PHYSIO II: Unit 1

• Endurance training increases capillary density and mitochondrial activity
• Resistance training increase hypertrophy + increases actin and myosin
• Cardiac endurance training causes eccentric hypertrophy to increase blood volume adds cells in series to form longer chain.
• What is the change in cardiac muscle when endurance training?

  Volume change
• Cardiac resistance training causes concentric hypertrophy, thickens ventricle, and increases blood pressure.
• How does blood flow through the body?

  Parallel flow
• Some systemic floow uses series flow? Which ones and why?

  GI -> Liver because toxin disposal. (GI digests energy and toxins and needs to be filtered through liver)
• Coronary circulation feeds oxygen to blood specifically. Which arteries are involved?

  • Right coronary a.
  • Left coronary a.
  • Circumflex a.
  • ANT. interventricular a.
• Left coronary a. supplies 75% of the myocardium with blood.
• Right coronary a. supplies 25% of the myocardium with blood.
• Cardiac veins drain blood from heart muscle. Major v. is coronary sinus
• Blocked a. in heart/occlusion can lead to heart attack. How to solve? (2)

  Coronary angioplasty (non-invasive and fills stent)

  Coronoary bypass (invasive and bypasses occlusion)
• Heart doesn't require nerve input to continue beating aka autorhythmicity.
• 2 types of authorythmic cells are pacemaker cells and conduction fibers.
• Sinoatrial (SA) node is the pacemaker of the heart
• Which ion should be outside of the cell?

  Na+
• Which ion should be in the inside of a cell?

  K+
• Pacemaker cell does not have true resting membrane potential of -70mv and goes straight back up to threshold named the pacemaker potential.
• Phase 1: Repolarization of pacemaker cell

  • K+ leave cell until -70mv -> close
  • Funny channels open (doesn't have stim)
  • Allow Na+ and K+ moves (More Na+ in than K+ out)
• Phase 2: Pacemaker Potential

  • T-type channels allow a bit of K+ to enter the cell (closer to thresthold)
  • Funny channels close at -55mv
• Phase 3: Pacemaker cell

  • At -50mv T-type channels close, L-type channels open
  • Allows Ca2+ to enter cell very quickly
  • -50 mv -> +20-30mv (positive)
• Phase 4: Repolarization of pacemaker cell

  • L-type channels close
  • K+ channels open (allows K+ to leave the cell)
• Calcium channel blockers are used in cardiac patient medication on L-type and T-type channels.
• SA node has fastest rythym of 60-100bpm. (and controls other rates)
• If SA node is affected can heart still beat?

  Yes. It'll go to the next fastest one but it won't beat as fast so lower HR. Tired and lethargic.
• AV node momentarily pauses for atrium to relax and empty blood volume (to fully contract and bring blood into the ventricles).
• Gap junctions allow ions from one cell to neighbouring cell to depolarize. Which is important for cell to contract simulatenously.
• Phase 0: AP of myocardial cells

  • stim from pacemaker cell -> opens Na+ channels (rushes in)
  • -90mv -> +30mv
• Phase 1: AP of myocardial cells

  • Once depolarized: brief plateau
  • Slight drop bc inward rectifier K+ channels (allow a bit of K+ to escape so brief repolarization)
• Phase 2: AP of myocardial cells

  • inward rectifier K+ channels close
  • L-type Ca2+ channels open (allows Ca2+ in)
  • Plateau
• Phase 3: AP of myocardial cells

  • slight drop -> L-type channels close
  • delayed rectifier K+ channels open (allow a lot of K+ to leave the cell)
  • Repolarization
• Phase 4: AP of myocardial cells

  • inward and delayed rectifier K+ channels open
  • make membrane potential at -90mv
• How to modify HR?

  autonomic nervous system
• Sympathetic division of NS to increase HR

  • uses hormones: epinephrine and norepinephrine to stim faster HR
• Parasympathetic division of NS to decrease HR
• Parasympathetic inn. by vagus n. from medulla oblongata. Stim SA node and AV node.
• Sympathetic inn. by thoracic spine. Stim SA node, AV node, and myocardium. VERY FAST. Increase force of contraction and HR.
• Sympathetic and parasympathetic...one has to withdraw in order for one to increase and don't work at the same time.
• Refractory period is when another action potential CANNOT occur.
• Refractory period in skeletal muscle:

  • depolarization + repolarization: no AP can occur
  • hyperpolarization: AP can occur
  • peak tension goes up and stays up (incomplete tetanic contraction)
  • ADVANTAGE: creates sustained contraction longer