Blood glucose concentration Flashcards
What is an endocrine gland ? What is the difference between an endocrine and exocrine gland ?
A group of cells which are specialised to secrete hormones into the bloodstream
Exocrine glands secrete through ducts into organs
What is the difference between steroid and non - steroidal hormones ?
Steroidal are lipid soluble and can pass through the cell and form a hormone - receptor complex which acts as a transcription factor to promote or inhibit gene expression
Non steroidal are not lipid soluble therefore they bind to a receptor on the cell surface membrane to trigger a reaction through a second messenger
What are the differences between hormonal and neuronal communication?
Hormonal-
longer lasting effect
transmission by blood system, not by neurons
transmission is slow
response is widespread
What hormones are produced by the adrenal cortex?
Outer region of liver
Glucocorticoids :
Cortisone- regulates immune system and suppresses inflammatory
response
Cortisol- increases rate of gluconeogenesis to raise blood glucose levels to increase rate of respiration
Mineral corticoids:
Aldosterone- helps to control blood pressure ( loop of henle- increasing water reabsorption in the collecting ducts to increase blood pressure )
What hormones are produced by the adrenal medulla?
Inner region of liver
When the sympathetic nervous system is activated
Adrenaline - increases heart rate, receptors on the SAN
Increases blood glucose levels by conducting glycogenolysis, receptors on the liver
Noradrenaline- widening of pupils
widening of air passages in lung, relaxing of smooth muscle in bronchioles
narrowing of blood vessels for non essential organs
Describe the purpose of the pancreas as an endocrine and exocrine gland
Exocrine: producing enzymes such as amylase, lipase and protease secreted into the pancreatic duct (acini)
Endocrine: islets of langerhans are responsible for secreting insulin and glucagon into the bloodstream to regulate BGC
What is found within the islets of Langerhans?
Alpha cells- produce and secrete glucagon
Beta cells- produce and secrete insulin
How is BGC increased ?
Eating carbohydrate rich foods- broken down to release glucose
Glycogenolysis- glycogen stored in the liver and muscle cells is broken down and releases glucose into the bloodstream
Gluconeogenesis- production of glucose from non carbohydrate sources
How is BGC decreased ?
Respiration
Glycogenesis - excess glucose is converted into glycogen for storage
What is the role of insulin ?
B cells in islets of Langerhans detect a rise in BGC and secrete insulin
Lowers BGC by:
Increasing rate of absorption of glucose by cells
Increasing rate of glycogenosis
Increasing rate of glucose to fat conversion
Increasing respiratory rate of cells
Inhibiting release of glucagon from alpha cells
What is the role of glucagon ?
A cells in islets of Langerhans detect a rise in BGC and secrete glucagon
Raises BGC by:
Glycogenolysis
Reducing absorption of glucose by cells
Gluconeogenesis
How is insulin secreted by B cells?
Normal- potassium ion channels are open and diffusing out of the cell, potential difference is -70mV
Bgc rises- glucose enters the cell by a glucose transporter
Glucose is metabolised inside the mitochondria to produce ATP
ATP blocks the potassium ion channel and causes it to close
Depolarisation occurs at -30mV
This causes voltage gated calcium ion channels to open
Calcium ion diffuse into the cells and fuse with secretory vessels to release insulin by exocytosis
What is the difference between type 1 and 2 diabetes ?
Type 1- B cells in islets of Langerhans unable to produce insulin
Controlled by regular insulin injections
Type 2- Body cells lose responsiveness to insulin (glycoprotein insulin receptor may not be working properly)
Controlled by lifestyle changes
What are the treatments for diabetes ? Adv and dis for each one
Pancreas transplant- no symptoms and no more insulin injections
demand outweighs availability
immunosuppressant drugs to be taken- susceptible to infection
Stem cell therapy for B cells- immunosuppressant drugs
embryo must be destroyed- potential life
but they are spare embryos and one can provide treatment for many patients
no issue with donor availability- unlimited source
reduced likelihood of rejection
What is the action of adrenaline ?
Hydrophilic so cannot pass directly into the cell- has to bind to receptors on the cell surface membrane of the liver
When adrenaline binds to its receptor, the enzyme adenylyl cyclase is activated
This converts ATP to cAMP (second messenger)
cAMP acts as a transcription factor for enzymes (protein kinases) which convert glycogen into glucose
