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Home , Endocrine system

The Endocrine System (exocrine vs endocrine ) all major endocrine glands are richly supplied with blood capillaries no clear distinction between nervous and endocrine systems 2. most, if not all, organs produce

“officially” the endocrine system consists of several major glands =neuroendocrine system and many minor glands

they are intimately interrelated 3. Hormones are secreted in response to specific stimuli ! complement each other 3 mechanisms: neural, humoral, hormonal ! two ends of a single spectrum A. Humoral The Neuroendocrine System Endocrine System hormones secreted in direct response to changing localized effects: cell to cell widespread effects: throughout body blood levels of certain chemicals in blood targets: , muscle cells or glands targets: all organs and tissues transmission by impulses transmission as through blood uses chemical signals only cell to cell uses only chemical signals affect endocrine directly immediate response (ms to seconds) gradual response (seconds to hours) short lived (ms to minutes) longer lived (minutes to days) B. Neural Both both involved in coordination & control hormones secreted due to direct nervous stimulation both produce biologically active chemicals some parts of brain are glands/some glands are nervous some responses begin as nervous reflex and end as hormonal responses C. Hormonal

General Characteristics of Hormones = master gland

secretes several hormones that control the secretion of 1. a chemical is considered a hormone if it is secreted other endocrine glands and transported in the blood ! Tropic Hormones same chemical can also be a , or lymphokine, etc 4. Many endocrine glands secrete more than one hormone the major hormones are secreted from ductless glands directly into blood hormones can be secreted independently of one another

Human & : Endocrine System; Ziser, 2010.4 1 Anatomy & Physiology: Endocrine System; Ziser, 2010.4 2

5. hormone effects are highly specific to “target ! synergistic effects ” = presence of 1 enhances effects of other ! requires specific binding site ( ) ! antagonistic effects

even though every hormone comes in contact with every cell = 1 counteracts effects of other

receptor can be on the surface of the target cell or inside the ! permissive effects target cell = one hormone “primes” target organ for another target cells respond only to specific hormones hormone; 8. Hormones don’t accumulate in blood 6. At the cellular level each hormone can affect a target cell in only a few ways: those that bind to target cells are destroyed

a. can change in permeability ! half- ~ seconds – 30 minutes

eg. change in secretory activity of a cell excess are continually cleared by and

b. can alter metabolic pathway(s) therefore for prolonged effect eg. enzymes activated or inactivated ! hormones must be continuously secreted ! make new products ! cease making product

c. can change rate of cell division

eg. speed up or slow down Maybe different effects in different target cells for same hormone

7. Most cells have receptors for more than one type of hormone

hormones can interact with each other

Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 3 Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 4 Major Endocrine Glands ! in women: stimulates follicles to begin growing to ovulation

Pituitary Gland (=Hypophysis) ! in men: stimulates development of seminiferous tubules and sperm cells small but extremely important structure d. Leutinizing Hormone (LH) attached to a stalk (infindibulum) at base of ! in women: final maturation of follicle housed in sella turcica of sphenoid stimulates formation of consists of two separate glands [a temorary of pregnancy] Anterior promotes secretion of master gland ! in men: stimulates interstitial cells to secrete secretes tropic (or trophic) hormones: hormone =

a. Stimulating Hormone (TSH) if pituitary gland is removed by radiation or surgery, need hormone treatment rest of life or some other glands will ! stim development and secretions from shut down thyroid gland in addition to tropic hormones, Ant Pit also secretes some other (nontropic) hormones: b. Adrenocorticotropic Hormone (ACTH) e. (GH) ! normal growth and development of promotes growth of bone and soft tissue c. Follicle Stimulating Hormone (FSH) Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 5 Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 6

! stim synthesis Gland

amt of GH secreted decreases with age hormones released by direct nervous stimulation of

HYPERSECRETION of GH posterior pituitary during childhood ! during adulthood ! acromegaly a. Antidiuretic Hormone (ADH, =)

enlargement esp of of hands, feet, jaws and cheeks (=against production of urea)

HYPOSECRETION of GH ADH is released whenever receptors indicated during childhood ! dwarfism dehydration

ie. decreases urine output f. (PRL; = Lactogenic Hormone) conserves water

affects female: b.

! induces development during (=swift childbirth) pregnancy stimulates contraction of uterine muscles ! initiates milk secretion after childbirth during labor

prl release is stimulated by suckling causes milk ejection into ducts as result of no significant functions in males nursing infant [let down reflex] triggered by neural : suckling

functions in “societal memory”: affects ability to recognize & trust others

[deficiency may be correlated with autism]

Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 7 Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 8 located behind the midbrain and 3rd ventricle a temporary endocrine gland attached to roof of third ventricle behind , below thyroid not sure of all its functions in but seems to regulate cyclic activities large in fetus and child maximum size at Rene Descartes (1596-1650) thought it was the seat of degenerates in adult (replaced with fat) the human soul is light sensitive ! monitors photoperiod functions as endocrine gland and as part of a. secretes and related hormones main hormone it secretes is melatonin light suppresses production ! stimulates development of lymphatic organs dark stimulates production ! induces maturation and development of WBC’s !secretion rises at night, fluctuates seasonally particularly T- and with changing day length

in lower it helps regulate cyclic activities: hibernation estrous migration

In humans: ! may help regulate menstrual cycle ! inhibits onset of puberty in males

may be related to seasonal affective disorder and PMS

Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 9 Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 10

Thyroid Gland HYPERSECRETION of !Graves disease the largest endocrine gland in adults up to 30% increase in Metabolic Rate ! appetite surrounds just below weight loss nervous irritability consists of 2 lobes !usually described as butterfly HYPOSECRETION of Thyroid Hormones shaped During growing years ! cretinism Hormones: low metabolic rate retarded growth and sexual devel often mentally retarded a. Thyroid Hormones (T3, T4) As adult ! Myxedema activated by TSH from Ant Pit loss of mental and physical vigor weight gain contain Iodine atoms thickened skin

98% of body’s Iodine is in the thyroid gland b. inadequate iodine in diet ! goiter decreases blood Ca++ / promote bone thyroid hormones help to regulate deposition by in all cells: inhibiting osteoclasts stimulating osteoblasts ! increases metabolic rate & ATP production ! increase oxygen consumption and bld O2 levels ! promotes maturation and development of the its effects are significant only in children, nervous system negligable effect in adults ! increases protein synthesis !help maintain normal reproductive function HYPOSECRETION of Calcitonin many environmental stimuli can inhibit can cause ricketts in children (but usually due to Ca++ or Vit D deficiency) secretions of this gland:

cold temp, physical stressors, noxious stimuli Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 11 Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 12 Parathyroid Glands small round bodies attached to the posterior surfaces both an exocrine and endocrine gland of the thyroid gland exocrine (98% of mass of pancreas): usually 4 or 5, but varies secretes digestive enzymes a. (PTH) endocrine (<2% of mass of pancreas): helps maintain homeostasis of blood contains clusters of endocrine cells

antagonist to calcitonin = Islets of Langerhans (~1 Million clusters; each up to several 1000 cells) raises blood Ca++ levels: humoral regulation: monitors blood conc & levels !promotes Ca++ absorption by kidney tubules and intestine mainly secretes: regulate blood sugar levels ! stimulates osteoclasts to dissolve bone since bone contains both calcium and phosphorus this releases both into blood both are proteins

Calcium homeostasis is important in: a. Insulin neuromuscular function blood clotting synapses levels rise immediately after a meal to activate certain enzymes affects cell membrane permeability !moves glucose, amino acids and fatty surgical removal of thyroid gland requires PTH hormone replacement acids out of blood, into cells (except liver therapy if all parathyroids are removed at the time cells)

!lowers blood glucose concentrations

Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 13 Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 14

only brain, liver and red blood cells do not need insulin to take up glucose diabetes is a general name for a group of diseases b. Glucagon two major varieties: secretion rises between meals diabetes insipidus diabetes mellitis (Types I & II) acts mainly on liver Diabetes insipidus glucose synthesis and release into blood a disease associated with Posterior Pituitary

!increases blood glucose concentration deficiency in ADH causes low of water

antagonist to insulin large volumes of dilute urine are produced: both hormones maintain constant blood glucose levels (up to 10 gallons/day vs normal 1 qt/day)

! to feed brain cells esp leads to electrolyte imbalances etc

! to provide energy for all body cells Diabetes mellitis secretion of hormones directly controlled by blood most common of all endocrine disorders sugar levels: !18.2 Million (2004) diabetics in US,

after meal ! high blood sugar ! insulin 5-6 Million more may be borderline diabetics fasting ! low blood sugar ! glucagon diabetes is 7th leading cause of death & leading cause of blindness in US

!40,000 die anually as result of disorder

Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 15 Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 16 diabetes is a group of disorders characaterized by decreased glucose utilization high blood glucose concentrations levels of glucose build up in blood caused by: since glucose can’t be used alternate fuels are mobilized: inadequate insulin secretion by beta cells in Islets =Type I increased fat mobilization fats in blood rise to up to 5x’s normal lack of response by target cells to insulin as cells shift to fat catabolism =Type II ! produce ketone bodies ! lower blood pH = acidosis ! acetone breath 10% = Juvenile Onset Diabetes (Type I) ! increased risk of atherosclerosis 90% = Maturity Onset Diabetes (Type II) without insulin to stimulate protein Type I: Insulin Dependent Diabetes Mellitis synthesis they are instead broken down and converted to glucose in cells usually develops during adolescence ! tissue wasting is an autoimmune disorder triggered by 2 factors: high levels of glucose in blood lead to large 1. genetic component ! susceptibility quantities of glucose spilling into urine 2. environmental component ! still unknown, may be viral ! diagnostic test for disease (used to taste it, now have chemical indicators)

results in malfunction of Islet cells in pancreas ! this draws large amts of water into urine !dramatic decrease in the number of beta cells Type 2, Non Insulin Dependent Diabetes Mellitis

!insulin is not produced in sufficient quantities target tissues become less responsive to insulin = insulin resistance results in all body cells (target cells):

Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 17 Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 18

causes are poorly understood: most are obese ! but its not per se effects: seems to be a strong genetic component reduces life expectancy by ~1/3rd also associated with a sedentary lifestyle 25 x’s greater rate of blindness 17 x’s greater rate of kidney disease Immediate (Acute) Complications of both forms 17 x’s greater rate of gangrene 2 x’s greater chance of attack , ketoacidosis, electrolyte imbalances (as cations such as Na+ and K+ accompany ketones into urine)

Chronic Secondary Complications

often involve gradual changes over years

most common changes occur in vascular system 1. narrowing of large blood vessels in brain, heart and lower extermities ! can result in stroke, heart attack or limb loss

2. lesions in microvasculature are common leads to development of scar tissue ! especially affect kidneys and eyes

3. impaired nerve function esp autonomic fibers and peripheral sensory fibers leads to altered GI , bladder function and impotence and loss of sensation esp in lower limbs

Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 19 Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 20 Adrenal Glands and excreting K+ on top of kidneys 3. this also indirectly regulates water reabsorption divided into cortex and medulla which function as two separate glands [more salt reabsorbed ! more water reabsorbed] HYPOSECRETION by Adrenal Cortex Adrenal Cortex Addison’s Disease due to inadequate & cortex = outer layer of !comprises 80 –90% of adrenal gland b. Glucocorticoids (95% = absolutely essential for life (hydrocortisone)) regulated mainly by ACTH from Ant. Pituitary affect every cell in body secretes 30 - 50 different hormones secretion follows circadian rhythm

! highest ~8:00am; lowest ~12:00am all hormones secreted by adrenal cortex are 1. generally raise blood glucose levels: all are made from cholesterol 2. inhibit inflammation and tissue destruction these hormones can be categorized as 3 different also immunosuppressive kinds: 3. additional effects on a. Mineralocorticoids (90% = ) immunity wound healing ! aldosterone increases salt and water fetal devel of brain and reabsorption by kidneys

maintains constant blood Na+ levels by reabsorbing Na+ in kidney if needed Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 21 Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 22

HYPOSECRETION of Mineralocorticoids Addison’s Disease Kennedy had mild form low ACTH may also produce this unlike cortex, is not essential for life symptoms: bronzing of skin secretes epinephrine and kidney impairment (=catecholamines) water retention increased blood pressure also of sympathetic NS weight loss apathy cannot cope with !affect same structures as sympathetic NS: immunosuppression heart lethargy and muscle weakness smooth muscle glands HYPOSECRETION of Mineralocorticoids Cushing’s Syndrome serves to prolong or increase effects initiated by weakens skin and muscles sympathetic NS.

c. Sex Hormones (=gonadocorticoids; eg. DHEA, , progesterone, testosterone)

: promote protein synthesis normally not masculinizing

female hormones:

HYPERSECRETION of gonadocorticoids women in early puberty: adrenogenital syndrome masculinizing effect

Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 23 Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 24 & Testes Minor/Temporary Endocrine endocrine and reproductive function Glands secrete hormones Kidneys

the same that are found in adrenal cortex secrete most (85%) affect development and maturation of reproductive ! stimulates RBC production in organs and reproductive behavior Liver Steroid Abuse

Taking large amounts of Androgens (steroids): secretes ~ 15% of body’s erythropoietin stimulates RBC formation has negative effect on FSH & LH ! almost shuts down ! decreased sperm production Heart ! temporary or permanent sterility ! increased risk atria contain some specialized muscle cells that also when large amounts are take some is secrete Atrial Natriuretic (ANP) transformed into estrogen ! reduces blood volume, pressure, Na+ ! breast enlargement conc

Stomach &

mucosal lining secretes several hormones to help control :

enterogastrone Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 25 Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 26

regulates secretion of: gastric juices pancreatic enzymes

Adipose Tissue

releases

after uptake of glucose and lipids which is converted to fat

leptin binds to CNS neurons in hypothalamus ! produces sensation of satiety

Placenta

acts as temporary endocrine gland during pregnancy

releases 3 hormones:

a. chorionic gonadotropic hormone (CGH)

! maintains hormonal activity of

pregnancy test

b. & progesterone

Human Anatomy & Physiology: Endocrine System; Ziser, 2010.4 27