Endocrine System Flashcards
What is the classical definition of a hormone?
chemical substances produced by ductless glands and secreted into the blood supply to affect a tissue distant from the gland.
*now understood that hormones can be produced by single cells as well
What is Epicrine signaling?
Hormones pass through gap junctions of adjacent cells without entering extracellular fluid
what is neurocrine signaling?
hormones pass through synaptic clefts between neurons as do neurotransmitters; hormones can also be synthesized in a neuron and secreted directly into the blood from the axon (ex: oxytocin)
What is paracrine signaling?
hormones diffuse through interstitial fluid(ex: prostaglandins)
What is endocrine signaling?
hormones are delivered via the bloodstream (ex: growth hormone)
what is exocrine signaling?
chemical substance is secreted to exterior of the body (ex: pheromones) or into the digestive tract (ex: somatostatin)
What is Autocrine signaling?
when a cell is producing a hormone that is meant to affect that cell; the cell that it is producing (itself)
What’s the difference between a Neurohormone and a Neurotransmitter?
a NT is meant to effect the next nerve cell in the chain; a NH is meant to effect cell types not part of the nervous system and often times are being secreted directly into the blood or put into organs/tissues that may be distant.
What is interstitial fluid?
fluid between the cells, not to be confused with extracellular fluid, similar to plasma (no blood or urine)
Describe amines
derived from amino acid tyrosine; includes things like thyroid hormones and adrenal cateocholamines
Describe peptides
derived from peptides, polypeptides & proteins
Describe steroids
derived from cholesterol; includes things like estradiol, testosterone, cortisol, and progesterone
describe prostaglandins
derived from arachidonic acid; includes things like PGF2
Where is the hypothalamus located and what borders it?
at the base of the brain; bordered by the optic chiasma, mammillary bodies, thalamus, and sphenoid bone
how much does the hypothalamus weigh?
5-10 g in humans (1/300th of the total brain weight)
What does the hypothalamus control?
sexual cycles, pregnancy, lactation, growth, stress Reponses, temperature regulation, water balance, sleep, emotional reactions, etc.
what is the Hypoglamic nuclei?
region of the hypothalamus that is controlling one aspect of the body and the nerves there will communicate with the pituitary for hormonal secretion.
Pituitary=?
Hypophysis
Anterior Pituitary=?
Adenohypophysis
Posterior Pituitary=?
Neurohypophysis
Where is the pituitary located?
in the sella tunica at the base of the brain
Where is the Sella tunica located?
in the sphenoid bone. Sella tunica is a cavity within the sphenoid bone. DO NOT CONFUSE THESE
How is the pituitary connected to the brain?
via the hypothalamus and the portal blood supply
What is the pars distalis?
The principle part of the pituitary gland
What hormone do somatotropes release?
Growth Hormone
What hormone do corticotropes release?
corticotropin releasing hormone
what hormone do mammotropes release?
prolactin
what hormone do thryotropes release?
thyroid stimulating hormone
What hormones do gonadotropes release?
LH and FSH
What hormone is released from the pars intermedia?
Melanocyte stimulating hormone
What is the pars tuberalis?
layer of cells surrounding the neural stalk with no known function
What is the name of the portal system that carries hormones from the hypothalamus to the pituitary?
Hypothalamo-hypophyseal portal system
What are some characteristics of the Hypothalamo-Hypopphyseal portal system?
1) allows rapid response
2)little dilution of peptide hormones
3)peptide hormones have short 1/2 life
What is the function of growth Hormone?
regulates growth, metabolism; acts on liver to cause production of somatomedins and somatomedin binding proteins
What is the function of adrenocorticotrophic hormone?
stimulates adrenal cortex to release cortisol and aldosterone, involved in metabolic regulation
What is the function of gonadotrophic hormones
follicle stimulating hormone; stimulates follicular growth in the ovary
Luteinizing hormone; stimulates ovulation and growth of corpora lutea
what is the function of thyroid stimulating hormone?
stimulates release of thyroxine from thyroid gland
What is the function of prolactin?
stimulates mammary development and lactation
what is the function of beta-lipotrophin?
secreted by corticotropes; involved in pain relief
Define posterior pituitary gland
an outgrowth of the hypothalamus and contains the terminal axons from two pairs of nuclei
what does the supraoptic portion of the posterior pituitary do?
secretes antidiuretic hormone
what does the paraventricular portion of the posterior pituitary gland do?
secretes oxytocin
what does ADH do?
regulates reabsorption of water in the kidney
what does oxytocin cause?
milk ejection reflex
