Chapter 17 - Endocrine system (Specific systems) Flashcards
What connects the hypothalamus with the pituitary gland (hypophysis)?
Infundibulum
What is the posterior pituitary gland lobe made of?
- Neural tissue (nervous tissue)
- Post. lobe is also called neurohypophysis
What is the anterior pituitary gland lobe made of?
- Glandular tissue (endocrine tissue)
- Ant. lobe is also called adenohypophysis
3/4 of the mass of the pituitary gland is the ______ lobe
Anterior pituitary (secretes hormones into general circulation)
What is a portal vein?
Any vessel located between 2 capillary beds
What is the primary plexus (primary capillary plexus)?
Capillary network associated with the hypothalamus
What is the secondary plexus (secondary capillary plexus)
Capillary network associated with anterior pituitary
What are the hypophyseal portal veins?
Path in which blood is drained from the primary plexus and transported to the secondary plexus
What is the hypothalamo-hypophyseal portal system?
- The name of the whole blood vessel network
- Carries releasing and inhibiting hormones (regulatory hormones) to anterior pituitary to regulate hormone secretion
What does the hypothalamus synthesize and release?
HINT:
Releasing –> “The Pretty Girl Goes Crying”
Inhibiting –> Please Go
RELEASING:
1.) TRH (Thyrotropin-releasing hormone)
2.) PRH (Prolactin-releasing hormone)
3.) GnRH (Gonadotropin-releasing hormone)
4.) GRH (Growth hormone-releasing hormone)
5.) CRH (Corticotropin-releasing hormone)
INHIBITING:
1.) PIH (Prolactin-inhibiting hormone)
2.) GIH (Growth hormone-inhibiting hormone)
What does the anterior pituitary synthesize and release?
HINT: TP FLAG
1.) TSH (thyroid-stimulating hormone)
2.) PRL (prolactin)
3.) FSH (Follicle-stimulating hormone)
4.) LH (Luteinizing hormone)
5.) ACTH (adrenocorticotropic hormone)
6.) GH (Growth hormone)
What is the hypothalamo-hypophyseal tract?
- Where the unmyelinated axons of neurons extend through the infundibulum – Neural pathway
- Synaptic knobs are within posterior pituitary
The hypothalamus synthesizes ______ and ________ while the posterior pituitary gland lobe stores and releases them
- ADH (Antidiuretic hormone) –> synthesized by supraoptic nucleus in the hypothalamus
- Oxytocin –> synthesized by periventricular nucleus in the hypothalamus
- ADH and oxytocin are made of 9 amino acids but differ in 2
What is oxytocin?
- Secreted by hypothalamus (paraventricular nucleus)
- Stimulates uterine contraction, milk ejection, and emotional bonding
- Uses PIP2-Calcium second messenger system
- Helps with male ejaculation
What is ADH (antidiuretic hormone)
- Stimulates water retention by kidneys
- Anti-urination hormone
- Hypothalamus contains osmoreceptors –> if solute concentration is too high, posterior pituitary will secrete ADH
- Triggered by pain, low blood pressure, and drugs
- High concentration causes vasoconstriction (vasopressin)
What is growth hormone (GH)
- Causes liver to secrete insulin-like growth factors 1 and 2
- GH and IGFs (from liver) function synergistically to stimulate cell growth and division
- Produced by somatotropic cells
- Stimulates glycogenolysis, gluconeogenesis, and lipolysis
- Ghrelin stimulates GH release
- Major targets are bone and skeletal muscle
What is thyroid-stimulating hormone (TSH)
- Release triggered by TRH from hypothalamus –> TSH is released from thyrotropic cells of anterior pituitary
- Also called thyrotropin
- Causes release of thyroid hormone (TH) from thyroid gland
- Inhibited by rising blood levels of thyroid hormones that act on pituitary and hypothalamus
What is adrenocorticotropic hormone (ACTH)
- Release triggered by CRH from hypothalamus in daily rhythm
- Secreted by corticotropic cells of anterior pituitary
- Causes release of corticosteroids (ex: aldosterone and cortisol) by adrenal cortex (adrenal gland)
What is follicle-stimulating hormone (FSH)
- Stimulates ovarian follicle maturation and production in females
- Stimulates sperm production in males
- Stimulates gamete production
- Absent from the blood in prepubertal boys and girls
- Triggered by GnRH during and after puberty
- Suppressed by gonadal hormones (feedback)
What is luteinizing hormone (LH)
- Regulates function of gonads
- Triggers ovulation and stimulates ovarian production of estrogen and progesterone in females
- In males, promotes testosterone production
- Stimulates gonadal hormone production
- Absent in the blood in prepubertal boys and girls
- Triggered by GnRH during and after puberty
- Suppressed by gonadal hormones
What is prolactin (PRL)
- Release triggered by PRH from hypothalamus
- Secreted by prolactin cells of anterior pituitary
- Inhibited by PIH from hypothalamus –> dopamine
- Causes milk production, mammillary gland growth in females
- Sucking stimulates PRL release and promotes continued milk production
________ of the hormones of the anterior pituitary are proteins
ALL
All hormones of the anterior pituitary except ______ activate cyclic AMP second messenger systems at their targets
Growth hormone (GH)
Which 4 hormones of the anterior pituitary gland are tropic hormones (regulate secretor action of other endocrine glands)
1.) TSH (thyroid-stimulating hormone)
2.) FSH (Follicle-stimulating hormone)
3.) LH (Luteinizing hormone)
4.) ACTH (adrenocorticotropic hormone)
What is glycogenolysis?
Breakdown of glycogen (stored glucose) into glucose
What is gluconeogenesis?
Conversion of nutrients to glucose
What is glycogenesis?
Synthesis of glycogen (stored glucose)
What is lipolysis?
Breakdown of triglycerides
What is lipogenesis?
Formation of triglycerides
The thyroid gland is connected at midline by narrow ________
Isthmus
Thyroid gland is composed of what types of cells?
Follicular cells and parafollicular cells
What are follicular cells
- Partly makes up the thyroid gland
- Synthesizes thyroglobulin (TGB)
- Produces and releases thyroid hormone (TH)
- Follicle lumen houses colloid (viscous, protein-rich fluid)
What are parafollicular cells
- Cells between follicles
- Makes calcitonin (decreses Ca2+ levels)
What two compounds makeup thyroid hormones?
T4 (thyroxine) –> Has 2 tyrosine molecules and 4 bound iodine atoms
T3 (triiodothyronine) –> Has 2 tyrosine molecules and 4 bound iodine atoms
- Regulates metabolic rate, thermoregulation, promotes growth and development
What is thyroid hormone (TH)
- Secreted by thyroid gland
- Made of T4 and T3
- Affects virtually every cell in body
- Increases metabolic rate and heat production (calorigenic effect)
- Regulation of tissue growth and development (skeletal, nervous system, reproductive capabilities)
- Maintenance of blood pressure
Order of hormone release of thyroid hormones
- Hypothalamus (TRH) –> Anterior pituitary (TSH) –> Thyroid gland (TH) –> target cells
- TH inhibits hypothalamus and anterior pituitary
Transport and regulation of thyroid hormone (TH)
- hypothalamic pituitary thyroid axis –> hypothalamus releases TRH and this causes anterior pituitary to release TSH
- TSH binds receptors of follicular cells –> triggers release of TH
- T4 and T3 transported by thyroxine-binding globulins (TBGs) –> T3 is 10 times more active
- Peripheral tissues convert to T4 to T3
- Negative feedback regulation of TH release
Note: TRH can overcome negative feedback during pregnancy or exposure to cold - TH increases metabolic rate and protein synthesis in targets
What diseases can result from hypo and hypersecretion of TH?
- Hyposecretion in adults –>
1.) Myxedema (goiter if due to lack of iodone)
2.) Cretinism - Hypersecretion –>
1.) Graves disease
What is calcitonin?
- Produced by parafollicular (C) cells in response to high calcium level
- Also be stimulated from exercise
- Antagonist to parathyroid hormone (PTH)
- Decreases blood calcium levels by inhibiting osteoclast activity
- Inhibits bone resorption
- Increases urinary excretion of calcium
What are parathyroid glands?
- Tiny glands embedded in posterior aspect of gland
- Made of oxyphil cells and parathyroid cells
- Secrete parathyroid hormone (PTH)
What is parathyroid hormone?
- PTH is the most important hormone in calcium homeostasis
- Increases calcium levels in blood by stimulating 3 target organs
1.) Skeleton (increased osteoclast activity and causes calcium and PO4 -3 release in blood)
2.) Kidney (increased calcium reabsorption in kidney tubule and increased activation of vitamin D by kidney)
3.) Intestine (increased calcium absorption from food in small intestine) - Hyperparathyroidism –> due to tumor
- Hypoparathyroidism following gland trauma or removal or dietary magnesium deficiency
What is the adrenal medulla?
- Inner core of adrenal gland
- Nervous tissue
- Part of sympathetic nervous system
- Releases epinephrine (80%) and norepinephrine (20%)
What are the layers of adrenal cortex?
- made of glandular tissue that synthesize and secrete corticosteroids
1.) Zona glomerulosa - Secrete mineralocorticoids (ex: aldosterone)
2.) Zona fasciculata - Secrete glucocorticoids (ex: cortisol)
3.) Zona reticularis - Secrete gonadocorticoids (ex: androgens)
What are mineralocorticoids?
- Hormones that regulate electrolyte levels
- Made in zona glomerulosa
What are glucocorticoids?
- Hormones that regulate blood sugar
- Made in zona fasciculata
- Maintain blood pressure by increasing action of vasoconstrotors
- Include cortisol (hydrocortisone) –> only one in significant amounts and released in response to ACTH
What diseases are connected to hyper and hyposecretion of glucocorticoids?
- Hypersecretion –> cushing’s syndrome/disease
- Hyposecretion –> Addison’s disease
What are gonadocorticoids?
- Sex hormones
- Made in zona reticularis
What is the pineal gland?
- Gland hanging from roof of third ventricle
- Pinealocytes: Secrete melatonin, derived from serotonin
Melatonin: COntrols daily sleep/wake cycle
What is the pancreas?
- Triangular gland partially behind stomach
- Has both exocrine and endocrine cells
Acinar cells (exocrine) –> produce enzyme-rich juice for digestion
Pancreatic islets (Islets of Langerhans) –> Contain clusters of endocrine cells - Alpha cells produce glucagon
- Beta cells produce insulin
What does insulin do?
- Lowers blood glucose levels
- Inhibits glycogenolysis and gluconeogenesis
- Participates in neuronal development and learning and memory
- Once blood glucose falls, beta cells stop secreting insulin
- Not needed for glucose uptake in liver, kidney, or brain
What is diabetes mellitus 1?
- Problem with insulin (doesn’t have insulin)
- Most of the time due to autoimmune condition when the immune system is attacking the body and destroying Langerhans cells
- Not reversable
What is diabetes mellitus 2?
- Problem with receptors
- Too much insulin –> receptors disappears
- Reversable
What are the three cardinal signs of Diabetes mellitus (DM)?
Polyuria: Huge urine output (glucose acts as osmotic diuretic)
Polydipsia: Excessive thirst
Polyphagia: Excessive hunger and food consumption
What is the thymus?
- Present in organ/gland that disappears once puberty hits and becomes a thin layer of fat that sits on the heart
- Secretes thymosin
Thymosin: Hormone that helps with differentiating and stimulating the production of white blood cells –> don’t need this extra support once immune system fully develops
