The larger waves represent ventricular contraction because the ventricles of the heart are much stronger than the atria. The amplitude did not change with frequency because the heart has a long stimulation refractory period.Moreover, why is it only possible to induce an Extrasystole during relaxation?
Extrasystole is only possible during relaxation because no new stimulation can take place during the absolute refractory period. Due to this wave summation tetanus can't be achieved and the extrasystole can't occur until relaxation.
Furthermore, why is it important that summation not occur in heart muscle? 3. Wave summation and tetanus do not occur in cardiac muscle because the flow of blood through the heart is dependent upon the atria contracting fully and the ventricles contracting fully. Summation would pre- vent the heart from pumping properly.
Also Know, what was the effect of stimulating the heart during ventricular contraction?
The AV node slows the impulses from the SA node, firing at a normal rate of 40-60 bpm, and causes depolarization of the ventricular muscle tissue and ventricular contraction. Sympathetic nervous stimulation increases the heart rate, while parasympathetic nervous stimulation decreases the heart rate.
Why is Ringer's solution required to maintain heart contractions?
Describe why Ringer's solution is required to maintain heart contractions. it contains all the ions, pH, glucose, ATP need to keep the heart beating. Explain the effect that increasing the temperature had on the frog heart. -Slows the sodium pump, which lets more Na+ accumulate heart muscle cells.
What does an Extrasystole correspond to how did you induce an Extrasystole?
An extrasystole corresponds to an extra ventricular contraction. We did this by inducing another cardiac action potential during the relaxation phase by using an electrical stimulus. Multiple stimulus did not cause the amplitude of the wave to increase because the heart has such a long refractory period.What would happen to the heart of the vagus nerve was cut?
Lowering the heart rate and blood pressure: If the vagus nerve is overactive, it can lead to the heart being unable to pump enough blood around the body. In some cases, excessive vagus nerve activity can cause loss of consciousness and organ damage.Why tetanus does not occur in heart muscle?
Cardiac muscle tissue contracts without neural stimulation, a property called automaticity. As a result, cardiac muscle tissue cannot undergo tetanus (sustained contraction). This property is important because a heart in tetany could not pump blood.Why wave summation and tetanus are not possible in cardiac muscle tissue?
Wave summation and tetanus are not possible in cardiac muscle tissue because cardiac cells have longer action potentials and a very long refractory period compared to other cells. This helps prevent the heart from cramping and seizing up.What causes vagal escape?
Vagal escape is characterized by a reduction in blood pressure due to muscarinic stimulation which is then compensated for stimulation from the sympathetic system to increase heart rate and thus blood pressure. When the heart is continuously stimulated via the vagus nerve, initially there is stoppage of heart beat.What effect does potassium have on the resting membrane potential of the cardiac cell?
What effect does potassium have on the resting membrane potential of the cardiac cell? Increasing extracellular potassium causes the resting membrane potential to become more positive. The cardiac cell plasma membrane is most permeable to _______________________.What effect does sympathetic nervous system stimulation of the heart have on cardiac output?
The sympathetic nervous system releases norepinephrine (NE) while the parasympathetic nervous system releases acetylcholine (ACh). Sympathetic stimulation increases heart rate and myocardial contractility.Where in a heart cell is calcium normally found?
sarcoplasmic reticulum
How do you calculate cardiac output?
Cardiac output is the volume of blood the heart pumps per minute. Cardiac output is calculated by multiplying the stroke volume by the heart rate. Stroke volume is determined by preload, contractility, and afterload.What measures the total time of the ventricular contraction?
Ventricular systole (see image below) follows the depolarization of the ventricles and is represented by the QRS complex in the ECG. It may be conveniently divided into two phases, lasting a total of 270 ms.What are the 4 phases of cardiac cycle?
The cardiac cycle involves four major stages of activity: 1) "Isovolumic relaxation", 2) Inflow, 3) "Isovolumic contraction", 4) "Ejection".What wave of the ECG tracing would be affected in atrial fibrillation?
Atrial Fibrillation The ECG tracing will not show a distinct P wave since the rate is extremely rapid (350-600). The P waves appear as an atrial wave or in other words, wavering lines with no distinct P wave visible (see figure below). The patient's pulse is irregular.How do you measure stroke volume?
Stroke volume is calculated using measurements of ventricle volumes from an echocardiogram and subtracting the volume of the blood in the ventricle at the end of a beat (called end-systolic volume) from the volume of blood just prior to the beat (called end-diastolic volume).What does cardiac output mean?
Cardiac output: The amount of blood the heart pumps through the circulatory system in a minute. The amount of blood put out by the left ventricle of the heart in one contraction is called the stroke volume. The stroke volume and the heart rate determine the cardiac output.Why is there is a delay between the R wave on the ECG and the decrease in ventricular volume?
AV-NODAL DELAY: There is a delay in depolarization of about 90msec, once the impulse reaches the AV-Node. The function of this delay is to separate the contraction of the atria (i.e. atrial systole) from that of the ventricles (ventricular systole), so that more blood has a chance to fill into the ventricles.What produces the heart sounds heard with a stethoscope?
Normally, two distinct sounds are heard through the stethoscope: a low, slightly prolonged “lub” (first sound) occurring at the beginning of ventricular contraction, or systole, and produced by closure of the mitral and tricuspid valves, and a sharper, higher-pitched “dup” (second sound), caused…What is the main pacemaker of the heart?
The sinoatrial (SA) node or sinus node is the heart's natural pacemaker. It's a small mass of specialized cells in the top of the right atrium (upper chamber of the heart). It produces the electrical impulses that cause your heart to beat. These are called demand pacemakers. 
