BIO212 Exam 2 Review: The Heart, Respiratory System, and Vital Signs

The Heart and Cardiac Circulation

Blood Gas Composition

The heart pumps blood with varying oxygen and carbon dioxide content depending on the circuit:

• Oxygenated Blood: Found in the left atrium, left ventricle, and systemic arteries. It is rich in O2 and low in CO2.

• Deoxygenated Blood: Found in the right atrium, right ventricle, and pulmonary arteries. It is low in O2 and high in CO2.

Blood Vessels and Circulation Pathways

• Arteries: Carry blood away from the heart. Systemic arteries carry oxygenated blood; pulmonary arteries carry deoxygenated blood to the lungs.

• Veins: Carry blood toward the heart. Systemic veins carry deoxygenated blood; pulmonary veins carry oxygenated blood from the lungs.

Heart Anatomy

• Directional Orientation: The heart is located in the mediastinum (central thoracic cavity), with the base superior and the apex inferior and leftward. Ventral refers to the front, dorsal to the back.

• Chambers: Right atrium, right ventricle, left atrium, left ventricle.

• Valves:

  • Atrioventricular (AV) Valves: Tricuspid (right), Bicuspid/Mitral (left). Prevent backflow into atria.

  • Semi-lunar Valves: Pulmonary (right ventricle to pulmonary trunk), Aortic (left ventricle to aorta).

  • AV Valve Components: Cusps (flaps), chordae tendineae (tendinous cords), papillary muscles (anchor chordae).

• Myocardial Features: Thicker myocardium in ventricles (especially left), interventricular septum separates ventricles.

Structure Identification

• External and internal heart features (as seen in diagrams and preserved specimens):

  • Chambers, AV and semi-lunar valves, aorta, pulmonary trunk, superior vena cava.

Cardiac Circulation

• Linear Pathway: Right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary trunk/arteries → lungs → pulmonary veins → left atrium → bicuspid valve → left ventricle → aortic valve → aorta → body.

• Non-linear Pathway: Focuses on chamber-to-chamber flow, not including vessels.

Cardiac Conduction System

The heart's electrical system coordinates contraction:

• SA Node (Sinoatrial): Pacemaker; initiates impulse.

• AV Node (Atrioventricular): Delays impulse, allowing atrial contraction.

• Bundle of His: Conducts impulse from AV node to ventricles.

• Bundle Branches: Carry impulse through interventricular septum.

• Purkinje Fibers: Distribute impulse through ventricular myocardium.

Conduction Pathway: SA node → atria → AV node → Bundle of His → bundle branches → Purkinje fibers → ventricles.

The Respiratory System

System Function

• Pulmonary Ventilation: Movement of air in and out of lungs (breathing).

• Respiration:

  • External Respiration: Gas exchange between alveoli and blood.

  • Internal Respiration: Gas exchange between blood and tissues.

Anatomy of the Respiratory Tract

• Upper Respiratory Tract: Nose, nasal cavity, pharynx, larynx.

• Lower Respiratory Tract: Trachea, bronchi, bronchioles, alveoli, lungs.

• Conducting Zone: Passages that conduct air (nose to terminal bronchioles).

• Respiratory Zone: Sites of gas exchange (respiratory bronchioles, alveolar ducts, alveoli).

Key Structures and Functions

• Nose/Nares/Nasal Cavity: Filters, warms, humidifies air.

• Pharynx: Passage for air and food.

• Larynx (Voice Box): Produces sound; epiglottis prevents food entry; vocal folds vibrate for sound.

• Trachea: Windpipe; conducts air to bronchi.

• Bronchial Tree:

  • Primary (1o) Bronchi: Enter lungs.

  • Secondary (2o) Bronchi: Supply lung lobes.

  • Tertiary (3o) Bronchi: Supply bronchopulmonary segments.

  • Bronchioles: Terminal (end of conducting zone), respiratory (begin gas exchange).

  • Alveolar Ducts/Sacs: Lead to clusters of alveoli.

  • Alveolar Cells: Type I (gas exchange), Type II (secrete surfactant).

  • Surfactant: Reduces surface tension, prevents alveolar collapse.

• Lungs: Right (3 lobes), left (2 lobes); base (inferior), apex (superior).

• Pleura: Parietal (lines cavity), visceral (covers lungs); pleural fluid reduces friction.

Pulmonary Ventilation and Spirometry

• Pulmonary Ventilation: Air movement between atmosphere and lungs.

• Spirometry: Measures lung volumes and capacities.

Respiratory Measurements

Measurement	Definition
Tidal Volume (TV)	Air moved in/out during normal breath
Expiratory Reserve Volume (ERV)	Extra air exhaled after normal exhalation
Inspiratory Capacity (IC)	Max air inhaled after normal exhalation
Inspiratory Reserve Volume (IRV)	Extra air inhaled after normal inspiration
Vital Capacity (VC)	Total air exhaled after maximal inhalation
Residual Volume (RV)	Air remaining after maximal exhalation

Neural Control of Ventilation

• O2 and CO2 levels detected by chemoreceptors.

• Negative feedback mechanisms adjust breathing rate for proper gas exchange.

Breathing Actions

• Eupnea: Normal, quiet breathing.

• Dyspnea: Difficult or labored breathing (seen in COPD, emphysema).

Vital Signs and Electrocardiography

Vital Signs

• Pulse: Indicates heart rate and rhythm; reflects cardiac output.

• Blood Pressure: Force of blood against vessel walls; indicates cardiovascular health.

• Respiration Rate: Number of breaths per minute; reflects respiratory function.

• PERRLA: Pupils Equal, Round, Reactive to Light and Accommodation (neurological assessment).

Electrocardiography (ECG/EKG)

• Electrical Events: Depolarization (contraction), repolarization (relaxation).

• Terminology:

  • Wave: Deflection from baseline (e.g., P wave, T wave).

  • Segment: Flat region between waves (e.g., P-Q segment, S-T segment).

  • Interval: Time between events (e.g., P-Q interval, Q-T interval).

• P Wave: Atrial depolarization.

• P-Q Interval: Time from atrial to ventricular depolarization.

• QRS Complex: Ventricular depolarization (and atrial repolarization).

• Q-T Interval: Start of ventricular depolarization to end of repolarization.

• P-Q Segment: Atrial contraction.

• S-T Segment: Ventricular contraction.

• T Wave: Ventricular repolarization.

Exercise Effects

• Increases heart rate and contraction strength to meet metabolic demands.

Cardiac Cycle and Conduction Correlation

• Electrical events (ECG) precede and trigger mechanical events (contraction/relaxation) in the cardiac cycle.

Example: The QRS complex on an ECG corresponds to ventricular depolarization, which triggers ventricular contraction and ejection of blood.

Additional info: For practical exams, be able to identify heart and respiratory structures on diagrams and specimens, and interpret basic ECG tracings and vital sign measurements.