Introduction to Endocrine Physiology Flashcards
(58 cards)
The classical definition of a hormone defines one as a chemical messenger from an endocrine gland into the bloodstream and acts on a distant tissue. How does this differ from the modern definition of hormone?
The modern definition defines a hormone as any substance released from a cell that acts on another cell, near or far, regardless of the singularity or ubiquity of the source and regardless of the means of conveyance
Define autocrine action. Example?
Secreting cell and target cell are the same
Ex: prostaglandins
Define paracrine action. Example?
A hormone is secreted into extracellular space and targets cells in the surrounding area; diffuse short distances
Ex: Somatostatin
Define endocrine action. Example?
A hormone is secreted by specialized endocrine glands/cells directly into the blood; travel long distances
Ex: thyroxine
Define neural action. Example?
A product of a neuron that is secreted into synaptic spaces; travel short distances
Ex: Acetylcholine & Norepinephrine
Define neuro-endocrine action. Example?
A product of a neuron that is released into the blood
Ex: Oxytocin
What six hormones does the anterior pituitary secrete?
Follicle-stimulating hormone (FSH)
Leutinizing hormone (LH)
Adrenocorticotropic hormone (ACTH)
Thyroid-stimulating hormone (TSH)
Prolactin (PRL)
Growth hormone (GH)
Somatostatin is secreted from what two locations?
Hypothalamus
Pancreas
What two receptors are responsible for modulating the secretion of antidiuretic hormone (ADH)? What do they respond to?
Stretch receptors signal ADH secretion at low atrial pressures (hypovolemia)
Osmoreceptors signal ADH secretion when ECF osmolarity increases (dehydration)
What five hormones function to increase plasma glucose?
Growth hormone
Norepinephrine
Epinephrine
Cortisol
Glucagon
When is norepinephrine considered a hormone and when is it considered a neurotransmitter?
Hormone: when secreted by the adrenal medulla
Neurotransmitter: when released by sympathetic postganglionic neurons
What are the four types of hormones? Which ones are hydrophilic and which ones are hydrophobic?
Peptide and protein hormones (Hydrophilic)
Amino acid derivatives (Hydrophilic)
Steroid hormones (Hydrophobic)
Fatty Acid derivatives (Hydrophobic)
Where are peptide hormones produced? Where are their receptors typically located?
Produced by the pituitary gland as releasing factors (except insulin)
Act on receptors on cell surfaces of peripheral endocrine glands
What are the “pre” and “pro” segments of a preprohormone? What are their functions?
Pre: signaling peptide sequence; bind to signal recognition complex to pause translation until docked on the ER
Pro: Intervening peptide; holds the final product in the proper orientation; keeps hormone inactive until it is cleaved
What is the “C-Peptide”? What is its clinical significance?
“Pro” segment of pro-insulin
Unknown physiological function
Marker of insulin levels (used to diagnose diabetes)
How are peptide hormones stored and transported?
Secretory vescicles
Which hormone type requires use of a secondary messenger? Why?
Peptide/protein hormones
Receptors are located the cell surface; cannot freely diffuse through the cell membrane
True or false: protein/peptide hormones can be administered orally.
False. They will degrade in the stomach.
What hormones are derivatives of tyrosine?
Thyroid hormones
Catecholamines
Where are catecholamines synthesized within the cell (2)? What tissues synthesize them?
Synthesized in the cytosol in:
Adrenal medulla
Post-ganglionic fibers of the sympathetic nervous system
In the synthesis of catecholamines, what reaction does tyrosine hydroxylase catalyze?
Tyrosine –> DOPA
In the synthesis of catecholamines, what reaction does DOPA decarboxylase catalyze?
DOPA –> Dopamine
In the synthesis of catecholamines, what reaction does Dopamine β-hydroxylase catalyze?
Dopamine –> Norepinephrine
In the synthesis of catecholamines, what reaction does PNMT catalyze?
Norepinephrine –> Epinephrine
