Endocrine System Physiology 1 Flashcards
What do we call a chemical substance released by an endocrine gland into the blood in which it travels to another site in the body where it exerts its effect?
A hormone. Endocrine hormones are released directly into the bloodstream. Exocrine hormones are released into ducts to travel to the target tissue. Paracrine hormones act on cells within the vicinity of the secreting cell. Juxtacrine hormones act on neighboring cells. Autocrine hormones act on cells that produce the hormone.
What is the difference between an exocrine and endocrine gland?
An endocrine gland secretes substances into the bloodstream without the use of a duct. An exocrine gland uses a duct to secretes substances to a place that is external from where it resides.
What is an example of an exocrine gland?
Some examples are mammary glands, sweat glands, the pancreas, the liver, or salivary glands.
What is an example of an endocrine gland?
Some examples are the ovaries, the testes, or the adrenal glands
What are the 3 classes of hormones?
(1) Derived from amino acids
(2) Protein or peptide based
(3) Steroids
What amino acid serves as the starting point of most of the amino acid derived hormones?
Tyrosine
What 2 organs release tyrosine based hormones?
(1) Thyroid gland –> thyroxine
(2) Adrenal medulla –> Epi and Norepi
What type of receptor when bound to hormone causes an increase in cAMP?
Plasmalemma receptors
cAMP is an example of what?
Second messenger
What is the effect of an increase in cAMP?
It causes an increase in cytosolic calcium
What substances use plasmalemma receptors?
Polypeptide hormones like Norepi and Epi
What receptors use cytoplasmic receptors?
Steroids
How do steroids interact with the cytoplasmic receptor?
They bind to the receptor and the whole complex binds to DNA and induces gene expression to produce new proteins
What substances use nuclear receptors?
T3 and T4
What is the effect of T3 binding to a nuclear receptor?
Increased transcription and increased translation (production of proteins)
GH, ACTH, TSH, FSH, LH, and prolactin come from where?
Anterior pituitary
How is the hypothalamus and anterior pituitary connected?
Via portal vessels
What gland is controlled by hypothalamic releasing substances?
Anterior pituitary (adenohypophysis)
What gland is controlled by nerve signals from the hypothalamus?
Posterior pituitary (neurohypophysis)
What stimulates growth of ovum and sperm?
FSH
What stimulates the maturation and release of ovum?
LH
What stimulates the liver to release somatomedins?
Growth hormone
What promotes protein synthesis and uptake of various amino acids?
Growth hormone
What promotes increased use of fats, release of fatty acids, decreased use of carbohydrates and increased beta oxidation?
Growth hormone
Where are ADH and oxytocin released from?
Posterior pituitary
What stimulates the release of GH from the Anterior pituitary?
GHRH
What stimulates the release of GHRH from the hypothalamus?
Stress: malnutrition (especially protein), hypoglycemia, exercise, physical/mental trauma
How does the hypothalamus affect posterior pituitary?
Hormones are produced by hypothalamus and are transported down nerve endings to the posterior pituitary
What is target tissue for ADH?
Kidney collecting ducts. Collecting ducts contain lots of aquaporins and thus are highly permeable to water.
What is main stimulus for release of ADH?
Increased blood osmolarity sensed by hypothalamus