6. Endocrine System Flashcards
What is the main difference between endocrine and exocrine glands?
Endocrine glands secrete hormones into the bloodstream; exocrine glands secrete substances through ducts to a target organ or surface.
What are examples of endocrine glands?
Pituitary, pineal, thyroid, parathyroid, and adrenal glands.
What are examples of exocrine glands?
Sweat, salivary, lacrimal, and mammary glands.
What is merocrine secretion?
A type of exocrine secretion where products are released via exocytosis.
What is holocrine secretion?
A type of secretion where the entire cell disintegrates to release its contents.
What body functions are regulated by the endocrine system?
Growth, metabolism, behavior, reproduction, digestion, immune response, and more.
How does the endocrine system help maintain homeostasis?
By regulating hormone secretion in response to internal changes.
What are the two major classifications of hormones?
Water-soluble and lipid-soluble hormones.
What are examples of water-soluble hormones?
Insulin, growth hormone, ADH, and epinephrine.
What are examples of lipid-soluble hormones?
Testosterone, estrogen, cortisol, and thyroxine.
What are eicosanoids?
Local lipid-based hormones that affect nearby cells, like prostaglandins and leukotrienes.
What is the function of a hormone receptor?
To bind to a specific hormone and initiate a cellular response.
What is the second messenger in many hormone pathways?
Cyclic AMP (cAMP).
What are the three types of stimuli that regulate hormone release?
Neural, humoral, and hormonal stimuli.
What is upregulation in hormone receptors?
An increase in receptor number due to low hormone levels.
What is the permissive effect of hormones?
When one hormone enables another to act.
What is the antagonistic effect in hormone interaction?
When one hormone opposes the action of another, like insulin and glucagon.
What two nuclei of the hypothalamus are involved in hormone secretion?
Paraventricular nucleus (PVN) and supraoptic nucleus (SON).
What hormones are synthesized by the PVN?
Oxytocin (OT), antidiuretic hormone (ADH), and releasing/inhibiting hormones.
What hormone is synthesized by the SON?
Antidiuretic hormone (ADH).
What connects the hypothalamus and the pituitary gland?
The infundibulum.
What is the role of the hypothalamus in the endocrine system?
It acts as a command center coordinating between the nervous and endocrine systems.
What are the two lobes of the pituitary gland?
Anterior (adenohypophysis) and posterior (neurohypophysis).
What structure connects the pituitary gland to the hypothalamus?
The infundibulum.
Which lobe of the pituitary gland produces hormones?
Anterior pituitary.
Which lobe stores and releases hormones produced by the hypothalamus?
Posterior pituitary.
What is the function of the hypophyseal portal system?
To carry hypothalamic hormones directly to the anterior pituitary.
What is the primary blood supply to the hypophyseal portal system?
The superior hypophyseal artery.
Which hormone stimulates tissue growth and protein synthesis?
Growth hormone (GH).
Which hormone stimulates the thyroid gland?
Thyroid-stimulating hormone (TSH).
Which hormone stimulates cortisol production?
Adrenocorticotropic hormone (ACTH).
Which hormones are gonadotropins?
Follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
What hormone promotes milk production?
Prolactin (PRL).
Where are posterior pituitary hormones synthesized?
In the hypothalamus.
What is the function of oxytocin?
Stimulates uterine contractions and milk ejection.
What is the function of ADH?
Promotes water reabsorption in the kidneys and increases blood pressure.
What condition results from underproduction of ADH?
Diabetes insipidus.
What is the function of the thyroid gland?
Regulates metabolism and affects growth, development, and functioning of body systems.
Where is the thyroid gland located?
In the neck, anterior to the trachea, at the level of C7–T1.
What is the isthmus of the thyroid gland?
A central strip connecting the right and left lobes of the thyroid gland.
What is colloid in the thyroid gland?
A sticky fluid in follicles containing thyroglobulin, the precursor of thyroid hormones.
What do parafollicular (C) cells secrete?
Calcitonin, which helps lower blood calcium levels.
Which hormones are produced by thyroid follicular cells?
Thyroxine (T4) and triiodothyronine (T3).
What is the function of T3 and T4?
Increase metabolic rate, oxygen consumption, protein synthesis, and affect development and growth.
Which hormone is more potent: T3 or T4?
T3 is more potent.
What triggers the release of T3 and T4?
Thyroid-stimulating hormone (TSH) from the anterior pituitary.
What is the role of thyroglobulin?
Serves as a precursor for the synthesis of T3 and T4.
What hormone do chief cells of the parathyroid glands secrete?
Parathyroid hormone (PTH).
What does parathyroid hormone regulate?
Blood calcium, magnesium, and phosphate levels.
What does PTH do in the bones?
Stimulates osteoclasts to release calcium into the blood.
What is the effect of PTH on the kidneys?
Increases calcium and magnesium reabsorption and promotes calcitriol synthesis.
What is the effect of PTH on the intestines?
Indirectly increases calcium absorption by promoting calcitriol production.
What are the opposing hormones in calcium homeostasis?
Parathyroid hormone (raises calcium) and calcitonin (lowers calcium).
Which cells secrete calcitonin?
Parafollicular cells (C cells) of the thyroid gland.
Which cells secrete PTH?
Chief cells of the parathyroid gland.
What are the two main parts of the adrenal (suprarenal) gland?
The outer cortex and the inner medulla.
What are the three zones of the adrenal cortex?
Zona glomerulosa, zona fasciculata, and zona reticularis.
What hormones are produced by the zona glomerulosa?
Mineralocorticoids such as aldosterone.
What hormones are produced by the zona fasciculata?
Glucocorticoids such as cortisol, cortisone, and corticosterone.
What hormones are produced by the zona reticularis?
Androgens (sex hormones).
What cells in the adrenal medulla secrete catecholamines?
Chromaffin cells.
What is the function of aldosterone?
Regulates sodium and potassium levels to control blood pressure and volume.
What is the effect of aldosterone on the kidneys?
Increases Na⁺ and water reabsorption and K⁺ and H⁺ excretion.
What is the primary glucocorticoid in humans?
Cortisol.
What are the metabolic effects of glucocorticoids?
Stimulate gluconeogenesis, protein breakdown, and lipolysis.
How do glucocorticoids affect the immune system?
They suppress immune responses and inflammation.
What is the role of adrenal androgens during puberty?
Promote growth spurts and development of axillary and pubic hair.
What is the function of adrenal androgens in females?
Contribute to libido and are converted to estrogens after menopause.
Which hormones are secreted by the adrenal medulla?
Epinephrine and norepinephrine.
What triggers secretion of catecholamines?
Short-term stress signals from the hypothalamus via the sympathetic nervous system.
What are the effects of epinephrine and norepinephrine?
Increase heart rate, blood pressure, blood glucose, and divert blood to muscles.
What regulates aldosterone secretion?
The renin-angiotensin-aldosterone (RAA) pathway and high potassium levels.
What hormone stimulates cortisol release?
Adrenocorticotropic hormone (ACTH) from the anterior pituitary.
What initiates the release of ACTH?
Corticotropin-releasing hormone (CRH) from the hypothalamus.
What are the two major functions of the pancreas?
Endocrine regulation of blood sugar and exocrine digestion.
What is the exocrine role of the pancreas?
Secretion of digestive enzymes and bicarbonate via acinar cells.
What structure delivers pancreatic juice to the duodenum?
The main pancreatic duct (and sometimes an accessory duct).
What are the four parts of the pancreas?
Uncinate process, head, body, and tail.
What are the four types of endocrine cells in the islets of Langerhans?
Alpha, beta, delta, and F (PP) cells.
Which cell type produces insulin?
Beta cells.
Which cell type produces glucagon?
Alpha cells.
Which cell type produces somatostatin?
Delta cells.
Which cell type produces pancreatic polypeptide?
F cells.
Which hormone is released by epsilon cells?
Ghrelin.
What is the main function of glucagon?
Raises blood glucose by stimulating glycogenolysis and gluconeogenesis.
Which cells secrete glucagon?
Alpha cells of the islets of Langerhans.
What triggers glucagon secretion?
Low blood glucose or high amino acid levels.
What is the main function of insulin?
Lowers blood glucose by promoting uptake and storage of glucose.
Which cells secrete insulin?
Beta cells of the islets of Langerhans.
What triggers insulin secretion?
Elevated blood glucose, food intake, or GI hormones.
What is the function of somatostatin?
Inhibits insulin and glucagon secretion; slows GI nutrient absorption.
What does pancreatic polypeptide do?
Regulates pancreatic secretions and gallbladder contraction.
What is the primary action of ghrelin?
Stimulates hunger.
What are gonads?
Primary reproductive organs: testes in males and ovaries in females.
What do gonads produce?
Gametes and sex hormones.
What are the three main cell types in the testes?
Leydig cells, Sertoli cells, and germ cells.
What is the function of Leydig cells?
Produce testosterone.
What is the function of Sertoli cells?
Support sperm development and form the blood-testis barrier.
What is spermatogenesis?
The process of sperm production from spermatogonia.
Which hormone stimulates testosterone secretion?
Luteinizing hormone (LH).
What hormone stimulates spermatogenesis?
Follicle-stimulating hormone (FSH), enhanced by testosterone.
What hormone is secreted by Sertoli cells to inhibit FSH?
Inhibin.
What hormone stimulates FSH release?
Activin.
What are the actions of testosterone?
Stimulates sperm production, secondary sex traits, muscle growth, and aggression.
What are the main female sex hormones?
Estrogens and progestins (mainly progesterone).
Where are estrogens produced?
By granulosa and thecal cells in ovarian follicles and the corpus luteum.
What hormone triggers ovulation and corpus luteum formation?
Luteinizing hormone (LH).
What is the function of progesterone?
Regulates menstrual cycle and maintains pregnancy.
What hormone prepares the body for childbirth by relaxing pelvic ligaments?
Relaxin.
What secretes estrogens and progesterone during early pregnancy?
The placenta.
What is the function of human chorionic gonadotropin (hCG)?
Promotes progesterone synthesis and reduces immune rejection of the fetus.
What is the function of human placental lactogen (hPL)?
Prepares breasts for lactation.
What hormone does the pineal gland secrete?
Melatonin.
What is the primary function of melatonin?
Regulates sleep-wake cycles and circadian rhythms.
When are melatonin levels highest?
During darkness.
What inhibits melatonin production?
Light detected by the retina via the suprachiasmatic nucleus (SCN).
What type of cells produce melatonin?
Pinealocytes.
What is the primary endocrine function of the thymus?
Secretion of thymosins that promote T cell development.
Where is the thymus located?
In the anterior mediastinum, behind the sternum and in front of the trachea.
What happens to the thymus with age?
It atrophies and is replaced by adipose tissue.
What cells in the GI tract secrete hormones?
Enteroendocrine cells.
What does gastrin do?
Stimulates gastric juice secretion and stomach motility.
What does secretin do?
Stimulates bicarbonate secretion from the pancreas and inhibits stomach acid.
What is the function of CCK (cholecystokinin)?
Stimulates pancreatic enzymes and bile release.
What hormone stimulates insulin release in response to glucose?
GIP (glucose-dependent insulinotropic peptide).
What hormone stimulates hunger?
Ghrelin.
What is the function of hCG (human chorionic gonadotropin)?
Maintains the corpus luteum to support early pregnancy.
What does progesterone do during pregnancy?
Maintains the endometrium and inhibits uterine contractions.
What is the role of placental estrogens?
Stimulate uterine growth and prepare mammary glands for lactation.
What is the function of hCS (human chorionic somatomammotropin)?
Stimulates mammary gland development and regulates maternal metabolism.
What does placental relaxin do?
Increases pubic symphysis flexibility and promotes cervical dilation during labor.
What is a stress response?
The body’s attempt to counteract a stressor using homeostatic mechanisms.
What are the three stages of the stress response?
- Fight-or-flight, 2. Resistance, 3. Exhaustion.
What is eustress?
Good stress that enhances the body’s functional ability.
What is distress?
Harmful stress that negatively impacts the body.
Which hormones mediate the fight-or-flight response?
Epinephrine and norepinephrine.
What part of the adrenal gland releases epinephrine and norepinephrine?
Adrenal medulla.
What are effects of the fight-or-flight response?
Increased heart rate, dilated airways, glycogen breakdown, blood vessel dilation in muscles, reduced kidney blood flow.
What hormone initiates the resistance reaction?
Corticotropin-releasing hormone (CRH).
Which anterior pituitary hormone stimulates cortisol release?
Adrenocorticotropic hormone (ACTH).
What are the main effects of cortisol?
Stimulates lipolysis, gluconeogenesis, protein catabolism, suppresses inflammation.
Which hormone promotes glycogenolysis and lipolysis during stress?
Insulin-like growth factors (IGFs).
What do thyroid hormones do during stress?
Stimulate ATP production from glucose.
What happens during the exhaustion stage of stress?
Immune suppression, fatigue, depression, and potentially fatal conditions like heart attack.
What is the HPA axis?
The interaction between the hypothalamus, pituitary gland, and adrenal cortex in regulating stress responses.
Which hormones does the hypothalamus use to initiate the endocrine stress response?
CRH, TRH, and GHRH.
How does aging affect the endocrine system?
It alters hormone production, secretion, and catabolism.
What causes reduced muscle mass in elderly individuals?
Decreased human growth hormone from the anterior pituitary.
What happens to adrenal gland hormone levels with age?
Cortisol and aldosterone decrease; epinephrine and norepinephrine remain normal.
What hormonal changes occur during menopause?
Estrogen and progesterone levels decline.
What conditions are associated with low estrogen and progesterone levels in postmenopausal women?
Osteoporosis, atherosclerosis, and hyperlipidemia.
What is andropause?
A gradual decline in testosterone levels in aging males.
What effects does andropause have?
Reduced sperm quantity, quality, and motility.
How does aging affect thyroid hormone levels?
They decrease, lowering basal metabolic rate.
What happens to parathyroid hormone levels with age?
They increase, potentially contributing to osteoporosis.
Why does increased PTH contribute to osteoporosis?
It stimulates bone demineralization to raise blood calcium levels.
How does aging affect blood glucose levels?
Blood glucose spikes more rapidly and normalizes more slowly.
Why does glucose intolerance increase with age?
Due to a gradual decline in cellular insulin sensitivity.
