Week 5-2 Cardiac Cycle and Blood Pressure (1)

Course Overview

• Course Name: BIOL 103

• Credits: 5

• Week: 5

• Content Type: Anatomy & Physiology © McGraw Hill LLC

Course Outline

1. Anatomical Terminology (~2%)

   • Describe parts of the human body using anatomical terms.

2. Structure-Function Relationship (~60%)

   • Cardiac cycle

   • Blood pressure

3. Homeostatic Mechanisms (~10%)

   • Explain how the human body maintains homeostasis.

4. Microbiology and Body Defenses (~15%)

   • Discuss interactions with microbiology and how the body defends against infections.

5. Laboratory Activities (~15%)

   • Conduct hands-on laboratory sessions to complement theoretical knowledge.

Recap of Structural Components

• Structural parts of the cardiovascular system reviewed.

• Blood Flow: Through heart, lungs, and body tissues.

• Clinical Cases:

  • Atrial Septal Defect (hole in the heart) (Link to video)

  • Permanent Pacemaker Implant Surgery (Link to patient education video)

Heart Actions

• Constant Pumping: The heart continuously pumps blood.

• Key Phases:

  1. Systole: Contraction phase of heart chambers.

  2. Diastole: Relaxation phase of heart chambers.

• Cardiac Cycle:

  1. Atrial Systole: Atria contract; ventricles relax.

  2. Ventricular Systole: Ventricles contract; atria relax.

  3. Complete Relaxation: Brief pause before the cycle repeats.

Cardiac Muscle Cells

• Structure: Similar to skeletal muscle but arranged in branching networks.

• Intercalated Discs: Connect cardiac muscle cells to transmit impulses efficiently.

Cardiac Conduction System

• Definition: Initiates and transmits electrical impulses for each heartbeat.

• Major Components:

  1. Sinoatrial (SA) Node: Pacemaker of the heart, located in the right atrium.

  2. Atrioventricular (AV) Node: Delays impulses for proper chamber contraction.

  3. AV Bundle (Bundle of His): Conducts impulses into the interventricular septum.

  4. Bundle Branches: Left and right branches conduct impulses to ventricles.

  5. Purkinje Fibers: Distribute impulses through the ventricular walls.

Electrocardiogram (ECG)

• Definition: Records electrical changes during the cardiac cycle.

• Components:

  • P Wave: Atrial contraction.

  • QRS Complex: Ventricular contraction; atrial relaxation.

  • T Wave: Ventricular relaxation.

Heart Sounds

• Sounds: Produced by valve vibrations during closing.

• Descriptions:

  • Lubb: First heart sound during ventricular systole.

  • Dupp: Second heart sound during ventricular diastole.

  • Murmurs: Abnormal sounds due to valve damage.

Heart Rate and Cardiac Cycle Regulation

• Normal Adult Heart Rate: 70 to 75 bpm (60-100 bpm range).

• Factors Influencing Heart Rate:

  1. Blood pressure changes.

  2. Emotional shifts.

  3. Body temperature increases.

  4. Ion concentrations:

     • Hyperkalemia: Decreases heart rate.

     • Hypercalcemia: Increases heart action.

Autonomic Nervous System Influence

• Medulla Oblongata: Links cardiovascular and respiratory control.

• Neurotransmitters: Mediate communication between neurons affecting heart rate.

• Nervous System Divisions:

  • Sympathetic: "Fight or flight" response.

  • Parasympathetic: "Rest and digest" response.

Blood Vessels

• Types:

  • Arteries, Arterioles, Capillaries, Venules, Veins.

• Closed Circuit: Carries blood from the heart, delivers to cells, and returns.

Arteries and Arterioles

• Structure: Strong and elastic; three layers (tunica interna, media, externa).

• Function: Transport blood away from the heart.

• Regulation: Controlled by sympathetic impulses; vasoconstriction increases blood pressure.

Capillary Exchange

• Function: Site of nutrient, gas, and waste exchange.

• Mechanisms: Diffusion, filtration, and osmosis.

• Hydrostatic and Osmotic Pressures: Regulate fluid movement.

Venules and Veins

• Structure: Thinner walls than arteries, larger lumen, valves to prevent backflow.

• Function: Return blood to the heart.

Blood Pressure Overview

• Definition: Force exerted by blood on vessel walls.

• Types:

  • Systolic Pressure: Max pressure during heart contraction.

  • Diastolic Pressure: Min pressure during heart relaxation.

• Normal Reading: 120/80 mmHg.

Factors Influencing Blood Pressure

• Key Factors:

  1. Cardiac Output

  2. Blood Volume

  3. Peripheral Resistance

  4. Blood Viscosity

• Cardiac Output Calculation: CO = Stroke Volume x Heart Rate.

Blood Volume and Effects

• Blood Volume: Approximately 5 L in an adult; fluctuations impact BP directly.

Peripheral Resistance & Viscosity

• Peripheral Resistance: Friction forces in vessels; influences BP.

• Blood Viscosity: Higher viscosity increases resistance and pressure.

Control of Blood Pressure

• Mechanisms:

  1. Baroreceptor reflexes.

  2. Cardiac center of the medulla.

  3. Various other physiological factors (e.g., emotion, temperature).11