Term
| Which muscles are striated? |
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Definition
| Skeletal and cardiac muscles. Contain Sarcomeres. |
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Term
| Which muscles are autonomic? |
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Definition
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Term
| What features are similar between all muscle fibers? |
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Definition
| Have elongated cells, require actin and myosin |
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Term
| What are the three layers of a skeletal muscle and what do they wrap? |
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Definition
| Epimysium (wraps muscle), Perimysium (wraps fascicle), and endomysium (wraps fiber) |
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Term
| How is a skeletal muscle fiber/cell divided up? |
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Definition
| into myofibrils, and then microfilaments. Also contains mitochondria and satellite cells (repair injury). A sarcomere is from Z band to Z band. Sarcolemma - cell membrane |
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Term
| Why is Titin more present in skeletal muscles |
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Definition
| Skeletal muscles stretch more, have to be more distensible. |
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Term
| What is on a myosin head? |
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Definition
| A binding site for ATP, ATPase, and a binding site for actin. Myosin makes up thick filaments. ATP necessary for contraction. |
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Term
| What covers the binding site for myosin? |
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Definition
| Troponin complex, which regulates tropomyosin. TnI binds to actin/TnT binds to tropomyosyn/TnC binds calcium. Smooth muscle has no troponin. Actin makes up thin filaments. |
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Term
| How is calcium delivered to a skeletal muscle? |
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Definition
| Sarcolemma folds in to form a T-tubule that runs into the cell to form a triad (terminal cisternae, T-tubule, terminal cisternae of SR). Action potential travels down T-tubule, L-channel on T-tubule changes configuration of RyR on SR to release calcium. |
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Term
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Definition
| Another name for a triad. Membrane depolarization opens L-Calcium channels. Calcium releases and binds to TnC --> contraction. Internal calcium is absolutely necessary for skeletal muscle contraction |
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Term
| How is excess calcium disposed of? |
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Definition
| When an AP becomes positive, Ca-release channel closes and Calsequestrin reuptakes calcium |
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Term
| How does sliding filament work? |
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Definition
| Calcium binds to TnC, then TnT will move tropomyosin. Myosin then binds to actin, pulling towards center of sarcomere using ATP hydrolysis. ATP required for release. Active transportation of Ca back to SR |
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Term
| How do the bands change in the sliding filament theory? |
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Definition
| The H zone disappears, I band gets smaller. A band does not change. |
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Term
| How do neurons affect muscle contraction? |
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Definition
| N(m) junctions - vesicles containing acetylcholine. Ca allows vesicles to fuse, disperse across cleft. Ach activates receptor to allow sodium influx --> depolarization. Binds to alpha1 subunit in Ach receptor |
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Term
| What is the MIR site on an Ach receptor? |
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Definition
| main immunogenic region. Where antibody binds, endocytosis of receptor. Leads to M. gravis. Not the same as Ach binding site. |
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Term
| What is the result of depolarization of a muscle cell? |
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Definition
| Na concentration outside, K concentration inside. Ach binds, Na comes into cell and inside becomes positive/outside negative in a wave. K efflux to repolarize. |
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Term
| What is the anatomy of a cardiac muscle? |
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Definition
| Not as long/branched, less nuclei/more mitochondria. Only endomysium, no perimysium/epimysium. Intercalated disc = gap junctions and desmosomes. Contract as synctium - one whole muscle. Have T tubules and SR, Actin/Myosin/troponin. Needs extracellular calcium for CICR, no triad/NMJ |
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Term
| How does the heart get calcium? |
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Definition
| Extracellular calcium REQUIRED for contraction. Majority through L-channel in Sarcolemma, some RyR/SERCA. Ca removed mostly SR, less through sarcolemma. Calcium influx through L-channel, goes to RyR to release more Ca. Ca influx closes Ryr, efflux through SERCA and NCX |
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Term
| What is required for cardiac energy metabolism? |
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Definition
| Get ATP from lipids or carbs, NADH reduced to NAD+ to convert ADP to ATP. Get more total ATP yield from fats but requires more oxygen. Fatty acid --> Acyl CoA, carnitine needed from transport. Fatty acid byproduce NADH inhibits glycolysis |
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Term
| Involuntary contraction of a cardiac cell |
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Definition
| L-channel opens, calcium influx. Calcium goes to RyR on SR, calcium induced calcium release --> contraction. Also NE binds to B1, increase cAMP, active pKA. Increased calcium. |
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Term
| Relaxation of a cardiac muscle |
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Definition
| Calcium presence turns off RyR. Kinase A phosphorylates PLB to turn on SERCA, reuptake of Ca on SR. Ca/NaX on membrane. Also Ach binds to M2 receptor --> closes L-channels, K efflux, inhibits cAMP/pKa. |
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Term
| What are characteristics of smooth muscle? |
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Definition
| Makes up walls of hollow organs. No troponin, only calmodulin. MLCK acts on ATP. No T-tubules/NMJs. Contain dense bodies. Multiunit or unitary/visceral |
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Term
| How does calcium increase in smooth muscle? |
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Definition
| Entry through voltage gated L-channels, CICR of from the SR using IP3. If there is a depletion in Ca, entry through voltage-independent channels |
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Term
| What is the difference in smooth muscle between single unit and multi-unit cells? |
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Definition
| Unitary cells connected by gap junctions, allowing calcium flow and functioning with automaticity. Multiunits innervated by an autonomic nerve, found in iris and ciliary body. |
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Term
| How does calcium stimulate contraction in smooth muscle cells? |
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Definition
| NE or Ach binds to Alpha-1 or M3 --> L-channel opens, calcium induced calcium release, calcium binds to calmodulin --> complex phosphorylates MLCK. Increased calcium also from GPCR (IP3/DAG) |
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Term
| How is smooth muscle relaxed? |
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Definition
| B2 (Albuterol) and cAMP activates a GPCR, decreases intracellular calcium. cAMP inhibits MLCK, so no actin action. Ach binds to M3 --> IP3 pathway - nitric oxide converts GTP to cGMP --> decreases calcium |
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Term
| What are the different bands/lines in a sarcomere? |
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Definition
| An A band is mostly myosin with overlapping actin. M line- where myosin attaches. H zone - no overlapping actin. I band - actin and titinin. Z-disc - actinin |
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Term
| What is cardiac hypertrophy? |
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Definition
| An increase in the # of sarcomeres, not an increase in # of cells. |
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Term
| How does the diameter of a myelinated fiber affect conduction? |
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Definition
| Larger diameter = faster conduction |
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Term
| What Channels are on the sarcolemma? |
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Definition
- The L-channel for calcium
-The sodium/potassium ATP pump (Sodium influx, potassium efflux)
- The calcium/sodium exchanger (usually calcium in, sodium out) |
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Term
| What channels are on the sarcoplasmic reticulum? |
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Definition
| The RyR receptor (calcium into cell), and SERCA (requires ATP for calcium reuptake) |
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Term
| What happens if there is too much calcium in the cardiac cell? |
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Definition
| Taken up into mitochondria. |
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Term
| What are the sources of energy in cardiac muscle? |
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Definition
| Fatty acids majorly, glycolysis minorly. Fatty acids yield more ATP, Glucose more efficient. Need carnitine for fatty acid transport into mitochondria. |
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Term
| What function does NADH serve? |
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Definition
| reducing equivalent required for ATP formation. NADH inhibits PDH/citric acid cycle in high concentrations. |
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Term
| Which types of muscle has gap junctions? |
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Definition
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