Zoology

• The Heart's Own Blood Supply

  • Right coronary artery emerges from R side of aorta, descends in coronary sulcus between R atrium and R ventricle, supplies R atrium, most of R ventricle, and 80% of the time, the inferior portion of the L ventricle as well
  • Left coronary artery arises from L side of Aorta, VERY SHORT, major branches are Circumflex A and Anterior interventricular A (= anterior descending A) which supplies anterior wall of both ventricles and Circumflex which supplies L atrium and posterior part of L ventricle

  
• The Cardiac Cycle


  • It is the period of time that commences with the contraction of the atria and ends with ventricular relaxation
  • It is a carefully regulated sequence of steps that we think of as beating of the heart
  • Four Stages: 1) Atrial systole (0.1 sec) - both atria contract, forcing blood into the ventricles 2) Ventricular systole (0.3 sec) - both ventricles contract forcing blood out 3) Atrial diastole (0.7 sec) - ventricles remain contracted, atria begin refilling 4) Ventricular diastole (0.5 sec) - relaxation of ventricles, allowing them to fill with blood from the atria

  
• Systole and Diastole


  • Systole = the period of ventricular contraction
  • Diastole = the period of ventricular relaxation
• Heart Sounds


  • Closure of heart valves causes vibrations in adjacent heart walls and blood; these vibrations constitute the heart sounds
  • "Lubb": Produced by the closing of AV valves at the start of ventricular systole
  • "Dupp": Produced by the closing of the semilunar valves at the end of ventricular systole
• Systole = 1st heart sound, A-V valves close = "lubb"
• Diastole = 2nd heart sound, pulmonic and aortic semi-lunar valves close = "dupp"

  
• Maintaining the Heart's Rhythmic Beat

  • A region of the heart called the sinoatrial (SA) node, or pacemaker, sets the rate and timing at which all cardiac muscle cells contract
  • Impulses from the SA node travel to the atrioventricular (AV) node
  • At the AV node, the impulses are conducted through the bundle of His and then travel to the Purkinje fibers that make the ventricles contract
  • The impulses that travel during the cardiac cycle can be recorded as an electrocardiogram (ECG or EKG)
  • The pacemaker is influenced by nerves, hormones, body temperature, and exercise
• Blood Vessel Structure and Function


  • The "infrastructure" of the circulatory system is its network of blood vessels
  • All blood vessels are built of similar tissues and have three similar layers

  
• Maintaining the Heart's Rhythmic Beat


  Impulses during cardiac cycle can be recorded as an electrocardiogram (ECG or EKG)
• Pacemaker


  Influenced by nerves, hormones, body temperature, and exercise
• Systolic Pressure


  The pressure in the arteries during ventricular systole, the highest pressure in the arteries
• Diastolic Pressure


  The pressure in the arteries during diastole, lower than systolic pressure