Endocrine System Flashcards
Hypothalamic-hypophyseal tract
Bundle of axons that runs through infundibulum and connects the posterior pituitary to the hypothalamus
Arises from neurons in paraventricular and supraoptic nuclei of hypothalamus
Glandular anterior lobe origin
Epithelial tissue
Anterior lobe and hypothalamus connection
No direct neural connection
Vascular connection 👍
-primary capillary plexus in infundibulum communicates inferiority via small hypophyseal portal veins with a secondary capillary plexus in anterior lobe
Hypophyseal portal system
Primary and secondary capillary plexuses + intervening hypophyseal portal veins
Arrangement of blood vessels in which a capillary bed feeds into veins which in turn feed into a second capillary bed
Hypophyseal portal system ensures…
That the min. Quantities of hormones released by the hypothalamus arrive rapidly at the anterior pituitary w/o being diluted by the systemic circulation
Paraventricular neurons (of hypothalamus) primarily make
Oxytocin
Supraoptic neurons (of hypothalamus) mainly produce..
Antidiuretic hormone (ADH)
Oxytocin
Peptide from neurons in paraventricular nucleus of hypothalamus
Oxytocin regulation of release
Stimulated by impulses from hypothalamic neurons in response to stretching of uterine cervix or suckling of infant at breast
Inhibited by lack of appropriate neural tissue
Oxytocin target organs and effects
Uterus: stimulates uterine contractions; initiates labor
Breast: initiates milk ejection
Antidiuretic hormone (ADH)
“Vasopressin”
Peptide
From neurons in supraoptic nucleus of hypothalamus
ADH Regulation of release
Stimulated by impulses from hypothalamic neurons in response to increased blood solutes concentration of decreased blood volume; also stimulated by pain, some drugs and low blood pressure
Inhibited by adequate hydration of the body and by alcohol
ADH Regulation of release
Stimulated by impulses from hypothalamic neurons in response to increased blood solutes concentration of decreased blood volume; also stimulated by pain, some drugs and low blood pressure
Inhibited by adequate hydration of the body and by alcohol
ADH target organs and effects
Kidneys: stimulate kidney tubule cells to reabsorb water from the forming urine back into blood
ADH target organs and effects
Kidneys: stimulate kidney tubule cells to reabsorb water from the forming urine back into blood
ADH effects of hypo-secretion and hyper-secretion
Hypo: diabetes insipidus (intense thirst and huge urine output)
Hyper: Syndrome of inappropriate ADH secretion (SIADH)
ADH effects of hypo-secretion and hyper-secretion
Hypo: diabetes insipidus (intense thirst and huge urine output)
Hyper: Syndrome of inappropriate ADH secretion (SIADH)
Tropic hormone
“Tropin”
Regulates secretory action of other endocrine glands
-TSH
-ACTH
-FSH
-LH
Tropic hormone
“Tropin”
Regulates secretory action of other endocrine glands
-TSH
-ACTH
-FSH
-LH
Growth Hormone (GH)
“Somatotropin”
Protein
Produced by Somatotropic cells of anterior lobe
Anabolic (tissue building) hormone
Has metabolic and growth-promoting actions
GH direct actions on metabolism
-metabolizes fats from fat depots for transport to cells, increasing blood levels of fatty acids and encouraging their use for fuel
-decreases rate of glucose uptake and metabolism, conserving glucose
-anti-insulin effect of GH
-increases amino acid uptake into cells and their incorporation into proteins
Anti-insulin effect of GH
In the liver, it encourages glycogen breakdown and release of glucose to the blood
Raises blood glucose levels
GH indirect actions on growth
Indirectly via family of growth-promoting proteins= insulin-like growth factors (IGFs)
Liver, skeletal muscle, bone, and other tissues produce IGFs in response to GH
-IGFs produced by liver act as hormones, while IGFs made in other tissues act locally w/in those tissues (as paracrines)
IGFs stimulate actions required for growth
-uptake of nutrients from the blood and their incorporation into proteins and DNA, allowing growth by cell division
-formation of collagen and deposition of bone matrix
GH regulation of release
Stimulated by GHRH release, which is triggered by low blood levels of GH as well as by a # of secondary triggers including deep sleep, hypoglycemia, increases in blood levels of amino acids, low levels of fatty acids, exercise, and other types of stressors
Inhibited by feed back inhibition exerted by GH and insulin-like growth factors (IGFs), and by hyperglycemia, hyperlipidemia, obesity, and emotional deprivation via increased GHIH (somatostatin) or decreased GHRH release
GH target organ and effects
Liver, muscle , bone, cartilage, and other tissues: anabolic hormone; stimulates somatic growth; metabolizes fats; spares glucose
Growth-promoting effects mediated indirectly by IGFS
GH effects of hyposecretion and hypersecretion
Hypo: pituitary dwarfism in children
Hyper: gigantism in children; acromegaly in adults
Thyroid-stimulating hormone (TSH)
“Thyrotropin”
Glycoprotein
Tropic hormone that stimulates normal development of thyroid gland
Thyrotropic cells
TSH regulation of release
Stimulated by TRH and in infants indirectly by cold temp
Inhibited by feedback inhibition exerted by thyroid hormones on anterior pituitary hypothalamus and by GHIH
TSH target organ and effects
Thyroid gland: stimulates thyroid gland to release thyroid hormones
TSH effects of hyposecretion and hypersectretion
Hypo: hypothyroidism, may cause myxedema
Hyper: effects similar to those of Graves’ disease (antibodies mimic TSH)
Adrenocorticotropic hormone (ACTH)
“Corticotropin”
Peptide
Secreted by corticotropic cells
It is split from prohormone (large precursor molecule) with pro-opiomelanocotrin (POMC)
Stimulates the adrenal cortex to release corticosteroid hormones
ACTH regulation of release
Stimulated by corticotropin-releasing hormone (CRH); stimuli that increase CRH release include: fever, hypoglycemia, and other stressors
Inhibited by feedback inhibition exerted by glucocorticoids (block secretion of CRH and ACTH release)
ACTH target organs and effects
Adrenal cortex: promotes release of glucorticoids and androgens (mineralocorticoids to a lesser extent)
ACTH Effects of hyposecretion and hypersecretion
Hypo: rare
Hyper: Cushing’s disease
Gonadotropins
Follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
Regulate function of gonads
FSH stimulates production of gametes (sperm or egg)
LH promotes production of gonadal hormones
Almost absent from blood of prepubertal
During puberty, gonadotropic cells are activated and gonadotropin levels rise, causing gonad to mature
Follicle-stimulating hormone (FSH)
Glycoprotein
By gonadotropic cells
FSH regulation of release
Stimulated by gobadotropin-releasing hormone (GnRH)
Inhibited by feedback inhibition exerted by estrogens in females abdominal testosterone in males
FSH regulation of release
Stimulated by gobadotropin-releasing hormone (GnRH)
Inhibited by feedback inhibition exerted by inhibin, and estrogens in females and testosterone in males
FSH target organ and effects
Ovaries and testes
Females: stimulates ovarian follicle maturation and production of estrogens
Males: stimulates sperm production
FSH target organ and effects
Ovaries and testes
Females: stimulates ovarian follicle maturation and production of estrogens
Males: stimulates sperm production
FSH and LH effects of hyposecretion
Failure of sexual maturation
Luteinizing hormone (LH)
Chemical structure: Glycoprotein
Cell type: Gonadotropic cells
Luteinizing hormone (LH)
Chemical structure: Glycoprotein
Cell type: Gonadotropic cells
LH regulation of release
Stimulated by gonadotropin-releasing hormone (GnRH)
Inhibited by feedback inhibition exerted by estrogens and progesterone in females and testosterone in males
LH target organs and effects
Ovaries and testes
Females: triggers ovulation and stimulates ovarian production of estrogens and progesterone
Males: promotes testosterone production
Prolactin (PRL)
Chemical structure: protein
Cell type: prolactin cells