Recording-2025-02-24T21:08:59.410Z

Sinoatrial (SA) Node

• SA node is located at the start of the right atrium.

• It acts as the heart's pacemaker, setting the rhythm (average ~70 beats per minute).

• Receives nerve impulses from the brain that regulate heart rate.

Atrioventricular (AV) Node

• AV node is situated near the tricuspid valve, responsible for relaying impulses from the SA node.

• Important in coordinating the timing of contractions between atria and ventricles.

Electrical Conduction Pathway

• SA node initiates the impulse leading to atrial contraction.

• Impulse travels to the AV node and then to the ventricles through Purkinje fibers, allowing for synchronized contraction of the ventricles.

• Purkinje fibers act as "wires" distributing electrical impulses to ensure all parts of the ventricles contract effectively.

Heart Rate Regulation

• Heart rate controlled by the autonomic nervous system (ANS).

• Two branches of the ANS:

  • Sympathetic: Activates during stress (fight-or-flight response).

  • Parasympathetic: Promotes relaxation and slows heart rate.

Abnormal Heart Conditions

• Tachycardia: Heart rate exceeding 100 beats per minute, can lead to health issues.

• Bradycardia: Heart rate below 40 beats per minute, may indicate inadequate blood flow.

Heart Sounds

• "Lub-Dub" sounds are generated by the closing of heart valves—atrioventricular valves during systole and semilunar valves during diastole.

Valvular Issues

• Heart Murmurs: Occur when valves do not close properly, often the mitral valve.

• Inefficiency in blood flow can result when valves leak, potentially requiring surgery.

Pacemakers

• Artificial pacemakers can be implanted when the SA node fails to maintain a regular rhythm.

• They deliver electrical signals to the heart, mimicking the function of a healthy SA node.

Electrocardiogram (EKG/ECG)

• Measures electrical activity of the heart.

• Key components include:

  • P wave: Atrial contraction

  • QRS complex: Ventricular contraction (larger due to greater muscle mass)

  • T wave: Ventricular recovery (diastole).

Heart Attack Indicator

• A myocardial infarction can be identified by a missing recovery wave in the EKG, indicating ventricles are not relaxing properly.

Physical Response During Exercise

• Increased heart rate leads to more frequent QRS complexes on an EKG and reduced recovery time between beats.