Cardiovascular system: The Heart Flashcards
(44 cards)
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
