EKG and Blood Pressure

Sinoatrial (SA) Node: Acts as the natural pacemaker of the heart, located in the right atrium.
- Generates electrical stimuli that initiate heartbeats.
Atrioventricular (AV) Node: Receives the electrical impulse from the SA node.
- Pauses the impulse for approximately 100 ms to allow the atria to contract and complete pumping blood.
Impulse Conduction:
- Travels from the SA node to the AV node via the intraatrial bundle, causing atrial depolarization and contraction.
- After the AV node, the impulse proceeds down the conduction pathway through the bundle of His into the ventricles.
- The bundle of His bifurcates into right and left bundle branches, which stimulate the right and left ventricles respectively via Purkinje fibers.

Initial Activity:
1. SA Node Activation: Starts the action potential, which sweeps through the atria.
2. Atria Contraction: Atria contract due to depolarization.
Delay at AV Node: Approximately 100 ms, facilitating complete atrial contraction before ventricular stimulation.
Ventricular Contraction:
1. Begins after the impulse reaches the bundle of His and travels through the ventricular muscles.
2. Involves initial impulse spreading to the contractile fibers of the ventricles.

Definition: A graphical representation that records the electrical events of the heart.
- Helpful for diagnosing heart conditions.
Normal ECG Components:
- P wave: Depolarization of the atria.
- QRS complex: Depolarization of the ventricles.
- T wave: Repolarization of the ventricles.
ECG Leads: Includes aVR, aVL, aVF, V1, V2, V3, V4, V5, V6.

Positive Deflection: Indicates electrical current traveling towards the lead.
Negative Deflection: Indicates electrical current traveling away from the lead.

Phases in a Cardiac Cycle:
- Atrial systole: Atria contracting to push blood into ventricles.
- Ventricular systole: Ventricles contracting to eject blood into arteries.
- Atrial diastole: Atria relaxing and filling with blood.
- Ventricular diastole: Ventricles relaxing and filling with blood.
Isoelectric Line: Represents periods of no electrical activity.

Heart Rate Formula:
$Heart<br>ate = \frac{300}{\text{number of large squares in one R-R interval}}$
- Example Calculation:
- Given an R-R interval spans 4 large squares:
  Heart
  ate = \frac{300}{4} = 75eats ext{ per minute}
Heart Rhythm:
- Regular: Consistent R-R intervals.
- Irregular: Variability in intervals, can be categorized into regularly irregular and irregularly irregular (as seen in atrial fibrillation).

ST Segment Depression: Can indicate conditions like acute pericarditis.
ST Segment Elevation/Depression: Primarily indicates myocardial ischemia or myocardial infarction.
Effects of Tachycardia: A shortened TP segment which may be difficult to observe clearly.

Key questions to assess:
- Is the heart rhythm regular?
- Are individual EKG elements normal?
- Can normal and abnormal beats occur alternately or irregularly?

Blood Pressure Definition: Typically refers to systemic arterial pressure measured in mm Hg, typically acquired using brachial or radial arteries.
- Represents the force exerted by circulating blood against the walls of blood vessels.
- Pulse equates to heart rate, indicating how many times the heart beats per minute.

Procedure:
1. Position palm up, locate the space between the wrist bone and tendon on thumb side.
2. Use the fingertips of the other hand to locate the radial pulse, applying adequate pressure to feel each beat.
3. Count the pulse for 15 or 30 seconds, then multiply to determine beats per minute.

Systolic Pressure: The pressure in arteries during ventricular contraction (systole).
Diastolic Pressure: The pressure in arteries during ventricular relaxation (diastole).

Sit quietly for 5 minutes before measurement.
Ensure cuff is correctly placed, aligned with the wrist crease, and fastened securely.
Arm positioning: Bend elbow so wrist is at heart level, still, and avoid talking during readings.

Technique:
1. Inflate cuff until blood flow in brachial artery is stopped.
2. Listen for sounds with a stethoscope (Korotkoff sounds) as the cuff pressure decreases:
- First sound indicates systolic pressure.
- No sounds indicate diastolic pressure.

Factors impacting blood pressure include:
- Heart Rate: Frequency of heartbeats.
- Stroke Volume: Volume of blood ejected from the heart with each beat.
- Peripheral Resistance: Resistance in blood vessels which can be affected by diameter, elasticity, viscosity, and total blood volume.

Standing Up:
- When standing quickly, blood pools in legs; baroreceptors detect the drop in head and neck blood pressure, prompting an increase in heart rate and vessel constriction to prevent dizziness.
Fear or Stress:
- Triggers rapid heart rate and elevated blood pressure; baroreceptors help to normalize these changes.

Involves:
- Skeletal muscle signaling to the brainstem to adjust autonomic function, leading to heart rate increase and vasoconstriction in non-essential regions.
- Induces vasodilation in active muscles, countering peripheral resistance decrease while maintaining blood pressure and increasing cardiac output.

Suggestion: Design an experiment to observe changes in mean arterial pressure under various activities or stress conditions.