Endocrine Flashcards
Endocrine overview
Slide 2
The endocrine system works with the nervous system. It influences metabolic activities via hormones. Controlled mostly by negative feedback systems.
Endocrine glands
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Lack ducts
Produce hormones
Neuroendocrine organ
Slide 5
Hypothalamus
Hormones
Slide 7
Long distance chemical signals; travel in blood or lymph
Autocrines
Slide 7
Chemicals that exert effects on the same cells that secrete them
Paracrines
Slide 7
Locally acting chemicals that affect cells other than those that secrete them
Two main classes of hormones
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Amino acid-based hormones
Steroids
Possible third class of hormones
Slide 7
Eicosandoids
Target cells
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Tissues with receptors for a specific hormone
How do water soluble hormones act?
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Act on plasma membrane receptors
Act via G protein second messengers
Cannot enter cell
How do lipid soluble hormones act?
Slide 9
Act on intracellular receptors that directly activate genes
Can enter cell
Cyclic AMP second-messanger mechanism of water soluble hormones
Slide 10
G protein signaling mechanisms are like a molecular relay race
Intracellular receptors and direct gene activation
Side 11
Lipid soluble steroid hormones and thyroid hormones can diffuse into target cells and bind w intracellular receptors
Helps initial DNA transcription to produce mRNA
mRNA translated to specific protein
Hormone release
Slide 13
Controlled by negative feedback systems ^ hormone effects on target organs can inhibit further hormone release
Hormone release can be triggered by
-endocrine gland stimuli
-nervous system modulation
Humoral stimuli
Slide 14
Changing blood levels of ions and nutrients directly stimulate secretion of hormones
Humoral stimuli example
Declining Ca+ stimulates parathyroid glands to secrete PTH> PTH causes Ca+. concentrations to rise and stimulus is removed
Neural stimuli
Nerve fibers stimulate hormone release
Neural stimuli example
Slide 15
Sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines
Hormonal stimuli
Slide 16
Hormones stimulate other endocrine organs to release their hormones
Target cell specificity
Target cell activation depends on 3 factors
-blood levels of hormone
- relative # of receptors on/in target cell
-affinity (strength) of binding receptor and hormone
Up regulation
Target cells form more receptors in response to low hormone levels
Down regulation
Target cells lose receptors in response to high hormone levels
Half life
Time required for the level of hormone in blood level to decrease by half
Comparison between lipid and water soluble hormones table
Slide 20
Hypothalamus
Connected to pituitary glad (hypophysis) via stalk called infundibulum
Two major lobes of hypothalamus
Posterior pituitary and anterior pituitary
Posterior pituitary
Composed of neural tissue that secretes neurohormones
Posterior lobe + infundibulum make up neurohypophysis
Neurohypophysis
Posterior lobe+ infundibulum
Anterior pituitary (adenohypophysis)
Consists of glandular tissue
Posterior lobe maintains connection to hypothalamus via
Hypothalamic-hypophyseal tract
Hypothalamic-hypophyseal tract arises from neurons in
Paraventricular and supraoptic nuclei in hypothalamus
Runs through infundibulum
Secretes two neurohormones -oxytocin and ADH
ADH
Causes reabsorption of water and vasoconstriction
Oxytocin
Feeling of affection
Contracture of uterine musculature
ADH
Can cause vasoconstriction
Targets kidneys
Hypothalamus contains osmoreceptors that monitor solute concentrations
Clinical imbalance
Diabetes insipidus
Syndrome of inappropriate ADH secretion
ADH deficiency due to damage to the hypothalamus or posterior pituitary
Retention of fluid, headache, disorientation
Anterior pituitary hormones
All activate target cells via cAMP besides GH
GH
TSH
ACTH
FSH
LH
PRL
Growth hormone
Produced by somatotropic cells
Direct actions on metabolism
Regulation of GH
GHRH- stimulates GH release
GHIH- inhibits release
Clinical imbalance
Hypersecretion of GH- gigantism + acromegaly
Hyposecretion- pituitary dwarfism (children) adult no probs
Thyroid stimulating hormone
Also called Thyrotropin produced by thyrotropic cells release triggered by throtropin-releasing hormone from hypothalamus
Adrenocorticotropic hormone ACTH
Also called corticotropin secreted by corticotropin cells release triggered by corticotropin-releasing hormone CRH