Endocrine Function I
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5 basic functions of hormones
• Maintenance of consistency of chemical composition of extra and intracellular fluids • Regulation of growth and development of the body, plus development of male and female sex characteristics • Promotion of sexual maturation, maintenance of sexual rhythms and facilitation of the reproductive process • Regulation of energy production; stabilization of the metabolic rate; tight regulation of salt, water, CHO, fat, and protein metabolism • Helping the body adjust to stress
3 major classes of hormones
Protein Steroid Amino Acid Derivatives
Protein: - its specific chemical composition
amino acid chains (water soluble, travel through bloodstream without carrier)
Protein: - examples
All “P” organs: Pituitary, hyPothalamus, Parathyroid, Portions of the GI tract, and Pancreas
Protein: Mechanism of action
These (along with catecholamines or protein-bound hormones), effect their cellular action by binding to cellular receptors. They need a “second messenger” to pass their cellular message to interior of cell.
Why is a second messenger necessary?
The first messenger is the protein polypeptide, or catecholamine hormone itself, because it is not lipid-soluble, it cannot pass through the membrane.
The second messenger is _____ ______, formed by adenyl cyclase catalysis
cyclic AMP (cAMP)
Steroid Hormone: - derivation
derived from cholesterol
Steroid Hormone: - What is the nucleus for all steroid hormones
Perhydrocyclopentanophenanthrene
Steroid Hormone: - They are hydrophobic and require ____ _____ to be transported in blood. Must dissociate from carrier to be biologically active; the ______ hormone is biologically active
Carrier Proteins FREE
Steroid Hormone: - Metabolism
They must be catabolized by liver to water-soluble, inactive forms. Hydroxylation, Oxidation, or reaction with glucuronic acid or sulfate forms conjugates, which are excreted in urine
Steroid Hormone - mechanism of action
Lipid-soluble so pass through cell membrane, then they associate with a specific cytoplasmic receptor protein. This is transported to cell nucleus, inducing messenger RNA synthesis
Aromatic Amine Hormones are small molecules derived from the amino acid ________
tyrosine
Aromatic Amine Hormones: - examples
Includes both thyroid hormones and catecholamines hormones from the adrenal medulla
Aromatic Amine Hormone: - Are ______-_______ and require carrier proteins, principally albumin, for transport in bloodstream
water-insoluble
Aromatic Amine Hormone: - Catabolism and excretion
Catabolized in liver by deiodination or oxidation to inactive forms to be excreted
Aromatic Amine Action: - Thyroid Hormones use what pathway to enter the cell?
mRNA pathway
Aromatic Amine Action: - Catecholamines use what pathway to enter the cell?
use the second messenger (cAMP) pathway
ESSAY: What is the importance of feedback mechanisms?
without feedback, homeostasis is not maintained and person gets “sick”
ESSAY: Explain negative feedback
When you have too much final product, you send signals to the first and second steps to tell them not to produce any more stimuli.
ESSAY: Explain positive feedback
Usually in pregnancy, keep producing estrogen: increase estrogen -> increase in FSH/LH -> increase in feedback -> increase in estrogen
What does the hypothalamus synthesize from specialized neurosecretory cells?
neurocrine polypeptide releasing factors
What is the interaction of hypothalamic releasing factors and anterior pituitary hormones
The hypothalamus can produce releasing AND inhibiting factors that will work on the anterior pituitary to produce more hormones.
Antierior pituitary produces either trophic or direct-acting hormones. How do they elicit their effects on the target organ?
Trophic: stimulate another endocrine gland to manufacture a second hormone that affects metabolism Direct acting: elicit effects directly one the target organ