PHYS - Cardiovascular System

Question 1

COMPONENTS OF THE CARDIOVASCULAR SYSTEM

Answer 1

• Blood
• Heart
• Vessels
• Duplex pulsatile pump

Question 2

FUNCTIONS OF THE CV SYSTEM

Answer 2

• Supply O2 to tissues/organs
• Remove CO2 and metabolic by-products (ex: lactic acid)
• Other:
  
  • ​Regulate body temperature
  • Transport hormones
  • Maintain body fluid

Basal substrate of the heart = fatty acids

• Can also metabolize lactic acid/glucose
• Protein or AAs in extreme need

Question 3

PUMPS

Answer 3

• Right: Pulmonary –> low P (15-20 mmHg)
  
  • ​Blood is about equally divided between veins and arteries
• Left: System –> high P (100+ mmHg)
  
  • ​Most blood is veins
• Connected as a circuit in series
• Can respond to changes in volume
• Resting P of a stopped heart is 7-14 mmHg

Question 4

BLOOD RESERVOIR

Answer 4

• VEINS!
• 67% of all blood in systemic circulation
• During exercise, vasoconstriction will push blood back to heart

Question 5

CARDIAC CYCLE/

WIGGERS DIAGRAM

Answer 5

• P-Wave = Depolarization
  
  • ​Small increase in atrial P
  • Small increase in ventricle P and V
  • Atria contracts
  • Only contributes to 5-10% of ventricle filling (but about 40%+ during exercise)
• QRS Complex = Ventricles Fill, Ventricles Depolarization Triggered​
  
  • Ventricle begins to fill + isovolumic contraction –> Increase in P!
  • As P reaches ~80 mmHg, ejection begins: aortic valve opens, and AV valve closes
• T Wave = Ventricles Empty and Repolarize
  
  • ​Rapid ejection after reaching peak (~120 mmHg)
  • By isovolumic relaxation
  • Ejection fraction = 60% (50-65%); therefore, resting volume does not equal 0!
  • As pressure decreases, aortic valve overcomes unfavorable P gradient to stay open because kinetic blood flow is increased
  • Atria begins to fill
  • Aortic valve closes, AV valve opens

Question 6

HEART SOUNDS

Answer 6

• S1: AV valve opens

SYSTOLE

• S2: AV valve closes

DIASTOLE

• S3: Ventricle filling (only heard in children and pathology)
• S4: Atrial contraction

Question 7

CARDIAC CELL TYPES

Answer 7

• Pacemaker cells
  
  • ​SA Node (RMP = -40 mV)
  • AV Node (RMP = -70mV)
  • Purkinje fibers
• Conducting fibers
  
  • ​Bachmann’s bundle = internodal/interatrial
  • AV node
  • Bundle of Hiss
  • Purkinje
• Contractile cells (increased ion permeability)
  
  • ​Atrial/ventricular myocytes
  • Contract in syncytium because impulse propagates through tissue (compared to SkM, one fiber =/= excite other, CM cells excite surrounding)
  • Therefore, cannot increase strength of contraction by “recruiting” more CM
  • ​Contraction cannot summate into a tetanus (long, sustained contraction from several APs adding) because of a long ERP (effective refractory period)
    
    • Maintains heart rhythm
    • Prevents contraction before period of filling is complete

Question 8

ELECTRICAL PATH IN HEART

Answer 8

• SA –> internodal (130ms delay) –> AV –> Purkinje –> interventricular (transitional fibers)
• Purkinje fibers = fastest conductor
• SA node = pacemaker because a higher RMP allows it to depolarize more spontaneously
• Fibrous skeleton between internodal and AV fibers = insulator

Question 9

PROPERTIES OF ARTERIES

Answer 9

• Aorta/large arteries store energy (mechanical distension) from ventricular contraction to maintain pressure (by contracting) during diastole when ventricles relax.
• Arteries = thick, elastin, SM
  
  • ​Smaller arterioles have more smooth muscle and are regulated by ANS
• Decreased pressure and velocity occurs in arteriole blood flow because:
  
  1. Increased cross-sectional area
  2. Increased frictional resistance