Lesson 3: Endocrine Glands Flashcards
How does the endocrine system differ from the nervous system in communication?
The endocrine system uses chemical signals (hormones) via the bloodstream, while the nervous system uses electrical impulses for rapid communication.
What are the two feedback mechanisms that regulate hormone levels?
Negative feedback (inhibits further secretion) and positive feedback (enhances secretion).
What is an example of positive feedback in the endocrine system?
Oxytocin release during childbirth to enhance uterine contractions.
What is an example of negative feedback in the endocrine system?
Regulation of blood glucose by insulin and glucagon.
What are amine hormones derived from?
Amino acids such as tyrosine (e.g., epinephrine, T3, T4).
What are peptide hormones composed of?
Chains of amino acids (e.g., insulin, glucagon).
What are the precursors of steroid hormones?
Cholesterol.
How do lipid-soluble hormones (e.g., steroid hormones) affect target cells?
They cross the plasma membrane and bind to intracellular receptors to regulate gene expression.
How do water-soluble hormones affect target cells?
By binding to surface receptors and initiating second messenger pathways.
What are enteroendocrine cells?
Cells in the GI tract that release hormones like gastrin and secretin.
What hormone secreted by the stomach stimulates gastric acid production?
Gastrin.
What hormone secreted by the duodenum stimulates the pancreas to release bicarbonate?
Secretin.
What is the role of cholecystokinin (CCK)?
It stimulates secretion of pancreatic enzymes and the release of bile from the gallbladder and pancreatic enzymes.
What is the function of ghrelin?
To stimulate hunger.
What regulates the anterior pituitary?
Releasing and inhibiting hormones from the hypothalamus.
What is the target of thyroid-stimulating hormone (TSH)?
The thyroid gland.
What is the function of adrenocorticotropic hormone (ACTH)?
To stimulate the adrenal cortex to release cortisol.
What does prolactin regulate?
Milk production in mammary glands.
What hormones are transported along the hypothalamic-hypophyseal tract to the posterior pituitary?
Oxytocin and antidiuretic hormone (ADH).
Oxytocin and antidiuretic hormone (ADH).
To conserve water by reducing urine output.
What is the primary effect of growth hormone (GH)?
Stimulates growth and metabolism in tissues, particularly bone and muscle.
What condition results from excess growth hormone after puberty?
Acromegaly.
What is diabetes insipidus?
A condition caused by insufficient ADH, leading to excessive urine production.
What is the role of iodide in thyroid hormone synthesis?
It is essential for the production of T3 and T4.
How is thyroid hormone stored in the thyroid gland?
As thyroglobulin in the colloid of follicles.
What is a goiter?
An enlargement of the thyroid gland, often due to iodine deficiency.
How does calcitonin lower blood calcium levels?
By inhibiting osteoclast activity and promoting calcium deposition in bones.
What is Graves’ disease?
An autoimmune condition causing hyperthyroidism.
What is the relationship between PTH and calcitonin?
PTH raises blood calcium levels, while calcitonin lowers them.
How does PTH affect the kidneys?
It reduces calcium excretion and promotes phosphate excretion.
What is hypoparathyroidism, and what are its symptoms?
Low PTH secretion leading to hypocalcemia, causing muscle cramps and tetany.
What are the three layers of the adrenal cortex?
Zona glomerulosa, zona fasciculata, and zona reticularis.
What hormone is secreted by the zona glomerulosa?
Aldosterone - Regulates sodium and potassium balance, affecting blood pressure and fluid retention.
What hormone is secreted by the zona fasciculata?
Cortisol.
What is the function of cortisol?
To regulate metabolism, reduce inflammation, and assist in stress responses.
What is produced by the adrenal medulla?
Catecholamines (epinephrine and norepinephrine).
What does somatostatin secreted by delta cells regulate?
Inhibits insulin and glucagon secretion.
What is the primary function of insulin?
To decrease blood glucose levels.
What is pheochromocytoma?
A tumor of the adrenal medulla causing excessive catecholamine release.
What is Type 1 diabetes?
An autoimmune condition where beta cells are destroyed, leading to insulin deficiency.
What is Type 2 diabetes?
A condition where cells become resistant to insulin.
What are the long-term complications of diabetes?
Neuropathy, retinopathy, nephropathy, and cardiovascular disease.
What hormone stimulates ovulation in females?
Luteinizing hormone (LH).
What is the role of follicle-stimulating hormone (FSH) in males?
Stimulates spermatogenesis in the testes.
What hormone maintains the uterine lining during pregnancy?
Progesterone.
What is the function of testosterone?
Promotes male secondary sexual characteristics and spermatogenesis.
What hormone is secreted by the pineal gland?
Melatonin.
What is the role of melatonin?
To regulate circadian rhythms and sleep-wake cycles.
What is Cushing’s syndrome?
A condition caused by excess cortisol, leading to weight gain, moon face, and high blood pressure.
What is Addison’s disease?
Adrenal insufficiency leading to fatigue, hypotension, and hyperpigmentation.
What is the cause of goiter in iodine deficiency?
Decreased T3 and T4 production leads to TSH stimulation and gland hypertrophy.
What is the thymus gland’s role in immunity?
It produces thymosin, which promotes T-cell development.
What is the primary function of prostaglandins?
They act as local hormones mediating inflammation, pain, and vascular tone.
What are the 2 classes of hormones?
steroids (cholesterol-derived) gonads and adrenal cortex
protein based (amines, peptides, proteins) thyroid, pituitary gland, pancreas
What does a homeostatic regulatory mechanism involve?
A Receptor, which is a sensor sensitive to a particular environmental change or stimulus; A Control Center or integration center, which receives and processes the information provided by the receptor and issues a command
An Effector, which is a cell or organ that responds to the control center’s commands. Its activity either opposes the stimulus (negative feedback) or intensifies it (positive feedback).
What systems maintain homeosatsis?
Intrinsic autoregulation: cells automatically adapt to an environmental change
Extrinsic regulation:
Nervous system = rapid, short-term response, mediated by neurotransmitters and nerve impulses
Endocrine system: slower, longer-lasting responses, mediated by hormones.
How are endocrine glands classified based on the number of cells forming them?
Into unicellular glands (e.g., isolated cells) and multicellular glands (e.g., entire organs).
What distinguishes endocrine glands in terms of morphology?
Their arrangement is epithelioid tissue without an exposed surface.
What is the DNES (Diffuse Neuroendocrine System)?
A system where cells have both neuronal and endocrine properties, such as enteroendocrine cells and thyroid C cells.
What are examples of unicellular endocrine glands?
Enteroendocrine cells in the gastrointestinal tract and C cells in the thyroid.
What is the main function of DNES cells?
They secrete hormones or factors that regulate local tissue function.
What types of hormones are secreted by enteroendocrine cells?
Peptide hormones such as gastrin and somatostatin.
What are the primary roles of hormones secreted by DNES cells?
Regulating motility of the digestive tract and stimulating enzyme secretion.
Where are enteroendocrine cells predominantly located?
In the epithelium of the gastrointestinal tract.
What are the main hormones secreted by the stomach?
Gastrin, serotonin, histamine, and ghrelin.
What is the role of gastrin?
Stimulates gastric acid secretion and increases intestinal motility.
Which hormone increases hunger and is secreted by the stomach?
Ghrelin.
How does secretin function in the digestive system?
Stimulates bicarbonate secretion from the pancreas to neutralize stomach acid.
What is the role of peptide YY secreted by the large intestine?
Slows gastric emptying and promotes satiety.
What hormone increases insulin release and is secreted by the large intestine?
Glucagon-like peptide-1 (GLP-1).
What are the main hormones secreted by the small intestine?
cholecystokinin, serotonin, secretin, motilin
What are the main hormones secreted by the large intestine?
Peptide YY, glucagon-like peptide-1, somatostatin
What are the four morphological arrangements of multicellular endocrine glands?
Cords/clumps, islets, interstitial cells, and follicles.
Which glands have a cord-like arrangement of endocrine cells?
Pituitary, parathyroids, adrenal, and pineal glands.
Where are endocrine islets found?
In the pancreas as the islets of Langerhans.
What is the arrangement of endocrine cells in the thyroid gland?
Follicles filled with colloid and lined by follicular cells.
How are interstitial endocrine cells arranged?
hey are dispersed in connective tissue, as seen in the testes and ovaries.
What is the hypophyseal portal system?
A microcirculation system connecting the hypothalamus to the anterior pituitary.
What is the function of the hypophyseal portal system?
To transport hypothalamic hormones quickly to the anterior pituitary without entering general circulation.
Which structure delivers hormones from the hypothalamus to the anterior pituitary?
The hypophyseal portal system.
What are the three main components of the hypophyseal portal system?
Primary capillary plexus, hypophyseal portal veins, and secondary capillary plexus.
Where is the primary capillary plexus located?
In the median eminence of the hypothalamus.
What is the role of hypophyseal portal veins?
They transport hormones from the primary plexus to the secondary plexus in the anterior pituitary.
What is the function of the secondary capillary plexus?
To release hypothalamic hormones to the cells of the anterior pituitary.
What hormones are transported by the hypophyseal portal system?
Releasing hormones like gonadotropin-releasing hormone (GnRH), corticotropin-releasing hormone (CRH), growth hormone–releasing hormone (GHRH), and thyrotropin-releasing hormone (TRH).
Which hormones inhibit anterior pituitary hormone secretion?
Somatostatin (inhibits growth hormone) and dopamine (inhibits prolactin).
What are the target glands for gonadotropin-releasing hormone (GnRH)?
Gonads, stimulating the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
What is the effect of corticotropin-releasing hormone (CRH) on the anterior pituitary?
Stimulates the secretion of adrenocorticotropic hormone (ACTH).
Which hypothalamic hormone regulates thyroid activity?
Thyrotropin-releasing hormone (TRH).
What is the function of prolactin-releasing hormone?
Stimulates prolactin secretion from the anterior pituitary.
Which hormones are secreted by the posterior pituitary?
Antidiuretic hormone (ADH) and oxytocin.
How does oxytocin function during childbirth?
It induces uterine contractions.
What is the role of oxytocin in lactation?
Stimulates contraction of myoepithelial cells in the mammary glands for milk ejection.
What is the adenohypophysis?
The anterior lobe of the pituitary gland.
Why is the adenohypophysis called the master regulator?
It controls the function of multiple endocrine glands by releasing tropic hormones.
What is an example of a hormone induced by the hypothalamus in the adenohypophysis?
Adrenocorticotropic hormone (ACTH), which acts on the adrenal glands.
How are cells arranged in the adenohypophysis?
In clumps or cords separated by fenestrated blood capillaries.
What stimulates the production of adrenocorticotropic hormone (ACTH) in the adenohypophysis?
Corticotropin-releasing hormone (CRH) from the hypothalamus.
What are the three main cell types in the adenohypophysis?
Acidophils, basophils, and chromophobes.
What hormones do acidophils secrete?
Growth hormone (GH) and prolactin (PRL).
What hormones do basophils secrete?
Adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), and gonadotropins (FSH and LH).
What are chromophobes, and what is their function?
Cells that do not stain strongly; their function is not fully understood but may include serving as reserve or support cells.
What types of cells are found in the neurohypophysis?
Non-myelinated nerve fibers, glial cells (pituicytes), and secretory neurons.
What are Herring bodies, and what do they store?
Large vesicles in the neurohypophysis that store secretory granules, including ADH and oxytocin.
What is the primary role of pituicytes in the neurohypophysis?
To support the secretory neurons.
What are the two main hormones secreted by the neurohypophysis?
Antidiuretic hormone (ADH) and oxytocin.
What types of cells support neurons in the neurohypophysis?
Pituicytes, specialized glial cells.
What is the function of the network of fenestrated capillaries surrounding thyroid follicles?
To facilitate the exchange of hormones and nutrients.
What are the two main cell types in the thyroid gland?
Follicular cells and parafollicular cells (C cells).
What do follicular cells secrete?
Thyroid hormones T3 (triiodothyronine) and T4 (thyroxine).
What is the function of parafollicular cells (C cells)?
To produce calcitonin
What is the principal component of colloid within the thyroid follicles?
Thyroglobulin, the inactive storage form of thyroid hormones.
What are the main functions of T3 and T4?
They increase metabolism, oxygen and ATP consumption, body temperature, and support nervous system development.
How is the activity of follicular cells regulated?
By thyroid-stimulating hormone (TSH) from the pituitary.
How is the activity of C cells regulated?
By blood calcium levels, independent of the hypophysis.
Why is calcitonin considered a hypocalcemic hormone?
It lowers blood calcium levels and opposes parathyroid hormone (PTH).
What is the relationship between T3 and T4 potency?
T3 is more potent than T4, although more T4 is produced by the thyroid.
What enzymatic activity is essential for iodide oxidation in the thyroid?
Thyroid peroxidase (TPO).
What role does iodine play in thyroid hormone synthesis?
It is added to tyrosine residues in thyroglobulin to produce T3 and T4.
How is iodine transported into the thyroid gland?
Via active transport from the bloodstream.
What are the main types of thyroid disorders?
Hypothyroidism, hyperthyroidism, euthyroid goiter, and thyroid cancer.
What is the most common autoimmune cause of hypothyroidism?
Hashimoto’s thyroiditis.
What condition results from excessive thyroid hormone production?
Hyperthyroidism, often caused by Graves’ disease.
Where are the parathyroid glands located?
Posterior to the thyroid gland, embedded in its surface.
What are the two main cell types in the parathyroid glands?
Chief cells and oxyphil cells.
What is the primary function of chief cells in the parathyroid?
They secrete parathyroid hormone (PTH).
What is the function of PTH?
Increases blood calcium levels by stimulating osteoclast activity, reducing calcium excretion in the kidneys, and activating vitamin D.
What is the role of oxyphil cells in the parathyroid glands?
Their function is not well understood, but they appear in older individuals and may have a supporting role.
How does PTH regulate calcium levels in bones?
Stimulates osteoblasts, which in turn activate osteoclasts to release calcium from bones.
What is PTH’s effect on the kidneys?
Reduces calcium excretion and promotes the conversion of vitamin D into its active form.
What is the function of androgens from the adrenal cortex?
Precursors to sex hormones, contributing to secondary sexual characteristics.
What triggers the secretion of epinephrine and norepinephrine?
Sympathetic nervous system activation during stress.
