exam 3

• Heart


  An untiring pump
• Pumps and pipes analogy

  Describes the cardiovascular system

  
• 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

  
• Receives blood from


  • Venae cavae
  • Pulmonary veins

  
• Sends blood to


  • Right ventricle
  • Lungs
  • Left atrium
  • Body except for lungs

  
• Blood pathway in the heart

  1. Breathe in oxygen

  2. Venae cavae

  3. Right atrium

  4. Right ventricle

  5. Pulmonary artery

  6. Lungs (picks up oxygenated blood)

  7. Pulmonary vein

  8. Left atrium

  9. Left ventricle

  10. Aorta

  
• Blood flow


  • Determined by the pressure gradient (ΔP) and the resistance R
  • Bigger pressure gradient = ↑ blood flow
  • Only flows if theres a positive ΔP
  • No pressure gradient = no blood flow

  
• Resistance of tube B is 16 times higher than tube A

  • Tube A: r1= 2
  • Tube B: r2= 1
  • 𝑅 = 1/��4 ⇒ 𝑅1 = 1/24 = 1/16
  • 𝑅2 = 1/14 = 1
• 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
  • 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
• 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

  1. Autorhythmic cells: fire at their own rate

  2. Contraction cells: have gap junctions

  3. SA node (pacemaker) (autorhythmic)

  4. Internodal pathways

  5. AV node (autorhythmic)

  6. AV bundle

  7. Bundle branches

  8. Purjinke fibers

  9. Heart contracts immediately after
• ECG


  • Body fluids acts as a conductor
  • Recorded one lead at a time
  • Represents the summed electrical activity of all cells from the surface of the body
  • 1 mV/sec
  • P wave = atrial depolarization ⇒ SA node firing ⇒ atria contracts
  • PR segment (dont include the waves) = conduction through AV node and AV bundle
  • PR/PQ interval (includes waves) ⇒ atria contracts
  • QRS complex = depolarization of the ventricles ⇒ ventricles contract
  • ST segment
  • R wave = ventricle Na+ influx
  • 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
• Partial heart AV block

  • PR segment is lengthened only common conduction disturbance
  • It occurs in both healthy and diseased heart

  
• 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 (A-fib)


  • 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 (V-fib)


  • Disorganized heart signals cause the ventricles to twitch useless
  • As a result heart doesnt contract and pump blood to the rest of the body

  
• 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

  
• Preload


  Volume entering ventricles
• Afterload


  • Resistance left ventricle must overcome to circulate blood
  • Resistance in the aorta
• Factors affecting stroke volume


  • 
    
• Blood flow through a tube

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

  
• 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
• Arteries as 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)
  • Heart expands twice more in relaxation than contraction

  
• Determinants of MAP


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

  
• Tonic control: sympathetic system

  • Tonic control of arteriolar diameter
  • Arteriolar diameter is controlled by tonic release of norepinephrine
  • Increase NP release onto receptors ⇒ As the signal rate increases the blood vessels restrict
  • Decrease NP release onto receptors ⇒ As the signal rate decreases the bloos vessels dilate
• Baroreceptor reflex


  1. Negative feedback loop

  2. Maintains blood pressure

  3. Receptors located on aortic arch and arteries

  4. Sympathetic system more important for BP regulation

  
• With this stimulus...


  • BaroR firing rate will
  • Sympathetic output will
  • Parasympathetic output will
• Stimulus


  • Low BP
  • High BP
• Response


  • Decrease
  • Increase
  • Decrease
  • Increase
• Baroreceptor reflex


  • Stimulus: BP decrease
  • Receptors: baroreceptors
  • Integrating center: cardiovascular control center in medulla oblangata
  • Efferents: sympathetic
  • Effectors: SA node, contractile cells in the ventricles, arteriolar smooth muscle
  • More stimulus = more sensory neuron
• Gas exchange between lungs and blood

  • Analogous to the cardiovascular system
  • Pump and pump rate
  • Fluid flow
  • Site of regulation of R
  • Exchange surface
• Upper respiratory


  • Mouth
  • Nasal cavity
  • Pharynx
  • Larynx
  • Regulate temperature to protect alveoli
  • Humidify air by adding water vapor
  • Cilia to keep pathogens out

  
• Lower respiratory


  • Trachea
  • Bronchi
  • Bronchioles
  • Lungs
• Successful respiration


  • Requires all 4 processes
  • Exchange 1: atmosphere to lung (ventilation)
  • Exchange 2: lung to blood
  • Transport of gases in the blood
  • Exchange 3: blood to cells
• Lung tissue = alveoli


  • Type I cells: simple squamous (exchange) epithelium (95%)
  • Type II cells: secrete surfactant
  • Maintain low levels of fluids in the alveoli
  • Low levels of surfactants causes lung to collapse and not be able to expand