Exam 3

• Heart


  An untiring pump
• Cardio flow


  1. Right side of heart ⇒ deoxygenated blood

  2. Left side of heart ⇒ oxygenated blood

  
• Cardiac muscle

  • Spiral arrangement of ventricular muscle allows ventricular contraction to squeeze blood upward
  • Intercalated disks contain desmosomes that transfer force from cell to cell and gap junctions that allow electrical signals to pass through

  
• Blood pathway in the heart

  1. Breathe in oxygen

  2. Venae cavae

  3. Right atrium

  through tricuspid valve

  4. Right ventricle

  5. Pulmonary artery

  6. Lungs (picks up oxygenated blood)

  7. Pulmonary vein

  8. Left atrium

  through mitral valve

  9. Left ventricle

  10. Aorta
• Blood flow


  • Determined by the pressure gradient (ΔP) and the resistance R
  • Bigger pressure gradient = ↑ blood flow
  • No pressure gradient = no blood flow

  
• Flow and velocity of flow

  • Flow = velocity * area, so velocity = flow/area
  • Flow aorta = flow caps (flow is equal through out the body)
  • Velocity aorta * area aorta = velocity caps * area caps
  • ↑velocity aorta * ↓area aorta = ↓velocity caps* ↑area caps
  • So the slowest velocity is in the capillaries
• Adaptive significance


  • Aorta has a bigger area but theres only one of it
  • Capillaries have smaller area but theres millions of them
• Electrical event


  1. ATP binds to myosin (for relaxation)

  2. Myosin hydrolyzes ATP

  3. Power stroke

  4. Myosin releases ADP at the end of power stroke
• Excitation- contraction coupling and relaxation


  1. Initiation of muscle action potential

  2. Excitation- contraction coupling

  3. Relaxation phase
• Contractility in cardiac cells

  The force of contraction is proportional to the concentration of ICF calcium

  
• Electrical conduction in myocardial cells

  • Autorhythmic cells: fire at their own rate
  • Contraction cells: have gap junctions
  • SA node (pacemaker) (autorhythmic)
  • Internodal pathways
  • AV node (autorhythmic)
  • AV bundle
  • Bundle branches
  • Purjinke fibers
• ECG


  1. Body fluids acts as a conductor

  2. Recorded one lead at a time

  3. Einthoven's triangle represents the summed electrical activity of all cells from the surface of the body

  4. P wave = atrial depolarization ⇒ SA node firing ⇒ atria contracts

  5. PR segment (dont include the waves) = conduction through AV node and AV bundle

  6. PR/PQ interval (includes waves) ⇒ atria contracts

  7. QRS complex = depolarization of the ventricles ⇒ ventricles contract

  8. R wave = ventricle Na+ influx

  9. T wave = repolarization of ventricles ⇒ ventricles relax
• Sympathetic influence on pacemaker cells

  • Sympathetic → norepinephrine/epinephrine → adrenergic → β1 → ↑ heart rate
  • R-R interval would decrease complexes get closer together
  • VG Ca2+ channels open and Ca2+ enters the cell
  • Binds with troponin to initiate contraction

  
• Arrhythmias


  • Partial heart AV block: PR segment is lengthened only common conduction disturbance
  • Complete heart block: QRS are completely dissociated from P waves, Ventricles are beating at steady regular slow rate set by purkinje fibers, No communication between atria and ventricles
  • Atrial fibrillation: an irregular and often rapid heart rhythm (arrhythmia) that can lead to blood clots in the heart, Some impulses make it through the AV node → ventricles ⇒ normal QRS complex
  • Ventricular fibrillation: Disorganized heart signals cause the ventricles to twitch useless, As a result heart doesnt contract and pump blood to the rest of the body

  
• Mechanical event


  1. Heart cycles between contraction and relaxation

  2. Pressure volume curve

  3. The wiggers diagram

  
• Cardiac output

  • How much blood is being pumped out
  • Cardio output = Stroke Volume * Heart Rate
  • If HR increase, cardio output increases
  • If stroke volume decreases, cardiac output decreases

  
• Sterling curve

  Length- force relationships
• Preload and afterload


  • Preload: volume entering ventricles
  • Afterload: resistance left ventricle must overcome to circulate blood

  
• Fluid flow through a tube

  • Depends on the pressure gradient
  • Fluid only flows if there is a positive pressure gradient (ΔP)
  • Flow = ΔP/ R
  • Blood flows down a pressure gradient

  
• Arteries


  • Elastic arteries: Thick walls, Smooth muscle, Elastin
  • Arterioles: Thinner walls, Smooth muscle
  • Capillaries: Exchange epithelium only, One layer, Gas exchange
  • Veins/ venules: Thin walls, less smooth muscle
• Aorta vs Capillaries


  Aorta is like a big highway where blood rushes out from the heart, so it needs more pressure to push blood all around the body. Capillaries are like tiny streets where blood slows down to deliver oxygen and nutrients to tissues, so they don't need as much pressure

  
• Arteries


  • Arteries are a pressure reservoir
  • Ventricular contraction: contraction of the ventricles pushes blood into elastic arteries causing them to stretch
  • Ventricular relaxation: elastic recoil in the arteries maintains driving pressure during ventricular diastole

  
• Blood pressure


  • Systolic
  • Diastolic
  • Pulse pressure = systolic - diastolic
  • Mean Arterial Pressure (MAP) = diastolic + ⅓ (pulse)

  
• Blood pressure example


  • Systolic = 121 mmHg
  • Diastolic = 91 mmHg
  • BP = 121/91 mmHg
  • Pulse = 121 - 91 = 30 mmHg
  • MAP = 91 + ⅓ (30) = 101 mmHg

  
• Major determinants of MAP

  • Blood volume
  • Fluid intake
  • Fluid loss

  
• Arteries


  • Pressure reservoir
• Ventricular contraction


  Contraction of the ventricles pushes blood into elastic arteries causing them to stretch
• Ventricular relaxation


  Elastic recoil in the arteries maintains driving pressure during ventricular diastole
• Systolic


  Blood pressure measurement

  
• Pulse pressure

  Systolic - diastolic

  
• Mean Arterial Pressure (MAP)


  Diastolic + ⅓ (pulse)

  
• Heart expands twice more in relaxation than contraction

  
• Blood pressure example

  • Systolic = 121 mmHg
  • Diastolic = 91 mmHg
  • BP = 121/91 mmHg
  • Pulse = 121 - 91 = 30 mmHg
  • MAP = 91 + ⅓ (30) = 101 mmHg

  
• Normal human MAP = 93 mmHg
• Korotkoff sounds


  Used to measure blood pressure

  
• Major determinants of MAP

  • Blood volume
  • Cardiac output
  • Resistance of the system to blood flow
  • Relative distribution of blood between arterial and venous blood vessels

  
• Fluid intake


  Affects blood volume

  
• Fluid loss


  Affects blood volume

  
• Passive

  Fluid loss
• Regulated at kidneys


  Fluid loss