Lab 7

The pacemaker region of the heart is the

SA node

The conducting tissue of the heart located in the interventricular septum is the

Bundle of His

P wave

depolarization of the atria

QRS wave

depolarization of the ventricles

T wave

repolarization of ventricles

The electrical synapses between adjacent myocardial cells are called

gap junctions

An abnormally fast rate of beat is called ___ and abnormally slow rate is called ___

Tachycardia, bradycardia

An abnormally long P-R interval indicates a condition called

1st degree heart block

Leads I, II, III are collectively called the

standard limb leads

Which ECG wave must occur before the ventricles can contract?


Which ECG wave must occur before the ventricles can relax

T wave

What property makes the normal pacemaker region of the heart function as a pacemaker? Explain

The SA node fibers serve as the pacemaker of the heart because they open special ion channels and undergo spontaneous depolarization faster than any other fibers in the heart. Consequently, the SA node sets the pace, generating APs that are rapidly conduc

Describe the pathway of conduction from the atria to the ventricles and correlate this condition with the ECG waves.

Depolarization spreads through the atria producing the P wave. After a delay at the AV node, the depolarization and spreads down the bundle of His to the purkinje fibers in the ventricular myocardium. This produces the QRS wave. Repolarization of the vent

Compare supraventricular tachycardia with ventricular tachycardia in terms of its nature, ECG pattern, and

Supraventricular tachycardia is characterized by an abrupt rapid atrial beat that drives a rapid ventricular beat for short intervals for periods of time. The ECG is normal in appearance and the ventricles are able to pump blood during this brief conditio

What happens to the beating of the atria and ventricles during third-degree Av node block? Why does this occur?

In third-degree AV node block, none of the impulses from the atria reach the ventricles. No longer subservient to the SA node rhythm, the ventricle fibers beat at a much slower rate (20-45 bpm) and do not respond to any demands from the cardiovascular con

The ECG wave that occurs at the beginning of ventricular systole is the

QRS wave

The ECG wave that occurs at the end of systole and the begging of diastole is the

T wave

The ECG wave completed just before the end of ventricular diastole is the

P wave

The nerve that increases the rate of discharge of the SA node is a

sympathetic nerve

The specific nerve that, when stimulated, cause a decrease in the cardiac rate is the


The scientific term for insufficient blood flow to the heart muscle is


Describe the regulatory mechanisms that produce an increase in cardiac rate during exercise. Explain how these changes affect the electrocardiogram (ECG).

At the beginning of the exercise, there is a decrease in the activity of the parasympathetic (vagus) Innervation of the heart. This causes an increase in cardiac rate that is further raised during greater levels of exercise by increased sympathetic nerve

Describe the pressure changes that occur within the ventricles as each ECG wave is produced, and explain how these pressure changes are related to the ECG waves

During the P wave depolarization of the atria, pressure in the ventricles changes little.
During the Q to R the septum is depolarizing and starting to contract with only slight changes in the ventricular pressure.
The R to S interval completes depolarizat

When blood pressure measurements are taken, the first sound of Korotkoff occurs when the cuff pressure equals the ___ pressure


The last Korotkoff sound occurs when the cuff pressure equals the ___ pressure


The sounds of Korotkoff are produced by

turbulent blood flow

If a persons blood flow is 168/112

What's the systolic pressure: 168
What's the diastolic pressure: 112
What is the pulse pressure: 56
What is the mean arterial pressure: 130

What condition does a person with 168/112 have


The arterial blood pressure is directly proportional to two factors

cardiac output and total peripheral resistance

The scientific name of the device used to take blood pressure reading


Describe what is meant by "laminar flow" and "turbulent flow". Before you inflate the cuff, which term more closely describes the blood flow in the brachial artery? Explain.

Laminar or layered flow of blood through the arteries occurs when all parts of the fluid move smoothly in the same direction parallel to the axis of the vessel. Blood in the central axial stream moves the fastest, and blood closer to the artery wall moves

How are the Korotkoff sounds produced? When do you hear the first Korotkoff sound? When do you hear the last Korotkoff sound? Explain why this is true of the first and last sounds.

Vibrations heard through a stethoscope due to the turbulent flow of blood through a partially compressed brachial artery cause Korotkoff sounds. The narrowing of the lumen creates turbulent flow and the vibrations produced are characterized as Korotkoff s

How is the pulse pressure calculated, and how does it's value relate to the pulse? Also, describe how the mean arterial pressure is calculated, when explain its significance.

The pulse pressure is systolic minus diastolic pressure. As the blood pressure rises from diastolic to systolic values within an artery, The rise in hydrostatic pressure against the artery wall causes the artery to expand somewhat. This is the post you fe