Term
| What is the average heart rate |
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Definition
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Term
| What does it mean if our heartbeat is myogenic |
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Definition
| It originates within the heart (in vertebrates) |
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Term
| Why is the heart not dependent on the nervous system for rhythm? |
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Definition
| It has its own pacemaker and electrical system |
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Term
| True or false - both heart muscle and skeletal muscle are striated? |
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Definition
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Term
| How would you describe the appearance of cardiocytes |
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Definition
| Relatively short, thick, branched cells |
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Term
| Do cardiocytes have a nucleus? |
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Definition
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Term
| Is sarcoplasmic reticulum less developed in skeletal muscle or cardiocytes? |
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Definition
| Cardiocytes - they lack terminal cisternae |
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Term
| What is unusual about the mitochondria of cardiocytes? |
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Definition
| They are especially large |
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Term
| What are intercalated discs? |
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Definition
| Thick connections that join cardiocytes end to end |
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Term
| What are the three distinct features of intercalated discs not found in skeletal muscle |
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Definition
| Interdigitating folds, Mechanical Junctions, Electrical junction |
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Term
| What is meant by the fact that intercalated discs have interdigitating folds, and why is this important? |
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Definition
| Plasma membrane at end of cell folded - folds of adjoining cells interlock and increase surface areas of intercellular contact |
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Term
| Why is it beneficial that intercalated discs have interdigitating folds? |
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Definition
| Increases the surface areas of intercellular contact - folds of adjoining cells interlock |
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Term
| What are the two types of mechanical junctions found on intercalated discs of cardiocytes? |
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Definition
| Broad band, and Desmosomes |
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Term
| What are broad band mechanical junctions? |
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Definition
| Actin of microfilaments anchored to plasma membrane, each cell linked to next via transmembrane proteins |
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Term
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Definition
| Weld-like mechanical junctions between cells - prevent cardiocytes from pulling apart when contracted |
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Term
| Why are desmosomes important in cardiocytes? |
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Definition
| Prevent cardiocytes from pulling apart when contracted |
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Term
| Why are electrical junctions between cardiocytes important? |
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Definition
| Allow each cardiocyte to electrically stimulate neighbours |
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Term
| What is the purpose of gap junctions on intercalated discs between cardiocytes? |
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Definition
| Form channels where allow ions to flow from cytoplasm on one cardiocyte directly into next |
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Term
| True or false - The entire myocardium of two atria acts as single cell, but does not in ventricles |
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Definition
| False - the entire myocardium of the two atria acts as a single cell, and is the same for the ventricles |
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Term
| Nearly all of the repair of damaged cardiac muscle is through this process |
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Definition
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Term
| Cardiac muscle relies almost exclusively on which type of respiration? |
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Definition
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Term
| Cardiac muscle is rich in what two molecules that allow it rely almost exclusively in aerobic respiration? |
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Definition
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Term
| What percentage of fuel for cardiac muscle comes from fatty acids (when at rest)? |
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Definition
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Term
| What percentage of fuel for cardiac muscle comes from glucose (when at rest)? |
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Definition
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Term
| What percentage of fuel for cardiac muscle comes from other fuels such as ketones, lactic acid, and amino acids (when at rest)? |
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Definition
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Term
| Why is cardiac muscle not prone to fatigue? |
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Definition
| It makes little use of anaerobic respiration or the oxygen debt mechanism |
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Term
| What are the 5 phases of the conduction system of the heart (in order) |
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Definition
1 - Sinoatrial (SA) node generates signals
2 - Signals from SA node spread throughout atria
3 - Atrioventricular (AV) node acts as electrical gateway to ventricles
4 - Signals leave AV node through AV Bundle (Bundle of His), separates into right and left bundle branches
5 - Purkinje fibres send signals to cardiocytes |
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Term
| What is the sinoatrial (SA) node? |
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Definition
| A pacemaker that initiates heartbeat and determines heart rate |
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Term
| Where is the SA node located |
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Definition
| It is a patch of modified cardiocytes in the left atrium, just under epicardium near the superior vena cava |
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Term
| Where is the atrioventricular (AV) node located? |
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Definition
| Near right AV valve at lower end of interatrial septum |
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Term
| What is the role of the AV node? |
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Definition
| Acts as an electrical gateway to the ventricles |
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Term
| What acts as insulator, preventing currents getting to ventricles by any other route other than through the AV node? |
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Definition
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Term
| What is the Atrioventricular (AV) Bundle (bundle of His) |
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Definition
| The pathway by which signals leave the AV node |
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Term
| What does the AV bundle fork into? |
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Definition
| The right and left bundle branches |
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Term
| Where do the right and left bundle branches go? |
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Definition
| Enter interventricular septum and descend towards the apex of the heart |
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Term
| What are perkinje fibres? |
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Definition
| Nervelike processes that distribute electrical excitation to cardiocytes in the ventricles, from the AV bundle branches |
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Term
| Do perkinje fibres form an more elaborate network in the left or right ventricle? |
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Definition
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Term
| Once the Purkinje fibres have delivered the electrical signal to their limits, how do the cardiocytes perpetuate it? |
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Definition
| By passing ion flows from cell to cell through their gap junctions |
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Term
| What type of nerves does the heart receive? |
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Definition
| Both sympathetic and parasympathetic |
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Term
| What is the role of the nerve supply to the heart |
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Definition
| Modify heart rate and contractile strength |
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