Endocrine System Part 1 Flashcards
Learn the Endocrine System
Endocrinology
Study of hormones and endocrine organs
the Endocrine System acts with the __________ __________ to coordinate and integrate activity of body cells
nervous system
how does the endocrine system influence cellular acitivies?
via hormones transported in blood
Responses are _________ but also __________ lasting than the nervous system response
slower but also longer lasting
Endocrine glands
produce hormones, secrete into the blood stream but lack ducts
Exocrine glands
- produce non-hormonal substances (sweat, saliva, digestive enzymes) but have ducts to carry secretion to the membrane’s surface
What are examples of endocrine glands?
pituitary, thyroid, parathyroid, adrenal, and pineal glands
What kind of gland is the hypothalamus classified as?
a nueroendocrine organ
There are 6 other organs and tissues that produce hormones. Please list them.
Adipose cells
Thymus
cells in walls of small intestine
stomach
kidneys
heart
Endocrine tissues are….
diverse and decentralized (many types at many locations)
Hormones
long-distance chemical signals; travel in blood or lymph
autocrines
chemicals that exert effects on same cells that secrete them
paracrine
locally acting chemicals that affect cells other than those that secrete them
Autocrines and Paracrines are _______ _________ _______ and not considered part of the endocrine system
local chemical messengers
Endocrine Cells
releases hormones into the blood stream
- only cells with receptors for that particular hormone will respond
study the different kinds of signaling slide (12 on lecture 1)
…
Properties of hormones
- regulation of physiological processes
- variety in chemical structure
- released in very low quantities
- movement through plasma
- bind to receptors on or in target cells
- released in response to changes to maintain homeostasis
what are the 3 chemical families?
Amines, Peptides and proteins, and steroids
Amines
are derived from animo acids tyrosine or tryptophan (epinephrine, thyroid hormones)
Peptides and protiens
chains of amino acids (insulin, ADH)
Steroids
derived from cholesterol and are lipid soluble (testosterone, cortisol)
Synthesis of amino acied derivative hormone
biochemically synthesized from amino acids and stored within vesicles (epinephrine)
Peptide and protein hormones are synthesized in an _______ ________
inactive form
Peptide and protein synthesis is…
encoded in genes- multiple peptide hormones can be encoded by one gene
Signal Peptide
directs hormone to correct intracellular organelle for processing
Steroid hormones synthesis
biochemically synthesized from cholesterol (cortisol, estrogen, androgens)
What are the water soluble hormones
all the amino acid-based hormones except for the thyroid hormone
water soluble hormone properties
cannot enter the cell
act on plasma membrane receptors
Act via G protein coupled receptors and second messengers
What are all of the lipid-soluble hormones?
steroid and thyroid hormones
What are properties of lipid-soluble hormones?
- can enter the cell
- act on intracellular receptors that directly activate genes
- carried in plasma by plasma proteins
How are fat-soluble hormones transported through the blood?
99% are bound to a transport protein while 1% is free floating
How are water-soluble hormones transported?
100% free floating in the blood
Hormones are excreted in the ______ or ________ tract
urine, digestive
How are water-soluble, free hormones excreted?
they are smaller than the kidney filtration barrier, so they are excreted in the urine
How are lipid-soluble hormones excreted?
- some excreted in urine (if chemically modified to be more water-soluble)
- otherwise excreted in GI tract
Half life (T1/2)
time required to reduce blood concentration by 50%
Increases t 1/2
increased synthesis
increased secretion
binding to transport proteins
modification of structure
decreases t 1/2
decreased synthesis
decreased secretion
excretion by kidney or bile
enzymatic degradation
Hormone release is _______ - __________
amplitude- modulated
neurotransmitter
- release is “all or nothing”
- levels vary with frequency
How do hormones release?
- levels never approach zero
- fluctuate between high and low
- controlled by negative feedback systems
- increased hormone effects on target organs can inhibit further hormone release
Processes that influence hormone secretion
- changes in critical physiological factor (ions)
- direct input from the nervous system through neurohormone release
- actions of other hormones (hypothalamic regulation of pituitary gland)
- Mechanical stresses or cellular metabolism
Endocrine glands are stimulated to synthesize and release hormones in response to these three stimuli:
- humoral stimuli
- neural stimuli
- hormonal stimuli
Humoral stimuli
- changing blood levels of ions and nutries direction stimulation secretion of hormones
What is an example of humoral stimuli?
- Ca 2+ in the blood
- when calcium declines, stimulations parathyroid to secrete PTH (parathyroid hormone)
- PTH causes calcium conc to rise and stimulus is removed
Neural Stimuli
- Nerve fibers stimulate hormone release
- sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines (epinephrine, norepinephrine)
Hormonal Stimuli
Hormones stimulate other endocrine organs to release their hormones (tropic effect)
Hormonal Stimuli steps
- Hypothalamic hormones stimulate release of most anterior pituitary hormones
- anterior pituatary hormones stimulate targets to secrete still more hormones
- Hypothalamic- pituitary- target endocrine organ feedback loop
G- Protein coupled receptors (GPCRs)
- hormone receptors
- integral membrane proteins
- extracellular region binds hormone
- intracellular region interacts with G-proteins
study slide 29 of lecture 1
one-transmembrane spanning receptors (1-TMS)
- hormone receptors
- integral membrane proteins
- extracellular region binds hormone
- intracellular region contains a kinase domain; directly phosphorylates enzymes without G-proteins
Nuclear Receptors
- hormone receptor
- found inside the cell
- acts as a transcription factors
- generally cytoplasmic proteins
- hormone binding leads to translocation to the nucleus
Target cells must have…
specific receptors to which hormone binds
Target cell activation depends on what 3 factors?
- blood levels of hormone
- relative number of receptors on/in target cell
- affinity (strength) of binding between receptor and hormone
up-regulation
target cells from more receptors in response to low hormone levels
down- regulation
target cells lose receptors in response to high hormone levels
- desensitizes the target cells to prevent them from overreacting to persistently high levels of hormone (Type 2 diabetes)
Hormones regulate the ________ ________ of other hormones
receptor levels
How does upregulation regulate receptor levels of other hormones?
increasing receptor levels on target cells
How does downregulation regulate receptor levels of other hormones?
decreasing receptor levels on target cells
permissiveness
the process of hormones regulating the receptor levels of other hormones
in rare cases a hormone can…
regulate levels of its own receptor
Multiple hormones may act on…
the same target at the same time
Permissiveness (target cell response)
one hormone cannot exert its effects without another hormone being present (reproductive hormones need thyroid hormone to have effect )
Synergism
more than one hormone procduces same effects on target cell, causing amplification (glucagon and epinephrine both cause liver to release glucose)
Antagonism
one or ore hormones opposes action of another hormone (insulin and glucagon)
The Hypothalamus is connected to the ____________ ___________ vial stalk called _______________
Pituitary gland, infundibulum
Two major lobes of the hypothalamus
posterior pituitary
anterior pituitary
Posterior pituitary
composed of neural tissue that secretes neurohormones
anterior pituitary
consists of glandular tissue
anatomy of the hypothalamus
- located inferior to the thalamus; part of the limbic system
- contains many distinct nuclei that produce and release unique hormones
Hypophyseal Portal System
connects hypothalamus and anterior pituitary via two capillary beds in series
Anatomy of the pituitary gland
- located inferior to the hypothalamus
- composed of anterior, intermediate, and posterior lobes
Anterior lobe of pituitary gland
major controller of other endocrine organs
Posterior lobe of pituitary gland
secretes two hormones produced by neurons in the hypothalamus
Study slide 41 of lecture 1
…
Posterior Pituitary Hormones
Oxytocin, Antiduretic hormone (ADH)
Oxytocin
- strong stimulant of uterine contractions released during childbirth
- triggers milk ejection (letdown) all positive feedback mechanisms)
- social behavior- contentment, reduced anxiety, calmness
Antidiuretic Hormone (ADH)
Hypothalamus contains osmorecptors
- concentration too high posterior pituitary is triggered to secrete ADH
- targets kidney tubulues to reabsorb more water to inhibit urine formation
- release also triggered by low blood pressure (Vasopressin)
Osmoreceptors
monitor solute concentrations
Diabetes Insipidus
- ADH deficiency due to damage to hypothalamus or posterior pituitary
Polyuria
large volume of dilute urine
Polydipsia
must keep well hydrated, very thirsty
Anterior Posterior Pituitary is glandular tissue derived from an outpocketin of oral mucosa. This is vascularly…..
connected to hypothalamus via hypophyseal portal system
Hypothalamus secretes ____________ and _______________ hormones to anterior pituitary to regulate hormone secretion (tropic effect)
releasing and inhibiting
study slide 47 lecture 1
…
Hypothalamus releases hormones that act on _________ ___________ __________
anterior pituitary gland
Thyrotopin-releasing hormone (TRH)
- produces on parvocellular cells in the paraventricular Nucleus
- triggers TSH and prolactin release
Corticotropin-releasing hormone (CRH)
- produced on parvocellular cells in the paraventricular nucleus
- ACTH release
Growth Hormone- releasing hormone (GHRH)
- neuroendocrine cells of the arcuate nucleus
- GH release
Gonadotropin-releasing hormone (GnRH)
- neuroendocrine cells of the preoptic area
- FSH and LH release
Prolactin-inhibitory hormone (PH or dopamine)
- neuroendocrine cells of the arcuate nucleus
- inhibition of prolactin release
Growth hormone - inhibitory hormone (GIRH, Somatostatin)
- neuroendocrine cells of the periventricular nucleus
- inhibition of GH and TSH release
The six hormones secreted in the Anterior pituitary
- Growth hormone (GH) (tropic)
- Prolactin
- Thyroid-stimulating hormone (TSH) (tropic)
- Adrenocorticotropic Hormone (ACTH) (tropic)
- Follicle- stimulating hormone (FSH) (tropic)
- luteinizing hormone (LH) (tropic)
tropins
stimulate other glands to secrete their hormones
tropic hormones
promote growth and maintain size of target tissues and organs
- high blood levels cause target to hypertrophy
- low levels cause atrophy
growth hormone (GH)
- has direct actions on metabolism and indirect growth- promoting actions through insulin-like growth factor
GH release or inhibition chiefly regulated ____________ ___________
hypothalamic hormones
What are GH’s direct actions on metabolism?
- glucose-sparing actions decrease rate of cellular glucose uptake and metabolism (anti-insulin effects)
- triggers liver to break down glycogen into glucose (glycogenolysis)
- increase blood levels of fatty acids for use as fuel (lipolysis)
Growth hormone-releasing hormone (GHRH)
- stimulates GH release
- triggered by low blood GH
- hypoglycemia (low blood glucose)
- high amino acid levels
Growth hormone- inhibiting hormone (GHIH) (somatostatin)
- inhibits release
- triggered by increase in growth hormone and insulin-like growth factor levels (negative feedback)
study slide 54
gigantism (children)
hypersecretion of growth hormone usually caused by pituitary tumor
acromegaly
overgrowth of hands, feet, and head
Hyposecretion of GH
in children results in pituitary dwarfism
- in adults usually causes no problems
Thyroid- Stimulating Hormone (TSH) - anterior pituitary gland
- stimulates normal development and secretory activity of thyroid
- release triggered by thyrotropin-releasing hormone (TRH) from hypothalamus
- inhibited by rising blood levels of thyroid hormones that act on both pituitary and hypothalamus
study slide 57 of lecture 1
Prolactin (PRL) (anterior pituitary gland
- stimulates milk production in females; role in males not known
What hormone controls regulation of prolactin?
- prolactin-inhibiting hormone which is dopamine
PIH prevents the release of PRL until necessary which leads to…..
lactation
What stimulates PRL?
increased estrogen levels stimulate prolactin
- breast swelling and tenderness during menstrual cycle
- suckling stimulates PRL release and promotes continued milk production
Adrenocorticotropin hormone (ACTH) (anterior pituitary gland)
- stimulates adrenal cortex to release cortisol, mineralocorticoids, and androgens
How is ACTH release regulated?
- triggered by hypothalamic corticotropin-releasing hormone in daily rhytym (highest levels in the morning)
Internal and external factors that alter release of corticotropin-releasing hormone (CRH)?
fever, hypoglycemia, and stressors
Follicle- stimulating hormone(FSH) and Luteinizing Hormone (LH)
also known as gonadotropins
FSH (follicle-stimulating hormone)
stimulates the production of gametes (egg or sperm)
LH (Luteinizing hormone)
- promotes production of gonadal hormones
- in females helps mature follicles of egg, triggers ovulation, and release of estrogen and progesterone
- in males production of testosterone
What hormones are absent from blood in prepubescent boys and girls?
follicle stimulating hormone (FSH) and Luteinizing hormone (LH)
negative feedback control slide 62
How are hormones transported?
Through the blood
Study the anatomy of the thyroid gland
Thyroid hormones T4 and T3
Body’s major metabolic hormone
T4 (thyroxine)
consists of two tyrosine molecules with four bound iodine atoms (must be converted to T3 at tissue level)
T3 (triiodothyronine)
has two tyrosines with three bound iodine atoms
Thyroid hormone synthesis requires how much of iodine?
150 picograms
Thyroid gland secretes 80% T4 which is then converted to the active ____________ form at the ________________
T3 form at the tissues
Two mechanisms of the thyroid hormone:
1) Genomic actions through regulation of gene transcription
2) Non-genomic actions through metabolic activities
steps of the metabolic acivities:
- enters cell
- binds to receptors within nucleus
- triggers transcription
- increases metabolic rate and heat production
- regulates tissue growth and development
How does the thyroid hormone affect the lung?
increased ventilation
how does the thyroid hormone affect the liver?
increased basal metabolic
how does the thyroid hormone affect the heart?
increased heart rate, increased force of contraction, increased cardiac output
how does the thyroid hormone affect the adipose?
increased lipolysis
How does the thyroid hormone affect muscles?
increased protein catabolism
how is thyroid hormone regulated?
negative feedback
Hyperthyroidism
caused by an excess of thyroid hormones
Graves disease (autoimmune)
weight loss, heat sensitivity, increased appetite, heart rate, tremors, and nervousness
hypothyroidism
caused by a deficiency of thyroid hormones
often due to iodine deficiency
loss of functional thyroid tissue
weight gain, cold sensitivity, lethargy, metal fatigue
goiter
a diffuse enlargement of the thyroid gland, caused by a prolonged elevation of TSH
Thyroid nodule
a focal enlargement of a portion of the gland, caused by a benign or malignant neoplasm
Myxedema
swelling of the skin and underlying tissues (edema), low metabolic rate, feeling chilled
how to treat graves’ disease
include surgical removal of thyroid or radioactive iodine to destroy active thyroid cells
Calcitonin
produced by parafollicular (C) cells in response to high calcium levels
What does calcitonin do?
lowers blood calcium levels. Antagonist to parathyroid hormone (PTH)
Parathyroid gland
four to eight tiny yellow-brown glands embedded in the posterior aspect of thyroid
Parathyroid cells secrete….
parathyroid hormone (PTH)
What is the most important hormone in calcium homeostasis?
PTH
When is PTH secreted?
in response to low blood levels of calcium, and inhibited by rising levels of calcium
What is the effect of PTH on bone?
increased resorption
What is the effect of PTH on the kidney?
increased calcitriol (Vitamin D)
what is the effect of PTh on the intestine?
increased calcium reabsorption
Adrenal gland
paired, pyramid-shaped organs atop kidneys
- structurally and functionally it is two glands in one
adrenal cortex anatomy
three layers of glandular tissue that synthesize and secrete several different hormones
adrenal medulla anatomy
nervous tissue that is part of sympathetic nervous system, secretes adrenaline
study the anatomy of the adrenal glands
The adrenal cortex is the area of the adrenal gland that produces….
corticosteroids
Zona glomerulosa produces..
mineralocorticoids
zona fasciculata produces…
glucocorticoids
zona reticularis produces…
gonadocorticoids
Mineralocorticoids
regulate electrolyte concentration in extracellular fluid
aldosterone
most potent mineralocorticoid
- simulations Na reabsorption by kidneys and Potassium elimination by kidneys
- regulation of log term blood pressure
Glucocorticoids
- influence metabolism of cells
- help resist stress
- maintain cellular concentrations of enzymes to produce glucose between meals
cortisol (hydrocortisone)
only glucocorticoid in significant amounts in humans
Cortisol is released in response to»>
ACTH
acute stress interrupts cortisol rythm
Medullar chromaffin cells
synthesize catecholamines epiniphrine and norepinephrine
effects of catecholamines
- vasoconstriction
- increased heart rate
- increased blood glucose levels
- bronchial dilation
Gonadocorticoids (adrenal sex hormone)
weak androgens (male) converted to test, some to estrogen
- sex drive in women
- onset of puberty
- source of estrogens in postmenopausal
hypersecretion
- adrenogenital syndrome
- not noticable in adult males
- Boys- organs mature
females- facial hair, masculine pattern of body hair
Pineal Gland cells
secrete melatonin, derived from seratonin
melatonin affects:
day/ nigh cycles, sleep
physiological processes that show rhythmic variations (body temp, apetite_
the Pancreas
- triangular gland located partially behind the stomach
Acinar cells (exocrine)
produce enzyme-rich juice for digestion
Pancreatic islets
alpha cells produce glucagon
beta cells produce insulin
Glucagon
triggered by decreased blood glucose
extremely potent hyperglycemic protein hormone
raises blood glucose by telling liver to glycogenolysis and glucogenesis
glycogenolysis
break down glycogen into glucose
gluconeogenesis
synthesize glucose from lactic acid and other non-carbohydrates
Insulin
- secreted when blood glucose levels increase
how does insulin lower blood glucose
- enhance membrane transport of glucose into fat and muscle
- polymerize glucose to glycogen
- converts glucose to fat
Diabetes mellitus
Type 1: hyposecretion of insulin
Type 2: Hypoactivity of insulin
Glycosuria
excess glucose is spilled into urine
Polyuria
huge urine output
polydipsia
excessive thirst
polyphagia
excessive hunger and food consumption
Ketoacidosis
build up of ketones in the blood
untreated ketoacidosis…
causes disrupted heart activity, severe depression of nervous system that can lead to coma and death
Hyperinsulinism
excessive insulin secretion
- causes hypoglycemia: low blood glucose levels
“Insulin shock”
disorientation, unconsciousness, death
Gonads and placenta
produce same steroid sex hormones as those of adrenal cortex in greater amounts
Ovaries produce
estrogen and progesteron
- progesterone causes breast development and period
Testes
produces testosterone
- maturation of male
- necessary for normal sperm production
Placenta
secretes estrogens, progesterone, and human chrionic gondotropin to support pregnancy
