Results for "parasympathetic nervous system"

Cardiovascular System - Detailed Summary 1. Functions of the Cardiovascular System • The cardiovascular system is a closed system consisting of the heart and blood vessels. • Main functions: • Transport oxygen, nutrients, hormones, and waste. • Maintain blood pressure and circulation. • Aid in immune function (through WBCs in blood). 2. Anatomy of the Heart • Location: Thoracic cavity, between the lungs, within the mediastinum. • Size: About the size of a fist. • Orientation: • Apex: Points toward the left hip (bottom). • Base: Directed toward the right shoulder (top, where large blood vessels attach). Heart Layers (Inside to Outside) 1. Endocardium – Inner lining of the heart, smooth to prevent clotting. 2. Myocardium – Thick muscular layer responsible for contraction. 3. Epicardium (Visceral Pericardium) – Outer covering of the heart. • Pericardium: A double-walled sac surrounding the heart. • Parietal Pericardium: Outer layer. • Visceral Pericardium: Inner layer (epicardium). • Pericardial Fluid: Lubricates and reduces friction during heartbeats. 3. Chambers of the Heart The heart has four chambers: • Atria (Right & Left): Upper receiving chambers. • Ventricles (Right & Left): Lower pumping chambers. • Right Side of the Heart: Pumps deoxygenated blood to the lungs (Pulmonary Circulation). • Left Side of the Heart: Pumps oxygenated blood to the body (Systemic Circulation). 4. Heart Valves Valves prevent backflow of blood: 1. Atrioventricular (AV) Valves – Between atria and ventricles: • Right AV Valve: Tricuspid Valve • Left AV Valve: Bicuspid (Mitral) Valve 2. Semilunar Valves – Between ventricles and arteries: • Pulmonary Semilunar Valve: Right ventricle → Pulmonary artery • Aortic Semilunar Valve: Left ventricle → Aorta • Chordae Tendineae (“Heart Strings”) anchor AV valves to prevent them from inverting. 5. Blood Flow Through the Heart 1. Deoxygenated Blood Pathway (Blue): • Superior/Inferior Vena Cava → Right Atrium → Tricuspid Valve → Right Ventricle → Pulmonary Semilunar Valve → Pulmonary Artery → Lungs 2. Oxygenated Blood Pathway (Red): • Lungs → Pulmonary Veins → Left Atrium → Bicuspid Valve → Left Ventricle → Aortic Semilunar Valve → Aorta → Body 6. Electrical Conduction System (Intrinsic Conduction System) The heart has automaticity (can contract on its own). • Sinoatrial (SA) Node (“Pacemaker”) – Sets the heart’s rhythm (~75 bpm). • Atrioventricular (AV) Node – Delays impulse so atria can contract first. • AV Bundle (Bundle of His) – Carries signal to ventricles. • Purkinje Fibers – Cause ventricles to contract. Disruptions in this system can cause arrhythmias (irregular heartbeats). 7. Cardiac Cycle (Heartbeat) Each cycle consists of: 1. Atrial Systole – Atria contract, pushing blood into ventricles. 2. Ventricular Systole – Ventricles contract, pumping blood to the lungs/body. 3. Diastole – Heart relaxes and fills with blood. • Heart Sounds: • “Lub” – Closing of AV valves during ventricular contraction. • “Dub” – Closing of semilunar valves during ventricular relaxation. 8. Cardiac Output (CO) • Definition: The amount of blood pumped by each ventricle per minute. • Formula: • CO = Heart Rate (HR) × Stroke Volume (SV) • Average CO = 5.25 L/min Factors affecting CO: • Sympathetic nervous system → Increases HR (exercise, stress) • Parasympathetic nervous system → Decreases HR (rest, sleep) • Hormones (epinephrine, thyroxine) → Increase HR 9. Blood Vessels & Circulation • Arteries: Carry oxygenated blood away from the heart (except pulmonary artery). • Veins: Carry deoxygenated blood to the heart (except pulmonary vein). • Capillaries: Tiny vessels for gas/nutrient exchange. Blood Vessel Structure 1. Tunica Intima – Inner layer, smooth to reduce friction. 2. Tunica Media – Middle layer, made of smooth muscle (controls blood pressure). 3. Tunica Externa – Outer layer for support. 10. Major Circulatory Routes • Pulmonary Circulation: Right ventricle → Lungs → Left atrium. • Systemic Circulation: Left ventricle → Body → Right atrium. Special Circulations: • Hepatic Portal Circulation: Blood from digestive organs goes through the liver before reaching the heart. • Fetal Circulation: Blood bypasses the lungs using special shunts (foramen ovale, ductus arteriosus). 11. Blood Pressure & Disorders • Blood Pressure (BP): The force of blood against vessel walls. • Normal BP: ~ 120/80 mmHg • Hypertension (High BP): >140/90 mmHg – Can damage arteries. • Hypotension (Low BP): <90/60 mmHg – Can cause dizziness or shock. Factors affecting BP: • Cardiac Output (CO) • Blood Volume • Vessel Resistance (narrower arteries = higher BP) 12. Common Cardiovascular Disorders • Hypertension (High Blood Pressure): Can lead to stroke, heart attack. • Atherosclerosis: Hardening of arteries due to plaque buildup. • Myocardial Infarction (Heart Attack): Blockage in coronary artery cuts off oxygen. • Arrhythmia: Irregular heartbeats due to conduction system issues no

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