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 kidneysTwo 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

HEARTAtrial 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