17 Insulin, Glucagon, and Diabetes Mellitus Review

A set of 180 practice flashcards based on the lecture notes for Human Physiology regarding Insulin, Glucagon, and Diabetes Mellitus.

What is the general physiological definition of a hormone according to the lecture?

A chemical substance secreted into the internal body fluids by one cell or a group of cells that has a physiological control effect on other cells of the body.

According to the lecture, how quickly can some hormone effects occur?

Within seconds.

How long can some hormone effects last after requiring days to start to act?

Weeks.

Which organ secretes insulin and glucagon for glucose regulation?

The endocrine pancreas.

What is the function of the acini in the pancreas?

To secrete digestive juices into the duodenum.

Where do the islets of Langerhans secrete insulin and glucagon?

Directly into the blood.

Approximately how many islets of Langerhans are in the human pancreas?

$1$ to $2$ million.

What is the approximate diameter of an islet of Langerhans?

$0.3\,mm$.

What structures are islets of Langerhans organized around to facilitate hormone secretion?

Small capillaries.

What percentage of the cells in the islets of Langerhans are alpha cells?

$25\%$.

Which hormone is secreted by the alpha cells?

Glucagon.

What percentage of the cells in the islets of Langerhans are beta cells?

$60\%$.

Which two substances are secreted by beta cells?

Insulin and amylin.

What percentage of cells in the islets of Langerhans are delta cells?

$10\%$.

Which hormone is secreted by delta cells?

Somatostatin.

Which cells in the islets of Langerhans secrete pancreatic polypeptide?

PP cells.

What effect does insulin have on glucagon secretion?

Insulin inhibits the secretion of glucagon.

What A1C test result indicates diabetes?

$6.5\%$ or above.

What A1C percentage range is considered prediabetes?

$5.7\%$ to $6.4\%$.

What is the threshold for a normal A1C test result?

Below $5.7\%$.

What fasting blood sugar level indicates diabetes?

$126\,mg/dL$ or above.

What is the fasting blood sugar range for prediabetes?

$100$ to $125\,mg/dL$.

What fasting blood sugar level is considered normal?

$99\,mg/dL$ or below.

What glucose tolerance test result indicates diabetes?

$200\,mg/dL$ or above.

What glucose tolerance test range is considered prediabetes?

$140$ to $199\,mg/dL$.

What glucose tolerance test result is considered normal?

$140\,mg/dL$ or below.

What random blood sugar level indicates diabetes?

$200\,mg/dL$ or above.

Does a patient need to fast before a random blood sugar test?

No.

What does the A1C test specifically measure?

The percentage of red blood cells that have sugar-coated hemoglobin.

Which subunit of its receptor does insulin bind to?

The alpha subunit.

What happens to the beta subunit of the insulin receptor after insulin binds to the alpha subunit?

Autophosphorylation.

What specific enzyme activity is induced by the autophosphorylation of the beta-subunit receptor?

Tyrosine kinase activity.

What is the initial physiological effect after tyrosine kinase activity begins in the insulin receptor cascade?

A cascade of cell phosphorylation.

How does the insulin receptor cascade change enzymatic activity within a cell?

It increases or decreases the activity of enzymes, including insulin receptor substrates.

What happens to glucose transporters within the cell following insulin receptor activation?

They are moved to the cell membrane to assist glucose entry into the cell.

How does insulin affect amino acid uptake in cells?

It promotes the uptake of amino acids.

How does insulin affect the conversion of amino acids?

It promotes their conversion to proteins.

What effect does insulin have on protein breakdown?

It inhibits the breakdown of proteins into amino acids.

How quickly does the membrane of body cells become permeable to glucose after insulin binds?

Within seconds.

Approximately what percentage of body cells become highly permeable to glucose after insulin binding?

$80\%$.

Which two types of cells are described as typically becoming highly permeable to glucose due to insulin?

Muscle and adipose cells.

Which type of cells in the brain are not dependent on insulin for glucose permeability?

Neurons.

What is the result of decreased glucose uptake and utilization in cases of insulin deficiency?

Hyperglycemia.

What condition refers to the presence of glucose in the urine due to insulin deficiency?

Glycosuria.

What is polyuria and why does it occur in diabetes?

Excessive urination caused by osmotic diuresis.

Which sign of insulin deficiency results from polyuria and involves the eyes?

Soft eyeballs.

What is polydipsia?

Excessive thirst.

What metabolic process leads to weight loss during insulin deficiency?

Protein catabolism.

What is polyphagia?

Excessive hunger or eating.

The breakdown of glycogen into glucose in the liver is called what?

Glycogenolysis.

What is gluconeogenesis?

The synthesis of glucose from non-carbohydrate precursors.

Which two processes lead to lipidemia and ketoacidosis during insulin deficiency?

Lipolysis and ketogenesis.

What is ketonuria?

The presence of ketones in the urine.

What symptom related to breath is characteristic of ketoacidosis?

Acetone breath.

What electrolyte imbalances occur during insulin deficiency due to loss in urine?

Loss of sodium ($Na^+$) and potassium ($K^+$).

What respiratory sign is associated with acid-base imbalances in insulin deficiency?

Hyperpnea.

What are three gastrointestinal symptoms of severe insulin deficiency?

Nausea, vomiting, and abdominal pain.

What is the final stage of central nervous system depression in untreated insulin deficiency?

Coma.

Why does muscle use large amounts of glucose during moderate to heavy exercise even without insulin?

Exercising muscle fibers become highly permeable to glucose in the absence of the hormone.

What happens to glucose in the liver between meals when insulin levels are low?

Glucose is released from the liver.

How does insulin affect the liver regarding gluconeogenesis?

Insulin inhibits gluconeogenesis.

Why must blood glucose levels be maintained precisely for the brain?

Brain cells can only use other nutrients with great difficulty and are normally permeable to glucose without insulin.

What sequence follows untreated severe hypoglycemia?

Hypoglycemia leads to coma, which leads to death.

How is hypoglycemia biochemically defined in terms of plasma glucose?

A concentration lower than $3.5\,mmol/l$.

What kind of response does acute hypoglycemia stimulate to restore glucose?

A stress response.

What rhythm in the heart can be disturbed if plasma glucose falls too low?

Cardiac rhythm.

How does insulin affect the utilization of fat in cells?

It decreases the use of fat by increasing the utilization of glucose.

What happens to fat deposits when insulin is present?

They are preserved.

What happens to triglycerides when insulin levels decrease?

They are split into glycerol and fatty acids.

Besides fatty acids, what else does the liver release when insulin is low?

Phospholipids and cholesterol.

What is the primary function of glucagon?

To increase the blood levels of glucose.

What happens to glucagon secretion when blood glucose concentration is high?

It is inhibited.

How does glucagon affect liver glycogen?

It breaks down liver glycogen via glycogenolysis.

How does glucagon affect amino acids in the liver?

It stimulates the production of glucose from amino acids.

Which enzyme in adipose cells is activated by glucagon?

Adipose cell lipase.

How does glucagon affect the storage of triglycerides in the liver?

It inhibits the storage of triglycerides.

What is the effect of somatostatin on pancreatic hormones?

It inhibits glucagon and insulin secretion.

What gastrointestinal effects does somatostatin have?

It inhibits secretion of gastrointestinal hormones and stomach acid.

What is the effect of pancreatic polypeptide on the gallbladder?

It inhibits contraction of the gallbladder.

What is the effect of pancreatic polypeptide on the exocrine pancreas?

It inhibits the secretion of exocrine substances.

What characterizes the development of Type 1 Diabetes?

Insulin deficiency develops as the immune system attacks insulin-producing cells.

What is the first step in the immune response for Type 1 Diabetes mentioned in the notes?

Antigen Presenting Cells (APCs) are exposed to insulin-producing cells in the pancreas.

Where do APCs travel to prime B cells and T cells in Type 1 Diabetes?

The lymph nodes and other parts of the body.

What do B cells and T cells do once they are activated against insulin-producing cells?

They propagate the signal, proliferate, then search out and destroy the cells.

What type of nerves have a rich supply to the pineal gland?

Adrenergic nerves.

Which adrenal hormone are the neurons in the pineal gland sensitive to?

Epinephrine.

From which amino acid is melatonin derived?

Tryptophan.

What is the primary function of melatonin?

Regulating the circadian rhythm.

In response to what cycles does melatonin regulate circadian rhythm?

Light and dark cycles.

What hypothalamic hormone release is regulated by melatonin?

Gonadotropin-releasing hormone.

What pituitary hormones does melatonin influence?

Gonadotropins.

What are five functions influenced by the hypothalamus according to the summary?

Food intake, weight regulation, fluid intake and balance, thirst, body heat, and the sleep cycle.

What are the general functions of pituitary hormones?

Stimulate growth, egg and sperm development, milk secretion, and release of hormones by other glands.

What role may the pineal gland play in development?

Sexual maturation.

What are two roles of thyroid hormones in the heart and metabolism?

Regulate the metabolic rate of tissues and stimulate heart muscle contraction.

Thyroid hormones are necessary for normal growth and development during which two periods?

Before birth and during infancy.

Which three minerals are regulated by parathyroid hormone?

Calcium, phosphorus, and magnesium.

What three things do the adrenal glands regulate?

Salt and water retention, some immune reactions, and blood pressure.

Which specific structure in the pancreas regulates blood sugar levels?

The islets of Langerhans.

What is the role of hormones produced by the ovaries and testes?

Regulate the reproductive system and produce secondary sex characteristics.