The heart and cardiac muscle Flashcards
Where are the base and apex of the heart found?
Base is at top, apex is at bottom
What is the pericardium?
Covers heart; protects heart by providing lubrication during its constant movement; enveloped pericardia fluid
Which side of the heart is thicker, and what does this indicate?
Left, as it pumps blood around the systolic system, whilst right pumps blood around pulmonary system
What is the function of the vena cava (inferior and superior)?
Carry blood from the body to the heart; supplies deoxygenated blood to the right atrium
What is the function of the pulmonary artery?
Carry deoxygenated blood to the lungs
What is the function of the pulmonary veins?
Carry blood from the lungs; supplies oxygenated blood to the left atrium
What is the function of the aorta?
Carry blood to the body; supplies oxygenated blood
Which valve separates the right chambers?
Tricuspid valve; has three cusps
Which valve separates the left chambers?
Mitral valve; has two cusps
What are the names of the valves separating the ventricles from the arteries?
Pulmonary and aortic valves
What is the difference between the atrioventricular and semilunar valves?
Semilunar valves are stronger and more rigid
What feature prevents prolapse of the valves?
The papillary valves ensure valves shut but do not prolapse
What is the purpose of the valves within the heart?
Prevent backflow
How is cardiac muscle similar to skeletal muscle?
Striated; SR is a source of Ca ions; have t-tubules
How is cardiac muscle different to skeletal muscle?
Wider and shorter cells; mononucleate, centrally located; no attachments; less and smaller SR; less t-tubules; extracellular fluid a source of Ca2+; highly oxidative; more capillaries; muscle fibres lengthen when relaxed due to heart chambers filling
How is cardiac muscle similar to smooth muscle?
Is involuntary
Why can cardiac muscle not undergo tetanic contraction?
Prolonged duration of L-type Ca2+ channel current = prolonged ap = sarcolemma remains refractory for the duration of the twitch
What is the purpose of cardiac muscle not undergoing tetanic contraction?
Allows heart to be oscillating pump and alternate between being relaxed and contracting (filling and ejecting)
Outline the signal propagation in cardiac muscle?
SAN originated electrical current; electric current spreads by intercalated discs; contraction of muscle cells dependent on extracellular Ca2+; L-type v-gated Ca2+ channels (modified dihydropyridine receptors) open in t-tubules by depolarisation of membrane; Ca2+ enters cell from outside; trigger Ca2+ binds to ryanodine receptors on SR membrane; ryanodine receptor Ca2+ channel open; Ca2+ from SR into cytosol; cytosolic Ca2+ increased; enables muscle contraction; Ca2+-ATPase pumps within SR membrane sarcolemma and Na2+/Ca2+ transporters return Ca2+ to SR and extracellular fluid
How is force of cardiac cell contraction graded?
Graded with Ca2+ levels
