Chapter 7: Introduction to the Endocrine System Flashcards
chemical messengers released from endocrine cells or glands, where they diffuse into the blood and travel to target cells
hormones
are endocrine cells vasularized?
yes highly vascularized
will the various effects of hormones on body systems ever counteract one another?
no
what processes do hormones control?
- metabolism
- regulation of internal environment
- reproduction
- growth & development
what form do hormones take?
- classic hormone
- neurohormones
- cytokines
secreted by endocrine cells and glands)
classic hormone
secreted by neurons
neurohormones
- blur the line of hormone
- secreted by paracrine cell of the immune system
cytokines
what are the possible actions on target cells?
- control rates of reactions
- control transport across the membrane
- control gene expression and protein production
what are the two types of endocrine organs?
- primary endocrine organs
- secondary endocrine organs
- primary function is the secretion of hormones
- thyroid gland, thymus, adrenal gland
primary endocrine organs
- diffuse endocrine system, for which the secretion of hormones occurs secondary to some other function
- heart, liver, kidney
secondary endocrine organs
- located in hypothalamus glands
- primary target is anterior pituitary
- release or inhibit pituitary hormones
trophic hormones [peptide, amino acid derived]
- located in posterior pituitary neurons
- targets breast and uterus
- milk ejection; labor and delivery; behavior
oxytocin [peptide]
- located in posterior pituitary neurons
- targets kidneys
- water reabsorption
vasopressin (ADH) [peptide]
- located in anterior pituitary gland
- targets breast
- milk production
prolactin [peptide]
- located in anterior pituitary gland
- targets liver and many tissues
- growth factor secretion
- growth and metabolism
growth hormone (somatotrophin) [peptide]
- located in anterior pituitary gland
- targets adrenal cortex
- cortisol release
corticotropin (ACTH) [ peptide]
- located in anterior pituitary gland
- targets thyroid gland
- thyroid hormone synthesis
thyrotropin (TSH) [peptide]
- located in anterior pituitary gland
- targets gonads
- egg or sperm production; sex hormone production
follicle stimulating hormone [peptide]
- located in anterior pituitary gland
- targets gonads
- sex hormone production; egg or sperm production
luteinizing hormone [peptide]
- located in parathyroid gland
- targets bone, kidney
- regulates plasma, Ca2+, and phosphate levels
parathyroid hormone [peptide]
- located in thyroid gland
- targets many tisses
- metabolism, growth, and development
triiodothyronine and thyroxine [amino acid derived]
- located in thyroid
- targets bone
- plasma calcium levels
calcitonin [peptide]
- located in adrenal cortex gland
- targets kidney
- Na+ and K+ homeostasis
aldosterone [steroid]
- in adrenal cortex gland
- targets tissues
- stress response
cortisol [steroid]
- in adrenal cortex gland
- targets many tissues
- sex drive in females
androgens [steroid]
- in adrenal medulla neurons
- targets many tissues
- fight or flight response
epinephrine, norepinephrine [amino acid derived]
- in testes
- targets many tissues
- sperm production; secondary sex characteristics
androgens [steroid]
- in ovaries
- targets many tissues
- egg production, secondary sex characteristics
estrogen, progesterone
what are the chemical classifications of hormones?
- peptide hormones (majority)
- steroid hormones
- amine hormones
what is the size range of peptide hormones?
three amino acids to more than 20
where are peptide hormones made in the cell?
on ribosomes and RER and stored in vesicles
where are peptide hormones made in the body?
made in tissues all over the body
are peptide hormones water soluble?
yes (lipophobic), easily dissolved in plasma and transported throughout the body
what is the half life of peptide hormones
short (minutes)
where are the binding receptors for peptide hormones?
bind to surface receptors which initiates signal transduction pathways
what do peptide hormones end in?
“in”
what are steroid hormones derived from?
cholesterol
where are steroid hormones made?
made in only a few organs (adrenal cortex, gonads)
where are steroid hormones made in the cell?
- Synthesis in the smooth endoplasmic reticulum where they immediately diffuse out
- These hormones are made when needed and not stored
are steroid hormones soluble in water?
Are not water soluble (lipophilic
how are steroid hormones transported in the body?
- need carrier(escort)-proteins to travel in the blood plasma
- some have specific carriers and others are bound to general plasma proteins (albumin)
what is the half life of steroid hormones?
longer half life (60 minutes of more)
where are cell receptors located on steroid hormones?
cytoplasm or nucleoplasm
what are amine hormones derived from?
small hormones derived from the amino acid tyrosine and tryptophan
where are amine hormones produced?
- thyroid gland
- adrenal medulla
- pineal gland
what is derived from tryptophan?
melatonin
- water soluble amines) are neurohormones that bind to membrane receptors like peptide hormones (epinephrine, dopamine)
- derived from tyrosine
Catecholamines
- (lipid soluble amines) act more like steroid hormones with intracellular receptors for gene activation (T3, T4)
- derived from tyrosine
thyroid hormones
what do amine hormones usually end in?
“ine”
what are examples of simple reflex pathways?
endocrine cell senses stimulus and secrets hormone
- Parathyroid hormone (PTH), regulates plasma Ca2+
- insulin
what/how do parathyroid hormone regulate?
Parathyroid endocrine cells monitor Ca2+ concentration, when a certain number of G-protein-Ca2+ receptors are bound to Ca2+ PTH is inhibited, if fewer receptors are bound PTH secretion increases
how does insulin in pathways work?
- Insulin secreted by multiple pathways
- When blood glucose levels increase pancreatic cells secrete insulin
- Stretch receptors send signals to pancreatic cells as well as endocrine cells in the small intestine
function to regulate almost every body system
the hypothalamus and pituitary glands
- the primary endocrine gland secreting seven hormones, most of which affect the pituitary gland
- crossroads between the nervous system and endocrine system
hypothalamus
- divided into two structurally distinct regions
- anterior pituitary
- posterior pituitary
pituitary structure
True endocrine gland of epithelial origin, embryonic tissue from roof of mouth
Anterior pituitary or adenohypophysis
Extension of neural tissue of the brain and secretes neurohormones made in the hypothalamus
Posterior pituitary or neurohpophysis
sits in a protected pocket of bone, connected to the
brain by a thin stalk
pituitary gland
is the
stalk that connects
the pituitary to the brain
Infundibulum
an extension of the
neural tissue
Posterior pituitary
is a
true endocrine gland of
epithelial origin.
Anterior pituitary
- *stores and releases two neurohormones that were synthesized in different regions of the hypothalamus.
- Antidiuretic hormone (ADH
- oxytocin
posterior pituitary
acts on kidneys to regulate water balance, constrict blood vessels to increase blood pressure.
Antidiuretic hormone (ADH) or Vasopressin
involved in milk ejection during breast feeding, uterus contractions
oxytocin
how is the hypothalamic-anterior pituitary pathway connected?
by the hypothalamic-pituitary portal system or the hypothalamic-hypophyseal portal system
a specialized arrangement of blood vessels in which two capillary beds are located in series
portal system
hormones that control the secretion (release) of other hormones
tropic hormones
what are examples of tropic hormones?
- *Thyrotropin-releasing hormone (TRH)
- *Corticotropin-releasing hormone (CRH)
- *Adrenocorticotrophic hormone (ACTH)
where are the tropic horomones from?
hypothalamus
anterior pituitary
inhibits the release of prolactin
Prolactin inhibiting hormone (PIH) or dopamine
stimulates the anterior pituitary to release prolactin, which stimulates mammary gland development and milk secretion.
Prolactin releasing hormone (PRH)
- stimulates the release of thyroid stimulating hormone (TSH) form the anterior pituitary
- TSH then stimulates the secretion of thyroid hormones (T3, T4) by the thyroid gland. Thyroid hormones regulate metabolism
Thyrotropin releasing hormone (TRH)
stimulates the release of adrenocorticotropic hormone (ACTH) by the anterior pituitary
Corticotropin releasing hormone (CRH)
stimulates the secretion of glucocorticoids (ex. Cortisol), from the adrenal cortex
adrenocorticotropic hormone (ACTH)
main hormone that regulates metabolism when the body is stressed
cortisol
inhibits the secretion of growth hormone by the anterior pituitary
Growth hormone inhibiting hormone (GHIH)
stimulates the secretion of growth hormone (GH) by the anterior pituitary
Growth hormone releasing hormone (GHRH)
regulates growth and energy metabolism
growth hormone
stimulates the release of the gonadotropins, follicle stimulating hormone (FSH), and luteinizing hormone (LH) by the anterior pituitary
Gonadotropin releasing hormone (GnRH)
stimulates ovulation in females, and it stimulates the secretion of sex hormones (estrogens and progesterone in females and androgens in males) by the gonads
luteinizing hormone (LH)
promotes the development of egg cells in females and sperm cells in males
follicle stimulating hormone (FSH)
Hormones at the peripheral endocrine gland feedback to suppress the secretion of the anterior pituitary or hypothalamic tropic hormones
Long-loop negative feedback
Pituitary hormone feeds back to decrease hypothalamus secretion of the hormone
Short-loop negative feedback
how do , endocrine cells alter hormone secretion in response to two types of input?
- neural signals
2. humoral signals
directly regulate hormone secretin by the hypothalamus (tropic hormones), posterior pituitary gland (ADH, and oxytocin), and adrenal medulla (epinephrine), which can affect the secretion of other hormones
neural signals
- (bloodborne) signals
- classified into
- Hormones (hypothalamus-anterior pituitary pathway)
- Ions (blood K+)
- Metabolites (blood glucose)
humoral signals
what are the 3 general types of hormone interactions?
- synergism
- permissiveness
- antagonism
- hormones produce the same direction of effect, generally by different mechanisms
- humoral control of blood glucose level
- combined effect is grater than the sum
synergism
the presence of one hormone is needed for another hormone to exert its actions
permissiveness
what are examples of permissiveness?
- Epinephrine binds to adrenergic receptors
- reproductive system maturation
what happens when Epinephrine binds to adrenergic receptors ?
**Epinephrine binds to adrenergic receptors on smooth muscle cells of bronchioles causing airways to increase in diameter
**Thyroid hormones are essential for the synthesis of the adrenergic receptors in these target cells
no development of reproductive system
thyroid hormone alone
delayed development of system
Reproductive hormones alone
normal development
Reproductive hormones +thyroid hormone
the effects of the hormones oppose each other.
antagonists
what are examples of antagonists?
- Parathyroid hormone increases blood calcium levels, calcitonin decreases levels.
- Glucagon increases blood glucose levels, insulin decreases levels.
caused by hyposecretion or hypersecretion of hormones
disease conditions
inactive and tend to decrease secretion of endocrine cells
Nonfunctioning adenomas (tumors)
where tumor cells actively secrete hormone increasing hormone production
Functioning adenomas
- Causes can include benign tumors (adenomas) and cancerous tumors of endocrine glands
- caused by medical treatment (iatrogenic)
hypersecretion
- *Causes atrophy of gland due to some disease process (ex. Autoimmune response) and can occur anywhere along the endocrine control pathway
- insulin dependent diabetes mellitus
hyposecretion
what else can endocrine diseases arise from besides problems with endocrine glands?
problem with the responsiveness of the target to a specific hormone
**can occur if hormone levels stay abnormally high for extended periods of time
- *will cause the cells to decrease the number of receptors to diminish their responsiveness
- Hyperinsulinemia
down-regulation of hormone receptors
due to nonfunctional receptors or defect in the signal transduction pathway
Altered hormone receptor activity
what can diagnosis of endocrine pathologies be?
simple reflex
complex reflex
what are the complex reflex pathways?
- primary pathology
- secondary pathology
- tertiary pathology
hypo/hypersecretion arises in the last gland in the sequence
primary pathology
arises in the anterior pituitary
secondary pathology
arises in the hypothalamus (rare)
tertiary pathology
In Graves’ disease, the body makes antibodies (TSI) that are agonists of endogenous TSH. You would expect someone with Graves’ disease to exhibit…..
symptoms of hyperthyroidism
Which hormone class is most likely to undergo post-translational modification?
peptide
The hypothalamic-hypophyseal portal system is a(n)
modified capillary bed that transports hormones directly from the hypothalamus to the pituitary
