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Key points of the endocrine system.
- -ductless glands
- -specific target cells
Overall functions of the endocrine system.
- -regulate organic metabolism
- -regulate eater and electrolyte balance
- -induces heat to help body cope with stresses
- -promote growth and development
- -control reproduction
- -regulate RBC production
- -CV & GI control
Complexity of endorcine system.
- -1 gland makes & secretes multiple homones
- ex: pituitary
- -1 homone from multiple glands
- -ex: somatostatin
- -1 homone goes to multiple targets
- ex: vasopressin
- -cyclic secretion patterns
- -multiple hormones go to the same target
- -insulin vs. glucagon
Complexity of endocrine system cont.
- -same chemical messanger can be either nt or homone
- ex= NE
- -some organso of endocrine system perfrom non endocrine functions
- ex= testes, pancreas
What are the effects of the endocrine proportional to?
the amount of free homrone in plasma
ex: as secretion increases, amount of homone increases
Metabolism of free hormone:
- ex: thyroid hormone
- -T3 more potent than T4
Plasma protein binding of free hormones:
- lipophilic hormones
- -unbound H is monitored
- liver, kidney,etc.
In negative feedback of free hormones:
-output conteacts a change in input
In positive feedback of free hormone:
- -amplifies intital effect of hormone
- -a "vicous cycle"
ex: blood clot, allergic reaction, childbirthing + breastfeeding
What are Neuroendocrine reflexes?
produce sudden increase in hormone secretion
ex: adrenaline rush
Dinural (cicardian) rhythms are?
- -hormones that fluctaute over 24 hours
- -happens on a daily activity
- ex: melatonin
- -melatonin is highest at the night time
- 1*= decrease in secretion due to glandular abnormality
- =genetic, dietary, chemical toxicity, immunologica, 2nd to disease process, Iatrogenic ( some other disease but physicans medicine causes gland not to function), idiopathic
- 2*= decrease in secretion as a result in decrease in stimulus by trophic hormone
Endocrine disorders: Hypersecretion
- 1*=increase in secretion due to glandular abnormality
- 2*=increase in secretion due to increase stimulation of gland
- -tumors, immunological factors ( antiboitics that mimic TSH), substance abuse
Defintion of trophic hormone:
- 1. grow
- 2. secrete its hormone
Abnormal target cell responsiveness:
- -lack of receptos
- ex: testicular feminization syndrome=
- -external genitalia looks female
- - short blind puch vagina
- - no unterus, no ovaries, no fallopian tubes
- - testes located in abdomen (not descended)
- -lack of cellular component in response pathway
- ex: enxyme, 2nd messanger
Problems with Down Regulation:
- -so miuch homrone the cell stops responding to it
- ex: insulin insensitivity, individuals eat carbs all the time & insulin is chronically high
(-more internalization of receptor and u cannot replace empty receptors to membrane, so u lose response to insulin & you have chronic high glucose)
Effect of Other Hormones:
-one hormone must be present for full effect of another hormone
Effects of other hormones:
- several hormones are complimentary
- -combines effect greater than that of one
Effects of other hormones:
ex= progesterone prevents estrogen from causing uterine contactions during pregancy
- -body temperature
- -thirst and appetite
- -uterine contraction & milk ejection
- -ANs coordination center
2 most imporant parts of Hypothalamus:
-Anterior Pituitary Hormones
-Posterior Pituitary Hormones
- Bridge to endocrine:
- -stimulates or inhibts AP hormones secretion via releasing or inhibting hormones
- -synthesizes P.P. hormones
what is a biological clock?
- -has a 24 cycle for body functions
- ex: temp, gene expression, behavior, hormone secretion
what is the master clock?
- Suprchiasmatic nucleus (SCN)
- -cluster of neuron cell bodies above optic chiasm
- -input from each eye (establishment of inherent daily rthyms)
What are clock proteins?
- -"Self starting" generes of SCN neurons = synthesis of proteins
- **see synoposis made in notes
How do you synchronize biological clock with environment?
- -SCN is reset dauly by external cues (light intensity)
- **pineal gland secretes melatonin to synchronize
-if not adjusted, individuals circardian rhyms falls out of sync with day and night
- -different than for vision
- -specialized retinal ganglion cells
- -Pineal gland responds with cycle of melatonin (24 hr cycle)
- -secreted during periods of darkness
- -proposed roles=
- -can induce natural sleep, inhibits sex hormones, (puberty initated by melatonin levels), (in other species: hibernation, seasonal breeding), birth control (high levels shut down ovulation), antioxidant, slows againg process, enhances immunity (also slows regression of thymus)
Pituitary Gland: Hypophysis
Has two distinct tissues!
-Anterior Lobe: true glandular tissues "Adenohypophysis"
- -Posterior Lobe: extension of hypothalamus "Neurohyphophysis"
-Has 2 populations of neurosecretary neurons?
- -Suproptic Nucleus SON
- -Paraventricular Nucleus PVN
- -terminals in posterior lobe
- -SON & PVN contain neurons that produce peptide hormones (but only one hormone produced per cell!)
- - Vasopressin & Oxyctocin
aka Antidiuretic Hormone
-release triggered by?
- Release Triggered By:
- -hypothalamic osmoreceptors
- -left atrial volume receptors
- -acute infection, pain, trauma (inappropriate H20 retention)
- -arteriolar smooth muscle (**Crucial during hemorrhage)
-Release triggered by?
- Released by:
- -stimulation of cervical mechanoreceptors
- -stimulations of mechanoreceptors in nipple
- -at uterus, decrease threashold potentioal
- -at breast, increases myoethithial tone
- Also influences: maternal bleeding
Anterior Pituitary : Adenohypohysis:
-AP hormone secretion regulation
- -hypophsiotropic hormones
- -secreted in pulses
Define Hypothalamic relasing hormons.
Define hypothalamic inhibiting hormones.
hypothalamic releasing hormones= stimulates release of hormones from anterior piuitray cells
hypothalamic inhibiting hormones= inhibits release of hormone from anterior pitiuitary
Define Hypothalamic- Hypophyseal Portal System.
- -capillary to capillary link
- -direct route from hypothalamus to pituitary
(neurosecretory neurons terminate on the capillares of portal system)
-Multiple inputs regulate hypophysiotropic hormones
- -can be either stimulatory or inhibitory
- -neural connections with other portions of the brain
- -environment factors
- -chemical signals: hypothalamic regions unprotected by blood brain barrier
Typically target glands hormones suppress:
- suppress secretion of trophic hormones that is driving it
- -negative feedback control: once its hormonal signal is activated, its secretion does not continue unabated
5 major cell populations produce 6 six major hormones!
- -Lactotropes: Prolactin (protein similar to GH)
- -Somatropes: Growth Hormone
- -Thyrotropes: TSH
- -Corticotropes: ACTH
- -Gonadotropes: FSH & LH
Which are trophic hormones?
Under influence of:
- -under influence of growth hormone
- -net synthesis of proteins
- -increase in growth of long bones
- -increase in # of soft tissues
Other factors that affect growth:
- -freedom from disease & stressful environment
- -normal levels of growth influencing hormones:
- **thyroid hormone, insulin, sex hormones
- Fetal growth:
- -placental hormones
- -GH not involved!!!
- -genetic/environmental factors
- -postnatal growth spurt (1st 2 yrs)
- -pubertal growth spurt ( 11 yrs female, 13 yrs male)
- **Both T and E2= halt bone growth @ end of puberty
Metabolic effects on growth hormone"
- -GH is most abundant AP hormone secreted
- ---binds directly to target tissues: adipose, skeletal muscles, liver
**also stimulates protein synthesis