Endocrine System Flashcards
What commonalities exist in the overall functions of the nervous system (NS) and the endocrine system?
Both serve for internal communication and both use chemical transmitters.
Can a single chemical function as both a neurotransmitter and a hormone? If so, give examples.
Yes, norepinephrine, dopamine, and ADH
What structures constitute the endocrine system?
It is made up of all the glands, tissues, and cells that secrete hormones.
What is the definition of “gland”?
A bodily structure responsible for producing various substances, such as hormones, digestive fluids, sweat, tears, saliva, or milk.
Is the pancreas classified as an exocrine or endocrine gland? Why?
Both. Acinar cells release digestive enzymes into ducts and the pancreatic islets release hormones into the blood.
What are the islets of Langerhans, and where are they located?
Endocrine cell clusters are called pancreatic islets. They are scattered throughout the pancreas.
Which specific pancreatic cells are responsible for the production of the hormones insulin, amylin, and glucagon?
Beta cells produce insulin and alpha cells produce glucagon.
In the regulation of glucose homeostasis, which pancreatic hormones play a pivotal role?
Insulin, amylin, and glucagon?
Concerning the control of glucose levels, are the functions of insulin and glucagon similar or distinct?
Insulin and glucagon have antagonistic effects. Insulin has glucose-lowering effects while glucagon tends to raise circulating glucose levels.
What initiates the release of insulin from the pancreas?
Increase in blood glucose levels, such as after a meal.
Define glycogenesis and clarify whether insulin or glucagon promotes or inhibits these metabolic reactions.
Simulated by insulin, glycogenesis is the process by which glucose is converted into glycogen for storage in liver and muscle cells.
Define gluconeogenesis and clarify whether insulin or glucagon promotes or inhibits these metabolic reactions.
Gluconeogenesis is the synthesis of glucose from non-carbohydrate sources, such as amino acids and glycerol, primarily in the liver and kidneys. It is inhibited by insulin and promoted by glucagon.
Define glycogenolysis and clarify whether insulin or glucagon promotes or inhibits these metabolic reactions.
Glycogenolysis is the breakdown of glycogen into glucose, releasing it into the bloodstream to be used for energy. It is promoted by glucagon.
What are the overall effects of insulin on adipose tissue and muscle?
Insulin increases glucose uptake in adipose tissue and muscle.
Which metabolic reactions does insulin influence in the liver?
Stimulate glycogenesis in the liver while it inhibits gluconeogenesis.
When is amylin secreted, and what functions does it serve?
Amylin is simultaneously secreted with insulin, decreasing spikes in blood glucose by suppressing appetite, slowing gastric emptying, and inhibiting glucagon release.
What triggers the release of glucagon from the liver, and what are its primary functions?
Decrease in blood glucose levels, such as after a meal. Glucagon raises blood glucose levels by promoting the breakdown of glycogen into glucose (glycogenesis) and the synthesis of glucose from non-carbohydrate sources.
What is the role of GLUT 4?
GLUT-4 or glucose transporter type 4 is responsible for transporting glucose from the bloodstream into cells, particularly muscle and adipose (fat) cells.
What is the definition of diabetes mellitus (DM)?
A metabolic disease, involving inappropriately elevated blood glucose levels.
Describe type 1 diabetes mellitus.
Attack on the autoimmune system causes pancreatic B (beta) cell destruction subsequently causing a deficiency of insulin. Diagnosis occurs before the age of 30, and patients require insulin injections.
Describe type 2 diabetes mellitus.
Peripheral resistance to insulin action (decreasing sensitivity) and inadequate compensatory response of insulin secretion by the pancreas (progressive loss of β-cells function). Diganosis occurs after the age of 40.
What is “insulin resistance”, and which types of diabetes is characterized by this state?
Insulin resistance is unresponsiveness of the target cells to insulin, see in type 2 diabetes.
What is the alternate name for the pituitary gland?
Hypophysis
How many lobes does the pituitary gland possess, and what are their respective names?
(1) Anterior or adenohypophyis, (2) posterior or neurohypophysis.
Which area in the diencephalon plays a crucial role in maintaining homeostasis and serves as a link between the nervous and endocrine systems through the pituitary gland?
Hypothalamus
What structure connects the hypothalamus to the pituitary gland?
Infundibulum
How are hormone produced in the hypothalamus transported to the neurohypophysis and adenohypophysis?
Through the hypothalamo-hypophyseal tract (axonal connections) and hypophysial portal system, respectively.
In relation to the hypothalamus, what is the portal system?
Specialized network of blood vessels that connects the hypothalamus and anterior pituitary gland.
What are the primary functions of hypothalamic hormones that travel through the hypophysial portal system?
They bind receptors in the anterior pituitary gland affecting pituitary hormone production and release.
Describe releasing hormones.
Produced in the hypothalamus, they stimulate the anterior pituitary to release hormones. Abbreviated RH
Describe inhibiting hormones.
Produced in the hypothalamus, they suppress the they anterior pituitary secretion of hormones. Abbreviated IH.
Define tropic hormones.
Hormones which act on another endocrine glands and stimulate production of other hormones. Most are produced by the anterior pituitary.
Thyrotropin-releasing hormone (TRH)
Promotes secretion of thyroid-stimulating hormone (TSH) and prolactin (PRL)
Corticotropin-releasing hormone (CRH)
Promotes secretion of adrenocorticotropic hormone (ACTH)
Gonadotropin-releasing hormones (GnRH)
Promotes secretion of follice-stimulating hormone (FSH) and lutenising hormone (LH)
Growth-hormone-releasing hormone (GHRH)
Promotes secretion of growth hormone (GH)
Prolactin-inhibiting hormone (PIH, dopamine)
Inhibits secretion of prolactin (PRL)
Somatostatin (SS)
Inhibits secretion of growth hormone (GH) and thyroid-stimulating hormone (TSH)
Which hypothalamic hormones inhibit the release of GH and PRL from the pituitary gland?
Somatostatin (GH) & dopamine (PRL)
Which hypothalamic nuclei produce the hormones oxytocin and ADH, and how are they transported to the posterior pituitary for storage?
The paraventricular and supraoptic nuclei. Through the hypothalamo-hypophyseal tract.
Name the six hormones produced by the anterior pituitary gland and the two hormones produced by the posterior pituitary gland.
Anterior: (1) Follice-stimulating hormone (FSH, gonads), (2) Luteinizing hormone (LH, gonads ), (3) Thyroid-stimulating hormone (TSH, thyroid), (4) Adrenocorticotropic hormones (ACTH, adrenal cortex), (5) Prolactin (PRL, breasts), (6) Growth hormone (GH, bone and muscle)
Posterior: (1) Antidiurretic hormone (ADH, kidney), (2) Oxytocin (OT, breasts)
Which cells within the thyroid gland are responsible for producing thyroid hormone (TH), and what are the two types of thyroid hormones.
Follicular cells produce T3 (triiodothyronine) and T4 (tetraiodothyronine)
Which cells in the thyroid gland produce calcitonin?
Parafollicular cells located at the periphery.
What protein is present in the colloid of the follicles within the thyroid gland?
Thyroglobulin (Tg)
How are blood levels of TH regulated?
Circulating TH concentrations are via a negative feedback system at the level of the hypothalamus and the pituitary.
(a) Which hormone stimulates the growth of the thyroid gland and the secretion of TH, and (b) what stimulates its secretion by the pituitary gland?
(a) TSH (b) TRH (Thyrotropin-releasing hormone)
Where is the TH receptor located within the cell?
The nucleus.
How does TH utilize a negative feedback system?
An increase of blood levels of TH will inhibit their own secretion by decreasing the levels of TRH and TSH.
What are the two main components of the TH structure?
Iodine and tyrosine.
How does iodide from the diet enter the lumen of the thyroid follicles?
Through the sodium/iodide symporter.
What are the three actions of TSH on the thyroid gland?
TSH stimulates TH secretion through enhancing: iodide uptake, thyroglobulin synthesis, and thyroperoxidase activity
What is Hashimoto’s disease?
The immune system mistakenly attacks the thyroid tissue. The most common antibody associated with Hashimoto’s is thyroid peroxidase antibody (TPO antibody). Thyroglobulin antibodies may also be present.
What are some symptoms of hypothyroidism and hyperthyroidism?
Hypo: hair loss, weight gain, muscle pain, and cold intolerance
Hyper: Heat intolerance, irritability and anxiety.
