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5. Heart
Cardiac Muscle
18
Medical
Graduate
11/06/2012

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Cards

Term
Unique to cardiac muscle
Definition
Intercalated discs
-Look like stairs
-Interdigiting folds of sarcolemma at end of adjacent cells
-Link cells structurally and functionally
Term
Structure of Cardiac Muscle
Definition
-1 or 2 centrally located nuclei
-Cross striations- sarcolemma and myofibrils
-Branched
-Cylindrical
-Lipofuscin granules
-Store lots of glycogen
Term
2 Parts of Intercalated Disc
Definition
-Transverse portion
-Longitudinal portion
Term
Transverse Portion
Definition
-Adherins- like Z-line; connect thin filament to terminal sarcomere
-Desmosomes- bind cells together; keep from separating in contraction
Term
Longitudinal Portion
Definition
-Gap junctions:
1. ionic continuity
2. Ionic coupling
3. Spread of depolarization
Term
Major Histological Differences b/t Cardiac and Skeletal Muscle
Definition
1. Diad instead of Triad
2. Mitochondria
3. Myofibrils
Term
Diad
Definition
-1 terminal cisterna
-Larger
-Located near Z-line
-Lined by external lamina
Term
Mitochondria
Definition
Greater and more numerous
Term
Myofibrils
Definition
Not fully separated due to less developed sarcoplasmic reticulum
Term
Cardiac Conducting Cells
Definition
-Initiate, regulate, coordinate heart beat
-Found at SA and AV nodes, Bundle of His, Purkinje fibers
-Para/Sympathetic nerves that terminate at the nodes ONLY MODIFY the intrinsic contraction
Term
Cardiac Endocrine Cells
Definition
-Location: atrial wall and interventricular septum
-Action: produce small peptide hormones like atrial natriuretic polypeptide-->DECREASE BP
Term
Growth and regeneration
Definition
-NO REGENERATIVE CAPACITY
-Dead cells replaced with connective tissue
Term
Autonomic nervous system modify cardiac function by regulating:
Definition
a. Automaticity
b. Force of contraction
Term
Slow- response
Definition
-SA node
-AV node
Term
Fast-response
Definition
-Atrial and ventricular muscles
Term
Slow-Response Pacemaker Action Potential Phases
Definition
0- depolarization
3- repolarization
4- pacemaker potential/slow depolarization
Term
Slow/Pacemaker AP generation
Definition
0.-L type Ca channels open via DHPR-->Ca influx (depol.)
3.-L type Ca close; K open-->K efflux (repol.)
4- K close
-Funny open-->Na influx (slow/pacemaker)
-T-type Ca open- Ca influx (slow/pacemaker)
Term
What is necessary for cardiac muscle contraction?
Definition
Calcium induced calcium release
AP in T-tubule-->DHPR and L-type Ca open-->Ca enter cell-->Ca binds to RyR-2R releasing calcium to bind to troponin C
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