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47 Cards in this Set
- Front
- Back
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3 Cell types in Cardiac muscle:
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1. Cardiac myocytes
2. Endothelium (endocardium) 3. Cardiac fibroblasts |
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3 Similarities of cardiac muscle to skeletal:
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-Both have basal laminas surrounding individual cells
-Both are striated -Both have similar mechanisms of contraction |
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4 Major differences between Cardiac and skeletal muscle:
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-Cardiac is involuntary
-Cardiac has only 1-2 nuclei -Nuclei are CENTRAL -Cells BRANCH |
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How do cardiac myocytes compare to skeletal in terms of size?
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They are smaller
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How does the blood supply to cardiac muscle compare to skeletal?
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It is much more highly vascularized.
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What 3 things do cardiac muscles require to be supplied for their continual energy demand?
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-Mitochondria
-Myoglobin -lipid droplets |
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What type of creatine kinase is in:
-Skeletal muscle -Cardiac muscle |
Skeletal = MM
Cardiac = MB |
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What connects cardiac muscle cells together as a syncytium?
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Intercalated disks
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What 2 proteins from cardiac muscle indicate MI?
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-CK-MB
-Troponin I |
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What do cardiac myocytes have in place of the Triad?
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Dyads
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Where are Dyads located?
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At the Z-line, not the AI junction like in skeletal muscle.
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ARE cardiac myocytes a syncytium?
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No; they just can act like they are by the intercalated disks.
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2 components in a skeletal muscle intercalated disc:
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-transverse part
-lateral part |
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What is the transverse part made of?
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A half a z line
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2 structures that compose the "half z-line" of transverse parts of intercalated disks:
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-a Fascia adherens which does NOT encircle the cell
-Desmosome |
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What butts against the half-Z bands?
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Actin filaments and N-cadherins
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What 2 structures are found in the Lateral part of intercalated disks?
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-Gap junctions ( to allow cell-cell signalling/rythmicity)
-Desmosomes |
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Gap junctions are made up of:
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connexins
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How are Atrial myocytes in comparison to ventricular?
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-Smaller
-Fewer t-tubules |
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What special hormone is released from atrial myocytes?
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ANF (atrial natiuretic peptide)
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What are Atrial NODE myocytes like?
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Small and embedded in dense CT
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What are AV Bundle of his cells like? What are they called?
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Purkinje fibers - LARGE and have few myofibrils.
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What causes cardiac myocytes to become Purkinje cell fibers?
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Secretion of ENDOTHELIN from endothelial cells in developing coronary arteries.
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What is the Endocardium?
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The lining of cardiac endothelial cells
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What type of epithelium is the endocardium?
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Simple squamous
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What are the most abundant cells in the heart?
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Cardiac fibroblasts
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What is the major fuel for cardiac myocytes?
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Triglyceride (Fatty acids)
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Where are triglycerides stored in cardiac myocytes?
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In membrane bound lipid droplets near the nucleus.
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Does the heart undergo anaerobic metabolism?
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No; it's largely aerobic.
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Serum levels of MM-CK are diagnostic for:
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Skeletal muscle dystrophy
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Serum levels of MB-CK are diagnostic for:
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Myocardial infactions
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What innervates cardiac myocytes?
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The vagus nerve and sympathetics.
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When does myocyte death begin during a heart attack?
When does inflammation occur? When does Wound healing begin? |
Death - immediately
Inflammation - 12-16 hrs later Healing - 2-3 days later |
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What is synthesized during wound healing following an MI?
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-Collagen III
then -Collagen I |
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What secretes the collagen for wound healing?
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Cardiac fibroblasts
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What are the last 2 steps in wound healing?
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-Angiogenesis
-Scar formation |
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What does Scar formation consist of?
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Crosslinking collagen by lysyl oxidase
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What are 2 types of injury to cardiac myocytes?
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1. Hypertrophy
2. Ischemic |
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What characterizes pathological cardiac hypertrophy?
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Re-expression of embryonic cardiac genes
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Is the replacement of myocytes lost due to ischemia with with Fibroblasts a good idea?
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No; it would only create a non-contractile scar.
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Where might stem cells for cardiac myocyte regeneration be obtained?
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-Embryonic - but requires transplantion
-Adult - from bone marrow or the heart itself. |
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So 2 possible sources of adult stem cells for cardiac myocyte regeneration:
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-Bone marrow
-Heart itself (but neither is proven) |
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What are embryonic stem cells in terms of differentiation capability?
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Pluripotent
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Where are embryonic stem cells derived?
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From the inner cell mass of blastocyst stage embryos
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How do embryonic stem cells turn into beating cardiomyocytes in developing embryos?
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Precardiac endoderm induces Precardiac mesoderm to do it.
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What happens when precardiac endoderm is cultivated with ESCs?
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They are induced to become beating cardiac myocytes with VERY HIGH FREQUENCY.
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Can leftover adult cardiac myocytes be induced to regenerate infarcted myocardium?
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Maybe.
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