Cardio and Hormones Flashcards

Heart Chambers

• Four chambers:

  • Left atrium

  • Right atrium

  • Left ventricle

  • Right ventricle

• Atria: Receiving chambers.

• Ventricles: Discharging chambers (pump blood out).

Blood Oxygenation

• Right side: Oxygen-poor blood (from systemic circulation to lungs).

• Left side: Oxygen-rich blood (from lungs to body).

Veins Returning Blood

• To right atrium: Superior vena cava and inferior vena cava.

• To left atrium: Pulmonary veins.

Arteries Carrying Blood Away

• From right ventricle: Pulmonary trunk (splits into pulmonary arteries to the lungs), carries oxygen-poor blood.

  • Arteries always carry blood away from the heart.

• From left ventricle: Aorta.

Valves

• Atrioventricular valves: Between atria and ventricles.

  • Tricuspid: Right side.

  • Bicuspid (Mitral): Left side.

  • Prevent backflow with the help of chordae tendineae attached to papillary muscles.

• Semilunar valves: Between ventricles and receiving vessels.

  • Do not require tendinous cords; kept closed by backflow of blood in receiving vessels.

  • Pulmonary semilunar valve: Between right ventricle and pulmonary trunk.

  • Aortic semilunar valve: Between left ventricle and aorta.

Cardiac Cycle

• Systole: Contraction.

• Diastole: Relaxation.

Stages of Cardiac Cycle

• Atrial Systole:

  • SA node signal depolarizes atria.

  • Atria contract, AV valves are open.

  • Passive filling of ventricles (70%) before atrial systole.

  • Atrial contraction pushes remaining blood into ventricles.

• Atrial Diastole:

  • Atria relax and remain in diastole for the rest of the cycle.

• Ventricular Systole:

  • Ventricles depolarize and contract.

  • AV valves close (isovolumetric contraction).

  • Pressure builds; semilunar valves open.

  • Ventricular ejection (blood is pumped out).

• Ventricular Diastole:

  • Ventricles relax; cardiac muscle cannot reach tetany.

  • Semilunar valves close (isovolumetric relaxation).

  • Pressure decreases, AV valves open.

  • Passive filling of ventricles.

Pressure and Volume Changes

• Pressure gradients required for blood flow.

• Higher pressure in ventricles than atria closes AV valves.

• Higher pressure in ventricles than receiving vessels opens semilunar valves.

• Unequal pumping can cause:

  • Systemic edema: Right ventricle not keeping up; backlog in systemic capillaries.

  • Pulmonary edema: Left ventricle not keeping up; backlog in lungs.

Pressure Measurement

• Left atrium pressure increases during atrial contraction.

• Left ventricle contracts, AV valve closes, pressure increases (isovolumetric).

• Aortic valve opens when left ventricle pressure exceeds aortic pressure.

• Ventricular diastole begins, pressure drops; semilunar valve closes.

Heart Sounds

• S1 (Lub): Closing of AV valves.

• S2 (Dup): Closing of semilunar valves.

Cardiac Output (CO)

• CO = \text{Heart Rate} \times \text{Stroke Volume}

• Directly proportional relationship with heart rate and stroke volume.

• Measured in milliliters per minute (mL/min).

  • Heart rate: beats per minute.

  • Stroke volume: milliliters per beat.

  • \frac{\text{beats}}{\text{min}} \times \frac{\text{mL}}{\text{beat}} = \frac{\text{mL}}{\text{min}}

• Conversion to liters per minute (L/min):

  • 1 \text{ L} = 1000 \text{ mL}

• Cardiac output affects blood pressure.

Cardiac Centers of Medulla Oblongata

• Vital centers for heart rate, vasomotor control, and respiration.

• Cardioaccelerator center: Increases heart rate (sympathetic fibers).

  • Stimulates adrenergic receptors.

• Cardioinhibitory center: Slows heart rate (parasympathetic fibers, vagus nerve).

  • Vagal tone: Parasympathetic influence keeps resting heart rate lower than SA node's intrinsic rate.

• Cardiac centers: collections of cardioaccelerator and cardioinhibitory centers.

• Pink: cardio accelerator system.

• Parasympathetic: via the vagus, targets SA and AV node.

Pacemaker Potential

• SA node sets the pace; pre-potential or pacemaker potential caused by drifting sodium ions.

• Reaches threshold, action potential is sent.

Parasympathetic Innervation

• Acetylcholine (ACh) binds to cholinergic receptors, opening potassium channels.

• Potassium leaves the cell (hyperpolarization), extending repolarization.

• Slower time to reach threshold, decreasing heart rate.

Sympathetic Innervation

• Norepinephrine binds to beta one receptors, opening ion channels.

• Sodium gates open faster; shorter time to reach threshold, speeding up action potential.

Heart Rate Variability

• Normal resting heart rate various with age, general health, and physical conditioning.

• Bradycardia: Slower than normal heart rate (less than 60 bpm).

• Tachycardia: Faster than normal heart rate (greater than 100 bpm).

EKG and Cardiac cycle Correlation

• P wave: Depolarization of the atria (atrial diastole).

• QRS complex: Ventricular systole.

• T wave: Ventricular diastole.

  • Atrio systole: atria start contraction.

  • QRS complex, start ventricular systole.

Stroke Volume Calculation

\text{Stroke Volume} = \text{End Diastolic Volume} - \text{End Systolic Volume}

• End diastolic volume (EDV): Volume of the ventricles at the end of diastole.

• End systolic volume (ESV): Volume of ventricles at the end of systole (after contraction).

Stroke Volume Analogy

• Manual pump analogy: Volume pumped depends on handle movement.

Factors Affecting Stroke Volume

• End Diastolic Volume (EDV): Venous return (affected by blood volume, muscular activity),

  • Filling time (duration of ventricular diastole), and preload (myocardial stretching; Frank-Starling law).

  • Increase EDV increases stroke volume.

• End Systolic Volume (ESV): Contractility (force of contraction; influenced by sympathetic stimulation, thyroid hormone, glucagon, beta blockers, calcium channel blockers), and afterload (resistance ventricles overcome to eject blood).

  • Increase afterload increases ESV, decreasing stroke volume.

Venous Return Affects

• Blood Volume

• Muscular Activity (skeletal muscle pump)

• peripheral tissues

Arterial Compliance Affects

• Vasoconstriction

• Vasodilation

• Cardiac output varies depending on needs and demands; brain blood flow remains relatively constant.

• Heart failure: Inability of the heart to meet tissue demands.

  • Left ventricular failure: Pulmonary edema.

  • Right ventricular failure: Systemic edema.

• Cardiac output is affected by factors influencing heart rate and stroke volume.