Heart

The sinoatrial (SA) node (known as the heart's pacemaker) in the wall of the right atrium is where electrical signals originate and lead to contraction. It sets the rate of contraction; at rest this is about 70 to 80 bpm (beats per minute). The SA node causes the atria to contract (down from the top), forcing blood into the ventricles. The SA node can also be influenced by external sources (such as exercise, increased adrenaline, or drugs) that can increase or decrease the force of contraction (heart rate).

The atrioventricular (AV) node passes the electrical signals from the atria to the ventricles, then to the bundle of His. If the SA node is damaged, the AV node takes over its functions.

The bundle of His (also known as the atrioventricular bundle) is a tissue within the ventricular septum. It splits to form the right and left bundle branches. The bundle of His passes the electrical signals to the Purkinje fibers.

The Purkinje fibres pass the electrical signals to the myocardium (heart muscle) in the ventricles. The ventricles contract (up from the bottom), pushing blood into the aorta and pulmonary arteries.
Electrical conduction system of the heart is the class, a subclass of body part
SA Node (causes contraction of atria) to AV Node ( delay from SA to AV allows atria to contract before ventricles), to Bundle of His (atrioventricular bundle) where the fibers branch into twos and carry impulses down the center of the heart to both ventricles and at base of heartfurther branching into Purkinje Fibers, which trigger muscle fibers of ventricles to contract.

Generally, the most basic formula for calculating the maximum heart rate that is considered safe is:

220 - your age.

Your heart rate will naturally increase to that level as a reaction to a lot of things: like exercise, blood pressure drops and adrenaline surges. It is called sinus tachycardia.

That's the short answer. If you want more info, the long answer is to come ;)

The formula has at least 50 variations, any of them can only give a rough estimate, based on age alone. There are many other factors to be considered alongside this. The most reliable method of finding the maximum heart rate is through a Cardiac Stress Test, which is basically just running on a treadmill while hooked up to an ECG and occasionally increasing the speed and slope. The real maximum heart rate depends on your age, size, weight, fitness and a little genetic randomness.

Here's the kicker though: there's a lot of different types of fast heart rate, which is medically referred to as "tachycardia". It's almost never fast heart beat that causes death; your body often increases it's heart rate as a reaction to some other kind of stimulus, but if it continues for a while then the heart's increased workload and demand for oxygen can cause ischemia. It can also degrade into become arrhythmic (irregular beat) if the underlying problem is not solved - arrhythmia will definitely kill you. Then of course, there is always the possibility of full blown cardiac arrest.

Hope this helped you

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===other ping or tap under the valve covers==

sticking lifters, excessive clearances, some parts loose inside the valve covers, pushrod(s) bent

A farmers' method is to take a long screwdriver, put the handle against your ear and the blade against valve cover with engine running (be careful so nothing you wear nor any body parts are caught in the fan and the belts, and that you don't burn yourself on the engine or exhaust headers) - by moving the screwdriver blade front to back on the cover, and even down to the block between exhaust ports, you should be able to hear where the noise is located.

Galen stated that blood passed from the right to the left side of the heart but decided this was via tiny pores in the septum instead ofthe pumping action of the heart. He also believed that blood was formed in the liver and was circulated from there throughout the body in the veins. He showed that arteries contain blood, but thought they also contained and distributed "pneuma"/vital spirit.