Untitled Flashcards Set

1. Heart Anatomy – Major Structures

• Pericardium: Fibrous, double-layer serous membrane surrounding the heart; secretes fluid to reduce friction.

• Myocardium: Heart muscle (cardiac muscle).

• Atria: Receiving chambers (Left and Right).

• Ventricles: Pumping chambers (Left and Right).

Key Blood Vessels:

• Vena Cava: Carries low O₂ blood to the right atrium.

• Pulmonary Trunk: Carries low O₂ blood to the lungs, splits into right and left pulmonary arteries.

• Aorta: Carries high O₂ blood to the body from the left ventricle.

• Pulmonary Veins: Carry high O₂ blood from the lungs to the left atrium.

2. Electrical Conduction System (Important)

• SA Node (Sinoatrial Node): The pacemaker of the heart; sets the rhythm of the heartbeat (~100 bpm).

  • Spontaneous depolarization: Caused by leaky sarcolemma of cells in the SA node. Na+ leaks into the cell, reaching threshold without external neural input.

• AV Node (Atrioventricular Node): Slows the electrical signal, allowing atria to fully contract.

• AV Bundle (Bundle of His): Transmits signal from atria to ventricles.

• Left and Right Bundle Branches: Carry the action potential down the interventricular septum to the apex.

• Purkinje Fibers: Spread the action potential throughout the ventricles.

3. ECG Waves and What They Represent

• P Wave: Atrial depolarization (atria contracting).

• QRS Complex: Ventricular depolarization (ventricles contracting).

• T Wave: Ventricular repolarization (ventricles relaxing).

4. Cardiac Cycle and Stroke Volume

• Systole: Contraction phase (blood is pumped out).

• Diastole: Relaxation phase (heart fills with blood).

Key Volumes:

• EDV (End Diastolic Volume): Volume of blood in the heart after relaxation and filling.

• ESV (End Systolic Volume): Volume of blood left in the heart after contraction and ejection.

Stroke Volume (SV): Volume of blood ejected from the ventricles per heartbeat.

5. Cardiac Reserve

• Cardiac Reserve: The difference between max cardiac output (CO) during exercise and resting CO.

6. Regulation of Heart Rate (Important)

• Sympathetic Nervous System: Increases heart rate and contractility (e.g., during stress).

  • Norepinephrine: Increases heart rate at the SA node and AV node, increases contractility.

• Parasympathetic Nervous System: Slows heart rate (resting state).

  • Acetylcholine: Decreases heart rate but has no effect on contractility.

7. Factors Affecting Heart Rate (Important)

• Neural:

  • Proprioceptors (detect movement), Chemoreceptors (detect CO₂, O₂ levels), Baroreceptors (detect blood pressure) send info to the Cardiovascular Center in the medulla oblongata.

• Hormonal:

  • Epinephrine and Norepinephrine (increase HR and contractility).

  • Thyroid Hormones (increase HR and contractility).

• Temperature: Higher body temperature = higher HR.

Practice Questions:

1. What’s the difference between systole and diastole?

   • Systole = Contraction, Diastole = Relaxation.

2. Where does the SA node send the electrical impulse next?

   • To the AV node.

3. What’s the primary fuel used by cardiac muscle cells during rest?

   • Fatty acids.

4. Which valve is found between the left atrium and left ventricle?

   • The bicuspid (mitral) valve.

5. What does the T wave on an ECG represent?

   • Ventricular repolarization (ventricles relaxing).

Quick Review:

• Know the conduction pathway – from SA node to Purkinje fibers.

• Memorize the key ECG waves and what they represent.

• Understand the cardiac cycle, especially the relationship between EDV, ESV, and stroke volume.

• Regulation of heart rate and how sympathetic and parasympathetic systems affect it.