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Lecture 43
Principles of Endocrinology-Circadian Rhythms-Calcium Control
Term | Definition |
---|---|
Hormones | released from endocrine glands into the blood-go everywhere.bind to recpetors-effects on diff cell receptor dependent.hydrophilic hormones bind to membrne receptors.hydrophobic hormones bind to nuclear receptors.alter protein synthesis. |
Plasma Hormone Concentrations | controlled by feedback mechanisms.hydrophilic hormones can change concentration rapidly (mins).hydrophobic hormones often partition into adipose tissue.this buffers changes in plasma concentration (hours) |
Negative Feedback | concentrations vary minimally around a set point falling concentrations stimulate release mechanism.rising concentration inhibit release mechanisms |
Neuroendocrine Reflexes | neural activation can produce a rapid inc in hormone release |
Diurnal/Circadian Secretion | day-night/around a day rhythms-on a 24 hr cycle.entrained by sleep/wake or light/dark cycles.night shift workers put some pairs of hormones out of cycle-inc junk illnesses,recent reports of inc cancer risk,possibly due to altered melatonin release |
Endocrine Disorders | hyposecretion or hypersecretion-often related to endocrine or feedback cell receptor malfunction.target cell malfunction-no response from normal hormone level. |
Cell Responsiveness | controlled by the # or hormone recpetors available on target cell |
Down Regulation | desensitization due to chronic,elevated hormone level.internalization or chemical modification of receptors.type 2 diabetes has down regulation of insulin receptors |
Permissiveness | one hormone enhances the response of a second hormone. TH inc epinepherine receptor# on target cells |
Synergism | 2 hormones inc each others activities. FSH and testosterone each help the other inc sperm production |
Anatagonism | one hormone reduces the effect of another hormone.progesterone dec estrogen receptor # on the uterus |
Pineal Gland | releases melatonin to help regulate circadian rhythms |
Biological Clocks | controlled by the superchiasmatic nucleus in the hypothal.clock proteins in the SCN reg their own prod over a day.clock prot cont the neural output of SCN,which inturn controls some horm outputs,like cortisol.external cues keep the SCN on 24 hr rhythm. |
Melatonin | release from the pineal gland is controlled by light:M release is high in dark.controlls light/dark hormonal influx.may help sleep,dec aging nd free radicals,slow aging of the immune system:link w/ puberty questionable |
Plasma Calcium | 90% of phosphate stored in bone 99% of calcium stored in bone as calcium phosphate.ca2+ 2.5 mM in plasma. ~10-7 M in cells.regulated by PTH. |
Parathyroid Hormone | PTH inc reab of ca2+.first from bone fluid in spaces,and then from ca phos.necessary for life-no PTH leads to hypocalcemia. |
Hypocalcemia | low blood calcium.hyperactive nerve and muscle ( inc na+ entry). larynx and diaphragm spasms-no air. |
Vitamin D | control of ca2+ absorp.enhances PTH activity |
Osteoperosis | dec estrogen linked to OP> pth,vitamin d,ca2+ normal.dec in bone density less effect when bones are thivker at menopause.weight beaing work and exercise thickens bones. |