20.5 histology Flashcards
what is the fibrous ring around the valves?
heart skeleton
what are the fn of the heart skeleton?
supports valves
electrical insulation btwn atria and ventricles
provides a site for muscle attachment
describe a cardiac muscle cell
elongated, branching, 1-2 centrally located nuclie
what are the contractile proteins of cardiac muscle cells?
actin and myosin myofilaments
what are the specialized cell-to-cell connections in cardiac muscle cells?
intercalated discs
describe an intercalated disc
cell membranes interdigitate at ends
desmosomes act as staples to attach cells
gap junctions allow AP to move from one cell to the next
electrically, cardiac muscle cells of each atria and ventricle behave
as a single unit
describe the difference between the sarcoplasmic reticulum of cardiac and skeletal muscle cells
cardiac do not have a dilated terminal cisternae and comes in contact with t-tubule at various points
skeletal have dilated terminal cisternae and lie close to the t-tubule at one point only
where do the t-tubules form in cardiac muscle fibers?
at the z disks
do cardiac or skeletal muscle fibers have larger t-tubules?
cardiac
how is the orientation of t-tubules and sarcoplasmic reticulum of cardiac muscle cells responsible for the delayed onset of cntx and prolonged cntx phase
it is a casual orientation, not designed for easy access to ion movement/AP movement
what is the SA node and where is it located?
sinoatrial node
medial to the opening of the superior vena cava
what is the pacemaker of the heart
SA node
what is the SA node made of?
specialized cardiac muscle cells
how are the muscle cells of the SA node specialized?
they generate their own spontaneous AP
where does the AP travel after being generated in the SA node?
to the atrial muscle cells (to cntx)
to the AV node
what is the AV node and where is it located?
atrioventricular node
medial to the tricuspid valve
what are APs conducted more slowly in the AV node than other parts of the conducting system?
it ensures the ventricles only cntx after the atria have completed their cntx
where is the AV bundle located?
it passes through a hole in the cardiac skeleton to reach the interventricular septum
what do the R and L AV branches travel through and what is their destination
extend beneath the endocardium to apices of R and L ventricles
what are the purkinje fibers?
large diameter cardiac muscle cells that form myofibrils at the apices of the ventricles
describe the route of electrical current (AP) in the heart
originate in the SA nodes to AV node along AV bundle splits into R and L bundle branches purkinje fibers ventricle walls and papillary muscles
what differentiates purkinje fibers from other cardiac cells?
many cap junctions
