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 myocardium
2. lft and rgt atria contract
3. atria empty and ventricles fill
4. 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?
In the electrocardiogram, what happens during the QRS complex?
ventricular depolarization and atrial repolarization
In the Electrocardiogram, what happens during the T Wave?
What is special abou the QRS complex?
The atrial repolarization is not seen because overshadowed by the QRS complex.
this is the sequence of events in the heart b/w the start of one contraction and the start of the next.
the amount of blood pumped out by each ventricle in 1min.
Cardiac Output Equation
Cardiac Output=Stroke Volume*Heart Rate
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
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 layer
2. very thin, serous membrane
3. puts out fluid
4. forms the epicardium
is the outermost layer
Name four characteristics of the parietal pericardium.
1. outermost layer
3. forms the pericardial sac
4. 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
outer layer, thin, serous
thickest, middle layer, cardiac muscle
serous, thin, innermost layer of the heart...gives 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
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