Term
| Describe the three components of the circulatory system. |
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Definition
1. Heart - creates a pressure gradient for the purpose of pumping blood
2. Blood vessels - distribute blood throughout the body
3. Blood - transporting medium used for the purpose of transporting materials for the cells |
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Term
| What is the name of the upper two chambers of the heart? |
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Definition
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Term
| What is the name of the two lower chambers of the heart? |
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Definition
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Term
| What is the function of atria? |
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Definition
Atria receive blood returning to the heart from other parts of the body.
Right atrium receives blood from the venae cavae (systemic circuit).
Left atrium receives blood from the pulmonary circuit. |
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Term
| What is the function of ventricles? |
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Definition
Ventricles pump blood to the rest of the body.
Right ventricle receives blood from the right atrium and pumps it to the main pulmonary artery.
Left ventricle receives blood from the left atrium and pumps it to the aorta, where it will go to the rest of the body. |
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Term
| From which "circulation" does the left side of the heart receive blood? |
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Definition
| Systemic circuit - blood vessels from heart to systemic (body) tissues and tissues to heart |
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Term
| From which "circulation" does the right side of the heart receive blood? |
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Definition
| Pulmonary circuit - blood vessels from heart to lungs (alveoli of lungs) and lungs to heart |
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Term
| What is the function of the valves in the heart? |
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Definition
1. Ensure unidirectional flow
2. Passively open/close in response to pressure changes |
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Term
| What type of cell junctions are found in between cardiac cells? |
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Definition
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Term
| Why is the myocardium considered to be a functional syncytium? |
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Definition
| because all cardiac fibers are electrically coupled via gap junctions |
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Term
| Describe the physical properties of cardiac muscle. |
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Definition
- Aerobic muscle
- Cannot undergo hyperplasia/no cell division; grows by hypertrophy
- 99% contractile cells (for pumping)
- 1% autorhythmic cells (set pace) |
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Term
| What is the intrinsic source of excitation for cardiac tissue? |
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Definition
| autorhythmic cells (pacemaker cells) |
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Term
| What is the extrinsic source of excitation for cardiac tissue? |
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Definition
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Term
| Which ion is responsible for the depolarization of the pacemaker cells in the heart? |
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Definition
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Term
| Describe the intrinsic conduction pathway in the heart. |
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Definition
- SA node generates impulse; atrial excitation begins
- impulse is delayed at the AV node
- impulse passes to heart apex via the bundle branches; ventricular excitation begins
- ventricular excitation is complete when the Purkinje fibers conduct impulse |
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Term
| Why does the heart have a long refractory period? |
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Definition
| to prevent tetanic contractions, in order to keep pumping |
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Term
| What is end diastolic volume (EDV)? |
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Definition
| Maximum volume of blood in the ventricle at the end of diastole. |
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Term
| What is end systolic volume (ESV)? |
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Definition
| Blood volume remaining in ventricles at the end of systole |
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Term
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Definition
| Amount of blood pumped out by a ventricle with each beat |
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Term
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Definition
Amount of blood pumped by each ventricle in one minute
Stroke volume X heart rate = cardiac output |
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Term
| What are the three major factors that affect stroke volume? |
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Definition
- Preload - the amount the ventricles are stretched by blood before contraction
- Contractility - increase in cardiac cell contraction force (can increase by sympathetic NS activation)
- Afterload - back pressure exerted by blood in the large arteries leaving the heart that must be overcome to eject blood from the ventricles |
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Term
| Of the three factors that affect stroke volume (preload, contractility, afterload), which has the greatest influence? |
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Definition
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Term
| What happens to the heart under the influence of the sympathetic nervous system? |
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Definition
| increase in cardiac rate and stroke volume, so thus an increase in CARDIAC OUTPUT |
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Term
| What happens to the heart under the influence of the parasympathetic nervous system? |
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Definition
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Term
| Describe the events that are occurring in the heart during each wave of an EKG. |
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Definition
- P - atria depolarizes
- Q
- R - ventricle diastole
- S
- T - repolarizes and goes back to diastole |
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Term
| Describe an action potential in a contractile cardiac cell. |
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Definition
- Action Potential is initiated by pacemaker cells
- Change in membrane potential from resting at -90mV to +30mV
-- voltage gated sodium channels open
-- stays at +30mV: plateau phase
-- calcium ions slowly flow in
- potassium voltage gated channels are inactivated
--cell returns to resting potential |
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Term
| Describe the cardiac cycle. Begin with early ventricular diastole. |
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Definition
Early ventricular diastole
- BP is low as blood flows into ventricles
- atrioventricular valves are OPEN
Mid-to-late-ventricular diastole
- SA node reaches threshold
- electrical activity corresponds with P-wave
- atria contract
- end diastolic volume (max volume of blood in ventricle at the end of diastole) is reached
Ventricular systole
- atria relax; QRS complex
- rise in ventricular P; atrioventricular valves close
Isovolumetric contraction phase
- ventricles closed; blood volume constant
Ventricular ejection phase opens valves
- blood expelled into aorta
--isioovolumetric relaxation-early diastole
--end systolic volume (blood volume remaining in ventricles) is reached
-- ventricles relax
Ventricular filling
- atrioventricular valves open
- atrial repolarization and ventricular depolarization |
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Term
| What is the cardiac cycle? |
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Definition
| All events associated with blood flow through the heart during one complete heartbeat. |
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