The Endocrine System Chapter 9

 Communication and Control – slower and long lasting through hormones – chemical messages – that effect a target organ  Diseases (tumors) influence by:  Hyposecretion – too little secretion  Hypersecretion –two much secretion  All organs are glands:  Exocrine – secrete products into ducts  Endocrine – ductless glands  Heterocrine Gland - Both (pancreas)

Origin Of Hormones  Hormones affects target cells  Secreted by endocrine glands  Secreted by neurons (neuro-hormones) - neurosecretory cells  Secreted by individual cells or tissues (Growth Factors, prostaglandins, histamine)

Chemical Nature of Hormones  Derived from cholesterol  Derived from amino acids  Derived from fatty acids

Protein Hormones  Second Messenger Hypotheses  Cause specific affects on target organs only  Hormone binds to specialized receptor – “ first messenger ”  Second Messenger is Cyclic Adenosine MonoPhosphate (cAMP)  The bonding of the hormone activates activates a G4 protein, which in turn activates adenylate cyclase (enzyme) to react with ATP to produce cAMP

Steroid Hormones  Small – lipid soluble Hormones  Pass directly through the cell membrane of target organs  Go to nucleus, interact with DNA to allow transcription of certain proteins

Prostaglandins  PG ’ s - tissue hormone – produced on a tissue and acts on nearby cells  Three groups PGA, PGE, PGF  Might have a role in asthma, blood pressure disorders, and ulcers

Negative Feedback  Reverses a change in a body condition  Insulin – high blood-sugar content after a meal, pancreas secretes insulin to move blood-sugar into cells, thus decreasing levels

Other types of Negative Feedback

Positive Feedback  More Uncommon than negative feedback  Amplify changes rather than reverse them  Labor – the contractions are amplified through hormone control

Pituitary Gland  Gland in hind brain about the size of a pea  Anterior (adrenohypophysis)- gland / Posterior (neurohypophysis) - nervous

Anterior (adrenohypophysis)- gland - hypothalamin releasing hormones get anterior to release hormones Posterior (neurohypophysis) - nervous - nerve endings from hypothalamus cause hormones to be released

Hormones of Anterior Pituitary  Tropic Hormones – Stimulates another endocrine gland to grow and secrete its hormone

ANTERIOR GLAND - TROPIC  TSH - (thyroid-stimulating) Growth and secretion of the thyroid  ACTH - (adenocorticotropic) Growth of Adrenal cortex and secretions  FSH - (follicle stimulating) Growth and development of Ovarian Follicles - providers of ova (eggs), release of estrogen/progesterone  LH - (Luteinizing) Control ovulation - maturation and bursting of follicle - males - interstitial cells  ICSH - (Interstitial cell)Testosterone secretion of testes

 MSH - (melanin stimulating hormone) - synthesizes and spreads melanin - pigment  GH - (Growth Hormone) -stimulates growth by protein anabolism (building) - fat and glucose catabolism - enhances the movement of Amino acids across cell membrane  Insufficient GH - dwarfism  Oversecretion - giagntism  Prolactin - (lactogenic) - stimulates milk production, in males excess may decrease sex hormones

Posterior Pituitary Hormones  ADH- retention of water by kidneys (diuretic - loss of water by kidneys)- maintained by osmoreceptors in the brain  Oxytocin - stimulates uterine contraction - positive feedback

Thyroid Gland ---Parathyroid Gland  Located in the neck, below the larynx  Thyroxin (T4 - four atoms of iodine - accelerates metabolism  Calcitonin - decreases blood calcium, puts calcium into bones  Triiodothyronine (T3 three atoms of iodine) -energy for metabolism - five times as potent as thyroxin  Small (usually 4) found on the back of the thyroid  Increases Blood Calcium - breaks down bone

Adrenal Glands  Adrenal Glands - Lie on top of the kidneys  Two separate endocrine glands the adrenal cortex and the adrenal medulla

ADRENAL GLANDS  CORTEX  Glucocorticoids - maintain blood pressure, sugar, stress - cortisol  Mineralocorticoids - increase blood sodium, decrease blood potassium  sex hormones - small amount secreted, female converted to estrigens  Medulla  Produces epinephrine and norepinephrine for stress response - sympathetic inervation  The effects include increase heart rate, breathing rate, and all assoisiated sympahtetic responses

 Pancreatic Islets/ Islets of Langerhans  Alpha cells = glucagon, Beta cells = insulin

 Female and Male Sex Hormones  Ovaries – female, Testis - male  Female characteristics and fertility - release of estrogen and progesterone  Male - secretes testosterone - interstitial cells - controls male sexual development

 PLACENTA  Temporary endocrine gland  secretes choriongonadotropin hormone - maintains corpus luteum - high in urine = pregnancy  PINEAL  Small pine-coned shaped gland at the roof of the third ventricle of the brain  Also called third eye – responds to senses  Produces melatonin  inhibits ovarian activity  influences menstrual cycle  biorhythms

 HEART  Atrial Natriuretic Hormone – secreted by the walls of the atria – regulates fluid and electrolytes  THYMUS  Located in mediastinum. Has cortex and medulla  Houses lymphocytes  secretes thymosin - immune regulator