Histo Lecture 1
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What are intercalated discs?
- -Junction between adjacent myocardial cells
- -Contain gap junctions for easy ionic conductance
Mitochondria make up how much of the sarcoplasm?
What is the major fuel for cardiac cells?
- Fatty acids
- Minimal amount of glycogen present
Myocytes are connected by what?
What do gap junctions allow in the heart?
- Ionic conductance between cells
- Allows syncytium
What are the five differences between cardiac and skeletal muscle?
- Gap junctions
- Intercalated discs
- Single nucleus
- Less developed SR and T-tubules
- Autonomic innervation
- Multinucleate mass of cytoplasm resulting from the fusion of cells
- -Depolarization travels as a "wave" throughout the myocardium
- -Impulse to one area of heart results in contraction of entire myocardium
Syncytia portions (atria/ventricles) are separated by what?
The fibrous "ring" tissue surrounding the AV valves
Fibrous ring prevents what?
- Conduction of impulse from atria to ventricles
- -Allows atria and ventricles to contract separately
A plateau in an action potential is cause by what?
"Slow" calcium channels that remain open longer than sodium channels
Why is there a delayed repolarization period in cardiac muscle?
Caused by delayed movement of K+ out of cell
What is Systole?
- Ventricular contraction
- Heart ejects blood into pulmonary and systemic circulation
What is Diastole?
- Ventricular relaxation
- Atria and ventricles fill with blood
What is mean arterial blood pressure (MABP)?
Average pressure exerted by the blood against the walls of systemic arteries
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