The heart


bicuspid and tricuspid valves close


pulmonary and aortic semi-lunar valves close

Cardiac conduction system

contraction of the atria and ventricles occur automatically as a result of electrical impulses that originate in and are conducted by heart tissues.

What four things happen as a result of the sinoatrial node?

1. Depolarization spreads in the myocardium2. lft and rgt atria contract3. atria empty and ventricles fill4. impulse picked up by conduction fibers that stimulate #2

Where is the Atrioventricular node found?

on the floor of the rght atrim near septum

Where is the atrioventricular bundle found and what does it split into?

found in the upper part of the interventricular septum. Splits into the lft and right bundle fibers

What is step four in the cardiac conduction system and where is it located?

Right and left bundle fiber. Found in the septum

What happens as a result of the Purkinje Fibers?

the ventricular muscle fibers depolarize and the ventricles contract.

How are the ventricular muscle fibers arranged as a result of the Purkinje Fibers?

the ventricle muscles are arranged in whorls that "wring" the ventricles dry.

In the Electrocardiogram what happens during the P Wave?

atrial depolarization

In the electrocardiogram, what happens during the QRS complex?

ventricular depolarization and atrial repolarization

In the Electrocardiogram, what happens during the T Wave?

Ventricular repolarization

What is special abou the QRS complex?

The atrial repolarization is not seen because overshadowed by the QRS complex.

Cardiac Cycle

this is the sequence of events in the heart b/w the start of one contraction and the start of the next.

Cardiac output

the amount of blood pumped out by each ventricle in 1min.

Cardiac Output Equation

Cardiac Output=Stroke Volume*Heart Rate

Stroke Volume

the amount of blood pumped out by one ventricle w/ each beat.~70 ml/beat

What five things is stroke volume regulated by?

SA node, Autonomic Nervous System, temp, hormones, and ions

SA node produces how many beats per min?

75 beats per min

Parasympathetic nervous sys

inhibits heart rate

sympathetic ner. sys.

inc. heart rate


with inc in temp there is an inc in heart rate

The hormone epinephrine given off by the adrenal medulla will...

stimulate inc. HR

What is the name of the heart rate that will enhance the effects of the epinephrine and norepinephrine on the heart?

Thyroxin(T4) from the thyroid gland


because inc or dec K+ alters the polarized state.


slows down HR


slows up HR


needed for contraction of the cardiac muscle tissue


speeds up HR


slows down HR


fast beats over 100/min


slow beat <60/min


chamber contracts regularly but very fast 250-350 beats/min


rapid but uncoordinated contractions

During fibrillation

not all areas contract together

During fibrillation, during atrial fibrillation

one can survive

During fibrillation, during ventricular fibrillation

it can be fatal


due to conduction disorders. Any interference or block in cardia impulse conduction may be the cause.


the CT covering of the heart-made up of 2 layers

Name four characteristics of visceral pericardium.

1. inner most layer2. very thin, serous membrane3. puts out fluid4. forms the epicardium

Parietal pericardium

is the outermost layer

Name four characteristics of the parietal pericardium.

1. outermost layer2. thick3. forms the pericardial sac4. pericardial cavity

pericardial cavity

is the space b/w the 2 pericardial layers. It is fluid filled. For protection.

The heart wall is composed of 3 layers

1. Epicardium2. Myocardium3. Endocardium


outer layer, thin, serous


thickest, middle layer, cardiac muscle


serous, thin, innermost layer of the rise to the Purkinje Fibers that are specialized muscle fibers in the endocardium. Covers valves.

Atria and auricles

receive blood. Rt from body, left from lungs


pump bld out. Rt to lungs, left to body

Atrioventricular sulcus (coronary sulcus)

grooves b/w atria and ventricles, encircles the heart

Interventricular sulci

anterior and posterior, found b/w ventricles

Systemic circuit (left side of the heart)

left atrium->thru bicuspid valve-left ventricle-thru aortic semilunar valves-ascending aorta-aortic arch-descening aorta-arteries-arterioles-cap-venules-veins-superior or inferior vena cava-right atrium

pulmonary circuit(right side of the heart)

right atrium->thru tricuspid valve-right ventricle-thru pulmonary semilunar valves-pulmonary trunk-pulmonary arteries-pul.arterioles- pul. cap in lungs where gas exchange occurs-pul venules-pul. veins-left atrium

Right coronary artery has two main branches

posterior interventricular artery, marginal artery

posterior interventricular artery

feed the two ventricles

marginal artery

feeds the right atrium and right ventricles

left coronary artery has 2 main branches

circumflex artery, anterior interventricular artery

circumflex artery

feeds the left atrium and left ventricles

anterior interventricular artery

fees both ventricles

The cardiac veins run parallel to the arteries. They empty into what?

the coronary sinus that empties into the right atrium

Three vessels contribute to the coronary sinus.

1. Great Cardiac Vein2. Middle Cardiac Vein3. Small Cardiac Vein

Great cardiac vein

found in the anterior interventricular sulcus

Middle cardiac vein

found in the posterior interventricular sulcus

small cardiac vein

found in the inferior margin of the heart on the right