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42 Cards in this Set

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Describe smooth muscle.
Smooth muscle fibers are small spindles that lack visible striations and have elongated nuclei which lie in the center of the cell. They show slow and sustained contractions and are spontaneous with involuntary control
Describe striated muscle.
Skeletal muscle fibers form large individual strips and are strongly cross striated. The nuclei is found at the periphery of the cell and is round or oval. Striated muscle have strong and rapid, voluntary control
Describe cardiac muscle
Cardiac muscle fibers are weakly striated, possess intercalated disks and their elongated nuclei are in the center of cell.
describe smooth muscle in detail
collection of spindle shaped cells with contractile proteins- organization not visible in light microscope. has special basement membrane (matrix) around each cell that is molecularly attached around and connected to other cells. indiv cells, but act as syncitium, contraction via gap junction. Rich symp/parasymp innervation. act antag to enhance or inhibit contraction
What is mytenric plexus?
plexus of nerve cells lying between 2 muscle cell layers
what does smooth muscle cell look like?
torpedo shaped individual nucleus. surrounding by matrix and connective tissue. nuclei looks larger than in fibroblast
describe contraction of smooth muscle
smooth muscle cells twist up when contracting and nucleus twists up.
can smooth muscle proliferate?
yes- endometrium in pregnancy, sometimes not good, like in vascular and respiratory disease
hypertrophy of muscle cells
increase in cell size
What does sarcolemma refer to?
cell membrane of muscle fiber
What is sarcoplasm?
cytoplasm of muscle fiber
What is sarcoplasmic reticulum?
ER of muscle fiber
What is a syncitium?
shares nucleus
special features of skeletal muscle
individual cells are multinucleated, syncitium, cytoplasm filled with filamentous bundles- myofibrils
What is a sarcomere?
whole unit of myofibril organization
thick filaments vs thin
thick are myosin, thin are actin
they overlap and on contraction the thin and thick filament ratchet closer to each other. in slide,
m- line
mid line where filaments are anchored
what causes muscle contraction
change in polarization and conformation change caused by Ca concentration. uses ATP, for thin sliding past thick thus sarcomere shortens. Size of thin filament are shortens.
Transverse tubules
invaginations of membranes that dip down perpendicular to long axis of fiber
regulation of contraction
actin and myosin interact from conformational change by Ca binding to troponin
What causes depolarization
neural stimulation causes influx of extracellular calcium ions into cell
neural control of muscle contraction
an axon from a motor neuron has a terminal bud or end plate near the sarcolemma of muscle fiber
Release of acetycholine
end plate has synaptic vesicle with this and under stimulation the synaptic vesicle exocytoses acetylcholine causing local depolarization that is propogated
motor unit
motor neuron axon and muscle fibers that innervates
what causes atrophy?
loss of motor neuron input, like polio
endomysium
delicate layer of connective tissue surrounding each muscle fiber
perimysium
connective tissue around a bundle of muscle fiber
epimusium
surrounds muscle bundle
how does striated muscle contract
epimysium blends with connective tissue of tendons and transduces the force generated by contraction of muscle fibers
myoblasts
striated muscle pre-cursors
myotubes
myoblasts that fuse to form small multinucleated fibers
how does smooth muscle recover from injury since it is striated and is post-mitotic and does not divide
normally resting satellite cells proliferate in response to stimuli, giving rise to myoblasts. these become new muscle fiber
What are satellite cells?
muscle stem cells
cardiac muscle features
made of muscle fibers
not a synctium, individual cells with discrete membranes, connect to each other
acts like synctium because attached to transduce force, gap junctions, desmosomes, basal lamina, no satellite cells so no regeneration
myocytes
fibers of individual cardiac muscle cells
how does heart pump
electrical signal sent thru attachments points
what does cardiac muscle look like?
fibers, individual nuclei (centrally placed in fiber), Hallmark is intercalated disk. looks like rope and may make branch
Intercalated disk
run across cardiac fiber with desmosomes and gap junctions, with proteins. place for sending signal
fasicle
bundle of muscle cell
motor end plate
the site of innervation, where the nerve loses its myelin sheath and forms a dilated termination that sits in a trough in the muscle cell surface
acetylcholine
chemical mediator present in synaptic vesicle of all pre-ganglionic endings and parasympathetic postganglionic endings
Are you still awake?
who me?