the endocrine system 2 Flashcards
what are the major cell types of the endocrine pancreas
Alpha cells
beta cells
delta cells
functions of the;
alpha
beta and
delta cells
Alpha (A) cells secrete glucagon
Beta (B) cells secrete insulin
Delta (D) cells secrete somatostatin
what percentage of the pancreatic mass/volume does the endocrine pancreas account for
1%
what percentage of the pancreatic mass/volume does the exocrine pancreas account for
85%
what percentage of the pancreatic mass/volume does the extracellular matrix account for
10%
what percentage of the pancreatic mass/volume do the blood vessels and ducts account for
4%
what percentage of the islet mass do Beta cells account for
70
is the endocrine pancreas made of islets of Langerhans?
yes
where are beta cells located in the endocrine pancreas
centrally within the islet cells
where are the alpha and delta cells located in the endocrine pancreas
at the periphery of the islet
the principal function of the endocrine pancreas
to maintain glucose homeostasis
what are some of the substances released by the endocrine pancreas, in addition to glucagon and insulin
somatostatin, pancreatic polypeptide, c peptide, & amylin
insulin and glucagon are secreted by?
the endocrine pancreas
function of the pancreatic pancreas
controls pancreatic enzyme secretion and gallbladder contraction.
amylin is often co-released with which hormone
insulin
function of amylin
Amylin works alongside insulin to help regulate blood sugar. It slows down the rate at which the stomach empties after a meal, reducing the post-meal rise in blood glucose levels. This action helps prevent spikes in blood sugar levels after eating.
the types of chains in insulin
what bond links these chains
A chain
B chain
the disulfide bond
how many amino acids does the A chain and B chain of insulin have respectively
21 and 30
proinsulin
Proinsulin is a precursor molecule to insulin, and it is synthesized by beta cells in the pancreas. Proinsulin is not biologically active in terms of regulating blood glucose levels. Instead, it serves as a prohormone that is processed into the active hormone insulin.
how many peptide chains does proinsulin contain, name them
A chain
B chain
C-peptide
what are some stimulants of insulin
Glucose, amino acids, GIP (incretins), CCK, sulfonylurea compounds,
what are some inhibitors of insulin
somatostatin, amylin, pancreastatin, sympathetic nervous system
insulin regulates in it’s free form and has a half life of?
4-8 minutes
half life of c peptide
averages OVER 35 minutes
what is considered the stimulatory blood glucose(blood glucose at which insulin is released)
> 5.5mM
briefly describe the steps of glucose stimulated insulin secretion
Glucose Entry into Beta Cells:
Glucose from the bloodstream enters beta cells in the pancreatic islets through glucose transporters, primarily GLUT2.
Glycolysis and ATP Production:
Inside the beta cells, glucose undergoes glycolysis, producing ATP (adenosine triphosphate).
Closure of ATP-Sensitive Potassium Channels (KATP Channels):
Increased ATP levels cause the closure of ATP-sensitive potassium channels (KATP channels) in the beta cell membrane.
Membrane Depolarization:
Closure of KATP channels leads to membrane depolarization, as potassium ions can no longer exit the cell. This depolarization triggers the opening of voltage-gated calcium channels.
Calcium Influx:
Calcium ions enter the beta cell due to the opening of voltage-gated calcium channels.
Exocytosis of Insulin Granules:
Increased intracellular calcium levels stimulate the exocytosis of insulin-containing granules stored within the beta cell.
Release of Insulin into Bloodstream:
Insulin is released into the bloodstream in response to elevated blood glucose levels.
Biological Effects of Insulin:
Insulin acts on target cells, such as muscle and adipose tissue, promoting glucose uptake, storage, and utilization. It also inhibits glucose production in the liver.
function of the glucose transporter GLUT4
responsible for insulin stimulated glucose transport
in which tissues is GLUT4 found
Skeletal and cardiac muscle
white adipose tissue
It is not the main glucose receptor in the cardiac muslce, compared to the other two
function of the glucose transporter SGTL1
Na+ dependent active transport, for the co transport of glucose in the small intestines
for glucose transport in the kidneys
which biological process does insulin inhibit in the liver
gluconeogenesis
which biological processes are stimulated by insulin in the;
liver and muscle cells
other cells
glycogenesis
glycolysis
briefly describe the steps of insulin effect on the adipose tissue
Insulin Binding to Receptors:
Insulin binds to its receptors on the surface of adipose cells. These insulin receptors are present on the cell membrane.
Activation of Insulin Signaling Pathway:
Insulin binding activates a signaling pathway within the adipose cells, initiating a cascade of intracellular events.
Enhanced Glucose Uptake:
Insulin promotes the uptake of glucose into adipose cells by increasing the number and activity of glucose transporters (GLUT4) on the cell membrane.
Increased Lipogenesis:
Insulin stimulates lipogenesis, which is the process of synthesizing fatty acids from glucose. This involves converting excess glucose into triglycerides (fat) for storage.
Inhibition of Lipolysis:
Insulin inhibits lipolysis, the breakdown of stored fat into fatty acids and glycerol. This helps to preserve fat stores and prevents the release of fatty acids into the bloodstream.
Promotion of Fat Storage:
Insulin encourages the storage of triglycerides within adipocytes. These triglycerides are stored in lipid droplets in the form of fat.
Inhibition of Hormone-Sensitive Lipase (HSL):
Hormone-sensitive lipase is an enzyme involved in the breakdown of triglycerides. Insulin inhibits the activity of HSL, contributing to the suppression of lipolysis.
briefly describe the steps of insulin effect on protein metabolism
Insulin Binding to Receptors: Insulin binds to its receptors on the surface of target cells, including muscle cells and other tissues involved in protein metabolism.
Activation of Insulin Signaling Pathway: Insulin binding activates the insulin signaling pathway within cells, triggering a series of intracellular events.
Stimulation of Amino Acid Uptake: Insulin facilitates the uptake of amino acids into cells. Amino acids are the building blocks of proteins, and their increased uptake supports protein synthesis.
Activation of Protein Synthesis: Insulin stimulates protein synthesis by enhancing the activity of ribosomal machinery and promoting the incorporation of amino acids into growing polypeptide chains. This process is crucial for the formation of new proteins.
Inhibition of Protein Degradation: Insulin inhibits the activity of proteolytic enzymes involved in protein breakdown, such as the ubiquitin-proteasome system. This inhibition helps to preserve existing proteins within the cell.
Promotion of Cell Growth and Differentiation: The stimulation of protein synthesis by insulin contributes to cell growth and differentiation. Insulin’s effects on protein metabolism are particularly important during periods of growth, development, and tissue repair.
Inhibition of Autophagy: Autophagy is a cellular process that involves the degradation and recycling of cellular components, including proteins. Insulin can inhibit autophagy, thereby preserving cellular proteins.
which cells secrete glucagon
alpha cells of the islets of Langerhans
main physiological role of glucagon
increase blood glucose level through stimulation of glycogenolysis and gluconeogenesis
examples of stimulants of glucagon
fatty acids, glycogen, Amino acids, Cholinergic fibers, Sympathetic fibers, CCK
examples of inhibitors of glucagon
Glucose, insulin, somatostatin,
briefly describe the steps involved in glucose stimulated glucagon secretion
Glucose Entry into Alpha Cells: Glucose from the bloodstream enters alpha cells in the pancreatic islets.
Metabolism of Glucose: Inside the alpha cells, glucose undergoes metabolism, leading to an increase in intracellular ATP (adenosine triphosphate) levels.
Closure of ATP-Sensitive Potassium Channels (KATP Channels): Increased ATP levels lead to the closure of ATP-sensitive potassium channels (KATP channels) in the alpha cell membrane.
Membrane Depolarization: Closure of KATP channels results in membrane depolarization, causing the opening of voltage-gated calcium channels.
Calcium Influx: Calcium ions enter the alpha cell due to the opening of voltage-gated calcium channels.
Exocytosis of Glucagon Granules: Increased intracellular calcium levels stimulate the exocytosis of glucagon-containing granules stored within the alpha cell.
Release of Glucagon into Bloodstream: Glucagon is released into the bloodstream in response to elevated blood glucose levels.
which biological processes are stimulated by glucagon
liver proteolysis, gluconeogenesis, and urea cycle, ketogenesis
which cells secrete somatostatin
delta cells of the islets of Langerhans
major stimulants of somatostatin
High fat, protein rich , high carbohydrate meal
inhibitory effect of somatostatin
Inhibits the release of growth hormone
Inhibits the release of almost all peptide hormones
Inhibits gastric, pancreatic, and biliary secretion
what are the 4 main types of diabetes
Diabetes insipidus
Diabetes mellitus (type 1 and 2)
Gestational diabetes
diabetes insipidus
a rare disorder characterized by the inability of the body to properly regulate water balance, leading to excessive thirst and the production of large volumes of dilute urine
diabetes insipidus has something to do with blood sugar, true or false
false, has nothing to do with it
two main symptoms of diabetes insipidus
Extreme thirst (polydipsia) Passing large amounts of urine, even at night (polyuria)
hormone involved in diabetes insipidus
ADH
effect of diabetes insipidus
Lack of production of Anti Diuretic Hormone (ADH) means the kidney can’t make enough concentrated urine and too much water is passed from the body
Gestational diabetes
a type of diabetes that develops during pregnancy. It is characterized by elevated blood sugar levels, and it usually occurs in the second or third trimester
what factors makes it more likely for a pregnant woman to develop gestational diabetes
BMI is ≥ 30
Previously given birth to a large baby, weighing 4.5 kg (10lbs) or more
You have had gestational diabetes before
diabetes mellitus
Disease in which the body’s ability to produce or respond to insulin is impaired
what causes type 1 diabetes mellitus
T-cell mediated autoimmune response leading to the destruction of the pancreaticβ cells that produce insulin
how does type 1 diabetes affect the pancreas
it affects it’s ability to release insulin
in which age group is diabetes mellitus often diagnosed
children
main symptoms of diabetes mellitus
Polyuria
Polydipsia
Polyphagia
Weight loss
Stunted growth
Children
Ketoacidosis
what are the major macrovascular complications of diabetes
cardiovascular
brain
extremities that could result in lack of blood flow to the legs(gangrene)
what are the major microvascular complications of diabetes
Retinopathy
nephropathy
neuropathy
what are some tests for diabetes
Measure blood glucose levels
Glucose tolerance test: Measure blood glucose levels at given timepoints following ingestion of glucose
Glycated Haemoglobin (Hb A1c): Allows chronic measurement of glucose levels
the treatment for T1DM
Insulin injected subcutaneously or via a pump
what are some forms if insulin
Short acting
Intermediate acting
Long acting
what causes diabetes type 2
Caused by insulin resistance, the lack of the body’s response to insulin =insulin resistance
main symptoms of type 2 diabetes
Hyperglycaemia Polyphagia
Polyuria
Polydipsia
risk factors of type 2 diabetes mellitus
Obesity
Hypertension
Lack of exercise
Genetics is also likely to play a role
treatment options for type 2 diabetes
Lifestyle changes like, Increase in exercise, Healthy Diet
Pharmacological Treatments
types of pharmacological drugs used to treat T2DM and their mechanism of action
Insulin sensitizers: sensitize the body to insulin
Insulin secretagogues: evoke insulin secretion
Drugs which slow reabsorption of glucose
Incretins: stimulate insulin release or inhibit glucagon
three ways in which metformin works
Increases glucose uptake into cells and improves sensitivity of the insulin receptor
Decreasing hepatic glucose production
Decrease intestinal absorption of glucose
functions of sulfonylureas
stimulate the release of insulin
examples of drugs that classify as sulfonylureas
gliclazide, glipizide
functions of SGLT inhibitors
they inhibit the renal reabsorption of glucose
drugs that classify as SGLT inhibitors
Dapagliflozin, Canagliflozin
examples of drugs that classify as incretins
DPP-4 inhibitors – eg. Sitagliptin;
GLP-1 analogues –eg. Exenatide
