Endocrine System Flashcards
Glands
organs, known as glands that secrete hormones, signaling molecules
Types of hormones
peptides, steroids, or amino acid derivates
peptide hormones
made of amino acids, small (like ADH) to large (like insulin), derived from larger precursor polypeptides that are cleaved during posttranslational modifications –> smaller units are transported to the Golgi apparatus for further modifications that activate the hormones and direct them to the correct locations in the cell, bind to an extracellular receptor
peptide hormone–> first messenger, triggers the transmission of a second signal, known as the “second messenger”
rapid, but short-lived response, act through second messenger cascades
water soluble, don’t require carrier proteins
names often end with -in or -ine (insulin, vasopressin, thyroxine)
Signaling cascade
connection between the hormone at the surface and the effect brought about by second messenger within the cell, at each step is the possibility of amplification
cAMP, IP3, and calcium
common second messengers, cAMP can bind to intracellular targets like protein kinase A, which phosphorylates transcription factors like cAMP response element-binding protein (CREB)
Adenylate cyclase
binding of a peptide hormone triggers the receptor to either activate or inhibit an enzyme called adenylate cyclase, raising or lowering the levels of cAMP accordingly
steroid hormones
derived from cholesterol and are produced primarily by the gonads and adrenal cortex, derived from nonpolar molecules, can pass the cell membrane, impacts the DNA and transcription directly, takes longer, but changes last longer, alters amount of mRNA and protein present in a cell
common form of conformational change is dimerization (pairing of two receptor-hormone complexes)
must be carried by proteins in the blood stream, not water soluble; globulins help carry in the blood
ex. estrogen and testosterone
names often end with -one, -ol, or -oid
amino-acid derivative hormones
epinephrine, norepinephrine, triiodothyronine, and thyroxine; bind in different ways
usually derived from one or two amino acids
ex. thyroid hormones are made from tyrosine, modified by the addition of several iodine atoms
thyroid hormones–> bind intracellularly
catecholamines–> bind to a G-coupled receptor
catecholamines
epinephrine and norepinephrine, bind to a G protein-coupled receptor
Direct hormones
work directly on the target tissue
Tropic hormones
require an intermediary to act, ex. GnRH–> LH/FSH–> estrogen and testosterone; GnRH is tropic, these usually originate in the brain and anterior pituitary gland
Hypothalamus
bridge between the nervous and endocrine system, release of hormones by hypothalamus is regulated by negative feedback, secretes compounds into the hypophyseal portal system
secretes Gonadotropin-releasing hormone (GnRH), Growth hormone-releasing hormone (GHRH), Thyroid-releasing hormone (TRH), and corticotropin-releasing factor (CRF)–> causes the release
Prolactin-inhibiting factor (PIF)–> actually dopamine, causes a decrease in prolactin secretion
Hypophyseal portal system
blood vessel system that directly connects the hypothalamus with the anterior pituitary
hypophysis –> another name for the pituitary
Hypophysis
alternative name for the pituitary
CRF–> ACTH–> will cause the adrenal cortex to increase the level of….?
Cortisol
What does the posterior pituitary release?
Oxytocin and ADH/vasopressin
oxytocin
stimulates uterine contractions during labor, as well as milk letdown during lactation
has a positive feedback loop! (until delivery occurs)
Antidiuretic hormone (ADH)/vasopressin
increases reabsorption of water in the collecting ducts of the kidneys, its secreted to increase plasma osmolarity or increase concentration of solutes within the blood
secreted in response to low blood volume as sensed by baroreceptors or increased blood osmolarity (as sensed by osmoreceptors)
What does the anterior pituitary synthesize?
FLATPEG –> FLAT–> tropic PEG–> direct hormones
- Follicle stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Adrenocorticotropic hormone (ACTH)
- Thyroid-stimulating hormone (TSH)
- Prolactin
- Endorphins
- Growth Hormone (GH)
GnRH–> FSH/LH–> will stimulate the?
Gonads (ovaries and testes)
TRH (thyroid-releasing hormone)–> TSH (thyroid-stimulating hormone)–> will act on the …?
thyroid!
prolactin
stimulates milk production in the mammary glands
release of dopamine from the hypothalamus will decrease its secretion
Endorphins
decrease the sensation of pain
Growth hormone
promotes the growth of bone and muscle
in childhood:
excess of GH will cause gigantism
deficit results in dwarfism
as an adult–> can lead to acromegaly (causes hands, feet, and head to grow when they shouldn’t for adults)
Thyroid
on front surface of the trachea, sets the basal metabolic rate and promotes calcium homeostasis, releases T3 and T4 which carries out the second effect through the release of calcitonin
Triiodothyronine (T3) and thyroxine (T4)
produced by the iodination of the amino acid tyrosine in the follicular cells of the thyroid, capable of resetting the basal metabolic rate of the body by making energy production more or less efficient
Hypothyroidism
a deficiency of iodine or inflammation of the thyroid, thyroid hormones are secreted in insufficient amounts or not at all, needed for development, lack of them can cause cretinism
Hyperthyroidism
too much thyroid hormone, can result from a tumor or thyroid overstimulation
Calcitonin
tones down calcium levels in the blood, made by C-cells (parafollicular cells) in the thyroid
PTH, parathyroid hormone
parathyroid hormone, made in the parathyroids that sit on the posterior surface of the thyroid, serves as an antagonistic hormone to calcitonin, raises blood calcium levels
activates vitamin D, which is required for the absorption of calcium and phosphate in the gut
adrenal cortex secretes..?
corticosteroids–> steroid hormones that can be divided into three classes
- glucocorticoids
- mineralocorticoids
- cortical sex hormones
3 S’s
Salt (mineralocorticoids)
Sugar (glucocorticoids)
Sex (cortical sex hormones)
Glucocorticoids
steroid hormones that regulate glucose levels, affect protein metabolism, cortisol and cortisone
Mineralocorticoids
used in salt and water homeostasis, aldosterone (increases sodium reabsorption in the distal convoluted tubule and collecting duct), water follows sodium cations, also decreases the reabsorption of potassium and hydrogen ions in these same segments of the nephron, promoting their excretion in the urine
Renin-angiotensin-aldosterone system
Decreased blood pressure causes the juxtaglomerular cells of the kidney to secrete renin, which cleaves an inactive plasma protein, angiotensinogen, to its active form, angiotensin I. Angiotensin I is converted to angiotensin II by angiotensin-converting enzyme (ACE) in the lungs. Angiotensin II stimulates the adrenal cortex to secrete aldosterone
Cortisol sex hormones
androgens and estrogens, testes make a lot of androgens, ovaries secrete fewer, so women are more sensitive to disorders of the cortical sex hormone production
What does the adrenal medulla produce?
Epinephrine and norepinephrine (catecholamines)
pancreas
hormone-producing cells are clumped together in the islets of Langerhans
- alpha–> glucagon
- beta—> insulin
- delta —> somatostatin
Glucagon
secreted during times of fasting
when glucose levels are low, glucagon increases glucose production by triggering glycogenolysis, gluconeogenesis, and the degradation of protein and fat
CCK and gastrin can increase glucagon release from alpha cells
Glucagon levels are high when Glucose is Gone
Insulin
antagonistic to glucagon, secreted when blood glucose levels are high, induces muscle and liver cells to take up glucose and store it as glycogen for later use, in addition, bc it is active when glucose levels are high, insulin stimulates anabolic processes such as fat and protein synthesis
too much can lead to hypoglycemia
Diabetes mellitus
characterized by too much glucose in the blood (hyperglycemia), excessive glucose in the filtrate will overwhelm the nephron’s ability to reabsorb glucose, resulting in glucose in the urine, often have polyuria (increased urination), and polydipsia (increased thirst)
Type 1 diabetes
autoimmune destruction of the beta cells of the pancreas
Type II diabetes
result of receptor-level resistance to the effects of insulin, partially inherited, partially due to environmental factors
somatostatin
inhibitor of both insulin and glucagon secretion, decreases GH secretion, also made in the hypothalamus, high blood glucose and amino acid concentrations stimulate its secretion
testes
secrete testosterone in response to stimulation by LH and FSH, causes sexual differentiation of the male during gestation and promotes secondary sex characteristics
ovaries
secrete estrogen and progesterone in response to gonadotropins, estrogen is involved in the development of the female reproductive system and secondary sex characteristics
pineal gland
secretes melatonin, involved in circadian rhythms, makes you sleepy
What produces erythropoietin?
Kidneys, erythropoietin stimulates bone marrow to increase production of red blood cells, response to low levels of oxygen in the blood
What does hormone does the heart release?
Atrial natriuretic peptide (ANP)–> helps regulate salt and water balance, promotes the excretion of sodium and therefore increases urine volume
antagonist to aldosterone
LOWERS blood volume and LOWERS pressure, no effect on blood osmolarity
What does the thymus release?
Thymosin, important for proper T cell development and differentiation, thymus atrophies by adulthood and thymosin levels drop accordingly
