Heart Conduction

is a group of specialized cardiac muscle cells in the walls of the heart that send signals to the heart muscle causing it to contract

Cardiac conduction system

What are the main components of the cardiac conduction system?

SA node, AV node, bundle of His, bundle branches, and Purkinje Fibers

Cardiac muscle cells can and do contract…even if all nervous connections are severed.

Spontaneously and independently

Although cardiac muscles can be independent, the muscle cells in different
areas of the heart have different what?

Rhythm

Atrial cells beat how many times per minute and how many does ventricular beat per minute?

A→ 60/min

V→20-40/min

Two types of controlling systems act to regulate heart activity

Autonomous & Intrinsic

Heart system that act like “brakes” and “accelerators” to increase or decrease the heart rate

Autonomous

Another system of the heart that is either conduction system or nodal system

Intrinsic system

The intrinsic system is built into where?

Heart tissue

Is composed of special tissue found nowhere else in the body; it is like a cross between muscle and nervous tissue

Intrinsic conduction system

The intrinsic conduction system enforces a contraction rate of about…

75 beats/min

The intrinsic system keeps the heart beating as what type of unit?

coordinating unit

Parts of the Intrinsic Conducting System

Sinoatrial (SA) Node

Atrioventricular (AV) Node

Atrioventricular (AV) Bundle

Purkinje Fibers

Often called the pacemaker of the heart. Starts each heartbeat and set the pace (speed)

Sinoatrial (SA) node

Where is the SA node located?

Right atrium

Located at the junction of the atria and ventricles

Atrioventricular (AV) Node

Also called the Bundle of His. Divide into the right and left bundle branches

Atrioventricular (AV) Bundle

Where is the Atrioventricular (AV) Bundle located?

Interventricular septum

Spread out within the muscle of the ventricular walls.

Purkinje Fibers

Controls how fast or slowly your SA node sends electrical signals. This part of the nervous system directs hormones that control your heart rate based on what you are doing

Autonomous Nervous System

What system of the heart controls the increase in heart during exercise and decrease heart rate during sleep?

Autonomous Nervous System

The autonomous nervous system includes your

Sympathetic nervous system & Parasympathetic nervous system

(fight or flight response) makes your SA node work faster, which increases your heart rate

Sympathetic nervous system

(rest and digest response) makes your SA node work slower, which decreases your heart rate

Parasympathetic nervous system

Refers to the events of one complete heartbeat, during which both atria and ventricles contract then relax

Cardiac cycle

How long does the length of the cardiac cycle normally last?

0.8 sec

is the amount of blood pumped out by each side of the heart in one minute

Cardiac Output

What is the product of the heart rate and the stroke volume

Cardiac output

Is the volume of blood pumped out by a ventricle with each heartbeat

Stroke volume

What are the heart sounds

Lub

Dup

Murmur

First sound is caused by the closing of the AV valves. Longer and louder than the second heart sound

Lub

What causes the Lub sound of the heart?

The closing of the AV valves

Second heart sound heard occurring when the semilunar valves close at the
end of systole (contracts). Sound tends to be short and sharp

Dup

Dup occurs when the semilunar valves close at the end of what?

Systole (contracts)

Abnormal or unusual heart sounds

Murmur

SA node starts the signal which spontaneously generates what that starts the heartbeat?

Electrical impulses

After the SA node starts an electrical signal it spreads throughout where?

spreads across the muscle of both atria (Atrial myocardium)

Signals causes the atria to contract and push blood into the…

Ventricles

After the signal spreads throughout the atrial myocardium the signal is then received by what?

AV (atrioventricular) node

The AV (atrioventricular) node briefly delays the signal which is important because it gives the atria time to finish contracting before what occurs

Ventricles contract

How long are the delays at the AV (atrioventricular) node?

0.1s

After the signal enters the AV bundle (bundle of HIS) it carries the electrical impulse from the AV node toward the…

Ventricles

The AV bundle is divided into

Right & Left bundle branch

The signals travel through the right and left bundle branches which sends signals down to where?

The right bundle branch to the right ventricle

The left bundle branch to the left ventricle

Finally the signal reaches where that help spread the electrical signal rapidly throughout the ventricular walls

Purkinje fibers

B/c the Purkinje fibers spread the electrical signal throughout the ventricle wall it causes the ventricles to contract which causes what?

The blood to be pushed out of the heart