BIOL 0800 Reading- Chapter 11 Flashcards
What are hormones?
Chemical messengers that enter the blood, which carries them, from their site of secretion to the cells upon which they act
What is the difference between exocrine and endocrine?
Exocrine glands secret products into ducts to exit the body; whereas endocrine glands are ductless and release their secretory products into the interstitial fluid to diffuse into the blood
What are amine hormones?
Derivatives of the amino acid tyrosine
What are the two classes of hormones encompassed by “amine hormones?”
Thyroid hormones and catecholamines
What are the three catecholamines?
Epinephrine, norepinephrine, and dopamine
What are the two parts of the adrenal gland?
Inner adrenal medulla and outer adrenal cortex
What does the adrenal medulla secret more of, epinephrine or norepinephrine?
Epinephrine
Where is dopamine synthesized?
In thy hypothalamus, and released by a portal system to inhibit pituitary gland activity
What are prohormones?
The precursor to peptide hormones, which are cleaved from preprohormone by proteolytic enzymes in the RER, to be packaged in the Golgi to yield the active peptide hormones
Does a single prohormone create one kind of peptide hormone?
Nope, can create a whole bunch that are all released together
What are the three classes of hormones?
Amine hormones, peptide hormones, and steroid hormones
What are steroid hormones?
Primarily produced in the adrenal cortex and gonads
What is the general process of steroid hormones synthesis?
Anterior pituitary gland hormone binds to receptors in adrenal cortex/gonads, which are linked to G proteins for cAMP production, activating protein kinase A to facilitate the process through phosphorylation
What is the precursor to all steroid hormones?
Cholesterol
How is cholesterol introduced into and used by cells?
Enters as LDLs, which centers cells by receptor-mediated endocytosis and is stored in a liquid droplet until released by the enzyme cholesterol esterase, activated by a protein kinase; then carried to the mitochondria and processed into steroid hormones by cytochrome P450s
What are cytochrome P450s?
Attach hydroxyl groups to carbon atoms and cleave carbon-carbon bonds, to modify cholesterol into steroid hormones
What happens to steroid hormones after synthesis? Where are they stored?
Diffuse across plasma membrane into interstitial fluid and into circulation; not highly soluble in the blood, so primarily transported in plasma bound to carrier proteins like albumin
What are the five major hormones secreted by the adrenal cortex?
Aldosterone, cortisol, corticosterone, DHEA, and androstenedione
What is aldosterone?
A mineralocorticoid, since it affects kidneys’ mineral balances (potassium, sodium, hydrogen)
What hormone controls aldosterone production?
Angiotensin II
What steroid hormones are glucocorticoids?
Cortisol and corticosterone
What steroid hormone is a mineralcorticoid?
Aldosterone
What are cortisol and corticosterone?
Glucocorticoids because they affect glucose metabolism
What steroid hormones are androgens?
DHEA and androstenedione
What are DHEA and androstenedione?
Androgens, which includes testosterone
What are the three layers of the adrenal cortex?
Zona glomerulosa, zona fasciculata, and zona reticularis
What is the zona glomerulosa?
Outer layer of the adrenal cortex; only synthesizes/secretes aldosterone; coverts corticosterone to aldosterone, but do NOT code for genes that form cortisol and androgens
What is the zona fasciculata?
Middle layer of the adrenal cortex; secretes cortisol, primarily
What is the zona reticularis?
Inner layer of the adrenal cortex; secretes primarily androgens
What are the two hormones that make up the category “estrogens?”
Estradiol and estrone
Which estrogen is the major hormone secreted by the ovaries?
Estradiol
What gonadal hormone is secreted by the corpus luteum (ovarian structure after ovulation)?
Progesterone
How are most hormones transported in the blood?
Dissolved in plasma
How are steroid and thyroid hormones transported in the blood?
Bound to large proteins in the plasma, but a small concentration exists dissolved in the plasma as well
Why is the concentration of free hormone in the plasma more important than the total concentration of hormone-protein complex?
Because only the free hormones can diffuse out of capillaries to target cells
What are the two major organs that metabolize or excrete hormones?
Liver and kidneys
What kinds of hormone are removed from the bloodstream quickest? Why?
Peptide and catecholamine hormones are removed quickly because there are enzymes in the bloodstream that break them down quickly; steroid and thyroid hormones take longer because enzymes won’t break them down if they’re bound to proteins
What are the receptors for peptide and catecholamine hormones?
In the plasma membranes of target cells
Where are the receptors for thyroid and steroid hormones?
Inside the target cells
What is up-regulation?
An increase in the number of a hormone’s receptors in a cell, resulting from prolonged exposure to a low concentration of the hormone; temporarily increases target-cell responsiveness
What is down-regulation?
A decrease in receptor number, often from exposure to high concentrations of the hormone; temporarily decreases target-cell responsiveness and prevents overstimulation
How do up and down regulation affect responsiveness to hormones?
Up regulation increases, down regulation decreases
What is permissiveness?
When hormone A must be present for the full strength of hormone B’s effect
What are the three main controls of inputs to endocrine cells?
Changes in plasma concentrations of mineral ions or organic nutrients; neurotransmitters released from the neurons ending on the endocrine cells; or another hormone or paracrine substance on the endocrine cell
What is an example of input to endocrine cell controlled by plasma concentrations of mineral ions of organic nutrients?
Insulin secretion stimulated by high plasma glucose levels; PTH secretion stimulated by low plasma calcium ion levels
What is an example of input to endocrine cell controlled by neurons?
Insulin and gastrointestinal hormone secretion, stimulated by neurons of the parasympathetic nervous system and inhibited by sympathetic nervous system
How does the adrenal medulla relate to the sympathetic nervous system?
It’s a modified sympathetic ganglion, so it’s stimulated by sympathetic preganglionic fibers
Which group of hormones is under direct control of brain neurons themselves, rather than autonomic neurons?
Those secreted by the hypothalamus and co.
What is an example of input to endocrine cells controlled by other hormones?
Tropic hormone, which often stimulates secretion of other hormones as well as the growth of the gland itself
What are three causes of primary hyposecretion?
Partial gland destruction, enzyme deficiency, and dietary iodine deficiency
What is secondary hyposecretion?
Endocrine gland isn’t damaged, but is receiving too little of its topic hormone
What is primary hyposecretion?
When the endocrine gland can’t function normally
How does one diagnose primary or secondary hyposecretion?
Measure the level of tropic hormone in the blood; if elevated, then primary; if lowere, then secondary
What is the difference between primary and secondary hypersecretion?
Primary is when the gland is secreting too much hormone, and secondary is when the tropic hormone excessively stimulates the gland
How does one diagnose primary vs secondary hypersecretion?
Primary if decreased concentration of the tropic hormone because of negative feedback trying to turn off excessive hormone secretion; Secondary if both concentrations of hormone and tropic hormone are elevated.
What is an important example of hyporesponsiveness?
Diabetes mellitus, when target cells of insulin are hyporesponsive
What is one cause of hyporesponsiveness?
Lack of receptors, or defective receptor behavior, or deficiency in enzymes needed to catalyze the steps of the reaction
What is an example of hyperresponsiveness?
Hypersecretion of thyroid hormones causes hyperresponsiveness of epinephrine, which results in elevated heart rate
What is the infundibulum?
The pituitary stalk that connects the pituitary gland to the hypothalamus
Is the posterior pituitary actually a gland?
Nope, it’s technically an extension of the neural components of the hypothalamus
What happens to the axons in the infundibulum? Where do their terminals end up?
Directly on capillaries to release hormones into circulation
What is the median eminence?
The junction of the hypothalamus and infundibulum, where capillaries recombine to form the hypothalamo-pituitary portal vessels
What is a portal vessel?
A vessel that connects two capillary beds
Where are posterior pituitary hormones synthesized?
In the hypothalamus itself