Cardiovascular system: The Heart Flashcards
What is the shortest circulation in the body?
coronary circulation
Pericardial cavity is made up of what membrane coverings?
fibrous and serious (parietal and visceral pericardium)
Heart wall has how many layers?
3
What are the 2 blood flow circuits?
- pulmonary circuits
- systemic circuits
What arteries provide blood to the heart tissue?
coronary arteries
What are known as communication pathways of the heart?
gap junctions
Similarities of cardiac and skeletal muscle mechanism of contraction?
- striated - myosin/actin mechanism
- T-tubule mechanism - acting on sarcoplasmic reticulum
Differences of cardiac and skeletal muscle mechanism of contraction?
- cardiac muscle has a direct diffusion of Ca++
- cardiac muscle AP plateaus (resulting in a much longer time of contraction than skeletal muscle)
- cardiac muscle strength of contraction is dependent on extracellular Ca++
What is the main reason for why the heart continues to beat?
- calcium leaking out of the t-tubules
The more _______ present, the ________ the heart will contract.
The more calcium present, the harder the heart will contract.
Is the ability of cardiac muscle to depolarize and contract intrinsic or extrinsic?
intrinsic
5 components of the intrinsic conduction system?
- SA node
- intermodal pathways
- AV node
- AV bundle
- left and right bundle branches of purkinjie fibers
Features of the SA node?
- smaller diameter muscle fibers
- almost no contractile muscle fibers
- connect directly with atrial muscle fibers
- cell membranes naturally “leaky” to Na+ and Ca++ (less negative resting membrane potential)
- self-excitation
What causes the depolarization of the SA node?
the opening of the fast calcium channels once threshold is hit
How is the cardiac impulse recorded?
1) SA node generates impulse; atrial excitation begins
2) impulse delayed at AV node
3) impulse passes to heart apex; ventricular excitation begins
4) ventricular excitation complete
What does the p wave represent?
atrial depolarization
What does the QRS wave represent?
ventricular depolarization
What does the T wave represent?
ventricular repolarization
What does one cardiac cycle consist of?
events that occur from the beginning of one heartbeat to the beginning of the next
What is known as the amount of blood in the ventricle at the end of diastole?
end diastolic volume
What is know as the amount of blood left in the ventricle after it pumps it out?
end systolic volume
What is known as the period of relaxation, the heart filling with blood?
diastole
What is known as the contraction period, the heart ejecting blood?
systole
What is known as the fraction of blood being pushed out of the left ventricle into the body?
Ejection fraction - fraction of EDV ejected
atrial pressure changes are caused by what?
the backflow from the atria into the veins while the AV valves are closed
atrial contraction usually causes how much additional ventricle filling?
20%
atrial pressure changes during atrial contraction?
a wave
atrial pressure changes at the onset of ventricular contraction?
c wave
atrial pressure changes at the end of ventricular contraction?
v wave
What is known as the AV valves opening due to a build up of pressure in the atria causing a period of rapid filling of the ventricles?
ventricular filling
What is the period in which the AV valves are closed but the semilunar valves are not open yet? (the pressure continues to build but the volume remains the same)
period of isovolumic contraction
What is the period in which the semilunar valves close and the ventricles relax into diastole?
period of isovolumic contraction
What is known as the end-diastolic pressure when the ventricle is filled? (the amount of tension on the muscle when it begins to contract - right before ejection)
preload
What is known as the pressure in the artery leading from the ventricle? (load against which the muscle exerts its contractile force - the amount of pressure needed to overcome to get the blood to the body)
afterload
Where is energy for the cardiac contraction primarily derived from?
energy derived primarily from oxidative metabolism of fatty acids (70-90%)
some lactate and glucose (10-30%)
How much blood does the heart pump out per minute?
4-6 liters
What controls the heart rate and strength of heart pumping?
Autonomic Nervous System
What does the Frank-Starling Mechanism state?
intrinsic regulation – the heart automatically pumps incoming blood; amount of blood pumped determined primarily by rate of blood flow into heart
the ______ volume that goes into the ventricle, the ______ the pressure, the ______ the contraction
more
higher
harder
What controls the extrinsic regulation of the cardiac pump?
Sympathetic Nervous System – norepinephrine Parasympathetic Nervous System – acetylcholine
What controls the cardioacceleratory center?
Sympathetic nervous system
What controls the cardioinhibitory center?
Parasympathetic nervous system
Parasympathetic fibers (inhibitory) use what nerve?
Vagus nerve (vagal tone)
What happens when the vagal nerves are “disconnected”?
HR increases about 25 bpm almost immediately
