Module 5.4 Flashcards
What is the endocrine system
a communication system which uses hormones as signalling molecules .
what are hormones
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 special target organ or tissue .
What are target cells
for non steroid hormones , cells that possess a specific receptor on their plasma membrane . The shape of the receptor is complementary to the shape of the hormone molecule . Many similar cells together form target tissue .
what does the endocrine system use to transport and what is transported
The endocrine system uses the blood circulatory system .
-The signals released by the endocrine system are called hormones .
What is the first type of hormone
protein and peptide hormones and derivatives of amino acids (adrenaline , insulin and glucagon )
what is the second type of hormone
steroid hormones (oestrogen and tesosterone )
how do protein and peptide hormones work
these are not soluble in the phospholipid membrane and do not enter the cell . Protein hormones need to bind to the cell surface membrane and release a second messenger inside the cell ..
how do steroid hormones work unlike protein and peptide hormones
steroid hormones , however , can pass through the membrane and enter the cells and the nucleus that have a direct effect on the DNA in t the nucleus .
what are the endocrine glands
hormones are released directly into the blood from the endocrine glands . The endocrine glands are ductless glands , they consist of groups of cells that manufacture and release the hormone directly into the blood in capillaries running through the gland .
detecting the signals
hormones always a specific function , they are transported all over the body , they have an effect in one type of tissue only , target cells . ( they can also be widely dispersed )
how to target cells work for nonsteroid hormones
target cells and must possess a specific receptor on their plasma membrane , that is complementary in shape to the shape of the signalling moelcule (hormone ) the hromone binds to this receptor and intiiates changes int he cell .
benefits of having a receptor cell
then all the cells can respond to the signal , however , each hormone is different from all others . This means that the hormone can be carried in the blood without affecting the cells that do not possess the correct specific receptor . Only those specific target cells that possess the correct receptor will respond to the hormone .
Why are non steroid hormones first messengers
as they are signalling molecules outside the cell that bind to the cell surface membrane and initiate the effect inside the cell . They usually cause the release of another signalling molecule in the cell which is called the second messenger . This stimulates a change in the activity of the cell
Many steroid hormones act via a g protein in the membrane what does the g protein do
the g protein is activated when the hormone binds to the receptor . The g protein in turn activates an effector molecule usually an enzyme that converts an inactive molecule into the active second messenger .
What is the effector molecule in many cells
the effector molecule is adenyl cyclase which converts ATP to cyclic AMP cAMP , as shown in figure 2 , it is the second messenger . This second messenger 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 .
adrenal cortex
the outer layer of the adrenal gland
adrenal gland
one of a pair of glands lying above the kidneys which release , adrenaline and a n umber of other hormones known as corticoids such as aldosterone .
what is adrenaline
a hormone released from the adrenal gland , which stimulates the body to prepare for flight or fight .
what is the adrenal medulla
the inner layer of the adrenal gland
how is each adrenal gland divided
outer adrenal cortex and the inner adrenal medulla . Both regions are well supplied with blood vessels and produce hormones which are secreted directly into the blood vessels .
what is the outermost layer of the adrenal gland
ZONA GLOMERULOSA- the outermost layer , which secretes MINERALOCORTICOIDS - such as aldosterone .
what is the middle layer of the adrenal cortex
ZONA FASCICULATA - the middle layer which secretes glucocorticoids such as cortisol
what is the inner most layer of the adrenal cortex
ZONA reticularis- this is the inner most layer which is thought to secrete precursor molecules that are used to make sex hormones .
the adrenal cortex uses cholesterol to produce a range of hormones what does this mean .
it means that these hormones are steroid based and are 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 .
step 1 of steroid hormones
the steroid hormones passes through the cell membrane of the target clel .
step 2 of steroid hormones
The steroid hormone binds with a specific receptor (with a complementary shape ) in the cytoplasm
step 3 of steroid hormones
The receptor steroid hormone complex enters the nucleus of the target cell and binds to another specific receptor on the chromosomal material .
step 4 of steroid hormones
binding stimulates the production of messenger RNA mRNA molecules which code for the production of proteins .
Hormones from the adrenal cortex have a variety of roles in the body .
Mineralocorticoids (aldosterone) from the zona glomerulosa , help to control the concentration of sodium and potassium in the blood . As a result they also contribute to maintaining blood pressure .
-Aldosterone acts on the cells of the distal tubules and collecting ducts int he kidneys . IT INCREQASES absorption of sodium ions , decreases absorption of potassium ions increase water retention so increasing blood pressure .
Hormones from the adrenal cortex have a variety of roles in the body . (2)
glucocorticoids , from the zona fasciculata helps to control the metabolism of carbs fats proteins in the liver . Cortisol is released in response to stress or as a result of a low blood glucose concentration . It stimulates the production of glucose from stored compounds , glycogen fats and proteins in the liver .
Hormones from the adrenal cortex have a variety of roles in the body .(3)
cortisol , may also be released by the zona reticularis . However , if the correct enzyme , are not present for the release of cortisol , then the zona reticulitis’s , releases precursors androgens into the blood . These are taken up by the ovaries or testes are converter to sex hormones testosterone and oestrogen e.g , the. The sex hormones help development of the secondary sexual characteristics and regulate the production of gametes
adrenaline is released from the adrenal medulla into the blood is transported throughout the body .
adrenaline is a polar molecules derived from the amino acid tyrosine , this means it cannot enter through plasma membrane like steroid hormone .
-It must be detected by specialised receptor specialised receptors on the plasma membrane , of the target cells ..
many cells and tissues have adrenaline receptors , therefore the effects of adrenaline - works off
-relaxing smooth muscles in the bronchioles
-increasing stroke volume of the heart .
-increasing heart rate
-causing general vasocontraction to raise blood pressure .
adrenaline from adrenal medulla
-stimulating conversion of glycogen to glucose .
-dilating the pupils
-increasing mental awareness
-inhibiting the action of the gut
-causing body hair to stand erect .
beta cells
cells found in the islets of Langerhans that secrete the hormone insulin .
what is glucagon
a hormone that causes an increase in blood glucose concentration .
insulin
the hormone released from the pancreas that causes blood glucose levels to go down
what is the pancreas
the pancreas is a small organ lying below the stomach it is unusual in that it has both EXOCRINE AND ENDOCRIEN FUNCTIONS .
what are the two main secretions of 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 .
exocrine functions
exocrine glands secrete substances into a duct . Most cells in the pancreas synthesis and release digestive enzymes . This is the exocrine functions of the pancreas . The exocrine cells are in small groups surrounding tiny tubules . each group of cells is called an acinus .
what is the acini and what is its funciton
the acini are grouped together into small lobules , separated by connective tissues . The cells of the cini , secrete the enzymes tht synthesise into the tubule , at the centre of the group . The tubules from the acini join to form intraloulr ducts that eventually combine to make up the PANCRETAIC DUCT .
what does the pancrestic duct
it carries the fluid containing the enzymes into the first part of the small intestine the duodenum .
first enzyme in the pancreatic duct
pancreatic amylase - a carodhdyrase whidh digests amylose to maltose .
second enzyme in the pancreatic duct
tryspinogen - an inactive protease which will be converted to the active form trypsin when it enters the duodenum .
third enzyme in the pancreatic duct
lipase - it digests lipid moleucles
what is the fluid
the fluid also contains sodium hydorgencarbonate which makes its alkaline . This helps to neutralise the contents of the digestive system ,t ht have jsut elft the acid environemnt of the stomach .
endocirne function
-dispersed in small patches among hte lobules of acini are the islets of langerhans .
-THE ISLETS OF LANGERHANDS , contian alpha cells , and beta cells that make up the endocrine tissue int he pancreas . The alpha cells secrete glucagon nd the beta cells secrete insulin .
what does the insulin secreted from the ebt cells do
-when the insulin is secreted from the bet cells in the islets of langerhans , it brings about the effects that reduce blood glucose coNCENTRATION ISS TOO HIGH THEN IT IS IMPROTANT THAN INSULIN IS RELEASED FROM THE BETA CELLS . HOWEVEER , IF THE BLOOD GLUCOSE COCNENTRATION DROP TOO LOW IT IS IMPORTANT THAT INSULIN SECRETION STOPS .
Mechanisms for releasing insulin (1)
The cell membrane has potassium ad calcium ion channels .
Mechanisms for releasing insulin (2
the potassium ions channels are normally open - so potasisum ion flows out .
mechanismss for releasing insulin (3)
when blood glucsoe cocnentration is high ,t he glucose mvoes into the cell
mechanisms for releasing insulin (4)
glucose is metabolised to produce ATP .
mechanisms for releasing insulin (5)
the ATP closes the potassium ion channels
mechanisms for releasing insluins (6)
the accumulation of potassium ions alter the potential difference acors the cell membrane - the inside becomes less negative .
mechaanisms for releasing insulin (7)
the changes in potentila differences opens the calcium ion channels .
mechansism for insulin (8)
calcium ions causes the of insuiln to fuse with the cell membrane , releasing insluin b y exocytosis .
the blood glucose concentraation is carefully regulted
the nromal blood glucoe cocnentration of glucose is between four anf 6 mmoldm3
what is Hypogycaemia
-If a persons blood glucose is allowed to drop below 4mm and remain too low for longs periods , the person is said to be hypoglycaemic . THe main problem caused by HYPOGYCEMIA , is an inadequate , delivery of glucose to the body , tissues and in particular to the brain .
what are the symptoms of hypoglycaemia
mild hypoygcamiea may simply cauue tiredness and irritability , . however , in severe cases , there may be impaairmenet , of brain function and confusion , which ma lead ot seizures uncosncioussness and even death .
what is the symptoms of hyperglycaemia
if blood glucose concentration is allowed to rise too high for long periods of time this is known a shyperglycaemia , Permanenlty high blood glucose cocnentrations can lead to signficint organ damage . A blood glcose coenntration that is consistently higher than 7mmdm3 is used as the diagsnosis for diabetes mellitus .
what do the islets of langerhands so
the cells int he islets of langerhansa contantly the montior the concentration of glucose int heblood . If the cocnentration rises or falls wawy from the aceptable cocnentration then the alpha and beta cells int he islets of LANGERHANDS ,d etect the change .
-THEYR ESPOND , byr relesing the reveant hromone ; IF THE BLOOD GLUCOS EIS GHIGH - INSULIN
GLUCAGON IF IT IS TO LWO
How do the hromones glucagon , and insulin act
they act ont he liver hepatocytes which can store glucose int he orm of glcogen . When there is excess glucose int he blood it is convereted to glycogen . If glucose is needed to raise the blood cocnentration then glycgoegn is converted back to glucsoe .
if blood glucose rises too high (1)
-A high blood glucose cocnentration is detected y the beta cells int he islets of Langerhnds . The beta cells respond b y secreting insulin into the body . Insulin travels thorughout the body int he circulatory system . The target cells are the lvier cells , msucle cells and some other body cells including those int he brain .
HUman insulin is a small portein - therefore it is unable to pass through the cell surface memrbane
the target cells possess the speciifc memrbane boudn receptors for insulin .. When the insulin bidns , to the insulinr eceptors , this activates the enzyme tyroine kinase which is associated witht he receptor ont he isnide of memrbane
what does tyrose kinase cause
ohosphorylation of inactive enyzmes int he cell , this activates the enzyme leads to a cascad of enzyme controlled reactions inside the cell
effect 1 of insulin on the cell
more transporters , portein speicifc to glucose re placd into the cell surface membrane .. This is achieved b causing vesicles containign these transporter proteins to fuse with the memrbane ;
-More glucose enters the cell .
effect 2 of insulin ont he cell
-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 inrespiraiton
what happens if blood glucose drops too low (1)
a low blood glcuose cocnentrations is detected by the alpha cells in the islets of langerhans . The alpha cells then secrete te hormone glucagon into the blood .
what happens if blood glucose drops too low (2)
glucagon is a small protein contain 29 aaminoa cids It is tzrgets cells ae the hapoctytes which possess the specific receptors for glucagon . When blood cells pass these cells the glucagon bidns to the receptors . This stiumaltes , a G protein .
what happens if blood glucose drops too low (3)
-glycogen is converted to glucose (glcogenolysis) , by phosphorylase A , which is one of the enzymes acctivated in the cscae
-more fatty acid are used in respiraiton .
-Amino acids and fats re converted into additionl glucose by GLUCONEOGENSIS .
How is the negative feedback of blood glucose controlled
the concentrationo f blood glcose is controlled by a negative feedback mechnsimss , involving both thehormones and insluina nd glucgaon . The hormones ae antagnositc , they hae opposite effects on blood glucose concentration , one of the effects is to hihbit the effects of the opposing hormones .
RISE IN BLOOD GLUCOSE CONCENTRATIONS
-DETECTED BY BETA CELLS IN THE ISLETS OF LANEGRHANSS .
-BETA CELLS SECRETE INSULIN INTO THE BLOOD
-INSILIN DETECTED BY RECEPTORS ON LIVER AND MUSCLE CELLS . -LIVER AND MUSCLE CELLS REMOVE GLUCOSE FROM BLOOD AND CONVERT GLUCOSE TO GLYCOGEN
-GLUCOSE CONCENTRATION FALLS
FALL IN BLOOD GLUCOSE CONCENTRATION
-detected by alpha cells in the islets of langerhans ..
-alpha cells secrete gkucagon into the blood .
-glucgon detected by receptors on liver cer cells .
-if liver cells convert glycogen to glcuose and release glucose into the blood .
-glucose concentration rises .
