ENDOCRINE SYSTEM If max.
set point is exceeded
Principles of Chemical Communication Hormone production is halted
Chemical messengers – allow cells to communicate
with each other B. Positive feedback
Tropic hormones stimulate the release of
Secretion – controlled release of chemicals from a cell other hormones
Classes of Chemical Messengers Hormone Receptors and Mechanisms of Action
1. Autocrine – stimulates the cell that originally Receptors – where hormones exert action by binding to
secreted it; WBCs during an infection proteins
2. Paracrine – act locally on nearby cells; WBCs Receptor site – the portion of each receptor molecule
during allergic reactions where a hormone binds
3. Neurotransmitter – activate an adjacent cell Specificity – tendency of hormones to bind to one type
of receptor
4. Endocrine – secreted into the bloodstream by
certain glands and cells Target tissue – the responding tissue based on the
hormone released
Functions of the Endocrine System (MC 3 I2WHUT)
1. Metabolism. Classes of Receptors
2. Control of blood glucose and other nutrients. 1. LSH bind to nuclear receptors.
3. Control of reproductive functions. Interaction with cell DNA to regulate
4. Control of food intake and digestion. transcription.
5. Ion regulation. 2. WSH bind to membrane bound receptors.
6. Immune system regulation. Hormone receptor complex initiates a
7. Water balance. response inside the cell (G proteins,
8. Heart rate and blood pressure regulation. cAMP, protein kinase).
9. Uterine contraction and milk release.
10. Tissue development. Endocrine Glands and their Hormones
Pituitary and Hypothalamus
Characteristics of the Endocrine System Pituitary Gland/Hypophysis
Endocrine System – composed of endocrine glands + A small gland about the size of a pea
endocrine specialized cells Controls the functions of many other glands
Secrets hormones that influence growth, kidney
Hormones – chemical messenger that is secreted into function, birth, milk prod.
the blood
Hypothalamus
Target tissues – effectors; specific site An important ANS and endocrine control center
of the brain
Endocrine – Greek word; endo (within) + krino Controls the PG by hormonal control and direct
(secrete) innervation
Exocrine glands – have ducts that carry their secretions Infundibulum – a stalk that connects the pituitary gland
to the outside of the body and the hypothalamus
Endocrinology – study of the endocrine system Anterior pituitary – made up of epithelial cells derived
from embryonic oral cavity
Hormones
Greek word; hormone (to set into motion) Posterior pituitary – an extension of the brain;
composed of nerve cells
Chemical Nature of Hormones
1. Lipid-Soluble Hormonal Control of A. Pituitary
2. Water-Soluble Hypothalamic-pituitary portal system – capillary beds
and veins that transport the releasing and inhibiting
Control of Hormone Secretion hormones
Stimulation/Inhibition of Hormone
Release
1. Humoral Stimuli – blood levels of chemicals
2. Neural Stimuli – nervous system
3. Hormonal Stimuli - hormones
Regulation of Hormone Levels in the Blood
A. Negative feedback
Blood conc. of hormone declines
More hormone is secreted
ANTERIOR PITUITARY T H Y R O I D GLAND
1. Growth hormone (GH) 1. Calcitonin
Affects body growth by stimulating protein Decreases rate of bone breakdown
synthesis by increasing gene expression Prevents large increase in blood Ca2+ levels
Breakdown of lipids
Release of fatty acids from cells 2. Thyroid hormones
Increases blood glucose levels Increases metabolic rates
Essential for normal process of growth
Pituitary dwarf – deficiency in GH although
normally proportioned Thyroxine / Tetraiodothyronine - contains four
iodine atoms
Gigantism – excess GH; exaggerated bone
growth occurs Triiodothyronine – contains three iodine atoms
Acromegaly – abnormally large facial features & Isthmus – narrow band that connects the two
hands lobes of the thyroid gland
Insulin-like growth factors (IGFs) Thyroid follicles – where thyroid hormones are
synthesized and stored
2. Thyroid-stimulating hormone (TSH)
Promotes synthesis and secretion of thyroid Goiter – excess TSH; low in iodine diet
hormone
Hypothyroidism – lack of thyroid hormones
3. Adrenocorticotropic hormone (ACTH)
Increases secretion of glucocorticoid hormones Cretinism – congenital absence of thyroxine in
Increases skin pigmentation infants
4. Melanocyte-stimulating hormone (MSH) Myxedema – accumulation of fluid and other
molecules in subcutaneous tissue in adults
Increases melanin prod. in melanocytes
Hyperthyroidism – elevated rate of thyroid
5. Luteinizing hormone (LH)
hormone secretion
Promotes ovulation and
progesterone production on ovary Graves disease – hyperthyroidism that results
when the immune system produces abnormal
Interstitial cell-stimulating hormone (ICSH) proteins
Promotes testosterone synthesis and support for
sperm cell prod. in testis Exophthalmia – bulging of the eyes
6. Follicle-stimulating hormone (FSH)
P A R A T H Y R O I D GLAN D
Promotes follicle maturation and
estrogen secretion in ovary 1. Parathyroid hormone
Promotes sperm cell prod. in testis Increase Ca+ levels in the blood
Increases rate of bone breakdown by osteoclasts
7. Prolactin Increases vit. D synthesis (essential for
Promote development of breast maintenance of normal blood calcium levels)
during pregnancy
Stimulates milk prod. and Hyperparathyroidism (Hypercalcemia) –
prolongs progesterone secretion abnormally high rate of PTH secretion
Increases sensitivity to LH in males Tumor
Muscle weakness
PITUITARY GLAND Soft, easily deformed bones
1. Antidiuretic hormone Prone to kidney stone formation
Conserves water
Hypoparathyroidism (Hypocalcemia) –
Constricts blood vessels abnormally low rate of PTH; surgery
Syndrome of Inappropriate ADH (SIADH) Surgery
Diabetes Inspidus – large prod. of dilute urine Frequent muscle cramps or tetanus
Respiratory arrest
2. Oxytocin
CHVOSTEK’s sign & TROSSEAU sign
Swift birth
Increases uterine contractions
Increases milk letdown
ADRENAL MEDULLA Norepinephrine
1. Epinephrine (Adrenalin) & Fight-or-flight hormones
Increases cardiac output
Increases blood flow to skeletal muscles & heart PANCREAS
Increases release of glucose and fatty acids into
blood 1. Insulin
Prepares body for physical activity Secreted by beta cells
Increases uptake and use of glucose and amino
acids
ADREN AL CORTEX Released in response to elevated blood glucose
1. Aldosterone (Mineralocorticoids) level & parasympathetic stimulation
Regulates water balance
Increases rate of Na transport into body
2. Glucagon
Increase rate of K excretion Secreted by alpha cells
Increases breakdown of glycogen and release of
Renin – protein molecule that acts as an glucose into the circulatory system
enzyme Released in response to low blood glucose level
Renin Angiotensin Aldosterone System Glycogen – stored glucose in muscles & liver
(RAAS) – helps the body to address decreasing
blood volume Acidosis – reduced pH of body fluids
2. Cortisol (Glucocorticoids) Satiety center – area of the hypothalamus that
controls apetite
Increase fat & protein breakdown
Increase glucose synthesis from amino acids Diabetes mellitus – much urine + sweetened
Increase blood nutrient levels Type 1 – occurs when too little insulin is
Inhibit inflammation & immune response secreted from pancreas
Helps the body in stressful situations by Type 2 – caused by insufficient no. of
providing energy sources insulin receptors
Cortisone – artificial cortisol; anti- Hyperglycemia – high blood glucose levels
inflammatory effect
Polyphagia – increased appetite/eating
3. Androgens
Male sex hormone; stimulates the dev’t of male Polyuria – increased eating
characteristics
Increases female sex drive Polydipsia – excessive thirst
Addison’s disease – hyposecretion of adrenal TESTES
cortex hormones
1. Testosterone
Cushing’s disease – tumor in middle cortex Aids in sperm cell prod.
Maintenance of functional reproductive organs,
Hyperaldosteronism – hyperactivity of outer secondary sexual characteristics, sexual behavior
cortex
O V A R I E S
Hirsutism – masculinization (inner cortex) 1. Estrogen & Progesterone
Aid in uterine and mammary gland development
THYMUS and function, external genitalia structure,
1. Thymosin secondary sexual characteristics, sexual
Promotes immune system development and behavior, menstrual cycle
function
Helps the dev’t of certain WBC (T-cells) 2. Prostaglandins
Mediate inflammatory responses
PINE A L GLAND Increase uterine contractions and ovulations
1. Melatonin
Inhibits secretion of gonadotropin-releasing O T HE R H O R M O N E S
hormone (thus inhibits reproduction) 1. Erythropoietin
Biological clock (day & night cycle) Acts on bone marrow to increase the prod. of RBCs
2. Human chorionic gonadotropin (HCG)
Stimulated prod. of estrogen & progesterone
