5.4 hormonal communication Flashcards
define endocrine system
a communication system using hormones as signalling molecules released into the bloodstream
define hormones
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
define target cells
cells that posses a specific receptor on their plasma membrane and the shape of the receptor is complementary to the hormone molecules
what are the 2 different types of hormones
protein
steroid
Describe the difference between steroid and protein hormones
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
what are endocrine glands
ductless glands that consist of groups of cells that manufacture and release hormones directly into the blood capillaries running through the gland
define exocrine glands
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
what are non-steroid hormones also known as
first messengers
Describe the action of non-steroid hormones and the activation of the second messenger
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
what is the adrenal cortex
the outer layer of the adrenal gland
what is the adrenal gland
one of a pair of gland lying above the kidneys which release adrenaline and a number of other hormones known as corticoids
What is the adrenal medulla
the inner layer of the adrenal gland
What is the name of the outermost layer of the adrenal cortex
zona glomerulosa
what is the name of the middle layer of the adrenal cortex
zona fasciculata
what is the name of the inner most layer of the adrenal cortex
zona reticularis
what are the names of the layers in the adrenal cortex from out in
zona glomerulosa
zona fasciculata
zona glomerulosa
What is the function of the zona glomerulosa
secretes mineralocoricoids such as aldosterone which acts on absorption of sodium and decreasing absorption of potassium ions, therefore increasing water retention and blood pressure
What is the function of the zona fasciculata
secretes glucocorticoids such as cortisol which control metabolism of carbohydrates, fats and proteins in the liver and is also released in response to stress
what is the role of the zona reticularis
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
what kind of hormones does the adrenal cortex and medulla release
the medulla releases protein hormones such as adrenaline and noradrenaline whereas the adrenal cortex releases steroid hormones
Describe the action of steroid hormones
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
what hormones does the adrenal medulla release
adrenaline and noradrenaline
what are the effects of adrenaline on the body
causing body hair to stand erect
increasing heart rate
dilating the pupils
increasing mental awareness
inhibiting the action of the gut
describe the pancreas
they are a small organ below the stomach with both endocrine and exocrine functions
what are the two main secretions of the pancreas
pancreatic juice containing enzymes which are secreted into the small intestine
hormones which are secreted from the islets of Langerhan into the blood
where are the exocrine cells found in the pancreas
they are in small groups surrounding tiny tubules and each group is called an acinus or acini plural
Describe the exocrine function of the pancreas
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
Describe the contents of the pancreatic fluid
pancreatic amylase
lipase
trypsinogen
Explain why trypsinogen is in pancreatic fluid and not trypsin
because trypsinogen is an inactive form of trypsin and it is so that the pancreatic duct is not broken down by the protease enzyme
describe the structure and function of the endocrine system of the pancreas
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
describe the release of insulin from the beta cells
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
What is the name of the enzyme used in metabolism of glucose to make ATP
glucokinase
what is the normal blood concentration of glucose
4-6 mmol/dm3
define hypoglycaemia
when the blood glucose is too low for a long period of time
Define hypergylcaemia
When blood glucose remains too high for a long period of time
What happens if blood glucose concentration changes
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
Describe the effects of insulin on the cell
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
What are the effects of glucagon on a cell
glycogen is converted into glucose glycogenolysis
more fatty acids are used in respiration
amino acids and fats are converted into additional glucose by gluconeogenesis
Describe how insulin acts on a cell as a first messenger
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.
define diabetes mellitus
a condition in which blood glucose concentration cannot be controlled effectively
define stem cells
unspecialised cells that have the potential to develop into any type of cell
describe type 1 diabetes
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
describe type 2 diabetes
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
What are the treatments for type 1 diabetes
insulin injections
insulin pump therapy
islet transplantation
pancreas transplant
using stem cells to grow new islets of langerhan
How would you treat type 2 diabetes
changes in lifestyle
what is the source of insulin for treating diabetes
used to be extracted from the pancreas of animals such as pigs however more recently it is from bacteria that have undergone genetic modification
What are the advantages of using GM bacteria as a source of insulin and not animal insulin
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
