EXPH 386 Exam 3
neuromuscular system
coordination and integration of the muscles of the body together with the nerves
that supply them
cell body (soma) -peripheral
dictates the critical firing rate of the action potential. Larger cell bodies are
associated with higher critical firing rates. Also contain the structures involved in
replication and transmission of the genetic code
Dendrites
short neural branches that receive impulses through numerous connections and
conduct them toward the cell body
Axon
(Larger nerve--> larger axon)
extends from the cell body to deliver action potentials toward the muscle to the
motor endplate. Larger axons are associated with faster conduction velocities.
Myelin sheath
a lipoprotein membrane that wraps around the axon over most of its length; acts
as an electrical insulator that envelops the axon similar to the plastic coating
around an electrical wire.
myelin sheath
the speed of action potentials depend on this
Schwann cells
specialized cells that create or deposit the myelin sheath around the axon
,-makes myelin protein
Nodes of Ranvier
interrupts the myelin sheath every 1 to 2 mm along the length of the axon
-small breaks in myelin exposes this
saltatory conduction
the gaps or interruptions are insulated areas that allow the action potential to
jump from node to node, this is known as
slower
If no myelin were present, conduction velocities would be a lot _____
nerve terminal branches
multiple extensions of the axon that innervate individual muscle fibers
-each fiber is going to receive input from one terminal branch
motor endplate or neuromuscular junction
represents the interface between the end of the axon at the terminal branch and
the muscle fiber
fibers, which run parallel to eachother
( force is directed along the fibers long axis)
the skeletal muscles of the body are composed of multinucleated cylindrical cells
called _________, which ______
endomysium (connective tissue)
-between fibers
- a fine layer of connective tissue that wraps each muscle fiber and separates it
from the neighboring fibers
,perimysium (connective tissue)
surrounds a bundle of up to 150 fibers
fasiculus (connective tissue)
a large bundle of fibers
epimysium (connective tissue)
-deep fascia
- a fascia of fibrous connective tissue that surrounds the entire muscle
tendons (connective tissue)
dense connective tissue, the extension of the epimysium at the ends of the
muscle
periosteum (connective tissue)
bones outermost covering; tendons connect the muscle to this covering of the
bone
sarcolemma (skeletal muscle)
-wraps the fiber
- the muscles fiber membrane; a thin elastic membrane that encloses the fibers
cellular contents. the true fiber boundary
basement membrane (skeletal muscle)
-outside the muscle
a loose collection of glycoproteins and collagen; outside the muscle fiber
sarcoplasm (skeletal muscle)
, -inside fluid of fiber
contains the nuclei, substrates, and enzymes required for metabolism, the nuclei,
mitochondria, and other specialized organelles
sarcoplasmic reticulum (skeletal muscle)
-stores calcium within muscle
highly specialized network of tubular channels that allow a wave of depolarization
to spread rapidly from the sarcolemma to the inner environment through the T
tubules to initiate muscle contraction.
-also stores a large concentration of calcium in the muscle fiber
multinucleated
number of nuclei that run the length of that fiber to allow for transcription activity:
protein development of genes leading to fiber
myonuclei
true muscle fiber nuclei: muscle fibers are multinucleated residue directly under
the sarcolemma at the periphery of the fiber ... represents 85 to 90% of the total
nuclear pool
Myonuclear Domain Hypothesis
each nucleus wants to control its own domain of sarcolemma thats fixed
-make it bigger; more nuclei
hypertrophy
added nuclei to control own sarcoplasm
-more area
atrophy
lose nuclei if fiber gets smaller
-still fixed
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