Endocrine Physiology Flashcards
homeostasis means “ “?
“same state”
feedback mechanisms involve what four features?
system variable: regulated parameter
set point: optimal setting
detector: sensor mechanism
corrective mechanism
endocrinology?
the study of hormone action and the endocrine system
hormones are?
chemical messengers secreted into the blood by specialized cells
what do hormones do? (3)
Alter the rates of various metabolic processes in target cells.*
Act at very low concentrations: nano- to pico-molar range (10-9 to 10-12).
Control long-term homeostatic processes (growth, development, metabolism,
reproduction and internal environment regulation)
hormones act by binding receptors on or in what?
target cells
Hormones act by binding receptors on or in target cells to control (3)
the rates of enzymatic reactions
the movement of ions or molecules across membranes
gene expression and protein synthesis
hormones my act in (4)
neurocrine
endocrine
paracrine
autocrine fashion
Where are most hormones produced and released?
endocrine glands
neurocrine:
endocrine:
paracrine:
autocrine fashion:
Thyroid hormone: source and action
thyroid
Controls basal metabolism
source and action of Cortisol
adrenal cortex
energy metabolism, stress response
source and action of mineralocorticoids
adrenal cortex
Regulate plasma volume via effects on serum electrolytes
source and action of Vasopressin
posterior pituitary
Regulate plasma osmolality via effects on water excretion
source and action of parathyroid hormone
parathyroid gland
Regulates calcium and phosphorous levels
source and action of insulin
pancreas
Regulates plasma glucose concentration
source and action of:
thyroid hormone
cortisol
mineralocorticoids
vasopressin
parathyroid hormone
insulin
hormone chemical classifications (3)
- Aminehormones (derivatives of tyrosine)
a) Catecholamines (epinephrine, norepinephrine)
b) Thyroid hormones (Thyroxine (T4)) - Peptidehormones (insulin)
- Steroid hormones (estrogen, androgens, cortisol)
hormone solubility (polarity) classifications (2)
- Lipophilic (nonpolar) = fat-soluble
- Steroid hormones & thyroid hormones
- Usually bind to intracellular receptors
- Hydrophilic (polar) = water-soluble
- Peptide hormones and catecholamines
- Usually bind to extracellular cell membrane receptors
Hydrophilic (water-soluble) hormones ____ diffuse through the lipid bilayer of cell membrane
cannot
hydrophilic hormones include both (2)
Peptide hormones
Catecholamines (amine-derived)
what do hydrophilic hormones not include?
thyroid hormones
secondary messenger signaling has ____ affect on transcription of target genes
indirect
The hormone (the 1st chemical message) initiates the signaling cascade by binding to receptors on the _____ of the membrane, which are coupled to a ____ that then activates an intracellular second messenger cascade for signal transduction
surface
G-proteins
the second messenger used by most water-soluble hormones is the ___
cAMP (cyclic adenosine monophosphate)
what is the derivative of the two groups of amine hormones?
tyrosine
what are the two groups of amine hormones?
thyroid hormones
catecholamines
what are the two groups of amine hormones? and what do they bind to?
thyroid hormones:
lipophilic, binds to nuclear receptors
catecholamines:
hydrophilic, binds to cell membrane receptors
thyroid hormones characteristics (3)
triiodothyronine (T3) and thyroxine (T4)
very long half-lives
nuclear receptors (lipophilic)
catecholamines characteristics (3)
epinephrine and norepinephrine
very short half-lives
membrane receptors (hydrophilic)
what are the most numerous hormones?
peptide hormones
peptide hormones are ___-soluble
water-soluble (hydrophilic)
peptide hormones have a ___ half-life
short
peptide hormones are cell membrane ____
receptors (2nd messenger system)
peptide hormones are produced as large precursors called
prohormones
*inactive
prohormones or preprohormones are
inactive
peptide hormone processing (4)
- gene transcription (nucleus)
- translation (cytoplasm)
- pre-secretory processing (Golgi)
- post-secretory processing (after secretion)
steroid hormones are derived from
cholesterol
steroid hormones are ___-soluble
lipid
*intracellular receptors
steroid hormones are ___ permeable through cell membranes
freely
steroid hormones are carried in plasma by
hormone-specific plasma binding globulins
“Bound” fractions of steroid hormones serve as ____ for rapid release, as needed
reservoir
Lipid-soluble hormones cross the cell membrane to bind intracellular receptors. These include:
- Steroid hormones
- Thyroid hormones
Hormone-receptor complex moves toward nuclear chromatin, binds to a cell’s DNA forming a complex, and acts ____ as a transcription factor regulating the transcription of the target gene to mRNA.
directly
intracellular hormone receptor pathway (words)
Conversion of androgens to estrogens by
aromatase enzymes
In postmenopausal women,_____ is the primary source of estrogens.
adipose tissue
Negative feedback:
hormone shuts down either the stimulating or the releasing factors terminating the hormone action. (Homeostatic)
positive feedback:
hormones enhance releasing and stimulating factors thus perpetuating additional hormone action. (i.e., as in partuition) (Non-homeostatic)
In the hypothalamic-pituitary-target organ feedback loops:
anterior pituitary (_____) and the posterior pituitary (_____) have different target organs and mechanisms of communication with their target organs
adenohypophysis
neurohypophysis
Anterior pituitary aka
adenohypophysis
Posterior pituitary aka
neurohypophysis
Posterior pituitary (neurohypophysis) is NOT a separate organ, but an extension of the
hypothalamus
_____ ___connects the anterior pituitary gland to the hypothalamus
infundibular stalk
osmolality:
how much of one substance is dissolved in another substance
Serum osmolality
how much dissolved blood urea nitrogen, glucose, and sodium are in serum
275-299 mOsm
Homeostatic feedback systems regulate
serum osmolality
Vasopressin (ADH), is produced by the ____ and secreted at the posterior pituitary.
hypothalamus
Vasopressin (ADH), is produced by the hypothalamus and secreted at the ___ ___
posterior pituitary
The main control of vasopressin secretion is by
hypothalamic osmoreceptors
vasopressin vs blocked
vasopressin: water is reabsorbed into the blood (decreased urine volume)
vasopressin blocked: water is NOT reabsorbed into the blood (increase urine volume)
The hypothalamic-pituitary-adrenal (HPA) Axis is responsible for the body’s …
adaptive stress response
implication on the body from HPA axis in response to stress
o digestion,
o the immune system,
o mood and emotions,
o sexuality,
o serum osmolality
o energy storage/expenditure
All adrenocortical hormones are ____ hormone
steroid
three adrenocortical hormones
mineralocorticoids (zona glomerulosa)
glucocorticoids (zona fasciculata)
adrenal androgens (zona reticularis)
Adrenal medulla secretes _____ like (2)
catecholamines
EPI (epinephrine) and NE (norepinephrine)
Aldosterone promotes ____ reabsorption and ____ excretion by the renal tubular epithelial cells of the collecting ducts.
sodium reabsorption
potassium excretion
aldosterone also stimulates the secretion of … (not K)
K+ ions.
hypokalemia & muscle weakness, if aldosterone levels are
increased
hyperkalemia with cardiac toxicity, if aldosterone levels are
decreased
aldosterone escape
Persistently elevated extracellular fluid volumes can cause pressure diuresis in the kidney
Eosinophil and lymphocyte counts in the blood decrease with
atrophy of lymphoid tissue
glucocorticoids effects (cortisol)
increased serum glucose and glycogen stores in liver
anti-inflammatory effects
Hypothalamus is signaled by the following triggers to release corticotropin releasing hormone (CRH) (3)
normal circadian rhythm
stress
pro-inflammatory cytokines
Anterior Pituitary is stimulated by ___ to release adreno-corticotropic hormone (ACTH)
corticotropin-releasing hormone (CRH)
Adrenal gland stimulated by ACTH to increase ____ synthesis and secretion
cortisol
The glucocorticoid, cortisol, can feedback inhibit both ___ and ___ production/release at the pituitary or hypothalamus in a negative feedback loop.
CRH and ACTH
male sex hormones secreted by the adrenal cortex
DHEA
DHEA sulfate (DHEAS)
androstenedione
11-hydroxyandrostenedione
female sex hormones secreted by the adrenal cortex
progesterone
estrogen
*via aromatization
endocrine disorders
Endocrine gland hyposecretion (hormone deficiency)
Hormone resistance (Type II Diabetes Myelitis)
Hormone Excess (acromegaly, somatostatin, growth hormone)
- Graves Disease (thyroid hormone)
diabetes:
Addison’s disease:
Gigantism:
Diabetes: the most common
endocrine disorder diagnosed in
the U.S.
Addison’s Disease: adrenal gland
releases too little cortisol
gigantism (acromegaly): excess growth hormone
Cushing’s syndrome
excess ACTH results in overproduction of cortisol