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sc notes
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chapter endocrine
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  1. endocrine system
    • helps maintain normal function
    • prepares the body for exercise
    • mediates several adaptions
    • involved to some extent in every system
  2. how do the endocrine system operate
    by releasing a chemical messenger, transporting the chemical to specific target tissues, and eliciting a chain of events leading to the desired function
  3. hormone
    • chemical messenger of the endocrine system
    • most are released from endocrine glands although some are released from nerve, muscle, cardiac, fat cells, and other tissues
  4. actions of hormones
    when released hormones act as signal molecules and may regulate the cells that released them, adjacent cells, or enter circulation and travel throughout the body
  5. autocrine action
    when a hormone is produced by cells and act upon the same cells that produced it
  6. paracrine action
    hormones produced by cells, released by these cells, and then regulate activity of adjacent cells
  7. endocrine action
    most hormones enter general circulation where they travel systemically to specific target tissues
  8. releasing hormones
    hormones that cause the release of other hormones
  9. hypothalamus
    • is a segment of the brain that acts as an endocrine gland
    • provides a link between the nervous and endocrine system
    • synthesizes and releases neurohormones that are transported to the pituitary gland(anterior segment)
  10. what hormones do the hypothalamus release
    • corticotrophin releasing hormone
    • gonadotropin releasing hormone
    • growth hormone releasing hormone
    • growth hormone inhibiting hormone(somatostatin)yrotropin releasing hormone
    • prolactin inhibiting hormone
    • lh
    • fsh
    • tsh
  11. posterior pituitary
    • releases:
    • antidiuretic hormone (ADH or vasopressin)
    • oxytocin
    • unlike anterior pituitary, the posterior pituitary does not require releasing hormones to secrete these hormones
    • hormones released from the pituitary travel to all tissues to elicit specific physiologic action
  12. three forms of hormones
    • steroid hormones
    • amine hormones
    • peptide hormone
  13. steroid hormones
    • three 6-carbon rings and one 5-carbon ring.
    • all steroids are synthesized from cholesterol via synthetic pathways consisting of many intermediates. som of whic are biologically active
    • steroids are released into circulation, and arrive at the target tissue, diffuse through the cell membrane, and bind to a spcific cytoplasmic or nuclear bound receptor within the cell
  14. common steroids
    • androgens
    • testosterone
    • estrognes
    • mineralcorticoids( aldosterone)
    • glucocorticoids(cortisone)
    • progesterone
    • protaglandins
  15. anabolic steroids
    a common type of steroids used and abused by athletes
  16. peptide hormones
    • are proteins of various size
    • small chains of amino acids
    • are the direct product of mrna translation
    • cleavage from larger parent molecules, and or other postsynthesis modifications
    • the quantity and sequence of amino acids determine the function of each hormone although some partial sequences of amino acids may have biologic significance
    • prone to degradation
    • circulate unbound to a transport protein and partially dissolved in plasma
  17. secratogues
    amino acids with biologic significance
  18. actions of peptide hormones
    • peptides circulate and bind to specific receptors on the cell membranes of target tissues,
    • they are lipophobic and cannot pass through cell membranes so receptors need to be external for binding
  19. amine hormones
    • have an amine group at the end of the molecule
    • derived from amino acids, amines may be classified as protein hormones
    • amines include epenepherine, norepinephrine, and dopamine
    • amines must bind to a surface bound receptor on the target tissue
    • synthesized in advance and stored within vesicles until they are needed
    • produced from precursor molecues and stored in vesicles until release 
  20. sports adrenal medulla
    endurance athletes prodcue a more substantial catecholamine respnse to exercise
  21. catecholamines
    • synthesized from the amino acid tyrosine, somtiems phenylalanine(via conversion to tyrosine) and tryptophan
    • norepienepherine and dopamine can act as neurotransmitters in the autonomic nervous system
    • secreted by the andreal medulla
    • epinephrine is 80% and is predominatly secreted with norepinephrine(15-20)
    • respnse to stress physical heat etc
    • reflect the deemands of exercise
    • important for increaseing force production muscle conatraction rate energy avaiability
    • concetrations are increased with exercise with the magnitude dependent on the muscle mass invlovled and posture, intensity, and duration
  22. growth hormone function
    • tissue growth
    • protein synthesis
    • fat mobilization
    •  anobolic effects are mediated through the release of igf-1 and attaches to binding proteins gh- binding protein
    • and have a half life of 20-50 minutes
    • decreased glucose utilization,
    • increased collagen synthesis and cartilage growth
    • secreted by the anterior pituitary
    • is released in a pulsatile manner expecially during sleep
    • higeher volume  multiple set workouts produce larger gh elevations than single sets (body building workouts) produce substantial blood lactate reponses and high correlations between lactate and gh have been shown
  23. function of atch
    stimulate secretion of glucocorticoids
  24. beta endorphins
    • is a 31 amino acid peptide cleqved in the anterior pituitary from a parten molecule proopiomelanocortin
    • acts a a neurotransmitter in the nervous system
    • acts as analgesic, increase relaxations, and enhance immune function
    • exercise is a potent stimulus for secretion with the response dependent on hte intensity of duration
    • anaerobic exersice elevates endorphins in proportion to blood lactate and acth increases
    • aerobic exercise increases endorphins with the rise in intensity
    • rise in endorphines may help offset the acidosis by improving mood state and pain tolerance
  25. functions of lh
    • produce testosterone in males
    • ovulation and secretion of sex hormones in females
  26. functions of fsh
    • spermatogeneisi in males
    • maturation of graafian follicles of ovaries in females
  27. function of tsh
    t3 and t4
    • secretion of thyroxine T4 and triiodothyrone t3
    • RELEASED INTO CIRCULATION WHERE THEY TRAVEL MOSTLY BOUND TO TRANSPORT PROTEISN (thyroxine binding globulin, prealbumin, and albumin)
    • t4 is 20 times more and circulates as it has a longer half life than t3
    • in tissues t4 is mostly conveted into more potent t3
    • thyroid hormones increase basal metabolic rate, protein synthesis, and augmetn the actions of catecholamines
  28. functions of prolactin
    • stimulates milk production oin mammary glands
    • secretion of progesteroneq
  29. function of melanocyte stimulating hormone
    • stimulates melanocytes
    • skin pigmentation
  30. functions of adh
    increased reabsorption of water in kidneys
  31. funtions of oxytocin
    stimulates uterine contractions and milk release from mammary glands
  32. functions of t3 and t4
    • increased bmr and sensitivity to catecholamines
    • protein snythesis
  33. function of calcitonin
    • decrease blood calcium level
    • increased calcium uptake into bone
  34. thyrod gland secrets
    • t3
    • t4
    • calcitonin
    • these hormones are produced in follicular cells of the thyroid gland with the incoportation of iodine and stored in vesicles until released
  35. function of parathyroid hormone
    • secreted from parathyroid gland
    • increased osteoclast activity in bone
    • increased blood calcium
    • decreased blood phosphates
  36. functions of insulin
    • glucose/amino acid transport into cells
    • protein synthesis
  37. glucagon function
    • increas blood glucose
    • is a protein hormoe consisting of 29 amino acids syntesized from proglucagon in Acells in the islets of langerhans of the pancreas
    • the half life is 3 to 6 minutesuntil re removed by the liver and kidneys
    • glucagon secretion is inhibited by glucose levels and when secreted, glucoagon stimulates the breakdown of glycogen and increases energy avaiability
    • elevation occurs during exercise as energy demands increase
  38. the pancreas secrets
    • insulin
    • glucagon
  39. glucocorticoid receptor
    • the catabolic effects of cortisol are mediated through glucocorticoid receptors
    • cortisol and possiblly androgen concetrations may determine the leve of up or down regulation of glucocorticoid receptors
    • ecc restance exercise up regulates glucocorticoid receptor content and protein breakdown
    • up regulation is reduced following the second workout  indicationg a protective effect with exposure to ecc exersice
  40. testosterone/ cortisol ratio
    the ratio ahs been used as an indicator of the anabolic  catabolic status of skeletal muscle
  41. function of cortisol
    • gluconeogenesis
    • sparses glucose
    • fat breakdown
    • inhibit amino acids
    • incorportation into proteins
    • catabolic glucocorticoid released from the adreanl cortex in respnes to stress under the control of CRh and ACTH
    • accounts for about 95% of all glucocorticoid activity
    • about 10% are circulating cortisol is free
    • 15% are bound to albumin
    • 75% is bound to corticosteroid binding glbulin
    • stimulates  lipolysis in adipose cells, and increases proteind degradation
    • decreases protein stynthesis in muscle cells with greater effects in type 2 muscle fibers
    • greater concentrations will occur duting hit workouts
  42. functions of aldosterone
    sodium and water reabsorption
  43. the adrenal cortex secrets
    • cortisol
    • aldosterone
  44. catecholamines functions
    • fight or flight response
    • preparation ofr stress and exercise
    • secreted by the adrenal medulla
    • noreipinephrine  and dopamine act as neurotransmitters
    • circulate unbound to a transport protein and dissolved in plasma
  45. peptide f function
    • analgesia
    • immune funciton
  46. liver secrets
    • insulin like growth factors igf
    • angiotensin
  47. insulin like growth factors functions
    • increase protein synthesis
    • growth
    • development
    • are stucturally related to insulin and mediate many actions of gh
    • are small polypeptide hormones secreted by the liver in response to gh stimulation
    • increase proliferation and differenation of satellite cells
    • enhance muscle hypertrophy
    • are affected by other hormones including te and thryroid hormones
    • once released igf bind to igf binding proteins and circulate to the target tissue
  48. angiotensin
    • vasoconstriction
    • release of aldosterone
  49. ovaries secrets
    • estrogen
    • progesterone
  50. estrogens function
    • female sex characteristics
    • growth
    • bone fromation
    • increase hdls
  51. progesterone function
    • female sect characteristics
    • pregnacncy maintenance
  52. testosterone (androgens) functions
    • growth
    • male sex characteristics
    • protein synthesis
    • neural stimulation
    • blood volume
  53. function of atrial peptide
    • tegulates sodium
    • potassium
    • fluid volume
  54. renin
    kidney function
  55. erythropoietin function
    increased red blood cells
  56. leptin funciton
    • secreted by adipose tissue
    • increased energy expenditure
    • decreased appetite
  57. stomach secretes
    • ghrelin
    • neuropeptide y
  58. ghrelin function
    • stimulate appetie
    • gh
  59. neuropeptied y function
    • increased food intake
    • decreased activitly
  60. tyrosine
    is converted to catecholamines n the adrenal medulla
  61. half life
    • the time it takes for half of the hormone secreted to be degraded
    • therby limiting incteraction with target tissues
  62. transport (binding) proteins
    protect the hormone from metabolism and help deliver the hormone to its receptor
  63. hemoconcentration
    • a higher hormone value will be obtained when fluid volume is reduced despite having the same amount of hormones present
    • the resultant elevated hormone concetration makes it easier for receptor interaction
    • during exercise  hormone elevations do not neccessarily reflect an increase in synthesis and secretion, but rather reflect pv reductions and slower rates of tissue clearance and degradation
    • hormone meausrment express the amoun of home per volume of blood
  64. negative feedback control
    • control hormonal concentrations
    • elevate a hormone when it is low or reduce a hormone when it is elevated
    • system is predominate and provide multiple levels of control
    • ex: athletes who uses anabolic steroids will experience recutions in his own TE production as a result, testicular shrinkage can occur due to negative feedback inhibition of endogenous(produced within onces body) TE production
  65. receptor interaction
    • receptor binding leads to a cascade of cellular events that leads to the desired function
    • receptors for amines and peptieds lie withing the cell membrane wheras steroid and thyroid hormone receptors are located either in the nucleus or (thyroid) or cytoplasm(steroids)
  66. lock and key pricniple
    • receptors come in different forms but are specific to the hormone they are coupled with
    • only one hormone will unlock or activate the receptor
  67. cross reactivity
    • molecules that are similar to the hormone may act as a barrier for hormonal interaction whereas some bind to the receptor leading to activation.
    • allowws more thatn one hormone or molecule to activate a receptor
    • this can be of great value in the pharmaceutical industry where drug analoguse are produced
  68. second messenger system
    • amines and peptieds bind to a membrane bound receptor on the surface of the cell . other molecules mus mediate this signal intracellularly
    • second messengers are activated and initiate a cascade of evetns leading to the desired cellular response
    • many second messenger system are mediated by guanylyl (G) proteins that can stimulate or inhibit further cellular activity
  69. adenylate cyclase-cycle amp second messenger system
    • a stimulatory hormone binds to its receptor and activates a stimulating G protein that activates the enzyme adenylate cyclase to produce cyclic AMP from ATP.
    • cyclic AMP activates protein kinases
    • protein kinase A phophorylates several proteins/ substrates yielding numerous cellular effects
    • an inhibitory hormone activates an inhibiting G protein to limit these reactions
    • cyclic AMP has a short halp life and is rapidly degraded by the enzyme phosphodiesterase, which itself  is inhibited by caffeine
  70. steroids and receptors
    • steroids are lipophilic and diffuse through target cell membranes and bind to receptors in the cytoplasm or nucleus
    • many bind to receptors in the cytoplasm
    • receptors are bond to heat shock proteins in the cytoplasm pror to hormone binding
  71. heat shock proteins
    • receptors are bound to these proteins in the cytoplasm prior to hormoe binding
    • heat shock proteins dissociate and the hormone receptor complex moves to the nucleus where it binds to response elements on dna leading to protein synthesis
  72. thyroid hormones t3 t4
    enter the cell membrane via transporter proteins, travel to the nucleus, and bind with receptors to stimulate or inhibit gene transcription
  73. hormonal responses and adaptations entail four classification
    • acute response during exercise
    • chronic changes in resting concentration
    • chronic changes in the acute response to exercise
    • receptor changes
  74. testosterone
    • more than 95% of TE in men is secreted from the leydig cells of the testes, with the remainder prodcued by adrenals
    • skeletal muscel contains the necessary enzymes and may have the potential to produce small amounts of androgens as well
    • TE travesl boundt to shbg 60% adn albumin 38%
    • it is unbound free TEthat diffusesinto cells and interacts with receptors
    • TE occurs in the liver and kidneys where inactivated metabolities are excreted in urine
  75. sec hormone binding globulin
    • circulating te is mostly bound to shbg
    • a change in shbg concentrations may influence the binding capacity of te and the availability of free te
    • druing tt, differential responses like elevations, reductions, and no change have been reported
  76. testosterone precursors (prohormones)
    the syntesis of te contains may steps involving precursors such as dehydroepiandrosterone (dhea) androstendione, and androstenediol
  77. dhea
    • play a greater role in women beause of their lower levels of te.
    • women can convert a larger percentage of dhea to androstenedione and te and have higer baseline concentrations of androstenedione than men
    • elevations in shown in men and women during rt
  78. androgen receptor
    • ar consists of about 919 amino acids and is found in nearly all tissues in the human body except the spleen and adrenal medulla
    • the presence of ar correlates highly with the functions of androgens
  79. what are the four functional domains of AR
    • c terminal hormone binding doman
    • dna binding domain
    • hinge region
    • n terminal transcription activation domain
  80. function of AR-DNA interaction
    • is to induce transcription and translation of proteins necessary to fulfill specific functions. 
    • AR function is enhanced by coactivators  that form a bridge between the dna bound  AR and the transcriptional machinery and by facilitating hormal binding  
  81. concentration of ARs in the skeletal muscle depends on
    • the muscle fiber type
    • high in ft fibers
    • training status
    • and androgen concentrations
    • modifications of AR content are critical to strength and hypertrophy enchancement
  82. selective androgen receptor modulators (SARMs)
    • nonsteroidal molecules can activate the AR
    • they bind to the ARand have shown anabolic properties in bone and skeletal muscle
    • unlike androgens they produce minimal effects on prostate and secondary secual organs
    • they have the potential to separate androgenic and anabolic effects
    • there may be great clinical potential for these molecules but potential for abuse by athletes may exist
  83. muscle igf-1 adaptations to training
    • igf-1 has autocrine/ pacracrine functions within muscle cells
    • has three isofoms have been identified, eac functioning independently
    • igf-1ea and igf-1eb both are similar to circulating igf-1/ and igf-ec also know as mechano growth factor (mgf)
  84. mechano growth factor mgf
    • acts independently, is expressed earlier thatn other igf-1 isoforms in reponse to exercise and may have greater anabolic potency
    • overloaded muscle and mechanical damge, rt and protein supplementation are potent stimuli
    • high intensity workouts procduce great mecahnical loading  hypertrophy via up-regulation of muscle igf and mgf
  85. insulin
    • secreted from the islet of langerhans (b-cells) in the pancreas afeter modivication from its parent molecules, preproinsulin and proinsuline
    • is secreted in reponse to glucose intake and has a half life of 3-5 minutes
    • increases muscleprotein synthesis when adequate amino acid concetrations are available
    • insulin concentrations parallel changes in blood glucose, and the response is enhanced when protein carbohydrates are ingested prior to during or following exercise
    • concnetrations decrease during prolonged aerobic exercise and resistance exercise
    • elevations are mostly affected by blood glucose and or dietary intake rather thatn exercise levels
    • concumption of cargs amino acids or cominations of bother prior to during and or immediately afeter exercise is recommenced for maximizing insulins effects on tissue growth
    • arobice and anaerobic training improves insulin sensitivity and reduces insluin resistance
  86. proinsulin
    • 86 amino acids
    • is converted into insulin  and c peptide
  87. insulin resistance
    is a condition  that i s prominent in obese individuals elderly and diabetics, where normal amounst of insulin are inadequate to produce  a response
  88. fluid regulatory hormones
    • fluid homeostasis is critical to exercise performance
    • elevations influid regulatory hormones such as avp, atrial peptied, renin , aldosterone, and angiotensin II are seen during exercise
    • magnitude dependent on intensity, duration, fitness level, and hydration status
    • rt  elevates atrail peptide, renin, angiotensin II, and plasma osmolaity as early as after the first set
  89. arginine vasopression
    released from the posterior pituitary where it acts on the kidneys and blood vessels to increase fluid reabsorption , sodium, postassium, and chloride reabsorption, and vasocontriction
  90. atrial prptide
    is a 28 amino acids hormones released form the heart in response to increases in blood pressure to induce natriuresis( sodium excretion inurine and decrease in blood fluid volume)
  91. renin
    is a renal enzyme released in response to low blood pressure and reduced renal blood flow that stimulates production of angiotensinI
  92. angiotensionI
    is conberted to angiotensin II via the enzyme angiotensin converting enzyme (ACE) which stimulates the release of aldosterone from the adrenal cortex
  93. aldosterone
    secretion is controlled by changes influid volume, sodium and potassium content in the blood, stress, and changes in blood pressure. the resultant effect of aldosterone is to increase sodium retention and fluid volume to increase blood pressure

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