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10 Cards in this Set

  • Front
  • Back
Cardiac Muscle
myocytes are SEPARATE cells unlike skeletal
fibers beat in unison, functional syncytium not structural syncytium
Autonomic NS regulates(NOT generates) cardiac rhythm
Cardiac Muscle
Structure: light microscopy
ie how to ID
myocytes branch, cells are attached at intercalated discs
have more capillaries
myocytes are mono- or bi-nucleate and are centrally located
cross section - fibers are more uniform than smooth muscle but still different sizes and shapes
Cardiac Muscle
Structure: electron microscopy
- nuclear region also contains organelles
- intercalated discs( where the last Z-line in the cell would normally be)
- LOTS of mito
- Sarcomeres (contractile units similar to skeletal)
- SR and T tubules
SR and T tubules in cardiac muscle
less extensive, sometimes they dont even form a triad, one t-tubule attaches to SR instead of two SR's (forming a diad)

what does this mean for Ca?
?? pg 316
intercalated discs
step like junctions(not all myofibrils in myocytes are equally long)

- gap junctions on longitudinal portions
- fasciae adherens, similar to zonula adherens except not belt-like (THIN FILAMENTS)
- maculea adherens (desmosomes)punctuate the fasciae adherens on the transverse side (INTERM FILAMENTS)
Cardiac Muscle
Impulse conduction system
composed of?
- modified muscle cells , NOT neurons

- SA node
- AV node
- AV bundle (bundle of HIS)
- right and left bundle branches, cells gradually become purkinje fibers
Nodal Fibers
what are they
bigger or smaller than myocytes?
membrane potentials
conduction from where to where
SA AV nodes:
smaller in diam than myocytes
attached via gap junctions
oscillating membrane potentials
conduction goes from SA to AV
AV node
AV electrically connected to conducting fibers (Purkinje) in the AV bundle(branches of bundle of HIS)
Purkinje fibers
larger than myocytes
more glycogen(paler)
gap junctions with eachother
branching bundles run under endocardium toward heart apex, then bend back and make gap junctions with ventricular myocytes
smooth muscle
walls of organs that are tubular, or sac shaped(uterus/bladder)

slow contraction, low ATP consumption

most recently evolved tissue