Note taking guide

Chapter 15: CARDIOVASCULAR SYSTEM

Overview of circulation:
    Heart is two pumps in one

        Left side ! systemic circulation

                arteries !arterioles !capillaries (exchange of nutrients and wastes)
                    capillaries ! venules ! veins ! right side of heart

Artery - definition

Vein - definition

Right side ! pulmonary trunk !pulmonary arteries ! lungs (exchange of gases)
            Lungs ! pulmonary veins !left side of heart

Size

Location

Pericardium

Fibrous pericardium

Serous pericardium
            parietal

            visceral/ epicardium

            pericardial cavity ( a potential space)

                        Pericarditis

                        Cardiac tamponade

The Heart Wall
            3 layers:

              1.  epicardium

              2.  myocardium

                        Intercalated discs

                                        Desmosomes

                                        Gap junctions - functional syncytium

             3.   endocardium


Chambers:

        Atria (Atrium)

        Ventricles

                        Atrioventricular sulcus

                        Interventricular sulci

        Interatrial septum

                Fossa ovalis - foramen ovale

        Interventricular septum

       Trabeculae carnae

        papillary muscles

        chordae tendineae

Valves:

        Atrioventricular (AV) valves

                tricuspid

                bicuspid / mitral

        aortic semilunar valve

        pulmonary semilunar valve

        Rheumatic fever

HEART BLOOD SUPPLY
        Left coronary artery

                    circumflex artery

                    anterior interventricular artery

        Right coronary artery

                    posterior interventricular artery

                    marginal artery

                            anastamoses - collateral circulation.

        The great cardiac vein

        The middle cardiac vein

        the coronary sinus

Blood Flow Through the Pulmonary and Systemic Circuits
        Cardiac Cycle - one complete heart beat.

                systole (contraction)

                diastole (relaxation)

    Heart Sounds
            The first heart sound (lubb)-
                    closing of the atrioventricular valves(at beginning of ventricular systole)

        The second sound (dupp)-
                    closing of semilunar valves (at beginning of ventricular diastole)

Heart murmurs

Conduction System and Pacemaker

    Autorhythmic Cells

    Begins in the sinoatrial (S-A) node (pacemaker)

    Passes through the fibers of the atrial syncytium.

    The atrioventricular (AV) node -

                "speed-bump"

    atrioventricular (AV) bundle (bundle of His)

    bundle branches
   
    Purkinje fibers (conduction myofibers

    ectopic pacemaker

Electrocardiogram (ECG)

    P wave (atrial depolarization)

    QRS complex (onset of ventricular depolarization)

    T wave (ventricular repolarization)

Regulation of Heart Rate
Cardiovascular center in the medulla oblongata.

Sympathetic impulses increase heart rate and force of contraction.

            Reach the heart by the accelerator nerves- secrete norepinephrine.

Parasympathetic impulses decrease heart rate

            sent through the vagus nerves.

Baroreceptors (stretch receptors) in the aorta and carotid arteries

            Increased pressure -increases parasympathetic output.

Stretch receptors in the venae cavae.

        If pressure here increases, the medulla sends out sympathetic impulses

Impulses from cerebrum or hypothalamus

Temperature

Ions - primarily K⁺ and Ca⁺⁺

Hormones

Hypoxia, acidosis and alkalosis all slow heart rate.

Arteries:

    structure:

        Lumen

        Tunica interna

        Tunica media

        Tunica externa

Arterioles

Metarterioles

Capillaries:

        only endothelium and basement membrane

        connects arterioles and venules

        precapillary sphincter

        Continuous capilllaries

        Fenestrated capillaries

        Sinusoids

        Tight junctions

Venules

Veins:

    same 3 tunics as arteries, but thinner tunica interna and tunica media

    Flow aided by muscle contractions and valves

    Blood reservoirs

Blood pressure

    Highest during systole - systolic pressure (90-135)

    Lowest during diastole - diastolic pressure (60-85)

    Expanding and recoiling of arteries can be felt as a pulse.

    Circulation time - right atrium to foot and back = 1 minute

    Velocity

Factors that influence Arterial blood pressure:

    Beating of the heart

    Cardiac output (CO) is the amount of blood ejected by the left ventricle (or right ventricle) into the aorta (or pulmonary trunk) per minute.

    CO(ml/min.) = SV (ml/beat) X HR (beats/min)
                This is close to the total blood volume.

Other factors:

        Blood volume

        Peripheral resistance

        Viscosity

Control of blood pressure and blood flow:

        B.P. Determined by C.O. And peripheral resistance       

        BP = CO X PR

Cardiac output is influenced by mechanical, neural and chemical factors.

        Starling’s law.

        Baroreceptors in the arteries
                If medulla sends parasympathetic impulses to S-A node (via vagus), the heart rate falls, and BP falls. - cardioinhibitor reflex

                Sympathetic impulses increase the heart rate- cardioaccelerator reflex, BP increases.

            Vasomotor center of the medulla regulates BP by changing arteriole diameter.

Other factors:

Fetal circulation:

        Two umbilical arteries to the placenta

        The umbilical vein returns oxygenated blood to the baby.
       
        The ductus venosus bypasses the fetal liver and dumps the blood into the inferior vena cava.

Two other structures bypass the developing lungs:
            The foramen ovale

            The ductus arteriosus