5.4 - Hormonal Communicaton Flashcards
(MA) What is the role of the adrenal medulla?
Makes and secretes adrenaline
(MA) What is the role of the adrenal cortex?
Produces steroid hormones e.g. glucocorticoids
(MA) How does adrenaline travel around the body and cause a response in the target cell?
- adrenaline is known as the first messenger as it transmits the signal around the body in the blood
- binds to receptors initiate change inside cell
- binding causes a G-protein to activate adenyl cyclase converting ATP to cyclic AMP
- cAMP is the second messenger as it transmits the signal inside the cell + causes more enzyme controlled reactions to take place + cause an effect on a cell
(MA) Describe the endocrine and exocrine glands of the pancreas.
- endocrine glands release hormones directly into the blood
- e.g. pancreas - alpha cells release glucagon + beta cells release insulin
- exocrine glands release molecules into ducts
- e.g. pancreas - releases digestive enzymes into pancreatic duct which leads to small intestine
(MA) What happens when blood glucose levels are too high?
- beta cells detect rise in blood glucose level
- rise inhibits glucagon secretion/production
- stimulates production of insulin (by beta cells)
- insulin secreted into blood
- insulin binds to receptors on hepatocytes (+ muscle cells)
- more glucose channels inserted into plasma membranes of target cells so more glucose enters hepatocytes (+ muscle cells)
- glucose converted to glycogen (glycogenesis)
- glucose converted to fats
- more glucose used in more respiration in target cells
- this results in less glucose in the blood
(MA) What happens when blood glucose levels are too low?
- fall detected by alpha cells
- fall inhibits insulin secretion/production
- stimulates secretion/production of glucagon (by alpha cells)
- into blood
- binds to receptor on hepatocyte
- stimulates hydrolysis of glycogen to glucose/glycogenolysis
- gluconeogenesis/detail of gluconeogenesis
- glucose leaves hepatocytes through glucose channels into the blood stream
(MA) How is insulin release controlled in a beta cell?
- glucose enters beta cell through carrier proteins
- glucose is phosphorylated in glycolysis + ATP is produced
- ATP causes K ion channels to close
- cell membrane becomes depolarised/more positive (as K+ can no longer leave cell)
- causes v-g Ca ion channels to open + Ca ions to enter
- Ca ions causes vesicles full of insulin to move towards the cell surface membrane, fuse with it + release the insulin
- via exocytosis
Where are hormones produced?
endocrine glands
What is the adrenal medulla?
Centre of the gland, makes + secretes adrenaline and noradrenaline
What does adrenaline cause?
- relax smooth muscles (widens airways, larger lumen, more O2 into lungs for aerobic respiration = energy)
- increases stroke volume of heart
- increase heart rate (more O2/glucose supplied for respiration)
- vasoconstriction (lose less energy, redirecting blood flow for more supplied to respiring cells)
- glycogen converted to glucose (more glucose availability for respiration)
- dilates pupil (more light enters eye = better vision)
- increase mental awareness (more alert + can respond quicker to danger)
- inhibits action of gut (less energy wasted in digestion)
- body hairs erect (hairs stand up, appear bigger)
What is a non steroid hormone?
Protein/amino acid based hormone (not lipid)
How can you recognise a steroid hormone from its name?
usually end in -(cortic)oid
What is the role of the adrenal cortex?
Uses cholesterol to produce steroid hormones
What are the 3 regions of the adrenal cortex and what are their functions?
- Zona Glomerulosa (nearest outside): secretes mineralocorticoids to help control Na+K in blood + blood pressure
- Zona Fasciculata: secretes glucocorticoids to help control metabolism of carbs, fats + proteins in liver
- Zona Reticularis (nearest medulla): secretes precursors to the sex hormones
How do steroid hormones cause a response in a cell?
- enter cells by dissolving in cell surface membrane
- bind w a receptor in cytoplasm, receptor-hormone complex enters nucleus, binds to another receptor on chromosome
- causes mRNA to be made which then produces proteins
Describe the endocrine function of the pancreas.
- majority of cells produce digestive enzymes (pancreatic juice)
- cells form groups (acini), secrete enzymes into tubules which lead to pancreatic duct which takes them to small intestine
What is in the pancreatic juice (involved in the exocrine function of the liver)?
- amylase
- trypsinogen
- lipase
- sodium hydrogencarbonate
Describe the endocrine function of the pancreas.
- islets of Langerhans contain alpha + beta cells
- they detect change in blood glucose levels
- alpha cells: produce + secrete glucagon hormone
- beta cells: produce + secrete insulin hormone
- hormones secreted directly into closely associated capillaries
What is the normal blood glucose levels?
90mg/100cm^3
How would you identify the parts of the pancreas on a micrograph?
- most cells = exocrine
- acini: groups of cells surrounding smallest hollow tubes
- tubules leading to pancreatic duct: slightly larger (circularish) hollow tubes
- islets of Langerhans: patches (circularish) w a different staining
Describe the process of gluconeogenesis.
-amino acids have amino group removed
-creates pyruvate (used as carbon skeleton)
-in presence of triode phosphate enzyme
-controls condensation reaction in glucose
amino acid –> pyruvate –(triode phosphate)–> glucose
What are the benefits of storing glucose as glycogen?
- insoluble: doesn’t affect water potential of cell
- branched: lots of endings for enzymes to attach to
- compact so more energy stored in less space
- unreactive
- cant diffuse out of cell
(MA) What does the term diabetes mellitus mean?
Can’t control blood glucose levels
(MA) Describe type 1 diabetes.
- insulin dependent diabetes
- beta cells have been damaged by body’s own immune system (autoimmune response)
- can’t produce sufficient glucose
- can’t store glucose as glycogen, excess glucose in blood, hyperglycaemia
- when blood glucose falls, no/little glycogen stored converted to glucose, causing hypoglycaemia
- can be inherited
- treated with injections of insulin into subcutaneous fat
(MA) Describe type 2 diabetes.
- non insulin dependent diabetes
- receptors on target cells for insulin become unresponsive to insulin (still produce insulin)
- treatment: diet low in carbs/sugars, regular exercise
- risk factors…
(MA) What are the risk factors that increase one’s chance of getting type 2 diabetes?
- increasing age
- obesity
- more common in males + some ethnic groups
- high blood pressure
- excessive alcohol intake
How do you treat type 1 diabetes?
- monitor blood glucose levels + insulin injections administered
- insulin pump: permanently pumps insulin at a steady rate
What is meant by the term hyperglycaemia and what can it cause in the long term?
Blood glucose too high, can lead to organ damage (long term)
What is meant by the term hypoglycaemia and what can it cause in the long term?
Blood glucose too low, not enough glucose to cells, especially brain. Causes tiredness + irritability, brain damage, seizures + death
What are the advantages of obtaining insulin from genetically engineered bacteria?
- if insulin wasn’t obtained from bacteria, would be obtained from animals (pigs)
- ethical issues i.e. vegetarian, religious
- lots can be made as bacteria reproduces quickly
- bacterial sources slightly more effective as produces human insulin
- cheaper from bacteria as lots made in one culture
- less chance of infection
- avoids side effects, allergies, immune response
