heart Flashcards
When the heart contracts
the the blood makes a round trip in and out of the heart
The heart pushes the body supply of 6 litters through the blood vessels 1000 times a day which means
it pumps about 6000 quarts of blood a day(1500 gallons)
Cardiac cell can contract
automatically and independently
The muscle cells in different parts of the hearts
have different rhythms
There are two main systems that regulate heart activity:
The Nervous System (Autonomic Nervous System)
The Intrinsic Conduction System (Nodal System)
the automatic system:
acts like gas and brake pedals to decrease or increase the heart rate,depending on which division is activated
intrinsic conduction system, or nodal system
this is built onto the heart tissue and sets its basic rhythm like a drummer sets the beat for a rock band playing a song
What is the intrinsic conduction system, and how does it cause heart muscle depolarization?
The intrinsic conduction system is composed of special tissue found only in the heart, which acts like a combination of muscle and nervous tissue. It causes heart muscle depolarization in only one direction—from the atria to the ventricles.
What is the Sinoatrial (SA) Node, how does the conduction pathway work, and what is heart block?
Sinoatrial (SA) Node: Located in the right atrium, the SA node initiates the heartbeat because it has the fastest rate of depolarization in the conduction system. It’s often called the heart’s “pacemaker.”
Conduction Pathway: The SA node initiates an impulse that spreads through the atria, causing them to contract. The impulse reaches the AV node, where there is a brief delay for the atria to finish contracting. It then travels through the AV bundle (bundle of His), the bundle branches, and the Purkinje fibers, resulting in ventricular contraction.
Heart Block: Damage to the AV node can block the impulse from the SA node, causing the ventricles to beat slower. The atria and ventricles are separated by connective tissue, preventing depolarization waves from reaching the ventricles directly.
Conditions Affecting the Conduction System: Damage to the SA node can result in a slower heart rate and may require the installation of an artificial pacemaker.
Sinoatrial (SA) Node: The impulse starts at the SA node, located in the right atrium. It generates an electrical signal that causes the atria to contract. This is what initiates each heartbeat.
Atria: The electrical impulse spreads through the walls of both atria, causing them to contract and push blood into the ventricles.
Atrioventricular (AV) Node: The impulse then moves to the AV node, located at the junction of the atria and ventricles. The AV node briefly delays the signal to allow the atria to finish contracting before the ventricles are stimulated.
AV Bundle (Bundle of His): After the AV node, the impulse travels through the AV bundle (or Bundle of His) down the interventricular septum (the wall between the ventricles).
Bundle Branches: The impulse then moves to the right and left bundle branches, which extend through the interventricular septum toward the apex of the heart.
Purkinje Fibers: Finally, the impulse travels through the Purkinje fibers that spread across the walls of the ventricles, causing the ventricles to contract and pump blood out of the heart.
What are the different heart conditions like ischemia, tachycardia, bradycardia, and fibrillation, and how can AEDs help?
Ischemia: Lack of blood flow to the heart muscle can lead to fibrillation, where the ventricles quiver instead of contracting properly. This is a life-threatening condition.
Tachycardia: A rapid heart rate (over 100 beats per minute), which can lead to fibrillation if prolonged.
Bradycardia: A slow heart rate (less than 60 beats per minute), which is not necessarily pathological but may require attention if symptoms arise.
Fibrillation: A chaotic, uncoordinated contraction of the ventricles, often caused by ischemia. It prevents the heart from pumping blood effectively and is a leading cause of death in heart attack patients.
AEDs (Automatic External Defibrillators): These devices are used in emergencies to correct fibrillation and save lives by restoring normal heart rhythm.
What is the cardiac cycle, and what are the terms systole and diastole?
Cardiac Cycle: The events of one complete heartbeat, during which both the atria and ventricles contract and relax. The average heart beats about 75 times per minute, making the length of the cardiac cycle approximately 0.8 seconds.
Systole: Refers to heart contraction. It typically refers to the ventricular contraction, as the ventricles do most of the pumping work.
Diastole: Refers to heart relaxation, during which the heart chambers (atria and ventricles) fill with blood in preparation for the next contraction.
