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Lecture 43

Principles of Endocrinology-Circadian Rhythms-Calcium Control

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.
Created by: danamarie9323