Endocrine system

• 1. Direct - Ions via gap junction
• 2. Paracrine - Paracrine factors via extracellular fluid
• 3. Endocrine - Hormones via blood circulatory system
• 4. Synaptic - Neurotransmitters across neural junctions

• By ions via gap junction.
• (sodium, potassium, calcium)
• Cells are touching, gap junction between them

• By paracrine factors via the extracellular fluid.
• (chemicals)
• In the same vacinity, gaps between cells, swim back and forth.

By hormones via the blood circulatory system.

Travels further communicating with organs across the body

• By neurotransmitters across neural junctions
• (nervous system)
• Synaptic cleft

• Hypothalamus
• Pituitary Gland
• Thyroid Gland
• Pineal Gland
• Suprarenal Gland
• Parathyroid Gland
• Pancreas
• They are well defined structurally and funtionally

• Kidneys
• Heart
• Intestines
• Thymus
• Gonads
• Adipose Tissue
• Found within organs. Produce hormones to help organ do its job.

Chemical regulators

Secreted into the blood and transported to target cells

Target cells have specific receptors on them

• 1. Steroids
• 2. Monoamines
• 3. Oligopeptides
• 4. Glycoproteins
• 5. Polypeptides

Lipids (fats) or cholesterol

ex. Vitamin D, sex hormones

A single amino acid which is modified or repeated

3-10 amino acids

ex. Oxytocin in the reporductive system

Carbohydrate-proteins

ex. luteinizing hormone

Made from 14-199 amino acids

ex. insulin and glucagon

• 1. stimulus
• 2. gland (with hormone)
• 3. hormone excretion
• 4. enters the blood stream
• 5. out to receptor of target cell
• 6. action of hormone is manifested
• ex. sugar - - - to - - - - insulin

• 1. Membrane
• 2. Cytoplasm
• 3. Nucleus

• nuclear receptors
• (nucleus)
• Associated with DNA transcription

• Cytoplasmic receptors
• (cytoplasm)
• on mitochondria and ribosomes

Cell membrane receptors

They activate a second messenger system (need help getting inside)

Hydrophilic

Water soluable not fat soluable.

Attach to receptors in the plamsa membrane. Then the second-messenger activation happens.

Hydrophobic

Fat soluable only

(most common)

endocrine gland hormones reach optium value

inhibits secretion of hypothalamic and anterior pituitary hormones that stimulate the endocrine gland

decreases secretions

• (rare)
• response to an endocrine gland hormone

hormone reaches optimal level

increases secretions of the hormone that stimulated the response

Central area of the basal brain limbic system

A large number of nuclei that modify and control the body functions via the hypothalamic hormones.

work on the pituitary gland which is the master organ of endocrine system.

• 1. Growth Hormone Releasing Hormone (GHRH)
• 2. Growth Hormone Inhibiting Hormone (GHIH)
• (Somatostatin)
• 3. Prolactin Releasing Hormone (PRH)
• 4. Prolactin Inhibiting Hormone (PIH) (Dopamine)
• 5. Corticotropin Releasing Hormone (CRH)
• 6. Gonadotropin Releasing Hormone (GnRH)
• 7. Thyrotropin Releasing Hormone (TRH)

• 1. Antidiuretic Hormone (ADH)
• 2. Oxytocin (OT)

• A small gland that is connected to the hypothalamus by the infundibulum.
• It had two parts
• Anterior pituitary gland (Adenohypophysis)
• Posterior pituitary gland (Neurohypophysis)

Neurohypophysis

Adenohypophysis

• Derived from the neural brain tissue
• Connects the hypothalamus to the posterior pituitary gland by the Hypothalamic Hypophuseal Tract axons

• Derived from ectodermal tissue in the roof of the embryonic mouth
• Connects the hypothalamus to the anterior pituitary gland by the Hypothalamic Hypophyseal Portal System.
• Seperior hypophyseal artery brings blood into the capillary beds of the Adenohypophysis of Pituitary gland. Hypophyseal veins carry blood away.

• Oxytocin is made in the Hypothalamus
• Ocytocin is stored in the Posterior Pituitary Gland
• Oxytocin is secreted from the Posterior Pituitary Gland

Smooth muscle of the reproductive system in both males and females.

• Stimulates semen propelling during ejaculation
• Stimulates uterine contractions during labor
• Stimulates milk ejection during suckling

OT

ADH

Vasopressin

• Made in the hypothalamus
• Stored in the Posterior Pituitary Gland
• Secreted from the Posterior Pituitary Gland

Target tissues are kidneys and blood vessels

• Increases waterreabsorption in the kidneys to increase blood volume
• Causes vadoconstriction of blood vessels to increase blood pressure

• hGH
• 190 Amino acids in humans

Secretions are controlled by hypothalamic GHRH (Growth Hormone Releasing Hormone) and GHIH (Growth Hormone Inhibiting Hormone)

All cells especially skeletal and muscle tissue

• Directly stimulates stem cell growth and differentiation
• Stimulates liver systhesis and release of somatomedins
• Somatomedins mediates growth hormone functions by stimulating stem cell growth and differentiation.
• Results in growth to adulthood and maintenance of skeleton and muscles in adulthood

Somatomedins mediates growth hormone functions by stem cell growth and differentiation

• Pituitary Dwarfism
• Gigantism
• Acromegaly

hyposecretion (decreased secretion hGH) in children and adolescents

hypersecretion (increased secretion of hGH) in infants and children

• hypersecretion (increased secretion of hGH) in adults resulting in distorted facial bones and features.
• (flat bones and soft bones will continue to grow)

TSH

Secretions controlled by hypothalamic TRH (thyroid releasing hormone)

Targets the thyroid gland

Secretions of the thyroid hormones

ACTH

Secretions controlled by hypothalamic CRH (cortiotropic releasing hormone)

Targets the Adrenal gland cortex

Stimulates secretions of the adrenal gland cortex hormones.

PRL

Secretions controlled by hypothalamic PRH (Prolactin Releasing Hormone) and PIH (Prolactin Inhibiting Hormone)

Targets mammary glands

Stimulates milk systhesis in the mammary glands

Secretions controlled by hypothalamic GnRH

FSH

LH

Hypophyseal Portal System

Hypophyseal Portal System

All controlled by negative and positive feedback systems

In the roof of the third ventricle of the brain.

• Neurons
• Neuroglia
• Pinealocytes that secrete melatonin

At night

During the day

• Timing of sexual maturity
• Protection
• Circadian rhythm setting

• Causes premature puberty in children
• (ages 4-5)

Protection in the CNS against damage by free radicals

• Increasaed melatonin secretion may cause Seasonal Affective Disorder (SAD) during winter.
• AKA Winter Depression

• Large butterfly-shaped gland in the neck below the voice box (larynx)
• It had two lobes connected by an isthmus
• made of follicles filled with a colloid (gel-like material)

Isthmus

Colloid (gel-like material)

Thyroglobulin

Hypothalamus secretes TRH to the Anterior Pituitary which secretes TSH to the Thyroid gland.

• 1. Iodide trapping by folicular cells (from blood) and transported into follicular lumen.
• 2. Synthesis of thyroglobulin by follicular cells and transported into follicular lumen.
• 3. Oxidation of iodide to iodine in lumen by thyroid peroxidase enzyme
• 4. Iodination of tyrosine molecules in the thyroglobulin chain to form T₁ and T_2.
• 5. Coupling of T₁ and T₂ to make T₃ or T₄.
• 6. Pinocytotsis of thyroglobulin chain by the follicular cells and digestion by lysosomal enzymes to produce free T₃ and T₄.
• 7. Secretions of T₃ (Triiodothyroanine) and T₄ (Tetraiodothyronine/Thyroxine) into the blood.
• 8. Transport of T₃ and T₄ in blood in the free form or bound to thyroid-binding-globulin (TBG)

Calcitonin

• 1. Increase the Basal Metabolic Rate (BMR) of all cells
• 2. Increase ATP production in mitrochondria of all cells by areobic cell respiration.
• 3. Promote normal growth synergistically (in collaberation with) with growth hormone

• Decreases blood calcium levels
• (produced by C-cells)
• (works with parathyroid hormone)

• 1. Cretinism (thyroid dwarfism)
• 2. Endemic goiter
• 3. Hypothyroidism (in adults)
• 4. Hyperthyroidism (in adults)

• Hypothyroidism during fetal development or during early infancy.
• Causes sever forms of mental and physical retardation in the newborn child. (if left untreated life span of 2 years, if treated with in 4 months it is reversable)
• Retardation is reversable only if horminal replacement therapy is started during the first 4 months of the newborns life.

• Hypothyroidism caused by iodine deficiency
• Insufficient dietary iodine to make T₃ and T₄
• Occurs mostly in arid, dry, desert inland regions
• Lack of negative feedback from T₃ and T₄ causes over stimulation and overgrowth of the thryoid gland by TRH and TSH
• goiter results (enlarged throid gland)

• Caused by too little T₃ and T₄
• Symptoms are:
• Decreased Basal Metabolic Rate (cell energy)
• Decreased Body Temp
• Cold intolerance
• Bradycardia
• Lethargy
• Weight gain
• Goiter
• Myxederma (fish skin, dry, scaley)

• Too much T₃ and T₄
• Grave's disease is the most common cause (autoimmune disorder)
• Symptoms:
• Increased Basal Metabolic Rate
• Increased Body Temp
• Heat intolerance (miserable in hot areas)
• Tachycardia
• Anxiety & irritability
• Weight loss
• Goiter
• Exophthalmia (exophthalmos) bulging eyeballs

Four small glands on the posterior surface of the thyroid gland

Contains Principal cells that secrete Parathyroid Hormone

Along with Calcitonin they regulate blood calcium levels

• Decreases blood calcium by:
• Increasing calcium excretion by the kidneys (out of blood and into urine by kidneys)
• Increasing calcium deposition in the bones

• Increases blood calcium by:
• Increasing calcuim reabsorption by kidneys (from urine back into the blood)
• Releasing calcium from bones into blood
• Activating Vitamin D which increases calcium absorption from intestines into the blood

• Adrenal Glands
• (located ontop of the kidneys)
• They have 3 zones
• Capsule, Cortex and Medulla
• Medulla is a gland all on its own producing different hormones.

• Outer zone secreting mineralocorticoids.
• (Minerals - Sodium and Potassium)

• Aldosterone is the major mineralocorticoid
• Increases retention of sodium by kidneys (takes back from urine into blood)
• Increases excretion of potassium by kindeys (potassium from blood into urine)
• Increases water retention and blood volume (increased blood volume = increased blood pressure)

Aldosterone secretion is regulated b sodium and potassium levels in the blood

Middle zone secreting glucocorticoids

• Cortisol is the major glucocortiocoid
• Increases glucose and glycogen systhesis (cells make more glycogen/glucose)
• Incease fatty acids (glucose) & protein (glycogen) breaking
• Reduces inflammation and allergic rashes

Hypothalmic CRH (cortiotropic releasing hormone) and Anterior Pituitary ACTH (adrenal corticotropic hormone)

• Inner zone secreting androgens (male sex hormone)
• (5% of male hormones come from Zona Reticularis and 98% from testes)

• Stimulates pubic hair growth in puberty
• promote muscle mass, formation of the blood cells and libido in females

Hypothalamic CRH (cortiotropic releasing hormone) and anterior pituitary ACTH (adrenal cortioctropic hormone)

• Addison's desease
• Cushings disease

• Suprarenal gland disorder
• Insufficient suprarenal cortex secretions
• Lack of energy
• weight loss
• inability to resist stress
• loss of sodium and water in urine
• John F. Kennedy had this disease

• Suprarenal gland disorder
• Excessive suprarenal cortex secretions
• muscle wasting due to breakdown of proteins
• spindly thin arms and legs
• body fat redistribution
• rounded face (moon face)
• Fatty hump between shoulders (buffalo hump)
• Large abdomen with hanging-down fat
• Virilization (facial hair) and musculinization (muscles) in females

Develops from the same nervous tissue as the sympathetic nervous system

• Suprarenal Medulla
• Chromaffin cells receive direct innervation from the sympathetic nervous system

sympathetic stimulation

• sympathetic nervous system neurotransmitters
• - their effects mimic those of the SNS
• - they cause fight or flight behavior

Epinephrine and norepinephrine

sympathetic nervous system

targets all body cells

• increased heart rate and strength
• increased blood flow to skeletal muscles, heart and brain
• increased dilation of airways
• increased fuel for energy
• increased blood pressure

• 5 inches long with a head, neck, body and tail
• most are exocrime cells producing digestive enzymes
• endocrine cells in pancreatic islets produce hormones

Islets of Langerhan

• alpha cells (20%) glucagon
• beta cells (70%) insulin
• delta cells (5%) somatostatin (brake controller for glucagon and insulin)
• F-cells (5%) pancreatic polypeptide (PP-cells)

• Insulin decreases blood glucose by:
• 1. Increasing uptake of glucose into cells (cells take glucose from blood)
• 2. Increasing synthesis of glycogen (storage form of glucose) in the liver for storage
• Insulin increases protein synthesis in cells
• Insulin increases fat synthesis in cells

• Glucagon increases blood glucose by:
• 1. Increasing synthesis od glucose from amino acids in the liver (making new)
• 2. Increasing breakdown of liver glycogen into glucose (already stored)
• 3. Increasing the release of glucose from liver into blood
• Glucagon increases fat breakdown in adipose tissue to free fatty acids (Lypolysis)

• Fed State
• stimulates the secretion of insulin and inhibits the secretion of glucagon

• Fasting State
• stimulates the secretion of glucagon and inhibits the secretion of insulin.

A metabolic disorder that produce high glucose levels in the blood. (Hyperglycemia)

• caused by genetic defects that
• 1. decrease insulin secretions
• 2. produce defective insulin
• 3. defective insulin receptors

• Juvenile Diabetes
• Insulin-Dependent-Diabetes-Mellitus (IDDM)

• Usually develop in people younger than 7 years of age
• Beta cells are destroyed by own immune system
• Insulin levels are low or absent
• Insulin injections are required for life

• Adult Diabetes
• Non-Insulin-Dependent-Diabetes-Mellitus (NIDDM)

• Most common type of Diabetes (90%)
• Mostly in people over 35 who are obese
• Insulin may still be secreted but the body cells are less sensitive to insulin actions due to blocking of the insulin receptors
• may be controlled by diet
• insulin injections may not be required (as long as beta cells are still alive)

• the 3 P's
• Polyuria - excessove urination
• Polydypsia - excessive water drinking
• Polypahgia - excessive eating

• Intestinal hormones coordinate activities of the digestive system
• Most important ones are Cholecystokinin (CCK), Gastrin and Secretin

• Calcitriol - is the active form of vitamin D that increases calcium absorption from the intestine.
• Erythropoietin - stimulates RBC production
• Renin(enzyme)-Angiotensin-Aldosterone - system affect blood volume and blood pressure

Natriuretic Peptide - increases sodium and water excretion by the kidneys to decrease the blood volume if the heart is struggling with too much blood

Thymosins - promote development and maturation of the T-Lymphocytes

• Testosterone and Inhibin in testes
• Estrogen and Progesterone in ovaries

Leptin - suppress appetite