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