Hormonal communication- pancreas and diabetes Flashcards
what is the endocrine system?
made up of endocrine glands which secrete hormones directly into the bloodstream
why is the pituitary gland and hypothalamus in close proximity?
ensures the nervous and hormonal responses of the body are closely linked and coordinated
what are exocrine glands?
secrete chemicals through ducts into organs or to the surface of the body (e.g digestive system)
what are hormones?
chemical messengers which carry information around the body
why are hormones secreted into the blood?
as a result of a change in concentration of a particular substance or as a result of another hormone or impulse
why are there different types of hormones?
it determines the way it causes its effect on a target cell
describe steroid hormones
lipid soluble and pass through the lipid component of the cell membrane and bind to steroid hormone receptors to form a hormone-receptor complex which facilitates of inhibits the transcription of a specific gene (e.g oestrogen)
Describe non-steroid hormones
hydrophilic and can’t pass through the cell membrane. They bind to receptors on the cell membrane, triggering a cascade reaction mediated by chemicals called second messengers (e.g adrenaline)
why is hormonal communication less specific and slower than neuronal communication?
because hormones are not released directly into their target cells
Why do hormones have a more long lasting and and widespread effect compared to neurones?
because they are not quickly broken down
describe the structure of the adrenal glands
located on top of each kidney and made of two parts: the adrenal cortex and adrenal medulla
what is the adrenal cortex?
the outer region of the glands which produces essential hormones such as cortisol and aldosterone
what is the adrenal medulla?
inner region of the glands which produces non-essential hormones (e.g adrenaline) to react to stress
what are the three main types of hormones produced int he adrenal cortex?
-glucocorticoids
-mineralocorticoids
-androgens
what are the hormones produced in the adrenal cortex controlled by?
controlled by by hormones released from the pituitary gland in the brain
describe the hormone, glucocorticoid?
-regulates metabolism by controlling how the body converts fats, proteins and carbohydrates into energy.
-regulates blood pressure and cardiovascular function in response to stress
-works with cortisol to regulate immune response and suppress inflammatory reactions. Release of these hormones are controlled y hypothalamus.
Describe the hormone, mineralocorticoids?
main one produced is aldosterone which helps control blood pressure by maintaining the balance between salt and water concentration the blood and body fluids. Release is mediated y signals triggered y the kidney
Describe the hormone, androgens?
small amounts of male and female sex hormones are released which have small impact but still important especially for women after the menopause
How are hormones released in the adrenal medulla?
released when the sympathetic nervous system is stimulated, when the body is stressed
what two glands is the pancreas?
exocrine gland-to produce enzymes and release them via a duct into the duodenum
endocrine gland-to produce hormones and release them into the blood
how does the pancreas act as an exocrine gland?
mostly exocrine glandular tissue which is responsible for producing digestive enzymes and pancreatic juice (alkaline fluid). This is secreted into ducts which lead to the pancreatic duct. Then they are released into the duodenum, the top part of the small intestine.
How does the pancreas act as an endocrine gland?
produces insulin and glucagon in the islets of langerhans
What is the difference between the islets of langerhans and the pancreatic acini when viewed under the microscope?
the islets o langerhans are lightly stained and are large spherical clusters. The pancreatic acini is darker stained and small berry like clusters
what is the role of alpha and beta cells?
alpha cells produce and secrete glucagon, beta cells produce and secrete insulin
glucose is normally maintained at what concentration?
90mg/cm cubed
What are the reasons to why blood glucose concentration can increase?
-diet: when you eat carbohydrate rich food, carbohydrates break down into glucose
-glycogenolysis: glycogen into glucose
-glucogenisis: production of glucose from non-carbohydrate sources
What are the reasons to why blood glucose concentration can decrease?
-respiration
-glyconesis
What happens when blood glucose is too high?
-beta cells detect rise in blood glucose concentration and secrete insulin into blood.
-insulin binds to glycoprotein receptor (all cells except RBC) causing a change in tertiary structure of glucose transport protein channels. This causes channels to open allowing more glucose to enter the cell.
-Insulin also activates enzymes within some cells to convert glucose into glycogen and fat
how does insulin decrease blood glucose levels?
-increasing rate of absorption of glucose by cells
-increasing respiratory rate of cells
-increasing rate of glycogenisis (glucose into glycogen)
-increasing rate of glucose to fat conversion
-inhibiting the release of glucagon from the alpha cells
where is glycogen stored?
liver and muscle cells
how is insulin broken down?
by enzymes in liver cells
What happens when blood glucose concentration is too low?
-alpha cels detect and release glucagon directly into blood stream
-only liver and fat cells respond to glucagon as they only have glucagon receptors
how does glucagon raise blood glucose levels?
-glyconenlysis: liver breaks down glycogen into glucose
-reducing the amount of glucose absorbed by liver cells
-increasing glucogenisis: conversion of amino acids and glycerol into glucose in the liver.
what is the mechanism by which insulin is released in the beta cells?
-at normal glucose levels, potassium channels in the plasma membrane of beta cells are are open and potassium ions diffuse out the cell. The inside of the cell is at the potential of -70mv with respect to the outside of the cell.
-when blood glucose rises, glucose enters cells through glucose transporter
-glucose is metabolised in mitochondria producing ATP
-ATP binds to potassium channels causing them to close (ATP sensitive potassium channels)
-as potassium ions can no longer diffuse, the potential difference becomes -30mv and depolarisation occurs
-depolarisation causes voltage gated calcium channels to open
-calcium ions enter the cell and cause secretory vesicles to release insulin they contain by exocytosis
What is type 1 diabetes?
-unable to produce insulin
-beta cells do not produce insulin
what is the cause of type 1 diabetes?
-auto immune response
-body attacks its own beta cells
-normally begins in childhood
-symptoms develop quickly
What is type 2 diabetes?
-cannot effectively use insulin and control blood glucose levels
-beta cells don’t produce enough insulin or body cells don’t respond properly to insulin, often due to glycoprotein receptor not working properly
what is the cause of type 2 diabetes?
-excess body weight
-physical inactivity
-risk increases with age
-less severe symptoms and develop slowly
how do you treat type 1 diabetes?
-regular insulin injections (insulin-dependent)
-by pricking finger and looking and blood glucose conc, they can determine the dose of insulin needed
what can happen if a person injects themselves with too much insulin?
-hypoglycaemia (very low blood glucose levels) can occur which can result in unconsciousness and death
How do you treat type 2 diabetes?
-regulate carbohydrate intake through diet and match to exercise
-increase exercise
-if diet and exercise is not enough, drugs can be used which stimulate insulin production, drugs that slow down the rate at which the body absorbs glucose from the intestine and insulin injections
How was insulin originally obtained for medicine and what were the problems?
-insulin obtained from the pancreas of cows and pigs which had been slaughtered for food
-this process was difficult and expensive (dependent on demand for food)
-this insulin could cause allergic reactions
How is insulin obtained now for medicine?
-through genetically modified bacteria
what are the advantages of using genetically modified bacteria for insulin?
-human insulin produced in pure form so allergic reactions do not occur
-can be produced at higher quantities
-production is cheaper
-religious and ethical concerns
what are the disadvantages and advantages of having a pancreas transplant to treat diabetes?
-although usually patients will have no symptoms of diabetes
-the demand outweighs the availability
-immunosuppressent drugs are needed which can make one susceptible to infections and can exhaust their capacity to produce insulin in beta cells- this is the same for injection of pancreatic beta cells
what are the advantages of using stem cells to treat diabetes?
-donor availability would not be an issue- stem cells could produce unlimited source of new beta cells
-reduced likelihood of rejection
-no longer need to inject insulin
what are the disadvantages of using stem cells to treat diabetes?
may induced tumours and unlimited cell growth
