CH. 13 Cardiovascular System: Cardiac Function Flashcards
What path is taken throughout the blood vessels?
heart - arteries - arterioles - capillaries - venules - veins
Function of erythrocytes?
transport oxygen and carbon dioxide
Function of leukocytes?
white blood cells that defend the body against pathogens
What is the path of the pulmonary circuit?
- supplied by right heart
- blood vessels from heart to lungs, and from lungs to heart
What is the path of the systemic circuit?
- supplied by left heart
- blood vessels from heart to systemic tissues, and from tissues to heart
Where does oxygenation of blood occur?
capillaries
What can occur from parallel blood flow within the systemic or pulmonary circuit?
independent regulation of blood flow to organs
What supplies the heart capillaries?
coronary arteries that arise from the aorta
What is the pericardium?
membranous sac surrounding the heart that lubricates the heart and decreases friction
What are the three layers of the heart wall?
- epicardium (outer)
- myocardium (middle)
- endothelium (inner)
What is the difference in muscle thickness of the left and right ventricle?
left ventricle is much thicker than the right
What do the heart valves allow for and how do they function?
they prevent the back flow of blood and open passively based on pressure gradient
What is meant by autorhythmicity?
the ability to generate its own rhythm
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How do autorhythmic cells function in the heart?
they provide a pathway for spreading excitation through the heart
How is the conduction system of the heart broken down?
pacemaker cells and conduction fibers
How do pacemaker cells and conduction fibers work together to coordinate and provide rhythm to the heartbeat?
pacemaker cells produce spontaneously depolarizing membrane potentials that generate action potentials that are then rapidly conducted to the myocardium by conduction fibers
Where are pacemaker cells of the myocardium found?
- sinoatrial node (pacemaker of the heart)
- atrioventricular node
Where are conduction fibers of the myocardium found?
- internodal pathways
- bundle of his
- purkinje fibers
What is the firing rate of the SA node at rest?
70-80 AP/min
What allows for the coordination of the conduction system of the heart?
presence of gap junctions and conduction pathways
What are intercalated disks?
junctions between adjacent myocardial cells
What causes spontaneous depolarizations of the heart autorhythmic cells?
closing of potassium channels
What occurs in the electrical activity in a pacemaker cell?
- pacemaker potential goes to threshold
- rapid depolarization
- repolarization brings down to -70mV
- process repeats
What are the 5 phases of electrical activity in cardiac contractile cells?
Phase 0: increased permeability to sodium
Phase 1: decreased permeability to sodium
Phase 2: increased permeability to calcium, decreased permeability to potassium
Phase 3: increased permeability to potassium, decreased permeability to calcium
Phase 4: resting membrane potential
How is calcium removed from the cytosol of cardiac muscle?
- Calcium/ATPase in sarcoplasmic reticulum
- Calcium/ATPase in plasma membrane
- Sodium/Calcium exchange in plasma membrane
What is an electrocardiogram?
external measure of electrical activity of the heart
What are the factors that distance and amplitude of spread of an electrocardiogram dependent on?
- size of potentials
2. synchronicity of potentials from other cells
What is ECG arrhythmias?
abnormal heart rates
What is a sinus rhythm?
- Tachycardia
- Bradycardia
- pace generated by SA node
- tachycardia is fast rhythm and bradycardia is slow rhythm
What comes as a result of an extra contraction on an electrocardiogram?
- results in an extra systole
- premature atrial contraction followed by an extra ventricular contraction
What comes as a result of a ventricular fibrillation on an electrocardiogram?
- loss of coordination of electrical activity of heart
- death can ensue within minutes unless corrected
What are the two main periods of the cardiac cycle?
- systole: ventricle contraction
2. diastole: ventricle relaxation
When do AV valves open and when do semilunar valves open?
- AV valves: when atrial pressure is greater than ventricular pressure
- Semilunar valves open when ventricular pressure is greater than arterial pressure
What are the 4 phases of the cardiac cycle?
- ventricular filling (diastole)
- isovolumetric ventricular contraction (systole)
- ventricular ejection (systole)
- isovolumetric ventricular relaxation (diastole)
How does the elasticity of the aorta and large arteries aid in maintaining blood flow through the entire cardiac cycle?
- acts as a pressure reservoir
- stores energy during systole as walls expand
- releases energy during diastole as walls recoil inward
What is the equation for stroke volume?
SV = end-diastolic volume - end-systolic volume
What causes the sound of a heart beat?
1st sound: AV valves close simultaneously
2nd sound: semilunar valves close simultaneously
What is cardiac output and what is the equation used to find this?
volume of blood pumped by each ventricle per minute
- cardiac output = SV x HR
What are the extrinsic and intrinsic regulation of cardiac output?
- extrinsic: neural and hormonal (autonomic)
- intrinsic: autoregulation
What occurs when the SA node is under control of the ANS and hormones and is at rest?
parasympathetic system dominates
What occurs when the SA node is under control of ANS and hormones and is excited?
sympathetic system takes over and heart rate increases
What two hormones help to control heart rate?
- epinephrine: interacts with beta one receptors
- increases AP frequency at SA node
- increases velocity of AP conduction in muscle fibers - glucagon: increases heart rate
What are the primary factors affecting stroke volume?
- ventricular contractility: how well ventricles contract
- end-diastolic volume
- afterload: how much blood is in arteries all together
What hormones can increase force of contraction?
thyroid hormones, insulin, and glucagon
What two factors affect end-diastolic volume?
- end-diastolic pressure: preload
- filling time
- atrial pressure
- central venous pressure - afterload: pressure in aorta during ejection
Describe what occurs at the different stages (A-H) of the left ventricular pressure-volume curve.
A: Phase 1 - ventricular volume increase B: Atrial contraction C: Phase 2 - Volume remains constant; pressure increases dramatically D: Semilunar valves blow open E: Phase 3 - volume decreases to 60 mL, pressure rises, then falls precipitously F: Semilunar valves shut G: Phase 4 - pressure continues to fall H: AV valves blow open
