Endocrine System Flashcards
Endocrine vs. Exocrine
Whats the differnce bw endocrine and exocrine glands?
- Endocrine glands secrete hormones into the blood (ductless)
- Exocrine glands secrete their products into a duct where it either enters another organ or exits the body (i.e., sweat)
pancrease has both, pituaitary gland in brain
Hormones - Released directly into blood
What are Hormones?
Chemical Messengers
What are Amine Hormones?
- Derivatives of the amino acid tyrosine
- Thyroid hormones (produced in the thyroid gland)
- Catecholamines
Amine Hormones
What are Catecholimines?
Where are they Produced?
Dopamine - Hypothalamus
Epi and NE - adrenal medulla
What are Peptide Hormones?
What is Proinsulin?
- Secreted through exocytosis
- Preprohormone -> prohormone -> active hormone
- Proinsulin cleaved to insulin and C-peptide (both active peptide hormones)
What are Steroid Hormones?
Primarily produced by adrenal cortex and gonads (ovaries and testes)
Derived from cholesterol
- Lipophilic nature allows for diffusion across cell membranes into circulation
- Typically bound to protein carriers like albumin to travel in the blood
How do the locations for steroid hormone receptors differ from peptide hormone receptors? Why?
Steroid Receptors - inside the cell becuase they can diffuse across the membrane
Peptide Receptors - found on the cell membrane, cant get across into cell due to nature
Hormone Metabolism
What does [Plasma] in the blood depend on?
The rate of secretion from the endocrine gland
The rate of removal from the blood
- Liver and kidney
- Endocytosis
- Enzymes in the blood
- Protein-bound hormones are protected
Path of a Hormone
Do hormones go to every cell?
No, Hormones have actions on only the cells that have receptors for them (allowing them to be highly specific)
Where are Peptides and Catecholamines receptors located?
receptors located on extracellular surface of target cell’s membrane (these hormones are hydrophilic)
Where are Steroid and Thyroid Hormone receptos located?
receptors are located intracellularly (these hormones are lipophilic)
alter gene expression - protein experession - cell function
What happens when a hormone binds to a receptor?
(quick and slow effects)
- Hormones bind to receptors and cause intracellular signaling cascades
- Altered enzyme activity and affected protein activity (quick effects)
- Activation or inhibition of certain genes -> change in rate of protein synthesis (slow effects)
How do Water Soluble Hormones get to a cell?
What do they do once they bine
Water - Soluble Hormone in blood unbound to any protein
Know Step 6
Hormone binds to a receptor, activating proteins and causing the function of the cell to change
How do Water inSoluble Hormones get to a cell?
- steroid hormone bound to prtoein, released and diffuses directly into the cell
- enter the nucleus and bonds to regulatory site on DNA
- Alters transcription and translation of protein,
- takes longer becasue it is creating new proteins not altering existing proteins
- ultimately changes the functions of the cell
How is hormone secretion controlled?
- Changes in [plasma] of mineral ions or organic nutrients
- Neurotransmitter release from neurons ending on endocrine cells
- Another hormone acting on the endocrine cell
Control of Hormone Secretion
How do Changes in [plasma] of mineral ions or organic nutrients affect hormone secretion?
- Major function of the hormone is to regulate the plasma concentration of the ion controlling that hormone, through negative feedback
What is an example of how hormones regulate plasma concentration of ion controlling it through negative feedback?
What is another example of how hormones regulate plasma concentration of ion controlling it through negative feedback?
Insulin stimulated by increase in blood glucose
Pancrease secretes insulin which goes to cells needing glucose for energy
This decreases blood glucose levels
Control of Hormone Secretion
How does Neurotransmitter release from neurons ending on endocrine cells affect hormone secretion?
Neuronal input to glands stimulate or inhibit hormone release
Mechanism of How NT affect hormone secretion
3
- Preganglionic sympathetic neuron stimulates the adrenal medulla
- Post-ganglionic neurons stimulate endocrine gland cells
- Neurons from that hypothalamus secrete hormones that affect the anterior and posterior portion of the pituitary gland
Control of Hormone Secretion
How does Another hormone acting on the endocrine cell affect hormone secretion?
- [Blood] of hormone A controls the release of hormone B
- Hormone A is referred to as a tropic hormone
Glucagon release from the pancreas increases in response to high blood glucose levels. When blood glucose drop, glucagon is no longer released. what type of mechanism of hormone regulation is this?
change in [plasma]
What are The Adrenal Glands?
- Found above each kidney
- Adrenal cortex secretes steroid hormones
How does the Adrenal Medulla Secrete Epi and noraepi?
Adrenal medulla secretes epi and NE
- Epi release is 4x that of NE because of the presence of the enzyme phenylethanolamine-N-methyltransferase (PNMT) which converts NE into epi
- Sympathetic nerves don’t express PNMT therefore they only release NE
epi needs an enzyme so only secreted when it is avalable
What hormone does the adrenal cortex secrete?
Aldosterone
Cortisol
Dehydroepiandrosterone (DHEA)
Androstenedione (androgens)
Cortex
what is aldosterone?
t plays a crucial role in regulating the balance of electrolytes (sodium and potassium) and fluid volume in the body.
Cortex
cortisol
Cortex
DHEA and androgens
What is the Pituitary Gland?
How is it connected to the hypothalamus
- Located in the sphenoid bone, just below the hypothalamus
- Connected to the hypothalamus via the infundibulum
- The infundibulum contains neurons from the hypothalamus and small blood vessels
- Comprised of the anterior lobe (anterior pituitary) and posterior lobe (posterior pituitary)
how are the anterior and posterior lobes of the pituitary connect with the hypothalmus?
anterior - no neural, blood vessels
posterior - nerves
What is the Posterior Pituitary?
- Axons of the supraoptic nuclei and paraventricular nuclei terminate close to capillaries
- Hormones are synthesized in the nuclei, travel to the posterior pituitary, accumulate in the axon terminals and are released into the blood
ADH and OT release from there
Posterior Pituitary
What is Oxytocin?
What are 3 of its functions?
Oxytocin – peptide hormone
Function 1
- Sensory cells in the nipples respond to the nursing baby -> stimulate hypothalamic cells that make oxytocin to activate and release it
- Stimulates contraction of smooth muscle cells in the breasts -> milk ejection during lactation
Function 2
- During labor, stretch receptors in the cervix send signals to the hypothalamus -> OT release -> uterine smooth muscle contraction until the delivery of the fetus
Function 3
- Systemic function in males in uncertain – may be involved in memory and behavior (i.e., pair bonding and emotions such as love)
Posterior Pituitary Hormones
What is Vasopressin aka antidiuretic hormone (ADH)?
antiduretic works to retain water
Vasopressin aka antidiuretic hormone (ADH) – peptide hormone
- Acts on smooth muscle cells to cause vasoconstriction -> increases blood pressure
- Acts on kidneys to decrease water secretion, retaining fluid in the body and maintaining blood volume (i.e., when someone is dehydrated)
What hormone secretion would be affect when someone loses a kidney?
Hormones secreted by adrenal glands
- norepi, epi, cortisol, aldosterone
Not ADH becasue ADH is secreted from the pituitary and ACTS on the kidneys
What is the Anterior Pituitary?
How is it connected to Hypothalamus?
What stimulates it?
No neural connections to the hypothalamus
- Connected to the hypothalamus via the hypothalamo-hypophyseal portal vessels (vessels that originate in the hypothalamus and drain into the vessels of the anterior pituitary gland)
- Stimulated by hormones that are secreted by the hypothalamus (hypophysiotropic hormones) release hormones that cause other endocrine glands to release hormones(with the exception of dopamine)
Anterior Pituitary Path
3 Hormones
What are Hypophysiotropic Hormones?
- Hormones created by the hypothalamus that control the release of hormones from the anterior pituitary gland
Need to Know
GnRH
TRH
CRH
Hypophysiotropic Hormones
What is GnRH?
What does it release from the anterior pituitary?
Gonadotropin-releasing hormone (GnRH)
Stimulates Secretion of:
- FSH (follicle stimulating hormone)
- LH (luteinizing hormone)
peptide
Where is the function of FSH and LH?
(follicle stimulating hormone)
(luteinizing hormone)
What is TRH?
What does it release from the anterior pituitary?
Thyrotropin-Releasing Hormone
Stimulates secretion of TSH (thyroid stimulating hormone)
What is the function of TSH?
(thyroid stimulating hormone)
What is CRH?
What does it release from the anterior pituitary?
Corticotropin-Releasing Hormone
Stimulates secretion of ACTH (adrenocorticotropic hormone)
What is ACTH
(adrenocorticotropic hormone)
ANterior pitautuay hiormones
FSH LH
TSH
ACTH
