Lec 2 - Cardiac Conduction & Cardiac Cycle

2. SA node ( The SA node automatically and rhythmically generates impulses, establishing a fundamental rate and rhythm.)

2. In a properly functioning heart what establishes the fundamental heart rhythm and is therefore called a sinus rhythm?

Internodal pathway

3 routes of the conduction system between the SA and AV nodes.

circulating hormones or by nerve fibers of either the P-ANS or S-ANS that innervate the SA node (Ex. P-ANS: Vagus Nerve S-ANS: Cardiac Accelerator Nerve)

3. The heart rate can be monitored by what two things?

vagus nerve (CN X) (SA nodal rate is set at 100beats per min or higher where resting heart rate is lowered to 60-80bpm due to vagus nerve )

4. What influences the SA heart rate to lower the typical resting heart rate of 60-80bpm?

the STRENGTH of the contraction

5. In addition to the change in heart rate because of the SA node, what else can be altered? It is caused by signals sent to the cardiac contractile fibers rather than conduction fibers.

Atrioventricular node ( from the internodel pathway, branches of this pathway extend to the right and left atria, allowing AP's to quickly depolarize with atria, resulting in the simulates contract of the atria)

6. From the SA node , impulses are propagated down the internodes pathway to the .... ?

allows time for the ventricles to finish filling with blood.

7. Meanwhile, an impulse reaches AV node. However there is a slight delay in electrical induction through the AV node that allows for what to happen?

Goes to ventricles by traveling through bundle of His, right and left bundle branches, and the Purkinje network of fibers, into the ventricular contractile cells, stimulating the simultaneous contraction of the two ventricles.

8. After the slight delay, electrical impulse continues into where, passing through what?

True

Action potentials are carried by the Purkinje fibers from the bundle branches to the ventricular walls. True/False

electrical impulse is the action potential of the heart.

Are electrical impulse and AP the same thing??

E.

In the heart, an action potential originates in the... A) urkinje fibers. B) bundle branches. C) atrioventricular bundle. D) atrioventricular node. E) sinoatrial node.

True

In the ventricles, the action potential travels along the interventricular septum to the apex of the heart, where it then spreads superiorly along the ventricle walls. True/False

True

T/F Any myocyte can imitate an impulse, but in a normally functioning heart the impulses originate at the SA node since theses cells have the FASTEST RHYTHMIC intrinsic rate.

A.

The sequence of travel by an action potential through the heart is... A) sinoatrial node, atrioventricular node, atrioventricular bundle, bundle branches, Purkinje fibers. B) atrioventricular node, sinoatrial node, atrioventricular bundle, bundle branches, Purkinje fibers. C) atrioventricular bundle, atrioventricular node, sinoatrial node, bundle branches, Purkinje fibers. D) Purkinje fibers, atrioventricular bundle, atrioventricular node, sinoatrial node, bundle branches. E) atrioventricular node, sinoatrial bundle, atrioventricular node, bundle branches, Purkinje fibers.

True (conducting and contractile)

There are two types of cardiac myocytes. T/F

Vagus nerve

What is responsible for establishing the RESTING HR?

3. ≥ 100 bmp

What is the rate that is typically established by the SA node alone? 1. ≤ 60 bmp 2. 60-80 bmp 3. ≥ 100 bmp 4. None of the above. The SA node does not establish the rate of the heart.

1. Myocardial contractile cells 2. myocardial conducting cells

What two major types of cardiac muscle make up the myocardium?

the AV node ( allows time for ventricles to finish filling with blood)

Where is there a slight physiological delay in the electrical conduction?

Myocardial Conducting Cells

-(1%) of the cells in the atria and ventricles - function is similar to that of a neuron, although they are specialized cells -initiate and propagate APs that travel throughout the heart and trigger the contractions.

AV bundle (bundles of His) step 3

-in the interventricular septum. -ONLY site where the AP's can conduct from the atria to the ventricles.

AV nodes ( atrioventricular node) step 2

-located in the interatrial septum. -conducts the normal electrical impulse from the atria to the ventricles. -this is were the AP slows down, providing time for the atria to empty their blood into the ventricles

Purkinje fibers (step 5)

-rapidly conduct the AP first to the apex of the ventricles and then upward to the remainder of the ventricular myocardium. -conduction fibers (fast conduction)

SA nodes (sinoatrial) step 1

-small specialized region of conducting myocytes in the right atrial wall. -is the pacemakers of the heart' - also called the sinus node - generates electrical impulses and conducts them throughout both atria via gap junctions in the intercalated discs of atrial fibers. -Allows atria to contract first the the ventricles.

1. In the SA node ( Any myocyte..type of cell I'm muscle tissue... can initiate an impulse.)

1. In a normally functioning heart where does the pathway for electrical impulses initiate? And what can initiate the impulse?

A.

Which of the following is true concerning the heart conduction system? A) action potentials pass slowly through the atrioventricular node. B) action potentials pass slowly through the atrioventricular bundle. C) action potentials pass slowly through the Purkinje fibers. D) action potentials pass slowly through the ventricle wall. E) action potentials pass slowly through the bundle branches.

Right and Left bundle branches (step 4)

after entering the AV bundle the AP comes through here on its way to the apex of the heart.

sinus rhythm

another word for heart rhythm?

autorhythmicity

cardiac muscle's ability to initiate an electrical potential at a fixed rate that spreads rapidly from cell to cell to trigger the contractile mechanism.

myocardial contractile cells

constitute the bulk of the cells in the atria and ventricles (99%)

Sick Sinus syndrome (SSS) ex. arrhythmia or dysrhythmias

describes an abnormally functioning SA node that initiates irregular heartbeats? give two ex.

SA node

establishes the fundamental rhythm of the heart?

neuroendocrine system

establishes the resting Heart Rate or rhythm and the contractility of the heart (force at which it pumps) by sending impulses?

Sinus Tachycardia

normal SA node rhythm, but rate is fast (>100)

Sinus Bradycardia

normal SA node, but rate is slow (<60bpm)

established by the SA node and also called the sinus rhythm

the heart rhythm is established by what and can also be called what?

Artificial Pacemaker that sends out small, regular electrical currents to stimulate myocardial contraction.

treatment of SSS?

1. electrical activity

what are the two types of skeletal muscle graphs?

1. Signals fro the ANS 2. Signaling hormones (Epinephrine)

what two things modify the rate and the strength of contractions?

in the floor of the right atrium near the intertribal septum.

where is the AV node located?

They modify the function of the heart in terms of rate and or strength of contraction, but they do NOT establish the FUNDAMENTAL rhythm.

How do signals from the ANS and signaling hormones (epinephrine) effect and not effect the heart?

1. SA nodes (sinoatrial node) 2. Internodal pathway 3. AV node ( atrioventricular node ) 4. AV bundle (bundle of His) 5. Right and left bundle branches 6. Purkinje fibers

Components of the intrinsic conduction system (ICS) 6 of them.

endocrine and nervous system.

Even though cardiac muscle has audtorhythmicity, a person's heart rate is by what?

Pathway of electrical impulses in cardiac system...

Pathways of electrical impulses in cardiac system...

SA node: rate ~100 AV node: rate 40-60 Vent. tracts: rate 20-40

SA node: rate ~100 AV node: rate 40-60 Vent. tracts: rate 20-40

Skeletal VS Cardiac muscle AP's...

Skeletal VS Cardiac muscle AP's...