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 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 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
PRL target organ and effects
Breast secretory tissue: promotes lactation
PRL effects of hyposecretion and hypersecretion
Hypo: poor milk production in nursing women
Hyper: inappropriate milk production (galactorrhea); cessation of menses in female; impotence in males
What is the key difference between the way the hypothalamus communicates with the anterior pituitary and the way it communicates with the posterior pituitary?
Hypothalamus communicates with ANTERIOR pituitary via hormones releases into a special portal system of blood vessels
It communicates with posterior pituitary via action potentials traveling down axons that connect the hypothalamus to the posterior pituitary
Zoe drank too much alcohol one night and suffered from a headache and nausea the next morning. What caused these “hangover” effects?
Alcohol inhibits ADH secretion from the posterior pituitary and causes copious urine output and dehydration
Describe structural and functional relationships between the hypothalamus and pituitary gland.
The pituitary gland hangs from the base of the brain and is enclosed by bone. It consists of a hormone-producing glandular portion ( anterior pituitary/adenohypophysis) and a neural portion (posterior pituitary or neurohypophysis) which is an extension of hypothalamus. The neurohypophysis includes: infundibulum and posterior pituitary
Describe structural and functional relationships between the hypothalamus and pituitary gland.
The pituitary gland hangs from the base of the brain and is enclosed by bone. It consists of a hormone-producing glandular portion ( anterior pituitary/adenohypophysis) and a neural portion (posterior pituitary or neurohypophysis) which is an extension of hypothalamus. The neurohypophysis includes: infundibulum and posterior pituitary
Comparison of NS and ES
NS:
Initiates responses RAPIDLY
SHORT-Duration responses
Acts via APs and NEUROTRANSMITTERS
Acts as SPECIFIC LOCATIONS determined by axon pathways
Neurotransmitters act over very SHORT DISTANCES
ES:
Initiates responses SLOWLY
LONG-DURATION responses
Acts via HORMONES released into the blood
Acts as DIFFUSE LOCATIONS- targets can be anywhere blood reaches
Hormones act over LONG DISTANCES
Major process that hormones control and integrate
-reproduction
-growth and development
-maintaining electrolyte, water, and nutrient balance of the blood
-regulating cellular metabolism and energy balance
-mobilizing body defense
Endocrine glands
-ductless
-well-vascularized
-Release hormones directly into blood or lymph
-pituitary
-thyroid
-parathyroid
-adrenal
-pineal
Autocrine
Short-distance chemical signal that exert their effects on the same cells that secrete them
Ex. Prostaglandins released by smooth muscle cells cause this smooth muscle cells to contract
Hormones
Long-distance chemical signals that travel in blood or lymph throughout the body
Hormones
Long-distance chemical signals that travel in blood or lymph throughout the body
Paracrines
Short-distance chemical signals
Act locally (w/in the same tissue) but affect cell types other than those releasing the paracrine chemicals
Ex. Somatostatin released by one pop. of pancreatic cells inhibits the release of insulin by a different pop. If pancreatic cells
Steroid hormones
Lipid soluble
Amino acid-based hormones
Water soluble except thyroid hormone
Where in the cell are steroid hormones synthesized? Where are peptide hormones synthesized? Which of these 2 type of hormone could be stored in vesicles and released exocytosis?
(A)Steroid hormones are synthesized on the membrane of smooth ER
(B)Peptide hormones are synthesized on rough ER
(C)Peptide hormones
Corpus-
Body (corpus callosum)
Corpus-
Body (corpus callosum)
Describe the 2 major mechanisms by which hormones bring about their effects on their target tissues.
Cell-surface receptor activation: hormone binds to a receptor protein on outside of cell membrane, which then activates intracellular processes. Used by amino acid based- can’t pass through cell membrane
Intracellular receptor recognition: hormone enters the cell and binds to a receptor, which changes cell’s protein synthesis. Used by steroid hormones, slower b/c involves protein synthesis
Cell responses to hormone stimulation may involve changes in…
-Membrane permeability
-enzyme synthesis, activation, or inhibition
-secretory activity
-Mitosis
Cyclic AMP system: 2nd messenger mechanisms employing G proteins and intracellular messenger: amino acid-based hormones interacting with target cells
1) hormone brands to a plasma membrane receptor that couples to a G protein
2)G protein is activated, then it couples to adenylate cyclase, which catalyzes the synthesis of cyclic AMP from ATP
3)adenylate cyclase converts ATO to cAMP (2nd messenger)
4) cAMP activates protein kinases
5) cellular response
Steroid hormones (and thyroid hormones) effecting responses: intracellular receptors and direct gene activation
Enter their target cells and effect responses by activating DNA, which initial messenger RNA formation (transcription) leading to protein synthesis
Which class of hormones consists entirely of lipid-soluble hormones? Name the only hormone in the other chemical class that is lipid soluble.
Steroids are all lipid soluble. Thyroid hormones are the only amino acid-based hormones that are lipid soluble
Hurmoral stimulus
Hormone release caused by altered levels of certain crustal ions or nutrients
Ex.
Stimulus: low concentration of Ca2+ in capillary blood
Response: parathyroid glands secrete parathyroid hormone (PTH), which increases blood Ca2+
Neural Stimulus
Hormone release caused by neural input
Ex.
Stimulus: APs in rehanging sympathetic fiber to adrenal medulla
Response: Adrenal medulla cells secrete epi and norepinephrine
Hormonal Stimulus
Hormone release caused by another hormones (a tropic hormone)
Ex.
Stimulus: Hormones from hypothalamus
Response: Anterior pituitary gland secretes hormones that stimulate other endocrine glands to secrete hormones
Explain how hormone release in regulated
(-) feedback mechanism- some internal and external stimulus triggers hormone secretion. As levels of a hormone rise, it causes target organ effects, which then feedback to inhibit further hormone release. Result: blood levels of many hormones vary w/in narrow range
Blood levels of hormones reflect…
A balance between secretion and degradation/excretion.
Liver and kidneys- major degrade hormones; breakdown products are excreted in urine and feces
Permissiveness
Situation in which one hormone must be present in order for another hormone to exert its full effects
Synergism
Occurs when 2 or more hormones produce the same effects in a target cell and their results together are amplified
Antagonism
Occurs when a hormone opposes or reverses the effect of another hormone
Identify factors that influence activation of a target cell by a hormone
Bloody levels of hormone
Relative #s of receptors for the hormone on or in the target cells
Affinity (strength) of the binding between hormone and receptor