121L act 3 and 4

• Cardiovascular System: Activity 3 and 4, Pharma 121L

Objectives:

• Identify the anatomical structures of the heart and describe their functions.
• Describe blood flow through pulmonary and systemic circulation, listing major heart structures involved.
• Differentiate arteries, veins, and capillaries.
• Explain the occurrence of pulse and identify different pulse sites in the human body.
• Study cardiac output and factors affecting it, relating it to blood pressure.
• Measure systolic and diastolic blood pressure.
• Discuss factors that maintain systemic blood pressure.
• Explain the intrinsic and nervous mechanisms involved in the regulation of blood pressure.

Topics to Discuss:

• Physiology of the heart and blood vessels.
• Circulatory routes.
• The conduction system.
• Pulse and blood pressure.
• Pathophysiology of Cardiovascular (CV) Disorders.

Physiology of the Heart

• Heart is located in the mediastinum.
• Heart is enclosed by the pericardium.
• Pericardium has an outer fibrous layer and an inner serous layer.
• The heart wall has three layers:
  • Epicardium: outer layer
  • Myocardium: thick middle layer of cardiac muscle
  • Endocardium: inner lining
• The heart contains four chambers: two atria (upper) and two ventricles (lower).

Blood Flow Through The Heart

• Superior/inferior vena cava
• Right atrium
• Tricuspid valve
• Right ventricle
• Pulmonary trunk
• Pulmonary arteries
• Lungs
• Pulmonary vein
• Left atrium
• Bicuspid valve
• Left ventricle
• Aortic valve
• Aorta
• Organs and cells.

Blood Vessels

• Blood vessels have three layers:
  • Tunica interna (intima): Inner lining in direct contact with blood.
  • Tunica media: Middle layer of smooth muscle and elastic fibers; vessel regulation.
  • Tunica externa: Outer layer providing support and protection.

Blood Vessel Characteristics

• Arteries:
  • Carry blood away from the heart.
  • Have thick, muscular, and elastic walls.
  • Have a narrow lumen to maintain high pressure.
  • Have no valves, except the aorta and pulmonary artery, which have semilunar valves.
• Veins:
  • Carry blood toward the heart.
  • Have thin walls with less muscle and elasticity.
  • Have a wider lumen to accommodate slow-moving blood.
  • Have valves to prevent backflow of blood due to low pressure.
• Capillaries:
  • Allow exchange of gases, nutrients, and wastes between blood and tissues.
  • Have a single layer of endothelial cells (tunica intima) for rapid exchange of substances.
  • Have an extremely small lumen, just wide enough for a single red blood cell to pass through.
  • Have no valves.

Circulatory Routes

• Pulmonary circulation
• Systemic circulation
• Coronary circulation
• Hepatic portal circulation
• Fetal circulation

Conduction System of the Heart

• Inherent and rhythmical electrical activity triggers its lifelong beat.
• Autorhythmic fibers in the SA node would initiate an action potential about every 0.6 second, or 100 times per minute.
• Action potential initiated by the SA node travels along the conduction system and spreads out to excite contractile fibers.

The Action Potential

• Rapid depolarization occurs due to Na+ inflow, then voltage-gated fast Na+ channels open.
• A plateau (maintained depolarization) occurs due to Ca2+ inflow when voltage-gated slow Ca2+ channels open and K+ outflow when some K+ channels open.
• Repolarization occurs due to closure of Ca2+ channels and K+ outflow when additional voltage-gated K+ channels open.

Pulse and Blood Pressure

• Pulse: Rhythmic artery expansion and recoil due to pressure waves of blood ejected from the heart during systole.
  • Normal pulse is 60-100 beats per minute (bpm).
  • Tachycardia is a fast pulse.
  • Bradycardia is a slow pulse.
• Blood Pressure: Force exerted by circulating blood against arterial walls.
  • Systolic pressure: pressure in arteries when the heart pumps blood.
  • Diastolic Pressure: pressure when the heart relaxes between beats.
  • Normal BP is less than 120/80 mmHg.
  • BP is determined by CO, blood volume, and vascular resistance.
• Blood Pressure (BP) = Cardiac Output (CO) x Vascular Resistance (VR)
• Cardiac Output: Volume of blood pumped out by the ventricle per minute
• Cardiac Output = Heart Rate (HR) x Stroke Volume (SV)
• Heart Rate: Beats per minute.
• Stroke Volume: Volume of blood pumped out by the ventricles per contraction.
• Mean Arterial Pressure (MAP) = Diastolic Blood Pressure + 1/3(Systolic BP - Diastolic BP)
• Vascular Resistance: Resistance to blood flow due to friction between blood and blood vessel walls.

Control of Blood Pressure

• Neural Control (Autonomic Nervous System):
  • Baroreceptor Reflex:
    • Pressure sensors are found in the carotid sinuses and aortic arch.
    • It detects pressure changes.
  • Chemoreceptor Reflex:
    • Chemical sensors are also in carotid and aortic bodies.
    • It detects changes in oxygen (O2), carbon dioxide (CO2), and pH levels.
• Hormonal Control (Endocrine System):
  • Renin-angiotensin-aldosterone system (RAAS).
  • Epinephrine and norepinephrine.
  • Antidiuretic hormone (ADH).
  • Atrial natriuretic peptide (ANP).
  • Angiotensinogen is a hormone produced by the liver.
• Triggers of Renin Release:
  • Beta-1 stimulation
  • Renal hypoperfusion
  • Renal hypotension

Interesting Facts

• Cancer cells "hijack" the body's angiogenesis process, to create new nutrient supplying blood vessels.
• "Stayin' Alive" by the Bee Gees (100-120 bpm) matches the ideal rate for chest compressions during CPR.
• First blood pressure measurement (1733) was done on a horse.
• IV drugs act in seconds/minutes, IA route delivers drugs directly to an organ.
• Systolic BP increases more than diastolic BP during exercise.

Heart and BV Disorders - Hypertension

• HIGH BLOOD PRESSURE, a condition in which the blood vessels have persistently raised pressure (WHO).
• Untreated hypertension damages blood vessels, accelerates atherosclerosis, and produces left ventricular hypertrophy.
• Abnormalities contribute to the development of IHD, stroke, heart failure, renal failure, and death.

Categories of Blood Pressure

• Normal: Less than 120/80 mmHg.
• Elevated: 120-129/Less than 80 mmHg.
• Hypertension Stage 1: 130-139/80-89 mmHg.
• Hypertension Stage 2: 140+/90+ mmHg.
• Hypertensive Crisis: Higher than 180/Higher than 120 mmHg.

Hypertension - Primary

• Primary (Essential) Hypertension:
  • A high BP with no identifiable cause
  • Develops gradually. Linked to lifestyle, genetics, and aging.
  • Risk factors: age, family history, high salt diet, obesity, smoking, stress, and inactivity.
  • Often asymptomatic ("silent killer"), mild headaches or dizziness.
• Secondary Hypertension:
  • High blood pressure due to an underlying medical condition.
  • Develops suddenly and severely.
  • Specific medical conditions (kidney disease, hormonal imbalances) or certain medications.
  • Vision problems, chest pain, shortness of breath, severe headaches.

Postural Hypotension

• AKA Orthostatic Hypotension, causes a sudden drop in BP when standing up; can lead to dizziness or fainting.
• Caused by;
  • Antihypertensives (beta-blockers, ACE inhibitors).
  • Diuretics (reduce blood volume).
  • Antidepressants (tricyclics, SSRIs).
  • Vasodilators (e.g., nitrates).

Ischemic Heart Disease

• AKA Coronary Artery Disease (CAD), arteries become narrowed, reducing blood flow to the myocardium resulting in:
  • ischemia
  • angina
  • myocardial infarction
• Angina: Results in oxygen consumption.
• Treatment:
  • Antiplatelets (Aspirin, Clopidogrel/Plavix), Prevents clot formation
  • Anticoagulants (Heparin, Warfarin), Prevents new clots from forming
  • Lower Cholesterol and reduce plaque buildup.
  • Beta-Blockers (Metoprolol, Atenolol), Reduce heart rate and oxygen demand
  • ACE Inhibitors( Lisinopril, Ramipril), Lower blood pressure, prevent heart remodeling
  • Statins (Atorvastatin, Rosuvastatin),
  • Nitrates(Nitroglycerin), dilate blood vessels and reduce chest pain
  • Diuretics(Furosemide, Hydrochlorothiazide), reduce overload/BP

Angina Pectoris

• Angina Pectoris characterized by:
  • Paroxysmal chest pain is beneath the sternum.
  • Pain radiates down the left arm/and/or shoulder.
  • Pain radiates/originates in the neck or upper back.
  • Decreased Coronary Blood Flow
• Vasospasm results in constricted long term flow
• Increased Oxygen Consumption
  • ↑ Heart Rate
  • ↑ Contractility
  • ↑ Afterload
  • ↑ Preload

Angina Pectoris Treatment Strategies

• Stable Angina
  • Chest pain occurs predictably during physical exertion/stress.
  • Relieves with rest.
  • Stress, cold weather, heavy meals.
  • Partial blockage due to atherosclerosis reduces blood supply during activity.
• Unstable Angina
  • Occurs at rest, unpredictably.
  • Lasts longer than stable angina.
  • Occurs anytime, even at rest.
  • Severe narrowing or rupture of a plaque leads to partial clot formation.
• Variant (Prinzmetal's Angina)
  • It is a rare type caused by spasms with a temporary reduced blood flow.
  • Sudden spasm of coronary arteries.
  • Healthy or young patients.
  • Triggered by Cold exposure, smoking, stress, or drugs (cocaine).

Arrhythmia

• Irregular heartbeat caused by disruptions in the heart's electrical system
• The heart can beat too fast, too slow or irregularly
• Disrupted Signal Generation:
• The SA node misfires.
• Other parts of the heart take over as pacemaker.
• Abnormal Signal Conduction:
  • Electrical signals get blocked or delayed causing skips/rapid, uncoordinated beats.
• Types of Aarrythmia:
  • Tachycardia
  • Bradycardia
  • Atrial Fibrillation
  • Supraventricular Tachycardia (SVT)
  • Ventricular Tachycardia Bradycardia- Sick Sinus Syndrome, Heart Block Fibrillation- heart flutter Extrasystoles- -Premature Atrial/Ventricular Contractions (PACs, PVCs)

Arrhythmia - Classes

• Sodium Channel Blockers- Quinidine, Lidocaine, Flecainide, treat Atrial & Ventricular arrhythmias
• Beta-Blockers-Metoprolol, Atenolol, Esmolo, treat SVT, AFib, Post-MI protection
• Potassium Channel Blockers- Amiodarone, Sotalol, Dofetilide, treat AFib, Ventricular tachycardia
• Calcium Channel Blockers-Verapamil, Diltiazem, treat SVT, AFib rate control

Heart Valve Disorders

Stenosis: Valve becomes stiff/narrowed, restricting blood flow. Insufficiency: Valve does not close properly allowing blood to leak backward.

Shock

• A life-threatening condition, where the body does not receive enough oxygen
• Can lead to organ failure, death.
• Types:
  • Hypovolemic Shock:
    • Severe fluid/blood loss
    • Reduces circulation volume.
    • Most common type by hemorrhage, dehydration, burns.
  • Cardiogenic Shock:
    • Heart failure, less ability to pump blood
    • Common by heart attack (MI), arrhythmias, or cardiomyopathy.
  • Distributive Shock:
    • Widespread vasodilation, causes blood pooling, low BP
    • Includes septic/ anaphylaactic/neurogenic shock
  • Obstructive Shock:
    • Blockage of blood flow
    • caused by pulmonary embolism, cardiac tamponade, tension pneumothorax