quiz cardiovascular physiology I

Cardiovascular System (Part I) - Study Notes

• Learning Objectives:
  • Describe the composition of blood
  • Describe the basic functions of the cardiovascular system
  • Explain cardiac circulation
  • Describe the electrical conducting system of the heart
  • Explain the role of calcium in cardiac muscle contraction and relate to the action potential graph
  • Explain the ECG
  • Describe the cardiac cycle, factors influencing cardiac output, stroke volume, and heart rate

Blood - Remarkable Fluid

• Composition:

  • Plasma (55% by volume): Primarily water (91%), proteins (7%), other solutes (2%)
  • Formed elements (45% by volume):
    • Red blood cells (erythrocytes): 4.2-6.2 million/mm³
    • White blood cells (leukocytes): 5-9 thousand/mm³ (Granulocytes: Neutrophils, Eosinophils, Basophils; Agranulocytes: Monocytes, Lymphocytes)
    • Platelets (thrombocytes): 250-400 thousand/mm³

• Key components and percentages by weight:

  • Albumins: 58%
  • Globulins: 38%
  • Fibrinogen: 4%
  • Ions: Small percentage
  • Nutrients
  • Waste products
  • Regulatory substances
  • Gases

Components of Blood

• Connective tissue
• Red blood cells (erythrocytes): Oxygen transport
• White blood cells (leukocytes): Immune function (different types with varying functions)
• Platelets (thrombocytes): Essential for blood clotting
• Plasma: Fluid component, 55% of blood

Blood Plasma

• Composition: Primarily water, and a mixture of proteins (albumin, globulins, fibrinogen), nutrients, amino acids, glucose, nucleotides, lipids, gases, electrolytes, and waste products

Functions of Blood

• Transportation: Carries oxygen, nutrients, hormones, and waste products
• Regulation: Maintains homeostasis (pH, temperature, fluid balance)
• Protection: Fights infection, prevents blood loss

Red Blood Cells

• Shape: Biconcave discs for efficient gas exchange
• Function: Transport oxygen throughout the body
• Hemoglobin: Iron-containing pigment; carries oxygen (bright red when oxygenated, darker red when deoxygenated)

White Blood Cells

• Granulocytes:
  • Neutrophils (55%): Phagocytosis (destroy bacteria and toxins)
  • Eosinophils (3%): Combat parasites and regulate allergic reactions
  • Basophils (1%): Release histamine (inflammation)
• Agranulocytes:
  • Monocytes (8%): Develop into macrophages (phagocytosis)
  • Lymphocytes (33%): Diverse roles in adaptive immunity

Blood Platelets

• Function: Crucial in blood clotting (hemostasis)
• Number: 130,000-360,000 per cubic millimeter of blood

Controlling Bleeding

• Hemostasis: The stoppage of bleeding
• Processes:
  • Blood vessel spasm
  • Formation of platelet plug
  • Blood coagulation (complex cascade of clotting factors)

Blood Vessels

• Arteries and Arterioles:
  • Carry blood away from the heart under high pressure
  • Strongest vessels with thick walls
• Veins and Venules:
  • Carry blood towards the heart under low pressure
  • Have valves to prevent backflow
• Capillaries:
  • Connect arterioles to venules
  • Thin walls for efficient diffusion of oxygen and nutrients

The Lymphatic System

• Function:
  • Collects interstitial fluid (lymph)
  • Returns lymph to the bloodstream
  • Transports lipids from the digestive system
  • Defends against disease-causing agents (pathogens)

Lymph Fluid

• Origin: Tissue fluid that enters lymphatic capillaries
• Structure: Contains valves to prevent backflow

Circulation of Blood

• Function: Transport oxygen and nutrients to all parts of the body, removing waste products
• Systemic circuit: Transports blood to and from the body
• Pulmonary circuit: Transports blood to and from the lungs for gas exchange

Systemic and Pulmonary Circulation

• Systemic circulation:
  • Blood flows from the left ventricle, through arteries, to capillaries where gas and nutrient exchange occurs, to the veins which bring the deoxygenated blood back to the right atrium
• Pulmonary circulation:
  • Blood flows from the right ventricle, to the lungs where gas exchange occurs, and returns to the left atrium as oxygenated blood.

Coronary Circulation

• Coronary arteries: Branch from the aorta, providing oxygenated blood to the heart muscle
• Anastomoses: Provide alternative routes for blood flow if major arteries are blocked
• Coronary veins: Collect deoxygenated blood and drain into the coronary sinus, which flows into the right atrium

Heart: A Special Muscle

• Cardiac muscle characteristics:
  • Shorter and less circular than skeletal muscle
  • Branched fibers with intercalated discs
  • Single, centrally located nuclei
  • Contains many mitochondria (high energy demand)

Autorhythmic Fibers

• Specialized cardiac muscle fibers that generate and conduct electrical signals
• Self-excitable (initiate their own action potentials)
  • Generate action potentials repeatedly for heart contractions
• Form the heart's conduction system (pathway of electrical signals)

Cardiac Conduction System

• Components:
  • Sinoatrial (SA) node
  • Atrioventricular (AV) node
  • Bundle of His
  • Right and left bundle branches
  • Purkinje fibers

Action Potentials and Contraction

• Depolarization: Inward movement of ions, causing contraction
• Plateau: Prolonged period of depolarization (maintained by calcium channels)
• Repolarization: Return to resting membrane potential

Electrocardiogram (ECG)

• Composite recording of action potentials from all heart muscle fibers
• Waveforms (P, QRS, T) reflect specific electrical events in the heart
  • P-wave: atrial depolarization
  • QRS complex: ventricular depolarization
  • T-wave: ventricular repolarization

Cardiac Cycle

• The sequence of events in one complete heartbeat
• Phases:
  • Atrial systole (contraction of atria)
  • Ventricular systole (contraction of ventricles)
  • Atrial and ventricular diastole (relaxation of all chambers)

Heart Sounds

• Auscultation: Listening to heart sounds
• "Lub" sound: Closure of atrioventricular valves
• "Dup" sound: Closure of semilunar valves

Cardiac Output (CO)

• Definition: Volume of blood ejected by the left ventricle per minute
• Calculation: CO = stroke volume (SV) × heart rate (HR)

Stroke Volume (SV)

• Amount of blood ejected from the ventricles with each contraction

• Factors regulating SV:

  • Preload (degree of stretching)
  • Contractility (strength of contraction)
  • Afterload (pressure against which ventricles pump)

• Preload: Determined by venous return (blood returning to the heart)

• Contractility: Influenced by hormones (epinephrine, norepinephrine) and ions

• Afterload: Determined by arterial pressure

Regulation of Heartbeat

• Autonomic nervous system (ANS):
  • Sympathetic: Increases heart rate and force of contraction
  • Parasympathetic: Decreases heart rate
• Hormonal factors: Epinephrine and thyroid hormones increase heart rate and contractility
• Ionic factors: An imbalance of ions can compromise the effectiveness of pumping blood

Exercise and the Heart

• Increased heart rate during exercise is a physiological response enabling more efficient oxygen and nutrient delivery to tissues and removal of metabolic wastes.