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46 Cards in this Set
- Front
- Back
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What is the function of the pericardium?
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- protects heart
- holds the heart in position |
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Name and describe the two main layers of the pericardium.
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- Fibrous pericardium - touch CT, loose fitting, doesn't adhere to heart's surface
- Serous pericardium (2 layers) - secretes fluid; pareital pericardium lines and ad heres to inner surface of fibrous pericardium; visceral pericardium/epicardium sticks to heart itself; divided by pericardial cavity filled with pericardial fluid |
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Describe the location and importance of the pericardial cavity.
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- Location: between the parietal pericardium and the visceral pericardium; the two layers of serous pericardium
- Importance: contains pericardial fluid secreted by serous pericardium; reduces friction; heart moves easily inside pericardium |
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Name and describe the 3 tissues of the heart wall.
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- Epicardium/visceral pericardium - secretes fluid, slippery, part of pericardium
- Myocardium - heart muscle, thickest layer, stabalized by network of CT - Endocardium - simple squamous ET that rest on thin layer of basal lamina (CT); smooth, protects tissue from friction/lets fluid flow past smoothly |
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What is the function of the fibrous skeleton of the heart?
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- a dense network of CT, collagenous, contains some elastic fibers
- stabalizes cardiac muscle in myocardium - stabalizes heart valves |
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Which layer of the heart wall is the thickest?
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- the myocardium - the heart muscle
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Which chamber of the heart has the thickest wall?
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- left ventricle - pumps blood through aorta into systemic circulation
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Trace the flow of blood through the heart, beginning at the right atrium.
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- right atrium
- through tricuspid valve (AV valve) - Right ventricle - out pulmonary Semilunar valve - into pulmonary trunk - r + l pulmonary veins - pulmonary circulation - in through pulmonary veins - left atria - through mitral valve - left ventricle - out through aortic SL valve and aorta - systemic circulation - back into right atria through superior and inferios vena cava, coronary sinus |
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Name the vessels that return blood to the right atrium.
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- superior vena cava
- inferior vena cava - coronary sinus |
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Name the vessels that return blood to the left atrium.
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- pulmonary veins
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Why is the heart referred to as a double pump?
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- right side pumps blood into pulmonary circuit
- left side pumps blood into systemic circuit |
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What is the function of the heart valves?
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- make blood flow in 1 direction when the heart pumps
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Describe the mechanism of operation of the atrioventricular (AV) valves.
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- cusps open and close in response to press differences
- Open: press in ventricle less than press in atrium - Closed: press in ventricle less than press in atrium - Cordae tendinea - anchored to papillary muscles and valve; keep the valves closed and from inverting - High pressure in ventricle closes valves! |
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Describe the mechanism of operation of the semilunar valves.
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- 3 cusps open and close in response to press differences
- Open: ventricle press greater than artery press - Closed: ventricle press less than artery press - blood flowing backwards into left ventricle fills cusps and closes valves - Low pressure in ventricle closes valves! |
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Which valves are associated with the chordae tendinae and papillary muscles?
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- the Atrioventricular (AV) valves - between the atria and the ventricle
-- the tricuspid valve (right) -- the mitral valve (left) |
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Name and describe the special intercellular juctions present in cardiac muscle tissue.
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- Intercalated discs... contain:
- desmosomes - strong, prevent fibers from pulling away from e. other - gap junctions - electrical synapse b/w adjacent cells; cells elecrically coupled to e. other; allow ion flow/current flow; = simultaneous depolarization |
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What is the functional significance of intercalated discs?
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cells elecrically coupled to e. other; allow ion flow/current flow; = simultaneous depolarization
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What is the significance of the large numbers of mitochondria and the rich blood supply to cardia muscle tissue?
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- can't work on anaerobicy glycolysis - quick eschemia
- depend on a continual O2 supply than skeletal muscle - not glucose dependant - can use lactic acid through krebs cycle or fatty acids |
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What is a functional syncytium?
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- a section of cardiac muscle to which the all or none rule applies
- like a skeletal muscle unit, only cardiac muscle |
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Identify the functional syncytia of the heart.
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- the myocardium behaves as a functional syncytium
- b/c cells couples by gap junctions - possibly the atria are one and the ventricles are one? |
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Describe the 3 main functional differences between skeletal and cardiac muscle.
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- means of stimulation - cardiac=autostimulation, self exciting; skeletal = stimulated by motor neuron
- synctium vs. motor unit - all or none law applies to synctium in cardiac muscle and to motor units in skeletal muscle - length of absolute refractory perioe (before musc. can contract again) - cardiac, 250 milisec. prevents tetany of the heart so it can pump; skeletal 1-2 milisec while waiting for enought Na ion channels to move back into resting state |
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Identify (in order) the compononts of the hearts conduction system.
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- sinoatrial (SA) node - spontaneously depolarizes; the hearts pacemaker
- atrioventricular (AV) node - near opening of coronary sinus; delay, then passed on - atrioventricular (AV) bundoe - ONLY electrical connection between atrium and ventricle - R+L bundle branches - AV branches; exciteds interventricular septum 1st, before the walls - Purkinje fibers - many; large diameter rapid conducting fibers in to papillary/cardiac wall muscles |
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What are the autorhythmic cells?
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- generate spontaneous depolarizations called pacemaker potentials
- have unstable resting membrane potentials; ion leakage slowly deoplarizes membrane towards threshold until they fire an AP - pacemaker function - form cardiac conduction system |
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What is a pacemaker potential?
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- spontaneous depolarizations called pacemaker potentials
- cells have unstable resting membrane potentials; ion leakage slowly deoplarizes membrane towards threshold until they fire an AP - ion leakage is from Na channels opening and esp K channels closing |
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Why are pacemaker potentials important?
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- creates the autorhythmicity of the heart mucle
- spontaneously contracts rhythmically, but not fast enough for tetany of the heart |
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What part of the myocardium normally has the fastest spontaneous depolarization rate?
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- the sinoatrial (SA) node
- 75X/min - 1st part of normal conduction system of heart |
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Compare and contrast the microscopic anatomy of cardiac muscle vs. skeletal muscle fibers.
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Cardiac - straited, contract via sliding fillaments; short, fat, branched/interconnected; 1-2 centrally located nuclei; fibers interconnect @ intercalated discs (desmosomes and gap junctions)
Skeletal - striated; contract via sliding filament mechanism; long, unbranched; multiple nuclei @ periphery to avoid the squeeze of muscle; no spontaneous depolarization |
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What is the functional significance of the 0.1 second delay in impulse transmission at the AV node?
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- allows atria to respond and contract before ventricles contract
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What is the function of the Purkinje fibers?
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- many of them
- large diameter, rapid conducting fibers - inervate papillary and cardiac wall muscles to make them contract |
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What part of the heart is excited by the left and right bundle branches?
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- "AV" branches
- excites interventricular septum 1st, so it contracts before the cell walls |
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What part of the conduction system serves as the sole elecrical connection between the atria and the ventricles?
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- the atriventricular (AV) bundle
- located in superior part of interventricular septum |
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What is the normal pacemaker of the heart?
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- the sinoatrial (SA) node
- 75x/min - why we say "normal sinus rhythm" to mean that the heart is beating at a normal rate |
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In cardiac muscle, what are the sources of Ca2+ which trigger contraction?
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- extracellular Ca2+ -
- Ca comes from SR, but not as much as in skeletal - during plateau phase, comes through slow Ca channels that let Ca in from the outside 10-20% of Ca comes from ECF - it binds to the Ca release valves in SR so it releases more Ca from SR |
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What produces the plateau phase of a cardiac muscle fiber's action potential?
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- during the rapid depolarization, the fast sodium channels were opened
- now they begin to close, but the slow Ca ion channels are starting to open, keeping cells depolarized longer - the slow Ca channels were activated by the threshold stimulus |
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What is the functional significance of the plateau phase in cardiac muscle?
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- sustains the contraction for long enough to create the force needed to eject the blood from the heart
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How does the all or none law related to cardiac muscle?
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- applies to a syncytium as opposed to a motor unit like in skeletal muscle
- cardiac conduction system and gap junctions ensure that the whole thing will contract as one unit - threshold = 75 mV |
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When does the refractory period in cardiac muscle end? What is the functional significance of this long refractory period?
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- lasts until all of the Na channels are back in resting state
- contraction phases = 250 ms, which is 30x longer than skeletal muscle - prevents tetanic contractions in healthy cardiac muscle - twitch ends when Ca removed from sarcoplasm into SR and ECF, so tropomyosin moves back over on active sites of troponin |
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Compare and contrast the action potential of skeletal and cardiac muscle cells.
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Cardiac - 3 phases: rapid depolarization, plateau and repolarization, long refractory period, autorhythmic
Skeletal: 2 phases: depolarization and repolarization, very short refractory period, also very short contraction period, not self-stimulated |
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mediastinum
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the part of the thoracic cavity between the lungs that contains the heart and aorta and esophagus and trachea and thymus
- where the heart is located! |
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Pleural cavities
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- contain the lungs
- heart in between the pleural cavities |
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Pericardial cavity
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- heart found within this cavity
- lies b/w the parietal and visceral pericardia - contains pericardial fluid secreted by serous pericardium - reduces friction so heart can move easily inside pericardium |
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anastomonses
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- alternative channel for blood flow from one artery to another
- important b/c heart is so O2 dependant - found in circle of willis (in brain) and in coronary arteries of the heart |
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intercalated disc
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- adjacent fibers interconnect at these junctions
- they contain gap junctions and desmosomes |
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autorhythmic cells
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- 1% of cells in myocardium
- spontaneously depolarize rhythmically - have pacemaker functions - form the cardiac conduction system |
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Sinus rhythm
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- normal sinus rhythm is set by the sinoatrial (SA) node
- 75x a min - the heart's pacemaker |
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desmosome
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- intercellular junctions
- strong, prevents fibers from pulling away from eachother - found as part of an intercalated disc |
