Lab #3 Cardiac Conduction and EKG

1. endocardium

2. myocardium

3. pericardial cavity

4. fibrous pericardium

5. parietal pericardium

6. visceral pericardium (epicardium)

cardiac muscle cells structure

intercalated discs between class that contain gap junctions. This is so action potential can be spread through a network of cells

what forms a functional syncytium

cardiac muscle fibers

functional syncytium

a mass of merging cells that function as a unit

2 functional syncytium in the heart

atrial synctium and ventricular synctium

what are cardiac muscle cells called

cardiomyocytes

what control cardiomyocytes

autonomic nervous system

what produces a current thorough the cardiac muscle cells

sinoatrial node

what do electrical changes in the heart tissue cause

mechanical changes (muscle contraction)

changes in membrane potential in heart tissue =

mechanical events

3 types of excitable cardiac muscle cells

1. pacemaker cells

2. specialized rapidly conducting cells

3. atrial and ventricular myocytes

what are the two types of pacemaker cells

SA and AV nodes

what are the specialized rapidly conducting cells in the ventricular walls called

purkinje fibers

cardiac conduction system def

group of clumps and strands of specialized cardiac muscle tissue, which initiates and distributes impulses throughout the myocardium

cardiac conduction system job

coordinates the events of the cardiac cycle

cardiac conduction system steps in the heart

1. SA node

2. atrial syncytium

3. junctional fibers

4. AV node

5. AV bundle

6. bundle branches

7. Purkinje fibers

8. ventricular synctium

sequence of electrical excitation in the heart

1. the SA node generates the impulse

2. the impulse pauses at the AV node

3. the AV bundle connects the atria to the ventricles

4. the bundle branches conduct the impulses the inter ventricular septum

SA node role

pacemaker that initiates rhythmic contractions of the heart

internodal atrial muscle

conducts impulses from SA node to aura

junctional fibers

conduct impulses form SA node to AV node

AV node

conducts impulses to AV bundle; delays impulse, so that atria finish contracting before ventricles contract

AV bundle

conducts impulses rapidly between AV node and bundle branches

Left and Right Bundle branches

split off from AV bundle, conduct impulses to Purkinje fibers on both sides of heart

Purkinje fibers

large fibers that conduct impulses to ventricular myocardium

EKG def

a recording of electrical changes that occur in the myocardium during the cardiac cycle

interval

waves that represent the depolarization and depolarization of the cardiac muscle

P wave

atrial depolarization; occurs just prior to atrial contraction

QRS complex

ventricular depolarization; occurs just prior to ventricular contraction

T wave

ventricular depolarization; occurs just prior to ventricular relaxation

arrhythmias

altered heart rhythms

fibrillation

uncoordinated, chaotic contraction of small areas of myocardium

atrial fibrillation danger

not-life threatening

ventricular fibrillation danger

often fatal

tachycardia

abnormally fast heartbeat

bradycardia

abnormally slow heartbeat

flutter

rapid, regular contraction of a heart chamber

premature beat

beat that occurs before expected in normal cardiac cycle; often originates from ectopic regions of heart

Ectopic pacemaker

damage to SA node may lead to AV node taking over, and act as secondary pacemaker, 40-60 min instead of 70-80

artificial pacemaker

device used to treat disorders of cardiac conduction system; implantable and battery powered

atrial fibrillation on EKG

will see multiple P waves before QRs complexes

Ventricular Fibrillation

all hell breaks loose

asystole

flatline

blood pressure

the force the blood pressure experts against the inner walls of the blood vessels

how does blood pressure change as blood moves throughout the system

moves from higher to lower pressure

when does arterial blood pressure rise

when the ventricles contract

systolic pressure

the maximum pressure reached during ventricular contraction

diastolic pressure

the minimum pressure remaining before next ventricular contraction

mean arterial pressure

average pressure in arterial system; represents average force driving blood to the tissues

blood pressure units

mm Hg

factors that increase blood pressure

1. blood volume increases

2. heart rate increases

3. stroke volume increases

4. blood viscosity increases

5. peripheral resistance increases

turbulent flow

when you open the vessel up after its been closed; the blood is hitting the walls of the vessels

laminar flow

when the sound disappears, flow is parallel and normal again