the endocrine system
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The Endocrine System
Chapter 18
Comparison of NS and ES, table 18.1 Nervous & Endocrine Systems coordinate functions
of all body systems: the neuroendocrine system ________________________
nerve impulses conducted along axons of neurons at synapse nerve impulses trigger release of mediator
molecules = _____________________ _______________________
releases mediator molecules = ________________ molecules leave glands blood
circulating blood delivers hormones to virtually all cells hormones affect only cells with the proper receptor
Comparison of control by NS & ES Nervous system
Neurotransmitters Act close to release site Muscles, glands, neurons Onset of action within
milliseconds Duration of action is
generally brief Lasting milliseconds
Endocrine system Hormones Act far from release site Cells throughout body Onset of action: seconds
to hours, to days Duration of action is
generally longer Lasting second to days
Exocrine vs. Endocrine
______________________ Exocrine glands secrete products into ducts that carry
secretions into: Body cavities Into the lumen of an organ Outer surface of the body
Sweat, oil, mucous, digestive ______________________
Endocrine glands secrete products (hormones) into interstitial fluid surrounding secretory cells rather than ducts From interstitial fluid blood(or directly to) target cells
Fig.18.01
Functions of hormones fig 18.1 Help ________________:
Chemical composition & volume of internal environment (interstitial fluid)
Metabolism and energy balance Contraction of smooth & cardiac muscle fibers Glandular secretions Some immune system functions
____________________________ Regulate reproductive system Help establish ____________________
Hormones
___________- secretion of endocrine cells, alters physiological activity of ______________
approximately 50 hormones each affects only a few cell types cell will only respond if has specific receptor for hormone have powerful effects in low concentrations
Hormones travel through body in the blood bind receptors on target cell various target cells respond differently to same hormone
If excess hormone present, receptors may = _______________________
Circulating vs. local hormones _____________________- most endocrine
are this type, circulate in the blood From secretory cells interstitial fluid blood
_______________- act on neighbor or same cell that secreted it, without entering blood ________________- beside or near ________________- self
Fig.18.02
Response to hormone
Various target cells– ______________________________________ Ex.) insulin:
stimulates synthesis of glycogen in liver cells stimulates synthesis of triglycerides in adipose cells
Responses are: _____________________ _______________________________ _______________________________ in or out _________________________ _________________________
Chemical classes of hormones, table 18.2 ____________________
Steroid hormones- derived from cholesterol Thyroid hormones- T3 and T4
Nitric oxide (NO)- hormone and neurotransmitter ____________________
Amine hormones- catecholamines, histamine, seratonin, melatonin
Peptide hormones- some have carb glycoprotein hormones
Eicosanoid hormones- important local, may circ prostaglandins leucotrienes
Lipid solublefig. 18.3
Water solubleFigure 18.4
Control of secretion
Release usually in ________________ Regulation __________________ production Hormone secretion regulated by:
______________________________ ______________________________ ______________________________
Most regulation works by feedback loops Negative feedback loop, 18.17 Positive feedback loop, 1.4
Negative feedback
Ex.) Glucocorticoids
Positive feedback
Ex.) Oxytocin
Hypothalamus & pituitary gland, 18.5 ___________________- “master” endocrine gland
secretes hormones that control other endocrine glands __________________- major link between NS & ES
important regulatory center in NS- can control pituitary crucial endocrine gland
Cells of hypothalamus synthesize 9 different hormones 2 of these are stored and secreted from the posterior pit.
Anterior pituitary secretes 7 hormones Together these16 hormones play important roles in
______________________________________________
Hypothalamus endocrine function At least 9 hormones synthesized by hypothalamus 5 releasing & 2 inhibiting hormones produced affect
_____________________ (___________________) produced by hypothalamic neurosecretory cells transported within axon & released from axon
terminals diffuse hypophyseal portal system 1° 2° plexus
target cells of anterior pituitary GHRH, GHIH, TRH, GnRH, PRH, PIH, CRH
Hypothalamic function (2)
Neurosecretory cells w/cell body in hypothalamus synthesize the 2 hormones that __________________ ______________ (___________________) where the axon terminals lie package into secretory vesicles travel to axon terminal and stored released from posterior pituitary due to nerve
impulse triggering exocytosis capillary plexus Oxytocin and Anti-diuretic hormone (ADH)
Regions of the pituitary gland Anterior pituitary -75% of total wgt of gland
Pars distalis, pars tuberalis- sheath around infundibulum Adeno= ________, hypophysis = __________________ Secretes hormones that reg. wide range
release _______________________ & suppressed ______________________________________
controlled by negative feedback loops Posterior pituitary – only oxytocin and ADH
Contains axons & axon terminals of >10,000 neurons from nuclei in hypothalamus Terminals associated w/ pituicytes- specialized neuroglia
Pars nervosa, infundibulum ________________________________________________
Pars media = atrophies during fetal development
Hypophyseal portal system
_______________________- blood flows from one capillary network into portal vein & then to 2nd capillary network without passing thru heart
Hypophyseal portal system- blood flows from capillaries in hypothalamus into portal vein that carries blood to capillaries of adenohypophysis Neurosecretory cells synthesize releasing & inhibiting
hormones in cell bodies vesicles axons 1° plexus Act immediately on anterior pituitary before diluted or
destroyed in general circulation
5 releasing hormones of hypothalamustable 18.3 Growth hormone releasing hormone (GHRH) =
somatocrinin Stimulates somatotrophs
Thyrotropin releasing hormone (TRH) Stimulates thryotrophs AND lactotrophs
Gonadotrophic-releasing hormone (GnRH) Stimulates gonadotrophs
Prolactin releasing hormone (PRH) Stimulates lactotrophs
Corticotropin-releasing hormone (CRH) Stimulates corticotrophs
2 inhibiting hormones of hypothalmustable 18.3 Growth hormone Inhibiting hormone (GHIH)
= Somatostatin released from hypothalamus inhibits activity of
somatotrophs Prolactin Inhibiting hormone (PIH) =
dopamine inhibits activity of lactotrophs
Cells of the Anterior Pituitary
____________________ – “somato” = body, “tropin” = change secrete ___________________________ (hGH) or
somatotropin Stimulates several tissues to secrete insulin-like growth
factors- general body growth regulate metabolism
___________________ - secrete thyroid stimulating hormone (TSH) or thyrotropin controls secretions & activities of thyroid gland
Cells of the anterior pituitary (2) _______________-- “gonado” = seed
Secretes _________________________ (FSH) Stimulates estrogen production in ovaries Initiates oocyte development Sperm production
Secretes _________________________ (LH) Stimulates secretion of progesterone & estrogen in
ovaries Stimulates ovulation, formation of CL Stimulates secretion of testosterone in testes Stimulates interstitial cell development in testes
__________________- “lacto” = milk Secrete prolactin (PRL)
initiating milk production in mammary glands __________________ - “cortico” = rind or bark
Secrete adrenocorticotropic hormone (ACTH) or corticotropin Stimulates the adrenal cortex to secrete glucocorticoids
Ex.) cortisol Some corticotrophs - remnants of pars intermedia secrete
melanocyte stimulating hormone (MSH) Role unclear May affect brain activity levels cause skin darkening
Cells of the anterior pituitary (3)
Negative feedback – corticotrophs
7 Anterior pituitary hormones & what they stimulate hGH- stimulates liver, muscle, cartilage,
bone, & others to synthesize & secrete IGFs IGF - promote body cell growth, protein synthesis,
tissue repair, lipolysis & blood glucose TSH- stimulates synthesis & secretion of
thyroid hormones by thyroid gland T3 and T4 - BMR, stimulate protein synthesis,
use of glu & f.a. for ATP syn, lipolysis, cholesterol secretion, body growth, development of NS
Anterior pituitary hormones (2) FSH- follicle stimulating hormone:
♀- initiate _____________________, induce ovarian secretion of ________________
♂- stimulates testes to ____________________ LH- luteinizing hormone
♀- stimulates secretion of _______________ & __________________, ______________, & ___________________________________
♂ stimulates ___________________ production
Anterior pituitary hormones (3) PRL - promotes milk secretion by mammary
glands ACTH –
stimulates secretion of ___________________ (for glucose metabolism) by adrenal cortex ____________________
MSH- exact role unknown, may influence brain activity, when present in excess can cause darkening of skin
2 Posterior pituitary hormones, table 18.5 ____________________ (OT)-
stimulates uterine smooth muscle contraction during childbirth
stimulates contraction of myoepithelial cells in mammary glands milk ejection
Pitocin is synthetic form _______________________ (ADH) or vasopressin-
Anti = against, dia= throughput, ouresis = urination conserves body water by decreasing urine volume decrease water loss thru perspiration raises bp by constricting arterioles
Thyroid hormones, table 18.6 & fig 18.10 T3 (_________________) and T4 (____________)-
BMR ↑ O2 consumption, metabolism of carbs, fats, protein ↑
Stimulate synthesis of Na+/K+ pump ↑ ATP production ↑ more heat ↑ body temp: calorigenic
Stim protein synthesis & glucose & fa use to make ATP ↑ lipolysis & enhance cholesterol excretion in bile
Enhance actions of catecholamines (NE and E) ↑ heart rate, ↑ b.p.
Accelerate body growth (w/ hGH & insulin) contribute to development of nervous & skeletal systems
Also a hormone produced in the thyroid: __________________ (CT)- parafollicular C
cells of the thyroid produce it lowers blood levels of calcium & phosphates
Inhibits bone reabsorption by osteoclasts & accelerating uptake of calcium & phosphates into bone matrix
High blood calcium levels stimulate secretion (low blood calcium levels inhibit secretion)
Formation, storage & release of T3 & T4, figures 18.11 and 18.12 Thyroid = only gland that stores large
quantities of its secretory product 100 day supply in colloid
Figure 18.11 shows synthesis Figure 18.12 shows control of secretion:
TRH from hypothalamus anterior pituitary causes releases TSH thyroid gland causes release of T3 & T4 negative feedback inhibition of both TRH & TSH
Thyroid problems
Deficiencies in thyroid hormones during fetal development, infancy or childhood causes: Severe mental retardation Stunted bone growth
______________________ symptoms include: ↑ heart rate, ↑b.p., force of heart beats
Removal of thyroid- __________________ _____________________ because cannot utilize calorigenic effect
Parathyroid gland hormones
_______________________ (PTH)- Specifically works by # & activity of _____________
bone resorption, releasing ionic Ca2+ & phosphates In the _________________:
Slows Ca2+ & Mg2+ loss to urine phosphate loss from blood to urine promotes formation of calcitriol by kidneys
Calcitriol = active form Vitamin D absorption rate of dietary Ca2+ , Mg2+ ,& phosphates
Blood Ca2+ directly controls _______________ (from thyroid gland) & PTH secretion via negative feedback
Adrenal glands = suprarenal glands CT capsule cover, highly vascularized (like thyroid) Adrenal ___________ – 80-90% of gland, peripheral
Produces steroid hormones essential for life Loss would lead to death due to dehydration &
electrolyte imbalance (few days to week) unless HRT
Adrenal ____________ – centrally located Produces 3 _____________________
Norepinephrine Epinephrine Dopamine (small amount)
Modified sympathetic ganglion of the ANS
Adrenal cortex hormones
______________ (mainly aldosterone) - affect mineral homeostasis, in zonula glomerulosa ↑ blood levels of Na+ & water decrease blood levels of K+ _______________________ promotes excretion of
H+ in urine Removing acids preventing acidosis
Adrenal cortex hormones
__________________ -95% _____________ = hydrocortisone, corticosterone, & cortisone, zona fasciulata affect glucose homeostasis, Regulate metabolism & resistance to stress
↑ protein breakdown (except in liver) stimulate gluconeogenesis in liver & lipolysis provides resistance to stress
Glucose at liver provides source of ATP to combat stresses: Exercise, fasting, Symp NS, temp∆, high altitude, bleeding,
infection, surgery, trauma, disease Raise bp- advantageous during blood loss
inflammation & depress immune responses
Sex hormones from adrenal cortex ________________-(mainly dehydropiandrosterone
or DHEA), small amounts of weak androgens that have masculinizing effects, in zona reticularis assist in early growth of axillary & pubic hair in both sexes Contributes to pre-pubertal growth spurt After puberty in males androgen- testosterone is released in
greater quantities by testes in females, contribute to libido & are converted to estrogens
by other tissues after menopause all estrogens come from this source
Adrenal medulla hormones
Adrenal medulla develops just as other sympathetic ganglia but the cells secrete hormones- called chromaffin cells Innervated by symp preganglionic neurons that release Ach
Both hormones are not essential for life but intensify ________________ responses in other parts of body ____________ = adrenaline, 80% of medullary cells secrete
Cortisol induces secretion of an enzyme to convert NE to E _________________ = noradrenaline, 20% of medullary
cells secrete because they lack converting enzyme
Pancreatic Islet hormones
_____________ – pan = “all,” creas = “flesh” Endocrine and exocrine 99% of cells arranged in acini- clusters that
produce digestive enzymes that flow thru ducts to the GI tract
Scattered among acini are clusters of endocrine tissue- _______________________ or islets of Langerhans
Abundant capillary supply
Islet cell types
Alpha cells = A cells - 17% of islets cells Secrete _________________ – blood glucose
by accelerating breakdown of glycogen in liver Converts other nutrients into glucose at liver Releases glucose into blood
Beta cells = B cells – 70% of islet cells Secrete _______________- ↓ blood glucose by
accelerating transport of glucose into cells Converts glucose into glycogen Decreasing glycogenolysis & gluconeogenesis Increases lipogenesis & stimulates protein synthesis
Islet cell types (2)
Delta cells = D cells – 7% of islet cells Secrete ________________ = growth hormone
inhibiting hormone paracrine effect to inhibit insulin & glucagon release slow absorption of nutrients from GI tract
F cells – remainder of pancreatic islets Secrete ____________________- inhibits
somatostatin secretion Inhibits gall bladder contraction Inhibits digestive enzyme secretion by pancreas
Regulation of insulin and glucagon ____________________ - most important regulator
but several hormones & NT regulate too ________________ secretion stimulated by:
hGH and ACTH Ach stimulates insulin secretion Amino acids: arginine & leucine GIP- glucose dependent insulinotropic peptide- released when
glucose in GI tract ________________ secretion stimulated by:
Symp NS activity Rise in blood aa if glucose low (mainly protein meal)
Ovaries table 18.10 Produce gametes Produce steroid hormones (work with FSH & LH):
__________________ - β-estrodiol, estrone, and estriol development of oocytes maintain repro structures appearance of 2° sex characteristics
___________________ – prepare endometrium of uterus for implantation mammary glands- milk production
___________________ – flexibility of pubic symphysis during pregnancy Dilate cervix during labor & delivery
___________________ – inhibits secretion of FSH
Testes table 18.10 Produce gametes Produce steroid hormones
_________________ – descent of testes spermatogenesis controls growth of development of male repro organs appearance of 2° sex characteristics body growth
_________________ – inhibits secretion of FSH
Diseases and disorders
Pituitary Gland disorders: hGH disorders: figure 18.22
Hyposecretion: _____________________________ - during growth years slows
bone growth & epiphyseal plates close before normal height, body proportions remain childlike Treatment- administer hGH during childhood
Hypersecretion: _______________________ – during childhood, abnormal ↑ long
bone length, tall but proportions normal ________________________ – during adulthood, hGH cannot
lengthen long bones but hands, feet, cheeks, jaws thicken and enlarge; eyelids, lips, tongue, & nose enlarge; skin thickens & develops furrows
Disease and disorders (2)
_____________________ – most common abnormality assoc w/ the posterior pituitary Due to defects with ADH receptors or inability to secrete
ADH Common symptom – excretion of large volumes of urine
resulting with dehydration and thrist Bed wetting common in children Person may die of dehydration if deprived from water for
a day or more Treatment – HRT for _____________, ________________
may involve diet restrictions (restriction of salt) depending upon details and specifics of kidney dysfunction
Thyroid gland disorders: Hyposecretion:
_________________________ (previously cretinism) - present at birth, devastating if not prompt treatment Severe mental retardation Stunted bone growth
Treatment- oral thyroid hormone treatment- birth thru life ______________ – in adulthood, 5x more common in ♀
Edema causes facial tissue to swell and look puffy Slow h.r., body temp, sensitivity to cold, dry hair & skin Muscular weakness and general lethargy Tendency to gain wgt easily Brain has matured no retardation, but might be less alert
Treatment = oral thyroid hormones to symptoms
Thyroid gland disorders (2): Hypersecretion:
_____________ –most common, 7-10X more ♀ < 40 yrs Autoimmune disorder, Ab mimic TSH Enlarged thyroid (2-3x normal size) Peculiar edema behind eyes = exophthalmus
Treatment – partial or full thyroidectomy, radioactive iodine to destroy thyroid tissue, antithyroid drugs
_____________ – enlarged thyroid gland Assoc w/ hyperthyroidism, hypothyroidism, or euthyroidism
(“good,” normal secretion) Dietary intake of iodine may be inadequate thyroid hormone in blood stimulates TSH enlarge
Parathyroid gland disorders: ___________________ – too little PTH
Deficiency of blood Ca2+ neurons & muscle fibers to depolarize and produce spontaneous AP
Twitches, spasms, tetany Leading cause: damage to parathyroid glands or their
blood supply during thyroidectomy ____________________– elevated PTH
Often due to tumor on one of the glands Excessive reabsorption of bone matrix
Raises blood calcium and phosphates, bone soft and easily fractured. ↑ blood Ca2+ promotes kidney stones
Fatigue, personality changes, lethargy
Adrenal gland disorders: Hypersecretion of cortisol: ______________________
adrenal gland tumor or tumor where ACTH is secreted stimulating excess cortisol
Breakdown of muscle protein, redistribute body fat Moon face, buffalo hump, hanging abdomen ↑ cortisol hyperglycemia, osteoporosis, weakness,
hypertension, ↑ risk of infection, stress resistance, mood swings
Hyposecretion of glucocorticoids & aldosterone: ___________________________ (leads to ↑ K+, Na+) most cases = autoimmune disorders: Ab block or destroy
binding of ACTH to its receptors, bacteria. symptoms: appear usually after 90% of adrenal cortex is
destroyed– mental lethargy, anorexia, nausea, vomitting, wgt loss, hypoglycemia & muscle weakness Treatment – replace glucocorticoids, mineralocorticoids, Na+
Pancreatic Islet disorders: _____________________- most common
endocrine disorder, inability to produce insulin 4th leading cause of death in US cardio damage Unavailable insulin ↑ glucose in blood spills into urine _________– person’s immune system destroys beta
cells, AKA insulin dependent diabetes mellitus (IDDM) Usually people under 20, persists thru life Time of symptoms- 80-90% beta cells destroyed Cardio problems, vision loss-cataracts, kidney problems
_________ – target cells less sensitive to insulin due to down regulation of receptors > 90% of cases, obese & over 35 Control by diet, exercise, weight loss, drug stim insulin
Pancreatic Islet disorders (2): _____________– diabetic injects too much insulin
Symptom – _______________- blood glucose level due to excess insulin causing uptake Results in secretion of epinephrine, glucagon, hGH
Anxiety, sweating, tremor, ↑ h.r., hunger, weakness Brain cell deprived of glucose mental disorientation,
convulsions, unconsciousness, and shock Death can result if glucose level is not raised
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