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Cardiac muscle is derived from
Splanchnic Mesoderm
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What are the only places that cardiac muscle are found
In the heart and the roots of large vessels that join the heart
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Each cardiac cell contains how many nuclei
One or two, never three
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What are some unique features in cardiac muscle cells that differentiate them from skeletal muscles
- Intercalating discs
- Lots of large mitochondria
- Stair stack configuration between adjacent cells
- Diad instead of Triad
- Small terminal cisternae
- Large T tubules
- SR not well developed
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In cardiac muscle, how are the sarcomeres attached to one another
- The transverse portion includes Zonula adherens and macula adherens (Desmosomes)
- The longitudinal portion has Gap Junctions for communication
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Where are the diads located in relation to the sarcomere
In the vicinity of the Z lines
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Calcium supply in cardiac muscle is different form skeletal muscles how
It is supplied by the extracellular matrix
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How do cardiac muscles create their own spontaneous rythmic contraction
By cardiac conducting cells like SA and VA nodes and fibers called purkinje fibers.
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Purkinje fibers store lots of
Glycogen
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Sympathetic and parasympathetic fibers terminating at the AV and SA nodes only do what
Modify the rate of the intrinsic cardiac muscle contraction
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What is considered the pace maker of the heart
SA node located in the superior vena cava
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Where is the AV node located
In the AV septum
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What are cardiac endocrine cells
Specialized cells that produce small peptide hormones, located in the atrial wall
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What is one of the Cardiac endocrine hormones and its function
Atrial Natriuretic polypeptide, It decreases blood pressure by triggering the kidneys to make more urine
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Cardiac muscle cells can't regenerate, so when they die they
Are replace by connective tissue
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Smooth muscle lacks what features compared to skeletal and cardiac muscle
- No T tubules
- No cross striations
- No sarcomere
- No Troponin
- No myofibrils
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Smooth muscle cells have how many nucleus's and what shape
- One nucleus centrally located
- Spindle shape with no branches
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How is the myosin different in the smooth muscle
They are all pointing the same direction
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Thin filaments in smooth muscle contain
Actin and tropomyosin but NO troponin
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Myofilaments are arranged in smooth muscle how
They criss cross obliquely forming a latticework and are attached to dense bodies (on cytoplasmic side)
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The psuedo Z lines in the smooth muscle are
Dense bodies (serve as insertion points for myofilaments and intermediate filaments)
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Caveolae in Smooth muscle (sarcolemmal vesicles) serve what purpose
May associate with sparse SR and may function in the release and sequestering of Ca++
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What does the inactive state of a smooth muscle myosin look like
It is twisted in a circle
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Smooth muscle doesn't have what rule
The all or none rule
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How does the contraction of smooth muscle work
- CA++ is released from caveolae
- Ca++ bind to Calmodulin
- Calmodulin Ca++ complex activates the myosin light chain kinase
- Actin binds (S1) to the unmasked myosin and contract
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When a hormone like Oxytocin is given to a female what happens
This activates the myosin light chains in the uterus creating contractions inducing labor
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What are the two different types of smooth muscle cells
- Multiunit
- Visceral (Unitary Smooth muscle)
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Multiunit smooth muscle has what characteristics
- They are richly innervated (each cell recieves inn.)
- They are specialized for precise, graded conduction
- Found in the iris of the eye, vas deferans
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Visceral smooth muscle has what characteristics
- Minimal innervation
- Few neuromuscular junctions
- Impulses transmitted via nexus
- Regulated by hormones (oxytocin) and stretching
- Found in hollow organs (uterus, intestinal wall, ect.)
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Smooth muscle cells can do what, that other muscle cells can't
Regenerate through mitosis, as well as arise from mesenchyme or pericytes
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What are two contractile non muscle cells
- Myoepithelial
- Myofibroblasts, used to close wounds
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Myoendothelium are most similar to what muscle and why
Smooth muscle, they have only actin and myosin, the contraction is similar to smooth muscle, they are activated by Oxytocin, and are calmodulin mediated
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What are the two main ways to distinguise between muscle cells
The presence of striations and the position of the nucleus
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Myoepithelial cells arise from
Ectoderm
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Myoepithelial cells are associated with
Glandular secretory units (basket shaped)
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