Endocrine Flashcards
endocrinology
- study of hormones
- chem that go thruought the body
hormones are responsible for what?
- long term ongoing fxns of the body
- metabolism (thyroid)
- regulation of the internal environment as a homeostasis
- reproduction
- growth
- development
hormones act in 3 basic ways
- (1) Rates of enzymatic reactions (speeds up rxn)
- (2) Transport of ions or molecules across cell membranes
- (3) Gene expression and protein synthesis (Ex: growth hormone)
cellular mechanism of action for hormones
- depends on binding to target cell receptors
- initiates biochemical responses
hormone action must be terminated
- half-life indicates length of activity
- measure how long molecules can degrade
most hormones are what
- peptides or proteins
peptide hormone synthesis, storage, and release
– Preprohormone is a large, inactive precursor
– Prohormone is processed to smaller form but still inactive
– Active hormone stored in vesicle; requires signal to be released
transported in the blood and half-life of peptide hormones
- relatively short half-life
cellular mechanism of action of peptide hormones
– Bind surface membrane receptors
– Cellular response through signal transduction system
steroids hormones are derived from cholesterol
- Made only in a few organs
– Adrenal cortex of adrenal gland and gonads - Steroid hormone synthesis and release
– Made as needed, not stored - Transport in the blood and half-life of steroid hormones
– Bind carrier proteins in blood
– Longer half-life (example: cortisol = 69-90 minutes in blood) - Cellular mechanism of action of steroid hormones
– Cytoplasmic or nuclear receptors stimulate genomic effects
– Cell membrane receptors stimulate nongenomic repsonses
some hormones are derived from single amino acid
- Derived from tryptophan
– Melatonin from pineal gland - Derived from tyrosine
– Single tyrosine give rise to catecholamines
▪ Epinephrine, norepinephrine, and dopamine
▪ Behave like peptide hormones
– Two tyrosine molecules give rise to thyroid hormones
▪ Behave like steroid hormones
stimulating hormones come from what?
anterior pituitary gland
inhibiting or releasing comes from what?
hypothalamus
anterior pituitary gland hormones
- thyroid stimulating hormones (TSH)
- luitenizing hormone (LH)
- follicle stimulating hormone (FSH)
- growth hormone (GH)
- prolactin (lactation)
- ACTH = adrenocortical tropic hormone (gets released when you’re stressed. goes to adrenocortex to release cortisol)
primary, secondary, teritary
- primary: think actual gland itself
- secondary: think pituitary gland
- tertiary: think hypothalamus
posterior pituitary gland
- anti-diuretic (vasopressin)
- oxytocin (milk outlet and stimulates pos feedback loop in birthing)
reflex pathways have similar components
– Stimulus, sensor, input signal, integration, output signal, one or more targets, & response
the endocrine cell is the sensor in simple endocrine reflexes
- parathyroid hormone (PTH)
many endocrine reflexes involve the what?
nervous system
neurohormones are secreted into the blood by what?
neurons
the posterior pituitary stores and releases two neurohormones
– Neural tissue
– Stores hormones produced in the hypothalamus
– When hypothalamus is stimulated, posterior pituitary secretes two
neurohormones: vasopressin (antidiuretic hormone (ADH) and oxytocin
the anterior pituitary secretes six hormones
– Epithelial origin, thus true endocrine gland
– Trophic hormones stimulate secretion of other hormones
– Prolactin (PRL), thyrotropin (TSH), adrenocorticotropin (ACTH), growth hormone (GH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH)
– Regulated by hypothalamic hormones
▪ Somatostatin (SS) = growth hormone-inhibiting hormone
portal systems
- encapsulation of veins
- consists of two sets of capillaries connected in series by a vein
hypothalamic-hypophyseal (pituitary) portal system
– Hypothalamic neurons produce trophic hormones
– Released into 1st capillary bed in portal system to anterior pituitary
– Anterior pituitary endocrine cells produce trophic hormones
– Released into 2nd capillary bed in portal system to target tissues
what does the portal system connect?
- hypothalamus and anterior pituitary
what does the portal system ensure?
- small amount of concentrated hormone is directed to its target
growth hormone
- Promotes growth of the entire body by affecting:
– Protein formation
– Cell multiplication
– Cell differentiation
physiological action of growth hormone
– Stimulate body growth
– Stimulates secretions of insulin-like growth factor-1
– Stimulates lipolysis
– Inhibits actions of insulin on carbohydrates and lipid metabolism
what is the most power lipid soluble hormone?
- growth hormone
antagonist for insulin
- glucagon
stimulations of growth hormone
- Decreased blood glucose
- Decreased blood free fatty acids
- Increased amino acids
- Starvation or fasting, protein deficiency
- Trauma, stress, and excitement
- Exercise
- Testosterone, estrogen
- Deep sleep (stages II and IV)
- Ghrelin (stimulates hunger/stomach releases it)
inhibits growth hormone
- Increased blood glucose
- Increased blood free fatty acids
- Aging
- Obesity
- Growth hormones (exogenous)
adrenocorticotrophic hormone controls what?
- the secretions of some adrenal hormones which
affect metabolism of glucose, proteins, and fats
physiological actions of ACTH
– Stimulates production of glucocorticoids and androgens by the adrenal cortex
– Maintains size of zona fasciculata and zona reticularis of cortex
ACTH releases 4 hormones (superficial to deep)
- aldosterone
- cortisol
- androgens
- epinephrine
ACTH cortex
– Zona glomerulus: Aldosterone
– Zona fasciculata: Cortisol
– Zona reticularis: Androgens
ACTH medulla
- epinephrine
aldosterone
- uptakes sodium, kicks out acid, kicks out potassium
- Regulates blood pressure by impacting the distal convoluted tubule of kidneys
- Renin-Angiotension-Aldosterone System
renin
- detects BP in kidneys
- if its too low = secrete angiotension 1 (liver) = turns into angiotension 2 (lung)
cortisol
- “Stress” hormone
- Stimulates gluconeogenesis
- Increases liver and plasma proteins
– Muscle anabolism - Mobilization of fatty acids
androgens
- Several moderately active male sex hormones are
continuously secreted by the adrenal cortex, especially during fetal life - Progesterone and estrogens (female sex hormones) are secreted within minute quantities.
epinephrine
- Neurohormone & neurotransmitter released in post ganglionic
sympathetic fibers
– Also secreted by adrenal medulla - Are post ganglionic sympathetic fibers of the autonomic nervous system part of the endocrine system? YES
thyroid stimulating hormone
- Controls the secretion rate of thyroxine (T4) and
triiodothyronine (T3) by the thyroid gland
– These hormones control the rate of most (if not all) intracellular chemical reactions in the body (i.e. METABOLISM)
▪ Functions of the two hormones are the same
– T4 is more common
▪ 93% of metabolically active hormone
▪ iodine is required to formulate T4
– T3 is more potent
▪ T3 can produce more powerful physiological effects
prolactin
- promotes mammary gland development and milk production
follicle stimulating hormone and luteinizing hormone
- Controls growth of ovaries and testis
- Control reproductive endocrinology activities
FSH
▪ Stimulates development of ovarian follicles
▪ Regulates spermatogenesis in the testis
LH
▪ Causes ovulation and formation of corpus luteum in the ovary
▪ Stimulates production of estrogen and progesterone by the ovary
▪ Stimulates testosterone production by the testis
antidiuretic hormone
- AKA vasopressin
- Controls the rate of water excretion into the urine within the collecting ducts of the nephron
– Thus helping the control of concentration of water in the body fluids
oxytocin
- Female Activity: Helps express milk from the glands of the breast to the nipples during suckling
– Helps in delivery of the baby at the end of gestation - Male Activity
▪ Some research suggest it’s associated with male ejaculation and sexual
desire in both sexes.
▪ Not enough research to make strong claim
hormones associated with the GI system
- Ghrelin
– Released by the stomach
– Stimulates hunger and appetite - Leptin
– Released by adipose tissue
– Stimulates “full” sensation
the pancrease secretes what?
- insulin and glucagon
- beta cells: insulin (high BS stimulates insulin)
- alpha cells: glucagon
the insulin to glucagon raio regulates metabolism
– In the fed state (eating), insulin dominates
– In the fasting state, glucagon dominates
insulin
- Insulin (break down glucose) promotes anabolism
– Insulin binds to tyrosine kinase receptors
▪ Activated
– Insulin lowers plasma glucose
▪ 1. Insulin increases glucose transport into insulin-sensitive cells
▪ 2. Insulin enhances utilization and storage of glucose
▪ 3. Insulin promotes fat synthesis
glucagon
- Glucagon is dominant in the fasted state
– Generally antagonist to insulin
– Glucagon prevents hypoglycemia
▪ Liver is primary target
▪ Stimulates glycogenolysis and gluconeogenesis
– Release stimulated by low blood glucose levels - increase sugar levels
parathyroid hormone
- released by parathyroid to increase blood calcium levels
calcitonin
- released by thyroid to decrease blood calcium levels
- tones the bone
- brings Ca+ into the bone
hematological modulated hormones
- Erythropoietin: detects all blood cells that go thru the kidney
– Kidney releasing hormone to stimulating production of red blood cells - Atrial Natriuretic Peptide
– Heart releasing hormone to lower blood pressure and control electrolyte homeostatis
long-loop negative feedback
– Peripheral endocrine gland produces hormone that suppresses secretion of anterior pituitary and hypothalamic trophic hormones
– Most dominant feedback mechanism
short-loop negative feedback
– Pituitary hormone suppresses hypothalamic trophic hormone production
– Secondary feedback mechanism
ultra-short-loop negative feedback loop
– Occurs in hypothalamus and pituitary
– Autocrine or paracrine signals to regulate secretion
hormone interactions
- In synergism, the effect of interacting hormones is more than additive
- A permissive hormone allows another hormone to exert its full effect
– Permissiveness - Antagonistic hormones have opposing effects
– One substance opposes the action of another
– Competitive inhibitors vs. functional antagonists
down-regulation
- sensitivity issues
– Decreased number of receptors in response to abnormally high hormone levels
– Target cell is attempting to diminish its responsiveness to the excess hormone
– Hyperinsulinemia
receptor and signal transduction
– Missing or nonfunctional receptors
– Cells fail to respond or respond inappropriately to hormone signals
hormone evolution
- Evolutionary conservation of hormone function
- Proteomics determines physiological role of hormones
- Example: Calcitonin
- Vestigial structures have lost functionality in humans
– Example: Intermediate lobe of pituitary and melanocyte-stimulating hormone - Comparative endocrinology is the study of endocrinology in non-humans to reveal possible functionality in humans
– Example: pineal gland and melatonin
