Lecture 1: Muscle Structure Flashcards
each muscle consists of _____ to ______ of individual contractile fibers
hundreds to thousands
connective tissue:
mostly collagen some elastin
epimysium
tough coat of tightly woven bundles of collagen which surround entire muscle, separating it from other muscles and structures
myotendinous junction
ends of the muscle where epimysium connects with the sarcolemma
why does the myotendinous junction have extensive folding of the epimysium and sarcolemma
to increase surface area
perimysium
- also tough and thick
- divides muscle fibers into fascicles or bundles
- provides pathways for arteries, veins and nerves
endomysium
surrounds each muscle fiber, connections to both the perimysium and the basement membrane
sarcolemma
consists of basement membrane and the plasmalemma
conduit arteries and veins
run in parallel along the surface of muscle
perforating arteries and veins
periodically branch and dive into belly of muscle in parallel, with several generations of branching
arterioles lead to capillaries which __________. note multiple branching within network
capillaries surround each fiber!!
nerves usually run in _____ with the arteries and veins
parallel
motor nerves make up ____% of the nervous innervation of skeletal muscle
60%
motor nerves represent ….
the final nerve in the path from the motor centers in the cerebrum to the target muscle
motor nerve impulses travel in an _____ direction
efferent (away from CNS)
due to the ________, impulses travel very fast along the axon
myelin sheath
near muscle fibers, the myelin sheath ends and the axon splits sending a _______ to each fiber
terminal branch
motor end plate
the region of muscle plasmalemma under the terminal axon
sensory nerves represent ____% of the nerves in skeletal muscle
40%
sensory nerves impulses run in a ______ direction
afferent direction (toward the CNS)
sensory nerve impulses rely on a variety of _____, ____, ____, ____
touch, pain, muscle tension, contraction information
skeletal muscle cells appear ______.
striated
sarcolemma
the cell membrane surrounding each cell
sarcoplasmic reticulum
membranous network that surrounds each myofibril
what is the primary role of the SR?
the release of Ca++ which initiates the contraction process
transverse tubules
membranous channels that extend inward from the sarcolemma and pass completely through the fiber
cisternae
enlarged portions of the SR that the t-tubules pass through
motor end plate is the site where the _____ ends and transmits depolarization signal to the muscle
alpha-motorneuron
does the alphamotorneuron touch the arcolemma?
no
neuromuscular or synaptic cleft
the space where the sarcolemma invaginates around the alpha-motorneuron synapse
steps in excitation contraction coupling
1 a-motorneuron depolarizes leads to release of ACh
- ACh binds causing Na+ to enter the cell, leading to the depolarization of the muscle cell (end-plate potential)
- depolarization wave on sarcolemma is transmitted down t-tubules
- calcium released from SR
- Ca++ binds to troponin initiating contraction process
- Ca++ pumped back into SR by SR Ca++ ATPase
- Ach is broken down by acetylcholinesterate
sliding filament theory steps
- rest
- excitation coupling
- active contraction
- recharging system
- subsequent response dependent on presence of Ca++
why when animals or people die do their bodies go into rigor?
run out of ATP
