which contract pushing the leaflets and cusps stopa.iii.4.AV node a.iii.4.a.Contains pacemaker cells a.iii.4.b.20 to 40 spontaneous deplorization a.iii.4.c.If your SA node gets wipe out, you can live due to AV node a.iii.4.c.i.Your heartbeats will be too low, required to use pacemakera.iii.4.d.Slows impulse propagation speed a.iii.4.e.Atria contract before ventricles a.iii.4.e.i.You don’t want that to happen at the same time because ventricles will win and the heart wont function properlya.iii.5.Cardic muscles can contract due to hormonal stimulation; they are modulated by the hormones and the nodes. a.iii.6.SA node and right atrial walla.iii.6.a.They conduct signals to the AV node via internoval fibers a.iii.7.SA nodal cell cannot hold a rmp (-60mv) – ions leak into cell and make it reach -40 action potential a.iii.8.Pre potential
a.iii.8.a.Spontaneous depolarization a.iii.8.b.Frequency of pre potentials is your heart rate a.iii.9.Why do we have a heart rate of around 70? a.iii.9.a.Because of vagal tone, the vagus nerve is sending a parasympathetic divison over to the SA node and dripping ACH and slowing down the heart ratea.iii.10.Exercising and increasing heart ratea.iii.10.a.Reducing your vagal tonea.iii.10.b.So when you first exercise so the first thing that jumps your heart rate up is the vagal brake which decreases your heart rate. a.iii.11.Parasympathic and Sympathetic nerve a.iii.11.a.They also intervede your myocardial cells a.iii.11.b.They drip chemicals on these cells a.iii.11.c.Heart is loaded with beta 1 receptors a.iii.11.c.i.So when sympathetic fibers release norepinepherine it massively activates your heart a.iii.11.c.ii.It’s called change in contractility (heart contracts harder) a.iii.12.Myocardial cells use calcium ions to excite the cell a.iii.12.a.You reduce the amount of calcium coming into yourheart cells, you reduce depolarization, you reduce contractility, you reduce the force, you reduce the blood pressure. b.The Electrocardiogram b.i.Responsible for the electrical events of your heart b.ii.Deflections b.ii.1.The amount of depolarization or repolarization b.iii.ECG characteristics b.iii.1.P wave
b.iii.1.a.Atrial depolarization b.iii.2.QRS complex b.iii.2.a.Where the atria is relaxing and the ventricle is contracting b.iii.3.T wave b.iii.3.a.Ventricular repolarization c.The Cardiac Cycle c.i.Phases of the cardiac cycle c.i.1.Atrial systole (contraction)c.i.1.a.Atria contract forces a small amount of blood into the ventricles c.i.2.Atrial diastole (relaxation)c.i.2.a.The first phase of ventricular systole c.i.2.a.i.The chamber is getting smaller so blood will go through the gaping hole – blood blasts av valves shut – first heartbeat c.i.2.b.Isovolumetric Ventricular Relaxation c.i.2.b.i.Blood is going no where, ventricle relaxation c.i.2.c.The second ventricular systole c.i.2.c.i.Rapid ejection phase c.i.2.c.ii.Eject blood into pulmonary circuit and systematic circuit c.i.3.Ventricular Diastole c.i.3.a.
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