The Endocrine Syste, Flashcards
Glands
organs of the endocrine system that secrete hormones
Hormones
signaling molecules that are secreted directly into the bloodstream to travel to target tissue
they bind to receptors and induce a change in gene expression or cellular function
Hormones can be classified into the following:
Peptides
Steroids
Amino Acid Derivatives
Peptide hormones
made up of amino acids and can be small to large
derived from larger precursor polypeptide cleaved during posttranslational modification; small units go to golgi apparatus for modifications to activate hormone and released by exocytosis
rapid but short lived effects as they act through transient second messenger system meaning easier to turn on and off
water soluble and do not require carriers, travel through blood stream
Because peptide hormones are ____, they cannot pass through the plasma membrane and must bind to _____
charged
extracellular receptor
First messenger
ie. peptide hormones
bind to receptor and trigger transmission of second signal/second messenger
Signaling Cascade
connection between hormone and the effect caused by the secon messengers
Amplification
one hormone may bind to multiple receptors before degradation
each receptor will activate multiple enzymes and trigger production of large quantities of second messengers
each step increases intensity of signal
Common Secondary Messnegers
cyclic adenosine monophosphate (cAMP)
inositol triphosphate (IP3)
Calcium
G Protein Coupled Receptor
1) Peptide hormone binds and triggers receptor to EITHER ACTIVATE OR INHIBIT adenylate cyclase
2) this raises or lowers levels of cAMP
3) cAMP binds to protein kinase A and phosphorylates transcription factors such as cAMP and then exert hormones true effect
Steroid Hormones
derived from cholesterol and produced in gonads/adrenal cortex
non polar molecules that easily cross the cell membrane
slower but longer lived than peptide hormones as they alter mRNA and protein present by affecting DNA
non water soluble and carried by protein
Receptors of steroid hormones are usually _____ or ______.
The hormone-receptor complex undergoes ______ which can the bind directly to ______ resulting in increased or decreased _________
intracellular (cytosol) or intranuclear (nucleus)
conformational change
DNA
transcription of genes
Dimerization
pairing of two receptor-hormone complezes
Steroid Carrying Proteins
specific and cary only one specific hormone
non specific
Note, homrones are inactive while in carrier protein
LEVELS OF CARRIER PROTEIN CAN IMPACT LEVELS OF ACTIVE HORMONE (more carrier protein, less hormone as it is bound to protei)
Amino Acid Derivative Hormones
less common than peptide and steroid hormones
derived from one or two amino acids with a few modifications
Catecholamines
epinephrine and norepinephrine
bind to g protein couple receptors while thyroid hormones bind intracellularly
Direct Hormones
secreted and act directly on a target tissue
ie insulin causing increased uptake of glucose by msucles
Tropic Hormones
require and intermediary to act , stimulate preoduction of another hormone to induce an action
ie: originate from the brain or anterior pityitary gland
Endocrine Glands
Hypothalamus Pituitary Thyroid Parathryoid Adrenal Pancreas Gonads Pineal
Kidney, gastroinsstial glands, heart and thymus secret hormones but are not endocrine organs because…
hormone production is not main function
Hypothalamus
bridge between nercous and endocrine systems
regulates pituitary gland hrough tropic hormones
Location: forebrain between thalamus and pituitary
release of hormones is regulated by negative feedback where hormone produced inhibits homrones earlier in pathway
Suprachiasmatic Nucleus
receives light input from retinae to control sleep wake cycle
Hypothalamus and Anterior Pituitary
hypothalmus secretes into HYPOPHYSEAL PORTAL SYSTEM and bind to receptors in anterior pituitary to stimulate release of hormones
Hypophyseal Portal System
blood vessel system connecting hypothalamus and anterior pituitary
hence hormones secreted by the hypothalamus cannot be in appreciable concentrations in systemic circulation
Hypophysis
alternative term for pituitary
Hypothalamus Tropic Hormones Affectiong Anterior Pituitary Hormones
GnRH -> LH and FSH
GHRH -> GH
TRH -> TSH
CRF -> ACTH
Exception in Hypothalamus and Pituitary Relation
Prolactin-inhibiting factor (dopamine) decreases prolactin secretion!
Three Organ Systems Axes
Hypothalamic-Pituitary-Adrenal (HPA)
Hypothalamic-Pituitary-Ovarian (HPO)
etc
Hypothalamus and Posterior Pituitary
axons of hypothalamus to pituitary
- Oxytocin Released: stimulates contractions during labor and milk
- ADH/Vasppressin: increases reabsorption of water in collecting ducts of kidney s
ADH is released from ______ and secreted in response to _____ or _______. It ______ the duct towards water and results in ______ of water leading to ____ blood pressure and volume.
posterior pituitary
increased plasma osmalarity
increased concentration of solutes within the blood
increases permeability
retention of
increase
Anterior pituitary secretes ____ tropic hormones and ____ direct hormones.
4
3
Tropic Hormones
cause he release of another hormone at the organ level
ex: GnRH stimulates release of FSH and LH from the anterior pituitary
Direct Hormones
Prolactin stimulates milk production
Endorphins decrease perception of pain
Growth Hormone promotoes growth of bone and muscle and is energetically expensive by preventing glucose uptake and stimulate the breakdown of fatty acids by some tissues so gucose is available for muscle and bone
Prolactin _____ from the release of dopamine from the hypothalamus
decreases
Gigantism vs Dwarfism
excess growth hormone vs less growth hormone in childhood
Acromegaly
GH impacts the smaller bones such as those in hands and feet
Posterior Pituitary contains ______ in the hypothalamus. ITs two hormones are _______. THey are produced in _____ and stored in _____
nerve terminals of neurons with cell bodies in hypothalamus
ADH and Oxytocin
hypothalamus
posterior pituitary
