​Cardiac Cycle

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​Cardiac Cycle

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 How long does the average cardiac cycle last?

Intrinsic (ANS)

• PNS and SNS​

Extrinsic

• ​Endocrine and Baroreceptors- stretch/pressure in the carotid artery

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Regulation of the Heart

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Sympathetic

Increases rate and forces contractions

Parasympathetic (branches of Vagus n.) Slows the heart rate

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Autonomic Regulation

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​Pacemaker

​The SA node or sinus node is able to spontaneously generate and propagate electrical impulses

generating the heart rate​

60-100 b​pm

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Sinoatrial node​

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• ​SA node

  • atrium contraction​

• ​AV node

• bundle of HIS

• right and left branching purkinje fibers

  • ventricle contraction​

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​Electrical innervation of the Heart

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Measures the electrical impulses ​of the heart

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Depolarization is the contraction phase (systole)

​Repolarization is the relaxation phase (diastole)

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P= atrial systole

QRS= ventricle systole

​T= ventricle diastole

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Electrocardiogram

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​Which of these terms refers to when the electrical impulse starts in the SA node and causes the atria to contract?

Electrocardiogram

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​Abnormal timing or contraction of the heart

• Bradycardia

  • ​resting heart rates that fall below 60 bmp

• Tachycardia

  • resting heart rate that is above 100 bpm

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​​Arrhythmia

​Abnormal timing or contraction of the heart

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• ​Ventricular tachycardia (vtach)

  • ventricles, rather than SA node, cause beat ​

​​Arrhythmia

​Abnormal timing or contraction of the heart

• ​Atrial fibrillization (afib)

  • atria contract faster than 350 bpm

• Ventricular fibrillation (vfib)

  • ventricles contract faster than 350 bpm

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​​Arrhythmia

​Abnormal timing or contraction of the heart

• ​Heart Block

  • impulse from SA node to AV node

    • first–impulse delayed

    • second–intermittently blocked

    • third–completely blocked

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​​Arrhythmia

Artificial Pacemakers

devices used to regulate the contraction of atriums or ventricles​

AED (automated external difibulator)

emergency ​device used to send an electrical impulse to help reestablish heart rhythm

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Medical Devices​

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What a heart attack looks like

A Heart Attack occurs when the blood flow that brings oxygen to the heart muscle has been slowed or stopped.

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Heart attack continued

This happens because coronary arteries that supply the heart with blood can slowly become thicker and harder from a buildup of fat, cholesterol and other substances, called plaque. It's similar to the stuff that grows on your teeth!

Heart attack continued

If the plaque breaks open and a blood clot forms that blocks the blood flow, a heart attack occurs. See image and next slide will show more.

Heart attack continued

The blood supply is less and tissues in the heart start to die, this is bad.

Heart Attack continued

That dead tissue is where the heart attack happens. Notice the heart how the color has changed. This is a sign the heart tissue is dying and there could be greater problems.

What is cardiac arrest?

cardiac arrest is caused when the heart’s electrical system malfunctions.

Is a heart attack the same as cardiac arrest?

No. Remember, a heart attack is caused by a blockage that stops blood flow to the heart. Cardiac arrest is an electrical problem in the heart.

Emergency Treatment of Cardiac Arrest

Here are the signs:

Sudden loss of responsiveness The person doesn’t respond, even if you tap him or her hard on the shoulders, or ask loudly if he or she is OK. The person doesn’t move, speak, blink or otherwise react. No normal breathing The person isn’t breathing or is only gasping for air.

What to do

Yell for help and tell someone nearby to call 911 or your emergency response number. Ask that person or another bystander to bring you an AED (Automated External Defibrillator) and start CPR!

Check breathing

If the person isn’t breathing or is only gasping for air, administer CPR. Look, listen and feel for 10 seconds while checking for breathing. Look at their chest to see it it's rising, listen to their nose for air movement, and feel on your cheek for moisture from the breath.

Give CPR: Push hard and fast

Remember to do chest compressions 30 times and 2 breaths. Compressions should be at a depth of 1 1/2 to 2 inches.

The three major ions that involve in generation of action potential of SA node are sodium, calcium and potassium.

There are three important events that before and during the action potential generation.

This slide is to show the relationship of electrical impulse conduction with the activity of the heart.

note refractory period for cardiac muscle fibers lasts as most as long as muscle contraction, in comparison to skeletal muscle fibers.

Parasympathetic stimulation decreases the heart rate. However sympathetic stimulation increases heart rate and force of contraction.