Endocrine systemPrepared by Ms. Azra Arif

D.A Degree college for woman

Phase VIII

ENDOCRINE SYSTEM

DEFINITION Endocrine glands are organs in the

body that produce hormones which are released directly into the bloodstream. Together these glands make up the endocrine system, which performs essential functions like regulating metabolism, growth and reproduction.

INTRODUCTION

Endocrine derives from the Greek words endo meaning inside, within, and crinis for secrete

Chemicals are released by these glands(hormones) hormone derived from Greek word which means ‘to excite

The field of study dealing with the endocrine system and its disorders is endocrinology, a branch of internal medicine.

In animals glands are of two types Exocrine gland: release products (enzymes) into

ducts› Ex) Sweat, digestive juices

Endocrine glands:– directly to bloodstream; NO DUCTS

› Ex) Hormones Features of endocrine gland: glands are, in general,

their ductless nature, their vascularity, and usually the presence of intracellular vacuoles or granules storing their hormones.

Endocrine system vs. nervous system

Endocrine glands Information

signaling system Effects are slow to

initiate Response are

prolonged (few hrs to week)

HORMONES release in blood stream

Nervous system Information

signaling system effects very fast

and quick Responses are short

lived. NEUROTRANSMITTER

travel through neurons release in synaptic cleft

CHIMCAL CLASSIFICATION OF HORMONES

1. Peptide/ Protein2. Steroid3. Amine derived from single amino acids (tryptophan,

tyrosine)4. Eicosanoid Produced from 20-carbon fatty acid Produced

in all cells except RBCs, 2nd messenger ,Prostaglandins and leukotrienes, inflammation

PEPTIDE HORMONE› Not lipid soluble› Received by receptors external to the cell membraneSTEROID HORMONE

Lipid solubleDiffuse through cell membranes

Hormone Actions

PEPTIDE HORMONE › React with specific receptors

outside the cell› This triggers an enzyme

reaction with lead to the formation of a second messenger (cAMP).

› cAMP can produce specific intracellular functions: Activates cell enzymes Change in membrane

permeability Promote protein synthesis Change in cell metabolism Stimulation of cell secretions

Hormone Actions Steroid Hormones

› Pass through the cell membrane› Binds to specific receptors› Then enters the nucleus to bind

with the cells DNA which then activates certain genes (Direct gene activation).

› mRNA is synthesized in the nucleus and enters the cytoplasm and promotes protein synthesis for: Enzymes as catalysts Tissue growth and repair Regulate enzyme function

Effects of hormonesOne tissue can respond to many hormones

•Synergistic effect- when two or more hormones work together to produce a resultExample: epinephrine and nor epinephrine have an additive effect to increase heart rate

•Permissive effect- one hormone enhances the effect of another hormone e .g . Glucocorticoid enhance effectiveness of catecholamine's (epinephrine and nor epinephrine)

Antagonist effect- one hormone opposes the effect of anotherEX: insulin promotes fat formation glucagon promote fat breakdownControl of hormone releaseEndocrine glands are activated by humoral , neural or hormonal stimuliHORMONE LEVEL INTHE BLOOD CONTROL BY NEGATIVE FEED BACK

Endocrine Glands Hypothalamus Pituitary

› Anterior lobe› Posterior lobe

Thyroid gland Parathyroid

glands Adrenal Glands

› Cortex› Medulla

Islets of Langerhans

Gonads› Ovaries› Testes

Pineal gland Thymus others

Hormonal Communication

Hypothalamus Neuroendocrine organ Central part of brain

attached by numerous nerves to pituitary gland

Weight is about 4g(human) Control the pituitary gland

by producing chemicals (releasing/stimulating or inhibiting hormones

Maintains homeostasis(heart rate, body temperature, water balance, and the secretions of the pituitary gland)

Pituitary gland(Hypophysis)

Pea size gland hang from the base of brain by stalk (infundibulum) loge in the bone of skull, weigh is about 5gm

In past considered as master gland but it itself under the control of hypothalamus

Hypothalamohypophyseal complex(master gland)

consists of a hormone-producing glandular portion

Have two lobes1.Anterior pituitary (adenohypophysis)2.Posterior pituitary (Neurohypophysis) .

Anterior pituitary –hypothalamus

(Adenohypophysis) Secretes six regulating

hormone(trophic hormone)

Growth / somatotropin hormone (GH)

Thyroid stimulating hormone (TSH)

Adrenocorticotropic hormone (ACTH)

Gonadotropin(Follicle stimulating hormone (FSH) Luteinizing hormone (LH)

Prolactin

Melanocyte stimulating hormone endorphins chemicals that act on the nervous system to reduce sensitivity to pain.

Anterior P. Homeostatic Imbalances

Growth /SOMATOTROPIN hormone (GH)

it is a non- trophic,anabolic hormone simulate the growth of all body tissue specially skeletal muscles ,bone and cartilage.

Control protein synthesis and general metabolism

imbalances Hyperseretion in youth produces

gigantism› Hyperseretion in adult produces

acromegaly› Hypo secretion in childhood

produces pituitary dwarfism

Posterior Pituitary or Neurohypophysis

Neurohypophysisdoes not synthesize hormones, however, it stores and releases two hormones produced by the neurosecretory cells of the hypothalamus

• It is an extension of hypothalamus

• ADH• Oxytocin

Pituitary—Posterior lobe Oxytocin

› Stimulates smooth muscle contraction of uterus & mammary glands.

Antidiuretic H.› Stimulates water

reabsorption in collecting ducts.

› Stimulates vasoconstriction (vasopressin)

Lack diabetes insipidus

ADH› Hypo secretion produces

diabetes insipidus “tasteless”

› Excessive thirst and urination

Thyroid Gland Location in neck Bilobed

› Inferior to larynx› Anterior & lateral to trachea

lobed are connected by thinn connective tissue called isthmus

› Weigh about 25-40gm Composed of follicles

› Follicle cells produce › Thyroxin

(Tetraiodothyronine(T4)Triiodothyronine (T3)

Regulates metabolism and energy balance› Both increase cellular metabolism and use of

oxygen ,rise heat production. increase protein synthesis, uptake of glucose

Parafollicular/ C cells Calcitonin

Decreases blood Ca2+ by depositing it in bones

Homeostatic imbalances

Hypothyroidism results› Myxedema (in adults)lethargy, gain

weight puffiness and thickening of skin

› Goiter—low levels of iodine› Cretinism (in children)mental

retardation,dwarfism,lack of sexual maturity

› Hashimotos disease(injury ,infections ,wrong treatment ,age)

Hyperthyroidism results› Graves disease or basedows

disease(enlargement of overall

gland along with exopthalamic goiter(excess accumulation of fat and mucus in eye orbit)

Parathyroid Glands Four small glands

embedded on the surface of thyroid

Weigh about 0.05g-0.3g› Parathyroid hormone

(PTH)› Antagonistic of calcitonin› Stimulated by falling ca in

blood and inhibiting by rising blood ca

› Stimulates osteoclasts to free Ca2+ from bone

› Stimulates Ca2+ uptake from intestine & kidney

Parathyroid ;Homeostatic imbalance

Hyperparathyroidism results in hypercalcaemia and all its effects and in extreme bone destructions.

Hypoparathyroidism leads to hypocalcaemia, evidenced by tetany and respiratory paralysis

Adrenal gland/ suprarenal gland

Triangular structure located at the top of kidney weigh of each gland is 5gm

Have two parts cortex ,medulla Adrenal cortex Produces three kinds of steroid

hormones Glucocorticoid(cortisol) Mineral corticoid(aldosterone) Small amount of sex hormone.

Adrenal cortex Cortex

› Activity stimulated by ACTH› Controls prolonged responses by

secreting corticosteroids.› Glucocorticoid

Cortisol regulate glucose metabolism and

the immune system.› Mineral corticoids

Aldosterone regulate salt and water balance

› Gonad corticoids Androgens

Adrenal Cortex Imbalances Hyper secretion leads to

Cushing’s disease ACTH-releasing tumors or side effects of

corticoid drugs. Weight gain Muscle loss and weakness Fragile skin Reduced sex drive Depression/inability to think clearly Hypo secretion leads to

Addison’s Disease› Deficits in glucocorticoid and

mineral corticoid. Fatigue, weakness, loss of appetite Muscle and joint pain Gastrointestinal problems (nausea,

vomiting, etc.) Darkening of the skin on the face, neck,

and back of hands Low blood pressure A craving for salt

Adrenal Medulla Medulla

› The adrenal medulla mediates short–term responses by secreting catecholamine hormones.

› Cells are modified neurons (lack axons) Epinephrine (adrenaline) Norepinephrine

(noreadrenaline) enable a rapid ( fight-or-flight

) responses to stress by increasing blood glucose and blood pressure and directing blood to the heart, brain, and skeletal muscles.

Pancreas Consists of two major types of

secretory tissues which reflects its dual function › Exocrine gland

secretes digestive juice localized in the acinar cells

› Endocrine gland releases hormones

localized in the islet cells (islets of

Langerhans) About a million” embedded in pancreas

Control centers for blood glucose› Insulin from beta cells› Glucagon from alpha cells

Pancreas Homeostatic ImbalancesDiabetes

Symptoms:•Polyuria•Polydipsia•Polyphagia

Blood Level Regulation in Diabetics

Gonads Ovaries

› Estrogens› Progesterone

Testes› Testosterone

Reproductive functions when we study reproductive system.

Gonads; homeostatic imbalance

OSTEOPOROSIS Osteoporosis is a condition in which bones become fragile and

more likely to break Many factors like decrease estrogen during menopause in

woman. Decrease in testerone in man due to increase in age. Fractured bone due to minor fall

Polycystic ovary syndrome more common endocrine system diseases, affecting between

7% to 10% of women aged 15 to 45. symptoms are irregular menstruation, male hormone excess

symptoms like hirsutism (increased and unwanted hair growth) and acne and difficulty to conceive.

have multiple egg-containing cysts on the ovaries. They are higher risk for metabolic complications like diabetes and hypertension.

Pineal gland Located in diencephalon

Melatonin(primary hormone) Melatonin have

antigonadotropic effect in humans› Inhibits early puberty› Day/night cycles› Timing of sleep, body

temperature, appetite Secretes melatonin during

darkness› Participates in setting the

body’s clock Melatonin is a potent antioxidant Melatonin is high when young

and is reduced as we age

Thymus gland

Lymphocytes that pass trough the thymus , transformed into T-cells

thymosins stimulate the development and differentiation of T lymphocytes

play a role in regulating the immune system by stimulating other kinds of immune cells

Non-Endocrine Gland Hormones

Stomach (gastrin) Small intestine (duodenum intestinal

gastrin, secretin, cholecystokinin) Heart (atrial natriuretic peptide) Kidneys (erythropoietin, rennin) Adipose tissue (leptin, resistin) Skin (cholecalciferol) Placenta (human chorionic gonadotropin,

human placental lactogen, relaxin)Development of endocrine gland All derived from three germ layers Those derived from mesoderm

produce steroidal hormone Others produced amino acid based

hormone

Others type of signalingParacrine: a form of cell signaling in which

the target cell is near the signal-releasing cell.

Autocrine: a form of signaling in which a cell secretes a hormone or chemical messenger (called the autocrine agent) that binds to autocrine receptors on the same cell, leading to changes in the cells

Juxtacrine: Juxtacrine signaling is a type of intercellular communication that is transmitted via oligosaccharide, lipid, or protein components of a cell membrane, and may affect either the emitting cell or the immediately adjacent cell Juxtacrine signaling requires physical contact between the two cells involved.