Physiology Chp. 12
What is a triad
A triad is combination of a pair of terminal cisternae and a T-tubule
What is the difference between Ca2+ at the axon terminal and Ca2+ in the sarcoplasmic reticulum.
Ca2+ voltage gated channels are stimulated by the arrival of an action potential at the axon terminal, and sarcoplasmic reticulum stores calcium in a muscle fiber.
Do each of the bands increase, decrease, or stay the same length?
I band-decrease H band-decrease A band-stays the same
What is the location and function of myosin
Located in the middle of the A band and connected by the M line, thick filament
What is sarcolemma
Muscle cell membrane
Describe troponin
Smaller protein which attaches to tropomyosin, binds calcium to allow for contraction
What is the location and function of actin
Thin filament, located in the Zone of Overlap of the A Band and extends into the I Band; connects to the Z line
Describe Tromomyosin
Wraps around actin; controls movement of troponin
What is dystrophin?
a large which is protein located under the sarcolemma within the I band of the striations; links actin filaments to transmembrane proteins in the sarcolemma.
What is myoglobin?
a red pigment that stores oxygen needed for muscular activity, within the sarcoplasm
What are myofilaments
bundles of protein filaments within myofibrils
What does it mean when a motor unit is large?
consist of a motor neuron innervating large numbers of muscle fibers and are typically used for large or powerful movements
What is a motor unit
consists of one nerve fiber and all the skeletal muscle fibers that it supplies
What is the A band of the sarcomere?
dark band consisting of both thin and thick filaments
What is titin?
elastic protein fibers that run through the core of each thick filament and anchor it to the "Z discs" at one end and "M line" at the other. Stabilizes myosin by centering it between the actin myofilaments.
What are t-tubules
extensions of the sarcolemma; run deep into the muscle cell so action potentials can effectively depolarize a muscle cell quickly and completely
What is terminal cisternae
form when the ends of the SR fuse and form expanded chambers
What are myofibrils?
hundreds to thousands cylindrical structures within a muscle fiber, contain proteins responsible for contraction
What is a nicotinic receptor?
ionotropic protein receptors imbedded in the sarcolemma that binds acetylcholine
What is nebulin?
large, inelastic protein that runs alongside the thin filament and attaches to the Z-line
What is the I band of the sarcomere?
light band consisting of of thin filaments only; extend from the A band of one sarcomere to the A band of the next sarcomere
What is the H band of the sarcomere?
lighter region on either side of the M Line; contains thick filaments but no thin filaments
What is the sarcoplasmic reticulum
modified form of the ER; found in muscle cells
What is the M line of the sarcomere?
myosin disc; center of the sarcomere at the midline of the A band
What is the Z line (disc) of the sarcomere?
protein disc that defines boundaries of a sarcomere
What does it mean that muscle tissue is excitable?
react to stimuli; exhibit electrical and mechanical responses
What does it mean that muscle tissue has conductivity?
responds to electrical excitation and conducted throughout the plasma membrane initiating contraction
What are the roles of acetylcholine and acetylcholinesterase in the sarcolemma
sarcolemma contains receptor sites for acetylcholine (neurotransmitter) and acetylcholinesterase (inactivator)
What is acetylcholinesterase
the inhibitor of acetylcholine
What is acetylcholine
the neurotransmitter associated with all neuromuscular junctions
What is a sarcomere?
this is the functional unit of the muscle; chain of smaller contractile units within the myofibril
What does it mean when a motor unit is small?
units consist of a motor neuron innervating only a few muscle fibers, allowing for precise muscle control
