Untitled Flashcards Set

1. Sympathetic vs. Parasympathetic Systems and the Heart

System

Effects on the Heart

Sympathetic (Fight or Flight)

- Increases heart rate (HR) 

- Increases stroke volume (SV) 

- Increases cardiac output (CO) 

- Increases blood pressure (BP) 

- Induces vasoconstriction

Parasympathetic (Rest & Digest)

- Decreases HR 

- Decreases CO 

- Decreases BP 

- No effect on myocardial contractility

  • Control Center: The medulla oblongata regulates autonomic input.

  • Neurotransmitters:

    • Sympathetic: Norepinephrine (↑ HR, contractility).

    • Parasympathetic: Acetylcholine via the vagus nerve (↓ HR).

2. EKG Basics: What Does Each Wave Mean?

Wave

Meaning

P-Wave

Atrial depolarization (atria contracting).

QRS Complex

Ventricular depolarization (ventricles contracting); also masks atrial repolarization.

T-Wave

Ventricular repolarization (ventricles relaxing).

P-Q Interval

Time between atrial depolarization and ventricular depolarization (signal delay at AV node).

3. Path of Depolarization Through the Heart ('Wiring')

  1. Sinoatrial (SA) Node – Pacemaker of the heart, initiates the signal.

  2. Internodal Pathways – Carries impulses through atria.

  3. Atrioventricular (AV) Node – Delays impulse for ventricles to fill.

  4. AV Bundle (Bundle of His) – Conducts impulse from AV node to ventricles.

  5. Right & Left Bundle Branches – Carries signal down the septum.

  6. Purkinje Fibers – Distributes impulse to ventricular muscle fibers.

4. Coronary Arteries

  • Function: Supply oxygenated blood to the myocardium.

  • Major Coronary Arteries:

    • Right Coronary Artery (RCA) – Supplies right atrium, right ventricle.

    • Left Coronary Artery (LCA) splits into:

      • Left Anterior Descending (LAD) – Supplies anterior ventricles.

      • Circumflex Artery – Supplies left atrium and lateral left ventricle.

5. Valves and Associated Structures (What Makes Valves Open/Close?)

  • Heart Valves:

    • Atrioventricular (AV) Valves):

      • Tricuspid (RA → RV).

      • Bicuspid (Mitral) (LA → LV).

    • Semilunar Valves:

      • Pulmonary Valve (RV → Pulmonary Artery).

      • Aortic Valve (LV → Aorta).

  • What Controls Valve Opening/Closing?

    • Pressure differences! Valves open when pressure behind them is greater and close when pressure in front is greater.

    • Chordae Tendineae & Papillary Muscles prevent AV valves from inverting.

6. Layers of the Heart

Layer

Function

Epicardium

Outer layer, contains blood vessels.

Myocardium

Thick middle layer, muscle layer for contraction.

Endocardium

Smooth inner lining, reduces friction.

7. How the Cardiovascular System Regulates BP Irregularities

  • Short-Term Regulation:

    • Baroreceptors (Carotid & Aortic): Detect BP changes → Adjust HR.

    • Sympathetic activation → Vasoconstriction (↑ BP).

    • Parasympathetic activation → Vasodilation (↓ BP).

  • Long-Term Regulation:

    • Renin-Angiotensin-Aldosterone System (RAAS):

      • Renin → Angiotensin II (vasoconstriction) → Aldosterone (↑ Na⁺, H₂O retention → ↑ BP).

    • Antidiuretic Hormone (ADH): Increases water retention → ↑ BP.

8. Cardiac Output Formula

CO=HR×SVCO=HR×SV

  • Cardiac Output (CO) = Volume of blood pumped per minute.

  • Heart Rate (HR) = Beats per minute.

  • Stroke Volume (SV) = Blood pumped per beat.

9. Capillary Density and Importance

  • Capillary Density = Number of capillaries per unit tissue.

  • Higher density:

    • More oxygen and nutrient exchange.

    • Found in muscles, brain, heart.

  • Lower density:

    • Found in cartilage, tendons (less metabolic demand).

10. Movement of Blood Through the Venous System

  • Mechanisms Helping Blood Return to Heart:

    1. Skeletal Muscle Pump – Muscle contractions push blood upward.

    2. Respiratory Pump – Breathing creates pressure changes in the chest.

    3. Venous Valves – Prevent backflow.

    4. Sympathetic Stimulation – Vasoconstriction increases venous return.

11. Overall Control of the Heart’s Electrical Activity

  • Intrinsic Control (SA Node):

    • Heart generates its own rhythm (pacemaker potential).

  • Extrinsic Control:

    • Sympathetic: Increases HR & force.

    • Parasympathetic: Decreases HR via vagus nerve.

12. Ions Involved with Cardiac Action Potentials

Ion

Role in Cardiac Depolarization

Na⁺ (Sodium)

Influx causes rapid depolarization.

Ca²⁺ (Calcium)

Plateau phase maintains contraction.

K⁺ (Potassium)

Efflux leads to repolarization.

13. Movement of Molecules in a Capillary Bed (Pressures)

Type of Pressure

Definition

Hydrostatic Pressure

Pushes fluid out of capillaries (filtration).

Osmotic Pressure

Pulls fluid into capillaries (reabsorption).

Oncotic Pressure

Due to plasma proteins like albumin, maintains fluid balance.

  • Arterial End: Hydrostatic pressure > Oncotic pressure → Filtration (fluid leaves).

  • Venous End: Oncotic pressure > Hydrostatic pressure → Reabsorption (fluid enters).

14. How Frank-Starling Law Affects Cardiac Function

  • Definition: The more the heart stretches (venous return), the stronger the contraction.

  • Mechanism:

    • Increased preload (venous return) → Increased stretch.

    • Stronger contraction → Increased stroke volume (SV).

  • Why It Matters:

    • Maintains equal output between left and right sides of the heart.

    • Ensures that the heart pumps all the blood it receives.