5.4 Hormonal communication Flashcards
(118 cards)
1
Q
What is the endocrine system?
A
A communication system using hormones as signalling molecules.
2
Q
What is a hormone?
A
A molecule (protein or steroid) that is released by an endocrine gland directly to the blood. Thye act as messangers, carrying a signal from the endocrine gland to a specific target organ or cell.
3
Q
What is a target cells for non-steroid hormones?
A
Cells that possess a specific receptor on the plasma membrane- recpeptors are complementary to the sah[e of the hormone molecule.
4
Q
What are the 2 types of hormones?
A
- Protein and peptide hormones
- Steroid hormones
5
Q
Are protein hormones soluble in the phospholipid membrane- how does this affect the hormone entering the cell?
A
Proteins are not soluble in the phospholipid membrane and do not enter the cell. Protein hormones have to bind the cell curface membrane and release a second messanger inside the cell.
6
Q
Are steroid hormones soluble in the phospholipid membrane- how does this affect the hormone entering the cell?
A
Steroid hormones are soluble in the phospholipid bilayer, so can pass through the membrane and enter the cell and the nucleaus, to have a direct effect on the DNA in the nucleus.
7
Q
Are steroid hormones soluble in the phospholipid membrane- how does this affect the hormone entering the cell?
A
Steroid hormones are soluble in the phospholipid bilayer, so can pass through the membrane and enter the cell and the nucleaus, to have a direct effect on the DNA in the nucleus.
8
Q
Where are hormones released from endocrine glands?
A
Directly into the blood.
9
Q
What is an endocrine gland?
A
Endocrine glands are ductless glands that consist of groups of celljs that manufacture and release the horone into the blood in capilaries running through the gland.
10
Q
What are the 7 major endocrine organs in the human body?
A
- Pituitry gland
- Thyroid gland
- Thymus
- Adrenal gland
- Pancreas
- Ovaries (in females)
- Testes (in males)
11
Q
What are the 2 types of in the mammailian body?
A
- Endocrine glands
- Exocrine glands
12
Q
What is an exocrine gland?
A
A group of cells surrounding a small duct, which leave the site where secretion is required.
13
Q
What are cells called that receive an endocrine signal?
A
Target cells
14
Q
For non-steroid hormaones, what must the target cell have?
A
The target cell must have a specific receptor on their plasma membrane that is complementary in dhape to the signalling molecule (hormone).
15
Q
Why is it significant that target cells for non-steriod hormones must have a specific repector?
A
It means a hormone can be carroed in the blood without affecting cells that do not pocess the correct specific shape.
16
Q
How do non-steroid hormones stimulate a change of activity in the cell? (First and second messengers)
A
- Non-steriod hormones (first messengers) bind to the specific receptor on the cell surfece membrane and initiate an effect on the inside of the cell.
- They release a second messanger, which stimulates and change in activity in the cells.
17
Q
Describe what is happening here?
A
- Hormone (first messenger) binds in compemem]ntary receptor.
- This activates the G-protein in the cell-surface membrane.
- The G-proetin ,molecule actovator an effector molecule (adenyl cyclase) which converts ATP to cyclic AMP (second mesenger).
- The second messenger can act directly of another protein or can initiate a cascade of enzyme-controlled reactions that alter the acttivity of the cell.
18
Q
What is the adreanl cortex?
A
The outer layer of the adreanl gland.
19
Q
What is the adreanl gland?
A
One of a pair of glands lying above the kidneys, which release adrenaline and a number of other hormones known as corticoids- such as aldosterone.
20
Q
What is adrenaline?
A
A hormone released from the adrenal glands ,which stimulates the bodu to prepare for fight or flight.
21
Q
What is the adrenal medulla?
A
The inner layer of the adreanal gland.
22
Q
What is the adrenal medulla?
A
The inner layer of the adreanal gland.
23
Q
What is each adreanal gland made up of?
A
Each gland is divided into the outer adreanal cortex and the. inner adreanal medulla. Both reigions are well suppied with blood vessels and produce hormones which are secteares directly into blood vessles.
24
Q
What 3 layer is the adreanl cortex made up of? Start from the outermost layer.
A
- Zona glomerulosa
- Zona fascicuata
- Zona reticularis
25
What is the outermost layer of the adreanal cortex?
Zona glomerulosa
26
What is the middle layer of the adreanal cortex?
Zona fasciculata
27
What is the innermost layer of the adreanal cortex?
Zona reticularis
28
What does that zona glomerulosa secrete? What does this do?
The zona glomerulosa sectretes mineralocorticoids such as aldosterone.
These help to control the concentrations of sodium and potassium in the blood, and blood pressure. Alderosterone increases the absorbtion of sodium ions, decreses the absorbtion of potassium ions ans increases water retention.
29
What does the zona fasciculata secrete? What does this do?
The zona fasciculata secretes glucocorticoids such as cortidol.
These help control the metabolism of carbohydrates, fats and proteins in the liver. Cortisol is released in the responce to stress or as the result of low blood glucose concentration. It stimulates the production of glucose from stored compounds.
30
What does the zona reticularis secrete and what does it do?
The zona reticularis secretes precursor molcules that are uused to make sex hoemones.
31
What sort of hormone is released from the adrenal cortex?
Steroid hormones.
32
How do steroid hormones create an action in a cell?
* The steroid hormone passes through the cell membrane of the target cell.
* The steroid hormone bonds with a specific receptor (complementary shape) in the cytoplasm.
* The receptor-steriod hormone comple enters the nucleus of the tsrget cell and binds to the specific receptor of the chromosomal material.
* Binding stimulates the production of messenger RNA (mRNA) which codes for the production of proteins.
33
Describe the hormone adrenaline?
Adrenaline is a polar molecule derived from the amino acid tryosine.
34
Adrenaline is poalr- What does this mean for the hormone?
Adrenaline cannot enter through the plasma membrane like a steroid hormone can.
35
What effects does adrenaline have on the body?
Many cells and tissues have receptors for adrenaline, therefore, the effect is widespe]read through the body, for example:
* increasing stroke volume of the heart
* vasoconstriction, raising blood pressure
* dialating pupils
* increwaseing mental awareness
* inhibiting the action of the gut
* causing body hair to stand on end
36
What are beta cells?
Cells found in the islets of Langerhans that secrete the hormone insulin.
37
What is glucgon?
A hormone that cuases an incerase in the blood glucose concentration.
38
What is insulin?
The gormone released from the pancreas, that causes blood glucose levels to go down.
39
Where is the pancreas in your body?
Lies below the stomach.
40
Why is the pancreas unusual?
It has noth exocrine and endocrine functions.
41
What are the 2 main secretions of the pancreas?
* Pancreatic juices containing enzymes into the small intestine.
* Hormones which are secreated from the islets of Langerhans into the blood.
42
What is the exocrine function of the pancreas?
Release digestive enzymes.
43
What is the exocrine part oof the pancreas?
The exocrine cells are in small groups of cells surrounding tiny tubules. Each group of cells is called an acinus. The acini are grouped together into lobules spearaated by connective tissue. The cells on the acini secrete enzymes they synthesis onto the tubules at the centre of the group.
44
What do the tubules from the acini join the interlobular ducts to make up?
Pancreatic duct
45
Where does the pancreatic duct carry fluid to?
The first part of the small intestines.
46
What enzymes does the fluid from the pancreatic duct contain?
* Pancreatic amylase- a catbohydrsase which digests amylose to moltose.
* Trysinogen- an inactive protease which will be converted to the active form trypsin when it enters the duodenum.
* Lipase- digests lipids.
47
What substance does the fluid from the bpancreatic duct contain that isn't an enzyme?
Hydrogencarbonate, which is alkaline. This helps to neutralise the contents of the digestive system that have just left the acidic enviroment of the stomach.
48
In what part of the pancrease is the endocrine function?
In the islets of Langerhans.
49
What makes up the islets of Langerhans?
The islets of Langerhans contain alpha and beta cells make up the endocrine tissue in the pancreas.
50
What do the alpha cell in the islets of Langerhans secrete?
Glucagon
51
What do the beta cell in the islets of Langerhans secrete?
Insulin
52
What does a cross-section through the pancreas look like?
53
Descrive what is happening in this stage of insulin secretion?
The potassium ion channels are normally open and the calcium ion channels are normally closed. POtassium ions diffuse out of the cell making the inside more negative; at rest the potential across the cell is about -70mv.
54
What is happening in this stage of insulin secretion?
When glucose concentations outside the cell are high, glucose molecules move into the cell.
55
What is ahppening in this stage of insulin secretion?
The glucose is quickly used in metabolism to produce ATP. This involves glucokinase.
56
What is happening in this stage of insulin secretion?
Extra ATP causes potassium ion channels to close- this means no potassium ions can leave, altering the cells potential difference- it becomes less negative inside.
57
What is happening in this stage of insulin secretion?
The change in the potential difference caused the calcium ion channels to open.
58
What is happening in this stage of insulin secretion?
Calcium ions enter the cells and cause the secretion of insulin by making the vesicles containing insulin move to the cell surface membrane and fyse with it, releaseing insulin by exocytosis.
58
What is happening in this stage of insulin secretion?
Calcium ions enter the cells and cause the secretion of insulin by making the vesicles containing insulin move to the cell surface membrane and fyse with it, releaseing insulin by exocytosis.
59
What is the normal blood concentration of glucose?
Between 4 and 6 mmol dm^-3.
60
What is said if a persons glucose concentration is allowed to drop below 4mmol dm^-3 and remains too long for a long person?
The person is said to be hypoglycaemic.
61
What is hypoglyceamia?
An inadequate delivery of glucose to the body tissues and, in particular, the brain.
62
What would mild hypogyceamia cause?
Tiredness and irratibility.
63
What would severe hypoglyceamia cause?
Imperment of brain function and coonfusion, which may lead to seizures, unconciousness and even death.
64
What is it called when blood glucose levels are allowed to rise too high for long periods of time?
Hyperglycaemia.
65
What would permanently high blood glucose concentrations lead to?
This can lead to significant organ damage.
66
What can be used as the diagnosis for diabetes mellitus?
A blood glucose concentration consistantly higher than 7mmol dm^-3.
67
What do the islets of Langerhans consistantly monitor?
They consistantly monitor the concentration of the glucose in the blood.
68
What do the islets of Langerhans do if they detect a change in the concentration of blood glucose?
If the concentration falls, away from the acceptable concentrations, then the alpha and beta cells repond by releasing the relavent hormone: insulin if glucose is high and glucagon if its low.
69
What cells do insulin and glucagon act on?
These hormones act on the cells in the liver (hepatocytes) which can store glucose in the form of glycogen or convert it back to glucose.
70
What is glucose converted into to store in the liver?
Glycogen
71
What is the enzyme called that is released if the glucose concentration is too high?
Glucagon
72
What is a high blood glucose concentration detected by?
Beta cells in the islets on Langerhans.
73
How do beta cells respong to a high blood concetration of glucose?
They secrete insulin into the blood, which travels throughout the body in the circulatory system. The target cells are the liver cells, muscle cells and some other body cells inculiding the brain.
74
How many amino acids make up the enzyme insulin?
51 amino acids.
75
Can insulin pass through the cell surface membrane of a target cell?
No. it contains 51 amino acids, so is too big to pass through.
76
As the insulin molecules cannot pass through the target cells surface membrane, how do they affect the cell?
The target cells process specific membrane-bound receptors for insulin. When the insulin binds, it aactivated the enzyme tyrosine kinase which is assiciated with the receptor on the inside of the membrane. Tyrosine kinase causes phosphorylation of inactive enzymes inside the cell, acitivating the enzymes leading to a cascade of enzyme-controlled reactions inside the cell.
77
What effect does insulin have on its target cell?
* More transported proteins specific to glucose are placed into the cell surface membrane. This is achieved by causing vesicles containing these transporter proteins to fuse with the membrane.
* More glucose enters the cell.
* Glucose in the cell is converted to glycogen for storage (**glycogenesis**)
* More glucose is converted to fats.
* More glucose is used in respiration.
78
What is going on in this stage of insulin acting on a liver cell?
The liver cells posses a specific membrane-bound receptor for insulin.
79
What is going on in this stage of insulin acting on a liver cell?
Once the insulin has bound to the membrane-bound receptor, it activates the enzyme tryosine kinase. Tyrsine kinase causes the **phosphorylation** of the inacttive enzymes, activating them leading to a cascade on enzyme-controlled reactions inside the cell.
80
What is going on in this stage of insulin acting on a liver cell?
After the inactive enzymes are activated which leads to a cascade of enzyme-controlled reactions, some of these cause vesicles containing glucose transporter proteins to be inserted into the membrane. This causes extra glucose to enter the cell which is converted to glycogen, fats and used in resipiation.
81
How is glucose taken into a liver cell?
Through specific transported proteins.
82
Which cells detect if the blood glucose concentration is too low?
The alpha cells in the islets of Langerhans.
83
What do the alpha cells in the islets of Langerhans secrete when they change the relavent change in blood glucose concentration?
When the blood glucose concentration is too low, the secrete glucagon into the blood.
84
How many amino acids does glucagon contain?
29 amino acids.
85
What are the target cells for glucagon enzymes?
Liver cells (**hepatocytes**), which pocess the specific receptor for glucagon.
86
How does glucagon act on a hepatocyte?
When the blood passes these cells gglucagon binds to the receptors. This stimulates a G protein inside the membrane, which activates adenyl cyclase inside each cell. The adenyl cyclase converts ATP to cAMP, which activated a series of enzyme-controlled reactions in the cell.
87
What effects does glucagon cause in a hepatocyte?
* Glycogen is converted into glucose by phosphorylase A.
* More fatty acids are used in respiration.
* Amino acids and fats are converted into additional glucose by gluconogenesis.
Overall, the blood glucose concentration increases.
88
By what process is glycogen, amino acids or fats conveted to glucose?
Glycogenesis.
89
When glucagon acts on a hetatocyte, how is glycogen conveted in to glucose?
By **glycogenesis** by **phosphorylase A**, which is one of the enzymes acitived in the cascade.
90
By what mechanism is the concentration of blood glucose controlled by?
Negative feedback.
91
Insulin and glucagon are antagonistic. What does this mean?
They have opposite effects on blood glucose concentrations. One of their effects is it inhibit the effects of their opposing hormone.
92
Will the concentration of glucose stay constant in the blood?
No, it will fluctuate around the required concentration.
93
What is diabetes mellitus?
A condition in which blood glucose concentrations cannot be controlled effectively.
94
What is A condition in which blood glucose concentrations cannot be controlled effectively?
Diabetes Mellitus
95
What are stem cells?
Unspecialised cells that have the potential to develop into ay type of cell.
96
What happens if in somebodys body if they have diabetes millitus?
Their body is no longer able to produce sufficient insulin to control its blood glucose concentration.
97
What is type 1 diabetes also known as?
Insulin-dependant diabetes or juvenile-onset diabetes.
98
When does type 1 diabetes usually start?
Childhood.
99
What is type 1 diabetes a result of?
It is the result of an **autoimmune responce** in which the body's immune system attacks and destroys the beta cells. It can also be a result of a **viral attack**.
100
What is a person with type 1 diabetes unable to do with excess glucose in their blood?
They cannot store excess glucose as glycogen therefore, excess glucose is not removed as quicklty, leaving a prolonged period of high concentration, but when it falls, there is no stores of glycogen that can be used to release glucose.
101
What is type 2 diabetes also known as?
Non-insulin dependant diabetes.
102
What does it mean if someone has type 2 diabetes?
They can produce insulin, but not enough.
103
What is the cause of type 2 diabetes?
Aspeople age, their responsivness to insulin declines beacuse the specific receptors on the surface of the liver and muscle become less responsive and the target cells lose their ability to respond to the insulin in the blood.
104
What is the blood glucose concentration like in a person with type 2 diabetes? What effects does this have?
In type 2 diabetes the blood glucose concentration is almost permenently raised, which cause damage the major organs and circulation.
105
What factors can cause early onset type 2 diabetes?
* Obesity
* Lack of regular exercise
* A diet high in sugars, particularly refined sugars
* Being of Asian or Afro-Caribbean origin
* Family history
106
What happens to diabetes over time?
The effects of diabetes are severe and become worse over time so its importents to diagnose it quickly so treatment can be started.
107
How is type 1 diabetes usually treated?
Using insulin injections- the blood glucose concentration is monitored and the correct odse of insulin is administered to keep the levels fairly stable.
108
What are alternative methords to treating type 1 diabetes that aren't insulin injections.
* Insulin pump therapy
* Islet cell transplantation
* A complete pancreas transplant
109
What is insulin pump therapy?
Used to treat type 1 diabetes its a small pump that constantly pumps insul;in into the bloodstream through a needle that is permenently inserted under the skin.
110
What is a islet cell transplantation?
used to treat type 1 diabetes, healthy beta cells from the pancreas of a deceased donor are implanted into the pancreas of the person with diabetes.
111
What has recent research shown could be used to treat type 1 diabetes?
Stem cells could be used to grow new islets of Langerhans in the pancreas.
112
How is type 2 diabetes treated?
It is usually treated by a change in lifestyle- they will be adbused to lose wieght, exercise regularly and carfully monitor their diet- making sure to match carbohydrate intake and use.
113
To treat type 2 diabetes, what can also be done aswell as a change in lifestyle?
Medication can be taken that reduces the amount of glucose the liver releases into the bloodstream or that boosts the amount of insulin that the pancreas releases.
114
In sever cases on type 2 diabetes, what can be done to help treat it?
Insulin injections, use of other drugs that slow down the absorption of glucose from the digestive system.
115
Where does insulin used to treat diabetes in humans come from?
Its extracted from the pancreas of animals- usually from pigs as this matches human insulin most closely. Also recently, insulin has been produced by *Eschichia coli* bacteria that have undergone genetic modification to manufacture human insulin.
116
What bacteria is used to produce insulin to treat diabetes in humans?
*Escherichia coli* bacteria
117
What are the advantages of using insulin from genetically modified bacteria:
* It is an exact copy of human insulin, so it acts faster and is more effective.
* There is less of a chance of developing tolerance to insulin.
* There is less chance of rejection due to the immune responce.
* There is a lower risk of infection.
* Its cheaper to manufacture the insulin than it is to extract it from animals.
* The manufacturing process is more adaptable to demand.
* Some people are less likely to have morol objections.
