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CVA Test 3
Musculature
34
Anatomy
Undergraduate 4
03/02/2011

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Term
Describe how muscle cells develop?
Definition
1. enlongation of mesenchyme to form myoblast
2. myoblast continue to divide and then stop
3. divides again as actin and myosin to form myofilaments
Term
What is the term for adult muscle cells?
Definition
myocytes or muscle fibers
Term
What are the 3 types of muscles?
Definition
1. skeletal
2. cardiac
3. smooth
Term
Which muscle type is the most common in the human body?
Definition
skeletal
Term
Why is skeletal muscle considered a "synctium"?
Definition
cells fuse embryonically, thus a single cell may contain several hundred nuclei
Term
where are the nuclei located in skeletal muscle?
Definition
at the periphery of cell
Term
What causes contractions in skeletal muscle? What is the term to describe this type of contraction?
Definition
nerve impluses; the term is neurogenic
Term
describe the steps for skeletal muscle contraction
Definition
1. single nerve cell or fiber (neuron) branches and terminates at a motor end plate, the action potential travels down the nerve stimulating the contraction
Term
Where is cardiac muscle found?
Definition
in the heart wall
Term
what are intercalated discs?
Definition
special junctions where the cardiac muscle cells are tightly joined
Term
What type of contraction occurs in cardiac muscle
Definition
myogenic (initiates in the muscle itself)
Term
Where does contraction initiate in cardiac muscle
Definition
sinoatrial (SA) node
Term
What are Purkinje Fibers?
Definition
specialized cells that carry action potentials to distant parts of the heart
Term
describe the shape of smooth muscle cells?
Definition
enlongated, spindle shaped
Term
describe positional information of nucleus of smooth muscle cells
Definition
single nucleus centrally located
Term
Where are unitary smooth muscle fibers found?
Definition
walls of digestive tract, uterus, and urinary tract
Term
describe the contraction of unitary smooth muscle
Definition
spontaneous, rhythmic contactions initiated by the stretching of the muscle as the organs fill
Term
What type of movement is unitary smooth muscle suited for?
Definition
slow, sustained contractions
Term
Where is multiunit smooth muscle located?
Definition
walls of blood vessels, iris of eye, wasll of sperm ducts
Term
What type of contraction is in multiunit smooth?
Definition
neurogenic
Term
define fasciculi
Definition
small bundles of skeletal muscle surrounded by endomysium, held together by perimysium
Term
what is the function of epimysium
Definition
surrounds and holds many fasciculi together to form individual muscles
Term
define tendons
Definition
atttach skeletal muscle to skeletal elements
Term
define aponeuroses
Definition
tendons that form broad, thin sheets
Term
define origin
Definition
attachment site that remains fixed in position when the muscle shortens

proximal locaton
Term
define insertion
Definition
end attached to the element that moves

distal location
Term
what is a motor unit
Definition
a motor neuron + the muscle fibers it supplies
Term
what is a myofibril?
Definition
groups of myofilaments that are seen with light microscope
Term
define sarcomere
Definition
functional units of myofibrils
Term
define muscle contraction
Definition
tension resulting from interaction of myosin and actin
Term
define isotonic contraction
Definition
muscle contraction that induces shortening of muscle against constant load or force
Term
define negative work contraction
Definition
muscle may increase in length during a contraction

(ex hamstring)
Term
define flexion
Definition
movement of a distal limb segment toward a more proximal one (decreasing the angle between the 2 segments)
Term
define extension
Definition
straightens the limb
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