Part 2 Study Tip Questions + Q of the day

Human Anatomy & Physiology: Heart

What is the difference between the pulmonary circuit and the systemic circuit?

Pulmonary circuit: Right side of the heart.

- Sends blood to the lungs via pulmonary trunk.

- Oxygen-Poor Blood.

Systemic circuit: Left side of the heart.

- Newly oxygenated blood to every tissue cell in the body.

- Returned back to the heart via aorta.

- Thicker and more muscular than the pulmonary side.

In which side of the heart would you find oxygen-poor blood?

Right side.

Pulmonary Circuit.

Which blood vessel carries blood away from the left ventricle?

The Aorta.

Which blood vessel(s) carry blood to the right atrium?

Superior Vena Cava.

Do the pulmonary arteries carry blood rich in oxygen?

No.

No, pulmonary arteries do not carry blood rich in oxygen; they carry oxygen-poor blood from the heart to the lungs to be oxygenated; making them the only arteries in the body to carry deoxygenated blood.

What is the function of the fibrous skeleton of the heart?

Separates the atria from the ventricles.

- Provides structural support & attachment for cardiac muscle and anchor for tissue valves.

- Critical for electrical insulation between atria and ventricles.

- Regulating coordination and timing of heart contraction.

What valve prevents the backflow of blood into the left ventricle?

Aortic Valve

What is the purpose of the right AV (Atrioventricular) valve? **

Control blood flow between atria and ventricles.

In between the right atrium and right ventricle.

Tricuspid Valve ~ 3 flaps

What is the purpose of the coronary circulation?

A circulatory system that serves the heart muscle - for oxygen and nutrients.

- Branches of the aorta.

- Shortest systemic circuit

Which blood vessels bring blood into the left atrium?

Pulmonary Veins

Pulmonary arteries are branches of the … ?

Pulmonary Trunk

Ventricles of the heart pump blood where?

Into arteries.

The QRS wave of an ECG represents what event in the heart?

Ventricle Depolarization

The second heart sound is associated with the closing of which valves?

Closure of Semilunar Valves

Softer + Sharper “dupp“

Pulmonary and Aortic Semilunar Valves.

What layer of the heart wall performs the actual work of the heart?

• The myocardium is the muscular layer that contracts to pump blood out of the heart and into the circulatory system.

• It is made up of specialized cardiac muscle cells that are capable of involuntary, rhythmic contractions.

• The thickness of the myocardium varies in different chambers of the heart, with the left ventricle having the thickest myocardium because it pumps blood to the entire body.

What are the names of the superior chambers of the heart?

Atria

What is different about the cardiac action potential compared with the skeletal muscle action potential you learned about in BIO 131?

Why do cardiac muscle cells have a long absolute refractory period?

Cardiac muscle cells have a long absolute refractory period to prevent tetanus.

• During period, heart muscle cannot be stimulated to contract again, ensuring that the heart has time to refill with blood.

• preventing the occurrence of multiple contractions before the heart has completed its pumping cycle.

The long refractory period is due to the plateau phase of the cardiac action potential, which results from the prolonged influx of calcium ions and the delayed opening of potassium channels.

This unique property allows for coordinated contractions and a rhythmic beating of the heart.

What is a gap junction and why is it significant to heart physiology?

Gap junctions are specialized connections between cardiac muscle cells that allow for direct communication and electrical coupling. They enable synchronized contractions of the heart by allowing ions and small molecules to pass freely between cells.

Where would you find the tricuspid valve and what is its function?

Right Atrioventricular “AV” Valve.

To control the blood flow between the right atria and right ventricle.

Can you draw and label the typical ECG?

The first sound is associated with the closing of which valves?

Closure of Atrioventricular Valves.

Tricuspid and Mitral/Bicuspid Valves.

What is happening in the heart during isovolumetric relaxation?

• Isovolumetric relaxation is a phase in the cardiac cycle that occurs immediately after the ventricles have contracted and ejected blood into the aorta and pulmonary trunk(during ventricular diastole).

• During this phase, the ventricles begin to relax, leading to a decrease in ventricular pressure.

• All four heart valves (the aortic, pulmonary, mitral, and tricuspid valves) are closed. preventing blood from entering ventricles or flowing back from arteries.

• Is essential, allows ventricles to decrease pressure without changing volume until the mitral & tricuspid valves open and next filling phase begins.

• Relaxation phase lasts for brief moment, is critical for ensuring that the heart chambers can refill with blood in preparation for next contraction.

When does most ventricular filling occur?

Most ventricular filling occurs during diastole, relaxation.

Approximately 70-80% of the filling happens passively as blood flows from the atria into the ventricles before atrial contraction contributes the remaining 20-30%.

What valves close when the ventricles relax?

The semilunar valves close when the ventricles relax. Specifically, this includes the aortic valve and pulmonary valve. This closure occurs during the isovolumetric relaxation phase of the cardiac cycle, preventing the backflow of blood from the aorta and pulmonary trunk back into the ventricles. This ensures proper circulation and maintains pressure within the arteries created by the previous ventricular contraction.

What is EDV?

Ventricle is at the end of its diastole.

End of relaxation.

Ventricle is as full as it is going to be before contracting.

What is the main symptom of right heart failure and why?

Right Ventricle Failure: Blood backs up in the Vena Cava causing systemic edema.

Swelling in either abdominal cavity of ankles and feet (extremities).

Eventually leads to total heart failure.

What is the "pacemaker" of the heart?

Sinoatrial node or SN is the pacemaker of the heart.

Both sets the heart rate and initiates hearts rhythm.

What is the significance of the AV node?

Critical component of the heart's electrical conduction system, located near the right AV valve at the lower end of interatrial septum.

• Electrical gateway to the ventricles.

• Primary significance, role as a gatekeeper, regulates the electrical impulses from the atria to the ventricles.

• It regulates impulses between the atria and ventricles, providing a 0.1-second delay for proper contraction sequence.

• Prevents simultaneous contractions, ensuring effective blood flow. Also acts as backup pacemaker at 40-60 beats per minute if the SA node fails.

What part of the hearts conduction system cause a delay in when transferring signal from atria to ventricles?

Atrioventricular node (AV Node)

The T wave occurs during which phase of the cardiac cycle?

Ventricular Repolaization

The P wave occurs during which phase of the cardiac cycle?

Atrial systole

The QRS wave occurs during which phase of the cardiac cycle?

Isovolumetric contraction

Where in the body has the lowest blood pressure?

Venae Cavae

Which vessels are known as resistance vessels?

Arteries specifically Arterioles

What vessels are the capacitance vessels and what does this mean?

Capacitance vessels are primarily veins,

They have a high capacity to store blood due to their large lumen and thin walls, acting as a reservoir for blood volume

 What does the QRS complex represent?

Ventricular depolarization (the electrical signal that causes the ventricles to contract).

What is the definition of cardiac output?

Amount ejected by each ventricle in 1 minute.

What is average resting cardiac output?

5 L/min

How would an increase in heart rate impact cardiac output? 

An increase in heart rate increases cardiac output, as long as stroke volume remains the same.

(Cardiac Output = Stroke Volume × Heart Rate)

However, if the heart rate gets too high, stroke volume may decrease, limiting the increase in cardiac output.

How would an decrease in heart rate impact cardiac output?

A decrease in stroke volume decreases cardiac output, as long as heart rate remains the same.

(Cardiac Output = Stroke Volume × Heart Rate)

If stroke volume drops, less blood is pumped with each beat, lowering overall cardiac output.

What variable govern stroke volume?

Preload

Contractility

Afterload

What is preload? 

The amount of tension in ventricular myocardium immediately before it begins to contract.

• Increased preload causes increased force of contraction.

• Exercise increases venous return, stretches myocardium.

• Increased cardiac output matches increased venous return.

What is afterload? 

Sum of all forces opposing ejection of blood from the ventricle.

• Hypertension increases afterload and opposes ventricular ejection.

  • Largest part of afterload is blood pressure in aorta and pulmonary trunk: Opposes opening of semilunar valves & limits stoke volume.

What is the Frank-Starling Law of the heart?

Stroke volume is proportional to End diastolic volume.

• Ventricles eject as much blood as they receive.

• The more stretched the harder they contract.

In what vessels is blood flow pulsatile?

Arteries, especially the aorta and large elastic arteries.

What factors contribute to venous return?

Pressure Gradient: High to low pressure

Gravity: Drains blood from head and neck

Skeletal Muscle: Contracting limb muscles squeeze blood out of compressed part of vein, valves keep blood moving toward heart.

Thoracic (respiratory) pump: Inhalation expands thoracic cavity

Cardiac suction: During contraction of the ventricle, valves are pulled downward and atrial space expands, slight suction draws blood into atria from venae cavae and pulmonary veins.

What force drive filtration at the arterial end of the capillary bed? 

Hydrostatic pressure drives fluid out. High on arterial end of capillary bed, (low on venous) pushing fluid and small solutes out of the capillaries into the surrounding tissue.

What force drives reabsorption at the venous end of a capillary bed?

Osmotic pressure COP draws fluid into capillary, results from plasma proteins (albumins) - more in blood

What are the main factors that influence peripheral resistance?

Blood viscosity (Thickness): RBC + Albumin concentration mainly raise viscosity.

Vessel Length: Farther a liquid travels through a tube, more friction it accumulates.

• Pressure and flow decline with distance.

Vessel Radius: Control blood flow directly.

• Most powerful influence on blood flow.

Vasoreflexes: Changes in vessel radius

• Vasodilation

• Vasoconstriction

What is the most important force driving filtration at the arterial end of a capillary

Hydrostatic Pressure is driving filtration at the arterial end of the capillary while Colloid osmotic pressure is driving reabsorption at venous end

What is the respiratory membrane?

What are the 3 layers?

Barrier between the alveolar air and blood.

• Squamous alveolar cells

• Endothelial cells of blood capillary

• Their shared basement membranes

What part of the autonomic nervous system can increase stoke volume by increasing contractility of the ventricular myocardium?

Sympathetic

What is hypovolemic shock?

Most common form of low venous return.

Loss of blood volume: trauma, burns, dehydration.

What is cardiogenic shock?

Inadequate pumping of the heart. (MI)

What is septic shock?

Bacterial toxins trigger vasodilation and increased capillary permeability.

What vessel takes blood to the lungs?

Pulmonary Artery.

What is the function of the epiglottis?

• Guards the larynx (voice box).

• During swallowing:

  • Closes the airway.

  • Directs food/drink to the esophagus.

• Prevents choking by keeping food out of the lungs.

What structures are part of the conducting zone of the respiratory system? 

The conducting zone includes all airways from the nostrils to the terminal bronchioles, which transport air but do not participate in gas exchange.

• Includes passages that serve only for airflow (no gas exchange).

• Structures:

  • Nostrils.

  • Pharynx.

  • Larynx.

  • Trachea.

  • Bronchi (primary, secondary, tertiary).

  • Bronchioles (up to terminal bronchioles).

What structures are part of the respiratory zone?

The respiratory zone includes the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli, where oxygen and carbon dioxide are exchanged between air and blood.

Consists of structures involved in gas exchange.

• Includes:

  • Respiratory bronchioles.

  • Alveolar ducts.

  • Alveolar sacs.

  • Alveoli (millions of thin-walled, microscopic air sacs where gas exchange occurs).

What is the respiratory membrane?   

Thin barrier between alveolar air and blood.

• Three Layers:

  1. Squamous alveolar cells.

  2. Endothelial cells of blood capillaries.

  3. Shared basement membrane.

• Function: Allows rapid gas exchange (O₂ and CO₂).

What is intrapleural pressure? 

Slightly negative pressure between pleural layers.

• Caused by: Cohesion of water in pleural fluid.

• Function:

  • Keeps lungs adhered to thoracic wall.

  • Helps lungs expand during inspiration.

  • Facilitates breathing.

What is intrapulmonary pressure? 

The pressure inside the alveoli of the lungs.

• Changes during the breathing cycle:

  • During inspiration:

    • Lung volume increases.

    • Intrapulmonary pressure drops below atmospheric pressure.

    • Air flows into the lungs.

  • During expiration:

    • Lung volume decreases.

    • Intrapulmonary pressure rises above atmospheric pressure.

    • Air flows out of the lungs.

What is the definition of pulmonary ventilation (breathing)?

The process of breathing, which includes:

• Inspiration (inhaling): Drawing air into the lungs.

• Expiration (exhaling): Expelling air from the lungs.

One complete cycle of inspiration and expiration is called a respiratory cycle.

What are the main factors that govern air flow?

1. Pressure Gradients:

   • Air flows from areas of high pressure to low pressure.

   • Governed by Boyle’s Law: Pressure and volume are inversely related.

     • Inspiration: Lung volume increases → pressure decreases → air flows in.

     • Expiration: Lung volume decreases → pressure increases → air flows out.

2. Resistance to Airflow:

   • Bronchiole Diameter:

     • Bronchodilation (increase in diameter) → increases airflow.

     • Bronchoconstriction (decrease in diameter) → decreases airflow.

   • Pulmonary Compliance:

     • Ease with which the lungs can expand.

     • Reduced by scar tissue or surface tension in alveoli.

3. Airway Resistance:

   • Influenced by the diameter of the airways and the viscosity of the air.

What is Boyle’s Law? 

The pressure of gas is inversely proportional to its volume.

• If volume increases, pressure decreases.

• If volume decreases, pressure increases.

What is Charles Law?

The volume of a gas is directly proportional to its absolute temperature (at constant pressure).

• If temperature increases, volume increases.

• If temperature decreases, volume decreases.

What is Dalton’s Law?

Definition: Total pressure of a gas mixture = sum of partial pressures of individual gases.

Partial Pressure: Pressure exerted by one gas in a mixture.

• Application:

  • Drives gas exchange (O₂ and CO₂ move from high to low partial pressure).

  • Example: O₂ moves from alveoli (high PO₂) to blood (low PO₂).

What pressure changes contribute to pulmonary ventilation?

1. Intrapulmonary Pressure:

   • Inspiration: Drops below atmospheric pressure → air flows in.

   • Expiration: Rises above atmospheric pressure → air flows out.

2. Intrapleural Pressure:

   • Always slightly negative.

   • Helps lungs adhere to thoracic wall.

   • Becomes more negative during inspiration → stretches lungs.

3. Atmospheric Pressure:

   • Reference pressure (760 mm Hg at sea level).

Which law states that the pressure of a gas is inversely related to its volume?

Boyles Law

PRESSURE + VOLUME PROPORTIONAL @ CONSTANT PRESSURE

What makes up the respiratory membrane?

• Simple Squamous Epithelial cells

• Capillary Epithelial Cells

• Shared Basement membrane