ENDOCRINE SYSTEM

INCLUDES ENDOCRINE ORGANS AND CELLS OF NON-ENDOCRINE ORGANS THAT PRODUCES HORMONES

ENDOCRINOLOGY

IS THE STUDY OF THE ENDOCRINE SYSTEM AND DIAGNOSIS AND TREATMENT OF ITS DYSFUNCTIONS

CELLS NEED TO COMMUNICATE..

•GAP JUNCTIONS

•NEUROTRANSMITTERS

•PARACRINE ( LOCAL ) HORMONES

•HORMONES – chemical messenger that it is secreted into bloodstream and stimulates physiological responses in TARGET ORGANS

COMPONENTS OF ENDOCRINE SYSTEM

•HORMONES – chemical messenger

•TARGET CELLS – have receptors x hormones

•ENDOCRINE GLANDS – produce hormones

ENDOCRINE AND NERVOUS SYSTEMS REGULATE ACTIVITIES OF THE BODY

•Endocrine uses chemical messengers, nervous system uses electrical and chemical

•NS reacts quickly and stop quickly, endocrine reacts slow, but effect remains longer

•NS adapts quickly, endocrine is more persistent

NS have effects targeted and specific ( one organ), endocrine have widespread effects on many organs

•SEVERAL CHEMICALS FUNCTION AS BOTH HORMONES AND NEUROTRANSMITTERS      ( norepinephrine, dopamin, ADH )

•SOME HORMONES ARE SECRETED BY NEUROENDOCRINE CELLS ( neurons )

•BOTH SYSTEMS REGULATE EACH OTHER    ( neurons trigger hormone secretion, hormones stimulate or inhibit neurons )

HYPOTHALAMUS

•PART OF WALLS AND FLOOR OF THIRD VENTRICLE

•ATTACH TO PITUITARY GLAND BY STALK      ( INFUNDIBULUM )

•MANY FUNCTIONS CARRIED OUT BY PITUITARY GLAND

PITUITARY GLAND
( HYPOPHYSIS )

•SUSPENDED FROM HYPOTHALAMUS BY THE INFUNDIBULUM

•HOUSED IN SELLA TURCICA OF SPHENOID BONE

•COMPOSED OF ADENOHYPOPHYSIS AND NEUROHYPOPHYSIS

HORMONES FROM HYPOTHALAMUS TRAVEL IN PORTAL SYSTEM TO ANTERIOR PITUITARY GLAND

HYPOTHALAMO-HYPOPHYSEAL PORTAL SYSTEM

PITUITARY HORMONES

•ANTERIOR LOBE

•PARS INTERMEDIA – absent from adult human although present in fetus

•POSTERIOR LOBE

ADENOHYPOPHYSIS ( anterior lobe )

•FSH – follicle stimulating hormone

•LH – luteinizing hormone

•TSH – thyroid stimulating hormone

•ACTH – adrenocorticotropic hormone

•PRL – prolactine

•GH – growth hormone

NEUROHYPOPHYSIS ( posterior lobe )

•STORES AND RELEASES OXYTOCIN AND ANTIDIURETIC HORMONE

•OT AND ADH PRODUCED IN HYPOTHALAMUS, TRANSPORTED DOWN TO POSTERIOR LOBE BY HYPOTHALAMO-HYPOPHYSEAL TRACT

PITUITARY HORMONE ACTIONS ( anterior lobe )

•FSH ( secreted by gonadotrope cells )

•Ovaries, stimulates development of eggs and follicles

•Testes, stimulates production of sperm

•LH ( secreted by gonadoptrope cells )

•Females, stimulates ovulation and corpus luteum to secrete progesterone and estrogen

•Males, stimulates interstitial cells of testes to secrete testosterone

•TSH ( secreted by thyrotropes )

•Stimulated growth of gland and secretion of Thyroid Hormone

•ACTH – ( secreted by corticotropes )

•Regulates response to stress, stimulates adrenal cortex to secrete of corticosteroids that regulate glucose, fat and protein metabolism

•PRL – ( secreted by lactotropes )

•Female, milk synthesis after delivery

•Male, increase sensitivity lo LH, thus increase testosterone secretion

•GH ( Somatotropin ) – ( secreted by somatotropes)

•Promotes tissue growth

GROWTH HORMONE

•PROMOTES TISSUE GROWTH

•Directly affects mitosis and cellular differentiation

•Indirectly stimulates liver to produce IGF-I somatomedins

•FUNCTIONS OF GH-IGF

•Protein synthesis (increase DNA transcription for increase mRNA, proteins synthesized, enhances aminoacid transport into cells )

•Lipid metabolism ( stimulates FFA and glycerol release from adipocytes )

•CHO metabolism

•Electrolyte balance ( promotes Na, K, Cl retention; Ca absorption )

•In childhood, Bone, cartilage and muscle growth

•In adulthood increase osteoblastic activity

POSTERIOR LOBE HORMONES

•ADH – targets kidneys to increase water retention, reduce urine, also functions as neurotransmitter

•OXYTOCIN – labor contractions, lactation, has a possible role sperm transport, emotional bonding

CONTROL OF HYPOPHYSIS

•ANTERIOR LOBE CONTROL – releasing hormones and inhibiting hormones of hypothalamus

•POSTERIOR LOBE CONTROL – neuroendocrine reflexes ( Hormone release in response to nervous system signals , Hormone release in response to higher brain centers )

also FEEDBACK from Target organs

PINEAL GLAND

•STRUCTURE LOCATED ON THE ROOF OF THIRD VENTRICLE

•Secretion peaks between ages 1 and 5, by puberty is 75% lower

•PRODUCES SEROTONIN BY DAY, CONVERTS IT TO MELATONIN AT NIGHT        ( melatonin increase in SAD + PMS, decrease with phototerapy )

THYMUS

•LOCATED IN MEDIASTINUM, SUPERIOR TO HEART

•INVOLUTION AFTER PUBERTY

•SECRETES HORMONES THAT REGULATE DEVELOPMENT AND LATER ACTIVATION OF T-LYMPHOCYTES  ( thymopoietin and thymosins )

THYROID GLAND

•LARGEST ENDOCRINE GLAND with a HIGH RATE OF BLOOD FLOW

•LOCATED ON ANTERIOR AND LATERAL SIDES OF TRACHEA

•TWO LARGES LOBES CONNECTED BY AN ISTHMUS

THYROID FOLLICLES

•Filled with COLLOID and lined with simple cuboidal epithelium ( FOLLICULAR CELLS ) that secretes two hormones: T3 and T4

•C ( CALCITONIN OR PARAFOLLICULAR ) CELLS

•Produce CALCITONIN that decrease blood Calcium concentration, promotes Ca deposition and bone formation especially in children

   THYROID HORMONE

•Increases body’s metabolic rate and O2 consumption

•Calorigenic effect

•Increase heart rate and contraction strength

•Increase respiratory rate

•Stimulates appetite and breakdown of CHO, lipids and prots

PARATHYROID GLANDS

•PARTIALLY EMBEDDED IN POSTERIOR SURFACE OF THYROID GLAND ( 4 )

•SECRETE PARATHYROID HORMONE (PTH)

•Increase blood calcium concentration by promoting synthesis of CALCITRIOL.

•Increase absorption of calcium

•inhibit Ca urinary excretion

•Increase bone resorption

ADRENAL GLANDS

ADRENAL MEDULLA

•CELLS INNERVATED BY SYMPATHETIC N.S.

•STIMULATION CAUSES RELEASE OF CATECHOLAMINES    ( epinephrine and norepinephrine )

•Increases BP and heart rate

•Increases blood flow to skeletal muscles

•Increases pulmonary air flow

•Decreases digestion and urine formation

•Stimulates gluconeogenesis and glycogenolysis

•STRESS causes medullary cells to stimulate cortex

ADRENAL CORTEX

HAS THREE LAYERS OF TISSUE:

  ZONA GLOMERULOSA ( outermost ) 

•MINERALOCORTICOIDS

  ZONA FASCICULATA ( middle )

•GLUCOCORTICOIDS

  ZONA RETICULARIS ( innermost )

•SEX STEROIDS

•MINERALOCORTICOIDS

•Control electrolyte balance, aldosterone promotes Na retention and K excretion

•GLUCOCORTICOIDS

•Especially cortisol, stimulates fat and protein catabolism, gluconeogenesis ( from a.a.s. and fatty acids ) and release of fatty acids and glucose into blood

•Anti-inflammatory effect becomes immune suppression with long-term use

•SEX STEROIDS

•Androgen ( including DHEA which other tissues convert to testosterone ) and estrogen ( important after menopause )

PANCREAS

•EXOCRINE AND ENDOCRINE ORGAN

•RETROPERITONEAL

•1-2 million of PANCREATIC ISLETS PRODUCING HORMONES:

•INSULIN

•GLUCAGON

•SOMATOSTATIN

                                                                              ( 98% of Pancreas produces digestive enzymes )

•INSULIN ( BETA CELLS )

•Secreted after meal with CHO raises glucose blood levels

•Stimulates glucose and amino acid uptake

•Nutrient storage effect (stimulates glycogen, fat, and protein synthesis)

•Antagonizes glucagon

•GLUCAGON ( ALFA CELLS )

•Secreted in very low CHO and high prot diet

•Stimulates glycogenolysis, fat catabolism, and promotes absorption of amino acids for gluconeogenesis

•SOMATOSTATIN ( DELTA CELLS )

•Secreted with rise in blood glucose and amino acids after a meal

•Is a paracrine secretion ( modulate secretion of alfa and beta cells)

OVARY

•GRANULOSA CELLS in wall of ovarian follicle produces ESTRADIOL, first half of menstrual cycle

•CORPUS LUTEUM ( follicle after ovulation ) produces ESTRADIOL and PROGESTERONE for 12 days or for 8-12 weeks with pregnancy

•FOLLICLE AND CORPUS LUTEUM SECRETE INHIBIN – suppresses FSH secretion

FUNCTIONS OF
ESTRADIOL AND PROGESTERONE

•Development of female reproductive system and physique including bone growth

•Regulate menstrual cycle, sustain pregnancy

  Prepare mammary glands for lactation

TESTES

•INTERSTITIAL CELLS ( between seminiferous tubules ) PRODUCE TESTOSTERONE AND ESTROGEN

•SUSTENTACULAR ( SERTOLI ) CELLS SECRETE INHIBIN WHICH SUPRESSES FSH SECRETION WHICH STABILIZES SPERM PRODUCTION RATES.

TESTOSTERONE

•DEVELOPMENT OF MALE REPRODUCTIVE SYSTEM AND PHYSIQUE

•SUSTAINS SPERM PRODUCTION AND SEX DRIVE

ENDOCRINE FUNCTIONS
OF NON-ENDOCRINE ORGANS

ARE

ORGANS THAT HAVE

HORMONE-SECRETING CELLS

( don’t belong to endocrine system )

•HEART

•ATRIAL NATRIURETIC PEPTIDE is released with an increase in BP 

•Decrease blood volume thus decrease BP by increasing loss of sodium and water by kidneys

•SKIN

•Keratinocytes help to produce Vit D3, first step in the synthesis of Calcitriol

•LIVER

•Converts vitamin D3 to calcidiol

•Source of IGF-I that works with Grow hormone

•Secretes about 15% of erithropoietin

•Secretes angiotensinogen ( a prohormone )

•PLACENTA

•Secretes estrogen, progesterone, and others

•Regulate pregnancy, stimulate development of fetus and mammary glands

•KIDNEY

•Converts calcidiol to calcitriol ( active form of vitamin D )

•Produces 85% of erithropoietin

•Convert angiotensinogen to angiotensin I

•STOMACH and SMALL INTESTINE

•Coordinate digestive motility and secretion

•More than ten enteric hormones

HORMONES

•STEROID HORMONES ( derived from cholesterol, includes Sex steroids and corticosteroids )

•PEPTIDE HORMONES ( oxytocin, ADH, all relasing and inhibiting hormones of hypothalamus, 

• MONOAMINES   ( BIOGENIC AMINES ) ( derived from amino acids, include catecholamines and thyroid hormones)

HORMONE TRANSPORT

•MONOAMINES and PEPTIDES are HYDROPHILIC so mix easy with blood plasma

•STEROIDS and THYROID HORMONE are HYDROPHOBIC and must bind to transport proteins for transport

•BOUND HORMONE – hormone attached to transport protein, prolongs half-life to weeks, protects from enzymes and kidney filtration

•Only UNBOUND HORMONE can leave capillary to reach target cell ( half-life a few minutes )

•TRANSPORT PROTEINS IN BLOOD PLASMA

•Albumin, thyretin, and TGB  ( thyroxine binding hormone ) bind to thyroid hormone

•Steroid hormones bind to globulins ( transcortin )

•Aldosterone has no transport protein – 20 min half-life

•HORMONE RECEPTORS

•Located of plasma membrane, mitochondria and other organelles, or in nucleus

•Usually thousands for given hormone ( on/off mechanism )

•Exhibit SPECIFICITY and SATURATION

HORMONE MODE OF ACTION

•HYDROPHOBIC HORMONES ( steroids and thyroid hormones ) PENETRATE PLASMA MEMBRANE- enter nucleus

•HYDROPHILIC HORMONES ( monoamines and peptides ) CAN NOT PASS THROUGH MEMBRANE SO MUST BIND TO CELL-SURFACE RECEPTOR

ENZYME AMPLIFICATION
one hormone molecule does not trigger synthesis of activation of just one enzyme, it activates thousands of molecules

HORMONE CLEARANCE

•HORMONE SIGNALS MUST TURNED OFF

•TAKE UP AND DEGRADED BY LIVER AND KIDNEY

•EXCRETED IN BILE OR URINE

MODULATION

HORMONE INTERACTIONS

•MOST CELLS SENSITIVE TO MORE THAN ONE HORMONE AND EXHIBIT INTERACTIVE EFFECTS

•SYNERGISTIC EFFECTS – two or more hormones act together to produce an effect that is greater than the sum of their separate effects

•PERMISSIVE EFFECTS – one hormone enhances target organ’s response to a second hormone that is secreted later

•ANTAGONISTIC EFFECTS – one hormone opposes the action of another

STRESS

•ANY SITUATION THAT UPSETS HOMEOSTASIS AND THREATENS ONE’S PHYSICAL OR EMOTIONAL WELL-BEING CAUSES STRESS

•THE WAY THAT BODY REACTS TO STRESS IS CALLED GENERAL ADAPTATION SYNDROME ( GAS )

•ALARM REACTION

•STAGE OF RESISTANCE

•STAGE OF EXHAUSTION

PARACRINE SECRETIONS

•CHEMICAL MESSENGERS THAT DIFFUSE SHORT DISTANCES AND STIMULATE NEARBY CELLS ( unlike neurotransmitters, not produced in neurons; unlike hormones, not transported in bloodstream )