Patho Ch 17

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Patho Ch 17
2014-10-30 15:38:28
Exam #4 Control of Cardiovascular Function
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  1. -------Body
           ↙        ↖
     Right           left 
    heart            heart
          ↘          ↗
    simplified path of blood flow
  2. Functions of Circulatory System

    •Delivers vital oxygen and nutrients to cells

    •Removes waste products

    •Transports hormones
  3. Two Parts of Circulatory System

    What does the systemic circulatory do?
    What side of the heart does it serve and what does it include?

    What does the pulmonary circulatory do?
    What side of the heart does it serve?

    • –Carries blood throughout the body to meet the body’s needs and remove waste products
    • –Served by the LEFT heart
    • –Includes arteries, veins, and capillaries
    • –Works with the lymphatic system


    • –Carries blood to and from the lungs for gas exchange
    • –Served by the RIGHT heart
  4. Blood Flow Through the Heart
    •Blood from the systemic circulation enters from the superior vena cava and the inferior vena cava

    •Blood empties directly into the right atrium

    •From the right atrium, blood travels through the tricuspid valve to the right ventricle

    •The right ventricle pumps blood through the pulmonic valve to the pulmonary arteries

    •The pulmonary arteries carries blood to the lungs for gas exchange  

    •Blood from the pulmonary circulation enters from the pulmonary veins

    • •Blood empties directly into the left
    • atrium

    •Blood leaves the left atrium through the mitral valve to the left ventricle

    •The left ventricle then pumps blood through the aortic valve to the aorta

    •From the aorta the blood is carried the rest of the body
  5. Distensibility and Compliance

    What is distensibility? What is most distensible?

    What is compliance?
    •Distensibility: ability of blood vessel to be stretched and accommodate an increased volume of blood.

    Veins are most distensible.

    •Compliance: total quantity of blood that can be stored in a given portion of the circulation for each millimeter mercury rise in pressure.

    •Compliance of a vein is approximately 24 times that of corresponding artery (8 X distensible; 3 X volume).
  6. Functional Anatomy of the Heart

    What are the four major parts of the heart?

    •Pericardium (outer sack around heart)

    •Myocardium (muscle tissue of the heart)

    •Endocardium (inner layer of the heart)

    •Heart Valves and Fibrous Skeleton (high density of a single structure of connective tissue that forms and anchors the valves and influences the force exerted through them)
  7. Conduction System

    What does the conduction system do?
    What are the three types of conduction systems and what are their roles to the cells?
    Organizes electrical impulses in the cardiac cells


    –Excitability – ability of the cells to respond to electrical impulses

    –Conductivity – ability cells to conduct electrical impulses

    –Automaticity – ability to generate an impulse to contract with no external nerve stimulus
  8. Conduction Pathway

    Where does the impulse originate and where is it located in the heart?
    When is there an atrial contraction?

    Where does it go after and where in the heart?
    At what point is there a delay and for what reason?

    Where do the impulses go after? What do they cause?
    •Impulses originate in the sinoatrial (SA) node high in the right atrium at a rate of 60-100 bpm

    •Impulses travel through the right and left atrium, causing atrial contraction

    •Impulses then travels to the atrioventricular (AV) node, in the right atrium adjacent to the septum

    –The AV node can initiate impulses if the SA node fails 40–60 bpm

    •Impulses are delayed in the AV node to allow for complete ventricular filling

    •Impulses then move rapidly through the bundle of His, right and left bundle branches, and Purkinje network of fibers, causing ventricular contraction

    –The ventricles can initiate impulses if the SA and AV nodes fail 20-40 bpm, which may be inadequate
  9. Electrical Activity

    Depolarization and Repolarization

    Describe what can be read by an EKG

    What is sinus rhythm? Dysrhythmias? What can they result from?

    • –Increase in electrical charge
    • –Accomplished through cellular ion exchange
    • –Generates cardiac contraction


    • –Cellular recovery
    • –Ions returning to the cell membrane in preparation for depolarization

    •Can be read by an electrocardiogram

    • P wave – atria depolarization
    • QRS complex – ventricular depolarization
    • T wave – ventricular repolarization

    •Sinus rhythm

    –Electrical activity when impulses originate in the SA node


    • Abnormal electrical activity
    • –Can result from issues such as myocardial infarctions and electrolyte imbalances
  10. Conduction Control

    What are the different electrolytes used as signals?

    What does the medulla monitor?

    What are the different effects that influence  conduction?
    •Electrolyte signals

    –Sodium, potassium, and calcium

    •Medulla monitoring

    –Autonomic nervous system, endocrine system, chemoreceptors, and baroreceptors


    –Chronotropic – rate of electrical conduction

    –Dromotropic – rate of contraction

    –Inotropic – strength of contraction
  11. The Basics of Cell Firing

    What charge do cells begin with? What is that called?
    What acts as a stimulus and what does it do?

    What happens during depolarization?
    Action potential

    How does the cell become negative again?
    • •Cells begin with a negative charge: resting membrane potential
    • •Stimulus causes some Na+ channels to open
    • •Na+ diffuses in, making the cell more positive


    • •At threshold potential, more Na+ channels open
    • •Na+ rushes in, making the cell very positive: depolarization
    • •Action potential: the cell responds (e.g., by contracting)


    • •K+ channels open
    • •K+ diffuses out, making the cell negative again: repolarization
    • •Na+/K+ ATPase removes the Na+ from the cell and pumps the K+ back in
  12. Cardiac Muscle

    3 types of ion channels

    What are the five phases
    • •Has 3 types of membrane ion channels that
    • contribute to voltage change.

    • 1) Fast sodium channels; 2) Slow calcium-sodium channels; 3) Potassium channels


    Phase 0 - the upstroke or rapid depolarization (1)

    Phase 1 - early repolarization

    Phase 2 - the plateau (2)

    Phase 3 - rapid repolarization (3)

    Phase 4 - the resting membrane potential
  13. Cardiac Action Potentials

    What produces a slow response?

    What produces a fast response?
    Two main types:

    •Slow response: initiated by slow calcium channels; found in SA node (natural pacemaker) and conduction fibers of AV node.

    • •Fast response: opening of fast
    • sodium channels;  occurs in normal myocardial cells of atriaventricles, and Purkinje fibers; do not normally initiate cardiac action potentials
  14. Cardiac Cell Firing

    What charge does the cells being with and what is this called?
    What makes the cells more positive?

    What channels open at threshold potential? What charge does this make the cells? What is it called?

    How does the cells become negative again? What is still able to enter into the cell? 
    What happens during and after the plateau?
    • •Cells begin with a negative charge: resting membrane potential
    • •Calcium leak lets Ca2+ diffuse in, making the cell more positive


    • •At threshold potential, more Na+ channels open
    • •Na+ rushes in, making the cell very positive: depolarization
    • •Action potential: the cell responds (e.g., by contracting)


    • •K+ channels open
    • •K+ diffuses out, making the cell negative again, but Ca2+ channels are still allowing Ca2+ to enter
    • •The cell remains positive: plateau
    • •During plateau, the muscle contracts strongly
    • •Then the Ca2+ channels shut and it repolarizes
  15. Cardiac Cycle—Diastole
    •Ventricles relaxed

    •Blood entering atria

    •Blood flows through AV valves into ventricles

    •Semilunar valves are closed
  16. Cardiac Cycle—Systole
    •Ventricles contract

    •Blood pushes against AV valves and they shut

    •Blood pushes through semilunar valves into aorta and pulmonary trunk
  17. Pressure, Resistance, Flow

    What does flow depend on?
    •Fluid flow through a vessel depends on:

    • Pressure difference b/w ends of the
    • vessel

    • ºPressure pushes the fluid through
    • ºPressure keeps the vessel from collapsing

    –The vessel’s resistance to fluid flow

    • ºSmall vessels= > resistance
    • ºViscous fluids= >resistance


    •Blood flow through a vessel depends on:

    Heart creating pressure difference between ends of the vessel

    •Heart pushing the blood through

    •Blood pressure keeping the vessels open

    –The vessel’s resistance to fluid flow

    Constricting arterioles increasing resistance

    Increased hematocrit increasing resistance
  18. Blood Flow

    What are the two types of circulation?

    Two types of blood flow.

    What determines BP?
    •Central Circulation: blood that is in the heart and pulmonary circulation

    •Peripheral Circulation: outside of central  circulation

    •Laminar Blood Flow: ideal streamlined blood flow where plasma is next to slippery endothelium.

    •Turbulent Blood Flow: stream is disrupted and flow becomes mixed. More pressure is required for turbulent flow than laminar flow. Can be caused by high velocity of flow, change in vessel diameter, and low blood viscosity. Often accompanied by vibration (murmur).

    BP = CO x PR

    Blood Pressure = Cardiac Output × Peripheral Resistance
  19. Preload
    •Preload: volume of work of the heart; load imposed on the heart before the contraction begins.; the amount of blood that the heart must pump with each beat; volume of blood stretching the ventricle at the end of diastole (end-diastolic volume); sum of the blood in the heart at the end of systole (end-systolic volume)
  20. Starling’s Law
    Increased force of contraction that accompanies an increase in ventricular end-diastolic volume.

    •Force of contraction is greatest when muscle fibers are optimally stretched just before the heart starts to contract.

    •Allows the heart to adjust its pumping ability to accommodate various levels of venous return.
  21. Afterload

    What BP is main source of afterload of left heart?
    Right heart?
    Pressure or tension work of the heart; pressure that the heart must generate to move blood into the aorta; the work presented to the heart after the contraction has started.

    Systemic arterial blood pressure is main source of afterload for left heart; pulmonary arterial pressure is main source of afterload for right heart.
  22. Think of the heart as a balloon…
    Preload is blowing up the balloon. It is the stretching of muscle fibers in the ventricle. It is the balloon stretching as air is blown into it. The more air, the greater the stretch.

    Contractility is the balloon’s stretch. It is the myocardium’s inherent ability to contract normally. Contractility is influenced by preload. The greater the stretch, the more forceful the contraction (Starling’s Law). The more air in the balloon, the greater the stretch, the farther the balloon will fly when air is expelled.

    Afterload is the knot that ties the balloon. Afterload refers to the pressure that the ventricle must generate to get blood out of the heart to overcome the higher pressure in the aorta. Resistance is the knot on the end of the balloon which the balloon has to work against to get the air out.