Exam 4 Flashcards
Length of cardiac muscle action potential and why is it important
250ms, therefore the refractory period is long and therefore under normal conditions the muscles cannot undergo tetanic contractions
Resting membrane potential of cardiac muscle
-90mv
General shape of the action potential of cardiac muscle
there’s a sharp depolarization and then the bulk is a plateau which then repolarizes quickly (not as quick as the depolarization)
SA node, how many action potentials per minute, and how many potentials make its way through the conduction system, how do the action potentials spread
sinoatrial node, pacemaker, near the cardiac sinus in the right atrium, automaticity; will undergo around 100 action potentials per minute under normal conditions; not every change in membrane will make its way through the rest of the conduction system and this is why the number isn’t the same as heart rate; potentials will spread through the rest of the atria due to cells being connected by gap junctions
Will conduction pass from the atria to the ventricles
no, due to the connective tissue it prevents the conduction to pass through
AV node
atrial ventricular node, connected to interventricular septum, sends conduction to the bundle of His
Automaticity
undergo regular patterns of action potentials independent of the nervous system
Interventricular septum
tissue that runs down the middle of the heart
Bundle of His
divides into two branches, the right branch innervates to myocardial tissue of the right ventricle, left branch innervates to myocardial tissue of the left ventricle, sends conduction to Purkinje fibers
Purkinje fibers
extensions of specialized myocardial cells that make their way throughout the myocardium of the right and left ventricle
P wave
atrial depolarization, point just before contraction of atrial muscle
QRS waves, why is this larger than P wave
ventricular depolarization; due to the increased amount of myocardial tissue in the ventricles
T wave
ventricular repolarization
Missing EKG wave
atrial repolarization, is overshadowed by ventricular depolarization
Nodal cell resting membrane potential
-55 to -60
Where and why is there thin myocardium
the left ventricle has thicker myocardium than the right ventricle due to the left ventricle moving blood into the systemic circuit while the right ventricle moves blood into the pulmonary circuit; myocardium in the atrium is not as thick as in the ventricles because the atria don’t do much work moving blood into the ventricles, the pressure of blood entering the chambers is almost always enough to push blood down into the ventricles , the atria gives it the final push
Ventricular myocardial action potential length and corresponding EKG waves, regulated by what
is 250-300ms long; depolarizes from -90 to +20mv corresponds to depolarization of ventricles QRS, repolarization corresponds with the T wave; regulated by changes in permeability of sodium, calcium, and potassium
What causes the gradual repolarization of ventricular myocardial action potentials
decrease in potassium permeability meaning that the potassium efflux is decreased and positively charged potassium stays within the cell, the increase of permeability of calcium due to T type calcium channels opening, f type sodium channels will pen when the cell is in its most hyperpolarized state
What leads to repolarization of myocardial cells
decrease of calcium permeability and increase of potassium permeability
Central nervous system
brain and spinal cord
Peripheral nervous system
everything else connected to brain and spinal cord, somatic and autonomic, sympathetic and parasympathetic, acramine
Acramine parasympathetic nervous system
salivation, lacrimation, urination, digestion, defecation
Sympathetic and parasympathetic activity
are always active but one could overpower the other
Cardiac output
HR*SV, average cardiac output is 5L/min