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Adrenaline (Epinephrine) - Short Notes

1. Basic Identity

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2. Synthesis (Catecholamine Pathway)

Key fact: Metyrosine inhibits tyrosine hydroxylase (rate-limiting step) - used in pheochromocytoma.

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3. Receptors Activated

• Low dose → β effects dominate (vasodilation)
• High dose → α effects dominate (vasoconstriction)

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4. Pharmacological Actions

Cardiovascular

• ↑ Heart rate (positive chronotrope - β₁)
• ↑ Myocardial contractility (positive inotrope - β₁)
• ↑ Cardiac output + ↑ O₂ demand
• ↑ Systolic BP (β₁)
• Slight ↓ diastolic BP (β₂ vasodilation in skeletal muscle)
• Vasoconstriction in skin, mucosa, viscera (α₁)
• Vasodilation in skeletal muscle and liver (β₂)
• ↑ Conduction velocity in AV node, His-Purkinje system

Respiratory

• Powerful bronchodilation (β₂)
• Inhibits histamine/leukotrienes from mast cells

Metabolic

• Hyperglycemia: glycogenolysis in liver (β₂) + ↑ glucagon (β₂) + ↓ insulin (α₂)
• Lipolysis (β₁/β₃)

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5. Clinical Uses

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6. Pharmacokinetics

• Onset: Rapid
• Duration: Brief (rapidly degraded)
• Routes: IM (anaphylaxis) > IV (emergencies) > SC > inhalation > endotracheal tube
• Metabolism: MAO (monoamine oxidase) + COMT (catechol-O-methyltransferase)
• Metabolites: Metanephrine → Vanillylmandelic acid (VMA) - excreted in urine
• Half-life: 10-100 seconds in circulation
• NOT oral (destroyed by gut enzymes)

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7. Adverse Effects

• CNS: Anxiety, fear, tremor, headache
• Cardiac: Arrhythmias (VT, VF), angina, tachycardia (especially with halothane anesthesia)
• Pulmonary edema (due to increased afterload from vasoconstriction)
• Hyperglycemia (caution in diabetics - may need more insulin)

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8. Precautions / Drug Interactions

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9. Breakdown / Termination of Action

• Uptake-1 (neuronal reuptake) - accounts for ~90% of removal; blocked by cocaine, tricyclic antidepressants
• Uptake-2 (extraneuronal) - metabolized by COMT
• Enzymatic degradation by MAO and COMT

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Insulin in Diabetes Mellitus - Short Notes (with Renal Physiology)

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1. Source and Structure

• Insulin = MW 5808; two chains (A + B) connected by disulfide bonds
• Synthesized as: Preproinsulin → Proinsulin → Insulin + C peptide (cleaved in Golgi)
• C peptide is secreted in equimolar amounts with insulin - useful as a marker of endogenous insulin secretion
• Half-life in plasma: ~6 minutes; metabolized by liver and kidney

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2. Mechanism of Insulin Secretion (Beta Cell)

1. Glucose enters via GLUT-2 transporter (proportional to blood glucose)
2. Glucokinase phosphorylates glucose → Glucose-6-phosphate (rate-limiting/glucose-sensing step)
3. Oxidation → ↑ ATP
4. ATP closes ATP-sensitive K⁺ channels → cell depolarizes
5. Depolarization opens voltage-gated Ca²⁺ channels → Ca²⁺ influx
6. Ca²⁺ triggers exocytosis of insulin granules

Drug link: Sulfonylureas (e.g. glibenclamide) block ATP-sensitive K⁺ channels directly → depolarize beta cell → ↑ insulin secretion

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3. Stimulators vs. Inhibitors of Insulin Secretion

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4. Metabolic Effects of Insulin

A. Carbohydrate Metabolism

• ↑ Glucose uptake (GLUT-4 in muscle, fat)
• ↑ Glycogen synthesis (liver and muscle) - activates glycogen synthase
• ↓ Glycogenolysis (inactivates liver phosphorylase)
• ↓ Gluconeogenesis (decreases liver enzymes + decreases amino acid precursors)
• Net: Lowers blood glucose

B. Fat Metabolism

• ↑ Fatty acid synthesis (liver)
• ↑ Lipoprotein lipase activity in adipose capillaries → fat storage
• ↓ Hormone-sensitive lipase → ↓ lipolysis
• Net: Fat sparer + fat storage promoter
• Insulin deficiency → ↑ lipolysis → ↑ free fatty acids → ↑ ketone bodies → ketoacidosis

C. Protein Metabolism

• ↑ Amino acid uptake into cells
• ↑ Protein synthesis
• ↓ Protein breakdown
• Insulin deficiency → tissue wasting

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5. Blood Glucose Regulation

• Normal fasting glucose: 80-90 mg/100 mL
• Post-meal peak: 120-140 mg/100 mL (returns to normal within 2 hours)
• The liver is the primary "glucose buffer" (stores ~100g glycogen = ~5-6% of liver mass)

1. Insulin falls → liver releases glucose
2. Glucagon rises → glycogenolysis
3. Epinephrine (sympathetic) → emergency glucose release
4. Prolonged: Cortisol + Growth hormone → ↓ glucose utilization, ↑ fat use

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6. Diabetes Mellitus

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7. Renal Physiology in Diabetes (Key Points)

A. Glucosuria (Glycosuria)

• Glucose is freely filtered at glomerulus
• Normally 100% reabsorbed in proximal tubule via SGLT2 (90%) and SGLT1 (10%)
• Renal threshold for glucose = ~180-200 mg/100 mL (tubular maximum reached)
• When blood glucose >200 mg/100 mL → glucose appears in urine (glucosuria)
• In severe DM: 100+ grams glucose lost per day in urine

B. Osmotic Diuresis

• Unreabsorbed glucose retains water in tubular lumen → osmotic diuresis
• Result: Polyuria (large urine output)
• Leads to: Dehydration → polydipsia (thirst)

C. Classic Triad of DM (from renal mechanism)

D. Cellular Dehydration

• Glucose doesn't cross cell membranes easily
• Hyperglycemia → ↑ extracellular osmolarity → water drawn OUT of cells → cellular dehydration

E. SGLT2 Inhibitors (Pharmacological Link to Renal Physiology)

• Drugs: empagliflozin, dapagliflozin, canagliflozin
• Block SGLT2 in proximal tubule → prevent glucose reabsorption → ↑ urinary glucose excretion → ↓ blood glucose
• Insulin-independent mechanism
• Side effects: diuresis (↓ BP, risk of dehydration/hypotension), UTI risk
• Extra benefit: cardioprotective + renoprotective effects in clinical trials

F. Renal Insulin Handling

• Kidney removes ~30-40% of circulating insulin
• In chronic kidney disease (CKD): ↓ renal insulin clearance → plasma insulin levels rise slightly → increased risk of hypoglycemia in patients on insulin therapy (dose reduction needed in CKD)

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8. Complications of Chronic Hyperglycemia

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9. Diabetic Ketoacidosis (DKA) - Type 1

• Insulin deficiency → ↑ lipolysis → ↑ keto acids (acetoacetic acid, β-hydroxybutyric acid)
• Released faster than tissues can use → metabolic acidosis
• Dehydration + acidosis → diabetic coma (if pH <7.0, death possible within hours)
• Compensation: Kussmaul breathing (deep, rapid) to blow off CO₂
• Treatment: IV insulin + IV fluids + electrolytes

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Hypothalamus - Short Notes (Simple Words)

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1. What Is It? Where Is It?

• Part of the diencephalon
• Forms the walls and floor of the 3rd ventricle
• Located just behind the optic chiasm
• Connected to the pituitary gland via the pituitary stalk (infundibulum)

H - Homeostasis (hunger, thirst, sleep, sex) E - Endocrine control (pituitary hormones) A - Autonomic control (heart, BP, gut) L - Limbic functions (emotions, behavior)

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2. Hypothalamic Nuclei - The Control Centers

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3. The 7 Big Jobs of the Hypothalamus

🌡️ Job 1: Temperature Regulation

• Anterior hypothalamus = detects overheating → triggers sweating, panting, vasodilation to cool you down
• Posterior hypothalamus = detects cold → triggers shivering, vasoconstriction to warm you up
• Lesion of anterior = hyperthermia (can't cool down)
• Lesion of posterior = poikilothermia (body temperature just follows the environment like a lizard)

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💧 Job 2: Water Balance (Thirst + ADH)

• Osmoreceptors in anterior hypothalamus detect when blood is too concentrated (dehydration)
• Response: feel thirsty (drink water) + release ADH from supraoptic nucleus (kidneys retain water)
• Lesion of supraoptic nucleus → Diabetes Insipidus (no ADH → massive water loss in urine)

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🍔 Job 3: Hunger and Appetite

• Leptin (from fat cells) acts on hypothalamus → ↓ appetite (tells brain: "we have enough fat stored")
• Ghrelin (from stomach) acts on hypothalamus → ↑ appetite ("feed me!")
• Lesion of lateral hypothalamus → stops eating → weight loss/starvation
• Lesion of ventromedial nucleus → can't feel full → obesity + rage

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😴 Job 4: Sleep-Wake Cycle (Circadian Rhythm)

• Suprachiasmatic nucleus = the body's master clock
• Gets light signals from eyes (via retinohypothalamic tract) → adjusts day/night cycles
• Anterior hypothalamus (VLPO area) = promotes sleep (releases GABA to inhibit arousal centers)
• Posterior hypothalamus = promotes wakefulness (histamine, orexin neurons)
• Lesion of anterior hypothalamus → insomnia
• Lesion of posterior hypothalamus → hypersomnia (sleeps too much)

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🫀 Job 5: Cardiovascular Control

• Posterior/lateral hypothalamus stimulation → ↑ BP, ↑ heart rate
• Anterior/preoptic area stimulation → ↓ BP, ↓ heart rate, bladder contraction
• Works via relays in the brainstem (pons and medulla)

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🧬 Job 6: Endocrine Control (via Pituitary Gland)

• Supraoptic nucleus → ADH (vasopressin) - water retention
• Paraventricular nucleus → Oxytocin - uterine contractions, milk letdown, bonding

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😡 Job 7: Emotions and Behavior

• Lateral hypothalamus stimulation → rage, fighting, aggression
• Ventromedial nucleus stimulation → calm, peaceful, satiety
• Periventricular nuclei stimulation → fear, punishment reaction
• Sexual drive controlled by anterior and posterior hypothalamus
• Oxytocin (made in hypothalamus) → increases nurturing behaviors

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4. Hypothalamus - Lesion Summary Table

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5. Quick Memory Tricks

Heat dissipation (cooling), Emotions calm, ADH + oxytocin production, Thirst sensing

Shivering, Heat conservation, Increase BP, Pupil dilation

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