenesis)
- more glucose is turned into fats (stored as energy source in cytoplasm)
- more glucose is used in respiration
∴ increased uptake up glucose, through the specific transporter proteins, REDUCES blood glucose conc.
81
What cells detect a low glucose conc.? How do they deal with this?
- a low glucose conc. is detected by the alpha cells of the IOL.
- the alpha cells then secrete GLUCAGON into blood
82
What is insulin?
A small protein (hormone) of 51 amino acids
83
What is glucagon?
A small protein containing 29 amino acids
84
Which cells does glucagon bind to and how?
Glucagon binds to specific receptors on the cell membranes of LIVER CELLS.
85
What happens after glucagon binds to the receptors?
- it stimulates a G protein inside membrane, which activates adenyl cyclase inside each cell.
86
What is the role of adenyl cyclase?
- converts ATP to cAMP, which activates a series of enzyme-controlled reactions in cell.
87
List the several effects of glucagon.
- glycogen = converted to glucose (GLYCOGENOLYSIS) by phosphorylase A (an enzyme activated in cascade)
- amino acids & fatty acids = converted into glucose (GLUCONEOGENESIS)
- more fatty acids are used in respiration.
