5.4 Flashcards
what are examples of exocrine glands
-pancreas
-salivary glands
-liver
-stomach
what are examples of endocrine glands
-pituitary gland
-thyroid gland
-adrenal gland
-islets of Langerhans in pancreas
-ovaries
-testes
what does the salivary gland secrete
secretes saliva
what does the pituitary gland secrete
secretes many hormones (e.g ADH)
what does the thyroid gland secrete
secretes parathyroid, secretes
what does the adrenal glands secrete
release adrenaline and a number of of other hormones known as corticoids
what does the islets of Langerhans in the Pancreas secrete
secretes insulin and glucagon which goes into the blood
what do the ovaries secrete
secrets oestrogen and progesterone
what do the testes secrete
secretes testosterone
what does the pancreas secrete
secretes pancreatic juice
what does the stomach secrete
secretes gastric juice
what does the liver secrete
secretes bile
what are the 2 types of gland
endocrine and exocrine
what are endocrine glands
endocrine glands secrete hormones directly into the bloodstream
what are exocrine glands
secrete hormones into a duct (tube) which carries the hormone to a specific part of the body e.g. salivary gland
why will hormones only affect certain target cells/tissue
the target cells/ tissues will have the specific receptor for the hormone
define the endocrine system
a communication system which uses hormones as signalling molecules
uses blood as the circulatory system to transport its molecules
what are hormones
Hormones are molecules (proteins or steroids) that are released by endocrine glands directly into the blood.
They act as messengers, carrying a signal from the endocrine gland to a specifc target organ or tissue.
What are the two types of Hormones?
- Protein and Peptide Hormones
(Adrenaline, Insulin, and Glucagon) - Steroid Hormones
(Oestrogen and Testosterone)
How do Protein and Peptide Hormones work?
Proteins are insoluble in the phospholipid membrane and do not enter the cell.
Protein hormones need to bind to the cell surface membrane and release and second messager inside the cell
How do Steroid Hormones work?
Steroid hormones are soluble in the phospholipid membrane and enter the cell and the nucleus, to have a direct effect on the DNA in the nucleus.
What are Target cells?
For non-steroid hormones
Target cells possess a specific receptor on their plasma membrane.
The shape of the receptor is complementary to the shape of the Non-Steroid Hormone molecule.
What are Endocrine glands?
Endocrine glands release hormones directly into the blood.
They are ductless and consist of cells that manufacture the hormone and then secrete it into capillaries running through the gland
What are Exocrine glands?
Exocrine glands do not secrete hormones, but usually enzymes.
They consist of cells surrounding a small duct which then leads to the site where the secretion is needed.
Why are Non-Steroid hormones known as First Messengers?
Non-steroid hormones cannot pass through the plasma membrane.
They are signalling molecules outside the cell that bind to the cell surface membrane and initiate an effect inside the cell.
It is often the release of another signalling molecule inside the cell, which is called the Second Messenger.
What are Second Messengers?
The Second Messenger stimulates a change in the activity of the cell.
What are the Steps of Action of Non-Steroid Hormones (adrenaline)?
- The Non-steroid hormone binds to a complementary receptor on a cell surface membrane. It is the first messenger.
- The G-Protein on the inside of a membrane is activated when the hormone binds.
- The G-protein in turn activates an effector molecule. This is usually an enzyme that converts an inactive molecule into an active second messenger.
In many cells, the effector molecule is the enzyme Adenyl Cyclase, which converts ATP to cyclic AMP (cAMP).
- The second messenger is cAMP which may act directly on another protein (such as an Ion channel), or it may initiate a cascade of enzyme-controlled reactions that alter the activity of the cell.
where is adrenaline secreted from
from the adrenal glands (adrenal medulla)
when is adrenaline sectreted
during fight or flight
is adrenaline a peptide or steroid hormone
peptide hormone
where are the receptors that adrenaline binds to
receptors on the cell surface membrane
detail of adrenaline
detail of adrenaline
detail of adrenaline
detail of adrenaline
Where are the Adrenal glands located?
The Adrenal glands are found anterior/ just above the kidneys. There is one on each side of the body.
What are the two main regions the Adrenal gland is divided into?
Each Adrenal gland is divided into the Outer Adrenal Cortex and the inner Adrenal Medulla
Both regions are well supplied with blood vessels and produce hormones that are secreted directly into the blood vessels.
which hormones are secreted by the adrenal medulla
adrenaline and noradrenaline
are the adrenal glands endocrine or exocrine, how do you know
endocrine (blood secreted into blood)
both regions of the gland are well supplied with blood vessels
What are the three regions of the Adrenal Cortext in between the capsule and the medulla?
- Zona Glomerulosa (Outer)
- Zona Fasciclulata (Middle)
- Zona Reticularis (Inner)
How does the Adrenal Cortex synthesise its Hormones?
The Adrenal Cortex uses Cholesterol to produce Hormones.
These hormones are steroid based and so are able to enter cells directly by dissolving into the cell surface membrane and having a direct effect in the DNA to cause Protein Synthesis.
What are the steps for the Action of Steroid Hormones?
- The steroid hormone passes through the cell membrane of the target cell.
- The steroid hormone binds with a specific receptor in the cytoplasm.
- the receptor-steroid hormone complex enters the nucleus of f the target cell and binds to another specific receptor on the chromosomal material
- Binding stimulates the production of mRNA molecules, which code for the production of proteins
What is the Zona Glomerulosa and what does it secrete ?
The Zona Glomerulosa is the outermost layer, which secretes Mineralocorticoids such as Aldosterone.
What is the role of Mineralocorticoids secreted from the Zona Glomerulosa?
-Mineralocorticoids control the concentration of Sodium and Potassium ions within the blood
- Maintain blood pressure
What is the role of Aldosterone? ( this is an eg of Mineralocorticoids)
Aldosterone acts on the cells of the distal tubes and the collecting ducts in the kidney.
- Increases the absorption of Sodium ions
- Decreases the absorption of Potassium ions
- Increases Water retention so increasing blood pressure.
What is the role of Zona Fasciculata and what does it secrete?
The Zona Fasciculata is the middle layer, which secretes Glucocorticoids such as Cortisol
What is the role of Glucocorticoids secreted from the Zona Fasciculata?
Glucocorticoids control the metabolism of Carbohydrates, fats, and proteins in the Liver
What is the role of Cortisol? (an example of a Glucocorticoid)
Cortisol is released in response to stress or as a result of low blood glucose concentration.
- It stimulates the production of glucose from stored compounds (glycogen, fats, and proteins) in the Liver.
what is the role of the Zona Reticularis and what does it secrete
The Zona Reticularis is the innermost layer, which also secretes Cortisol and molecules that are used to make sex hormones.
When will the Zona Reticularis release Sex Hormones?
If the correct enzymes for the release of Cortisol aren’t present, then the Zona Reticularis releases precursors Androgens which are taken up by the Ovaries and Testes for the production of Sex hormones.
What Hormones are secreted from the Adrenal Medulla?
The Adrenal Medulla is found at the centre of the Adrenal Gland and secretes Adrenaline and Noradrenaline.
How does the Adrenal Medulla synthesise its Hormones?
The Adrenal Medulla uses Amino acids to produce Hormones.
These hormones are Protein/Polypeptide based which means they are polar and so are unable to dissolve through the lipid membrane.
What is the role of Adrenaline?
- Prepares body for fight or flight response
- Flight, Flight, Fear, Flirt
Why does Adrenaline have a widespread effect in the body?
Adrenaline has a widespread effect as many cells and tissues have adrenaline receptors.
Its released from the adrenal medulla into the blood and is transported around the body
What are the effects of Adrenaline around the body?
-relaxing smooth muscle in the bronchioles
-increasing stroke volume of the heart
-increasing heart rate
-causing general vasoconstriction the raise blood pressure
-stimulating conversion of glycogen to glucose
-dilating the pupils
-increasing mental awareness
-inhibiting action of the gut
-causing body hair to stand erect.
what is high blood pressure detected by
-detected by stretch receptors (receptors in aorta/ carotid sinus/ carotid artery)
what two unusual functions does the pancreas have
the pancreas has both exocrine and endocrine functions
where is the pancreas found
just below the stomach
what are the two main secretions in the pancreas
-pancreatic juices containing enzymes which are secreted into the small intestine
-hormones which are secreted from the islets of Langerhans into the blood
what are the two roles of the pancreas
-controls sugar levels
-break down of food you eat
describe the cells that are responsible for synthesising and releasing pancreatic juices.
the cells responsible for synthesising and releasing pancreatic juices make up a structure called an acinus (plural acini) which has a tubule at the centre where the enzymes produced are secreted into. The tubules join to form intralobular ducts that eventually combine to make the pancreatic duct, here the fluid is moved into the small intestine (duodenum)
The acini are grouped together into small lobules separated by connective tissue.
what enzymes do the fluid from the pancreatic juices contain
contains:
-pancreatic amylase- a carbohydrase which digests amylose to maltose.
-trypsinogen- an inactive protease which will be converted to the active form trypsin when it enters the duodenum
-lipase- which digests lipid molecules
apart from the enzymes present in the pancreatic juices, what else does it contain
-the fluid also contains sodium hydrogen carbonate, which makes it alkaline. This helps to neutralise the contents of the digestive system that have just left the acid environment of the stomach
-the fluid contains water
what is dispersed in small patches among the lobules of acini
-islets of Langerhans
what are the islets of Langerhans made of and what is it more commonly made of
-made of a-cells
-made of b-cells
-beta cells are more abundant and are found in the centre portion of the islets
endocrine function:
what do the a-cells secrete
what do the b-cells secrete
-a-cells secrete glucagon
-b-cells secrete inulin
when beta cells in the islets of Langerhans secrete insulin, what effect does this have
it reduces blood glucose concentration
if blood glucose conc. drops too low what must not be secreted
insulin
describe the control of insulin secretion when blood glucose is too high
1.the cell membrane of the beta cells contain both calcium ion channels and potassium ion channels
- The potassium ion channels are normally open an the calcium ion channels are normally closed. Potassium ions diffuse out of the cell making the inside of the cell more negative, at rest the potential difference across the membrane is about -70 mV.
- if glucose concentrations outside the b-cell are high, glucose enters the b-cell (occurs by facilitated diffusion)
4.the glucose is then phosphorylated to produce ATP, this involves the enzyme glucokinase. This is called the glycolytic pathway/ glycolysis
- This extra ATP causes potassium ions to close
- K+ cannot diffuse out which alters the potential difference across the cell membrane- it becomes less negative inside (-30mV) membrane depolarises.
- Ca2+ channels that are normally closed then open in response to a change in potential difference/ membrane potential. Ca+ ions rush into the cell (voltage gated)
- the Ca2+ ion cause the vesicles to move to the plasma membrane and fuse with it which allows for the release of insulin (contained in vesicles) via exocytosis. Insulin will the convert glucose into glycogen
what is the normal blood concentration of glucose
between 4 and 6 mmol dm-3
when is a person said to be hypoglycaemic
when a persons blood glucose concentration drops below 4 mmol dm-3 and remain too low for long periods
-what is the main problem of hypoglycaemia
-what are mild effects of hypoglycaemia
-what are severe effects of hypoglycaemia
main problem: inadequate delivery of glucose to the body tissues and in particular, the brain
mild effects: tiredness and irritability
severe effects: impairment of brain function and confusion which can lead to seizures, unconsciousness and even death.
what’s hyperglycaemia
where blood glucose concentrations remain high for longer than normal periods (above 6mmol dm-3)
what effects can hyperglycaemia lead to when blood glucose conc. is permanently high
can lead to significant organ failure
how does the islets of Langerhans constantly monitor the concentration of glucose in the blood
if the conc. rises or falls, a and b-cells will detect this and will respond by producing glucagon or insulin
what does the hormones of insulin and glucagon act on
acts on the cells in the liver (hepatocytes) which can store glucose in the form of glycogen. when there is excess glucose in the blood its converted to glycogen, if glucose is needed to raise the blood conc. then glycogen is converted back to glucose.
when blood glucose level is too high…
what is the effect on the pancreas
what is the effect on liver and muscle (can store glucose as glycogen)
what is the effect on glucose level as a result
pancreas:
detection by b-cells that level is too high. Insulin secreted into the blood. Glucagon inhibited
liver and muscle:
glucose in blood moves into liver and muscle.
liver and muscle convert glucose into glycogen
result:
glucose concentration falls
when blood glucose level is too low…
what is the effect on the pancreas
what is the effect on liver and muscle (can store glucose as glycogen)
what is the effect on glucose level as a result
pancreas:
detected by a-cells, a-cells secrete glucagon into the blood
insulin inhibited
liver and muscle:
liver and muscle do not convert glucose into glycogen,
liver converts glycogen into glucose and release glucose into the blood
result:
glucose concentration rises
insulin travels through the circulatory system, where are insulins target cells found:
target cells are liver cells, muscle cells and some other boy cells including in the brain
why cant insulin and glucagon pass through the membrane
it is a protein hormone
describe the activation of insulin inside the liver cell
1-target cells contain specific membrane bound receptors for insulin
2- when insulin binds to the insulin receptor, this activates the enzyme tyrosine kinase which is associated with a receptor on the inside of the membrane.
3- tyrosine kinase causes the phosphorylation (addition of one or more phosphate groups) of inactive enzymes in the cell which makes the enzymes active (due to tertiary structure changes)
4-this activates the enzymes leading to a cascade of enzyme-controlled reactions inside the cell.
-active enzymes lead vesicles containing glucose transporter proteins
-insulin causes a conformational change in existing transporter proteins causing them to open so more glucose entering the cell
action of insulin on the liver cells:
what does the resulting glucose from active enzymes and opening of glucose transporter proteins in the cell converted to
-glucose in cell is converted to glycogen -glycogenesis
-conversion of glucose to fats
-glucose used in respiration
what are the several effects that insulin has on cells (e.g. liver cells)
-more transporter proteins specific to glucose are placed into the cell surface membrane. This is achieved by causing vesicles to fuse with the membrane
-more glucose enters the cells
-glucose in the cell is converted to glycogen for storage (glycogenesis)
-more glucose is converted to fats
-more glucose is used in respiration
the increased uptake of glucose, through the specific transporter proteins, reduces the blood glucose concentration
where are glucagon’s target cells
found in the hepatocytes (liver cells)
when blood glucose drops too low and glucagon passes hepatocytes, what occurs
-glucagon binds to specific receptors
-this stimulates a g protein inside the membrane, which activates adenyl cyclase
-adenyl cyclase converts ATP to cAMP, which activates a series of enzyme controlled reactions in the cell, this leads to the effects of glucagon (fc 86)
what are the 3 effects of glucagon
- glycogen is converted to glucose (glycogenolysis) by phosphorylase A, which is one of the enzymes activated in the cascade ( ref to. adenyl cyclase cascade)
-more fatty acids are used in respiration
-amino acids and fats are converted into additional glucose by gluconeogenesis
the overall effect is to increase blood glucose conc.
describe the negative feedback pathway for when there is a rise in blood glucose concentration (away from 4-6 mmol dm-3)
rise in blood glucose conc.
↓
detected by B-cells in the islets of Langerhans
↓
B-cells secrete insulin into the blood
↓
insulin detected by receptors on liver and muscle cells
↓
liver and muscle cells remove glucose from blood and convert glucose to glycogen
↓
glucose concentration falls
describe the negative feedback pathway for when there is a fall in blood glucose concentration
fall in blood glucose conc.
↓
detected by a cells in the islets of Langerhans
↓
a cells secrete glucagon into the blood
↓
glucagon detected by receptors on liver cells
↓
liver cells convert glycogen to glucose and release glucose into the blood
↓
glucose concentration rises
are insulin and glucagon antagonistic?
yes
define:
neo-
lysis-
genesis-
neo- new/ from scratch
lysis- breakdown
genesis- creation of/ making
define gluconeogenesis
the production of glucose from non-carbohydrate sources such as amino acids and lipids
define glycogenolysis
the breakdown of glycogen into glucose( by phosphorylase A
define glycogenesis
the conversion of glucose into glycogen for storage
what is diabetes mellitus
a condition in which the body is no longer able to produce sufficient insulin to control its blood glucose concentration.
what can diabetes mellitus lead to
can lead to prolonged very high concentrations of glucose (hyperglycaemia) after a meal rich in sugars and other carbohydrates.
It can also lead to the concentration dropping too low (hypoglycaemia) after exercise or fasting (glucose can’t be stored)
what is type 1 diabetes
Type 1 diabetes is known as insulin-dependent diabetes and usually starts in childhood
what is thought to cause type 1 diabetes
type 1 diabetes is thought to be the result of an autoimmune response in which the body’s immune system attacks and destroys beta cells.
type 1 diabetes may also result from a viral attack
what does type 1 diabetes cause
a person with type 1 diabetes is unable to synthesise sufficient insulin.
This means they are unable to store excess glucose as glycogen, meaning they have a high blood content.
However, when their blood glucose level falls (after exercise), there are no glycogen stores to replace the depleted glucose. This causes a low blood glucose content.
what is type 2 diabetes known as and when does it develop
type 2 diabetes is known as non-insulin dependent diabetes and usually develops later in life
what does type 2 diabetes cause
a person with type 2 diabetes can produce insulin but not enough.
In type 2 diabetes, the blood glucose concentration is permanently raised, which can damage the major organs and circulation
what factors seem to bring on an earlier onset of 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
what is thought to cause type 2 diabetes
as people age, their responsiveness to insulin declines.
This is probably because the specific receptors on the surface of the liver and muscle cells become less responsible and lose their ability to respond to insulin in the blood.
why is it important that diabetes is treated early on?
the effects of diabetes is severe and become worse with time, this is to ensure treatment can start early on
how is type 1 diabetes generally treated?
type 1 diabetes is usually treated using insulin injections. The blood glucose concentration must be monitored and the correct dose of insulin administered to keep glucose concentration fairly stable.
what are alternatives to giving insulin injections for treating type 1 diabetes (3)
-insulin pump therapy - a small device constantly pumps insulin ( at a controlled rate ) into the bloodstream through a needle that is permanently implanted 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 diabetes.
-a complete pancreas transplant
what does the future of treating type 1 diabetes look like
-it may be possible to treat type 1 diabetes using stem cells to grow new islets of Langerhans in the pancreas.
this would give the patient freedom from daily insulin injections
where can scientists find stem cells
-common sources are bone marrow or the placenta
-scientists have found precursor cells in the pancreas of adult mice. these cells are capable of developing into a variety of cell types and may be true stem cells. If these cells were found in the human pancreas then beta cells could be made
how can we treat type 2 diabetes
type 2 diabetes is usually treated by changes in lifestyle. This includes:
-losing weight, exercising regularly and carefully monitoring their diet, taking care to match carbohydrate intake and use.
This may be supplemented medication that reduces the amount of glucose the liver releases to the blood stream or that boosts the amount of insulin released from the pancreas.
in severe cases, further treatment may include insulin injections or the use of other drugs that slow down the absorption of glucose from the digestive system
how can we source insulin
Insulin used to be extracted from the pancreas of animals - usually from pigs as this matches human insulin most closely.
However more recently, human insulin has been produced by genetically modified bacteria
what are the advantages of using insulin from genetically modified bacteria?
-its an exact copy of human insulin, therefore it is faster acting and more effective
-there is less chance of developing tolerance to insulin
-there is less chance to rejection to an immune response
-there is lower risk to infection
-it is cheaper to manufacture insulin than to extract it from animals
-the manufacturing process is more adaptable to demand
-some people are less likely to have moral objections to using the insulin produced from bacteria than to using that extracted from animals
