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Cardiac and smooth muscles are controlled by
Autonomic innervation, paracrines, and hormones. Some are autorhythmic and contract spontaneously.
Skeletal muscles are always attached to the bone by tendons.
Falso; usually attached be tendons but not always.
Allows action potentials to move rapidly into the interior of the fiber and release calcium from the sarcoplasmic reticulum.
Why is the sarcoplasmic reticulum also known as a modified endoplasmic reticulum?
Unlike the normal function of ER, it has the ability to store and release calcium.
What is created between the binding of myosin and actin?
Crossbridges between thick and thin filaments.
A sarcomere is divided into
I Bands- THIN filaments only.
A Band- Runs the LENGTH of a THICK filament.
H Zone- Occupies THICK filaments only
Sliding filament theory of contraction
As a direct result from CROSSBRIDGE movement, during contraction overlapping thick and thin filaments slide past each other in an energy dependent manner.
Myosin releases Pi and the myosin head group attached to the actin filament tilts backwards, pulling the thick filament to overlap further with the thin filament. Energy from ATP is used and ADP is released.
A somatic motor neuron releases Ach which initiates a skeletal muscle action potential that leads to contraction.
The chemical and electrical events that triggers the mechanical events in a muscle fiber.
"Brief." The time between the end of the muscle action potential and the beginning of muscle tension development represents the time required for Ca2+ release and binding to troponin.
A condition in which a muscle is no longer able to generate or sustain the expected power output.
How are skeletal muscle fibers classified?
By the basis of their speed of contraction and resistance to fatigue: Fast-twitch glycolytic fibers, fast-twitch oxidative-glycolytic fibers, and slow-twitch oxidative fibers.
How is the tension of a skeletal muscle contraction determined?
By the length of the sarcomeres before contraction begins.
Composed of a group of muscle fibers and the somatic motor neuron that controls them. The number of fibers vary in one motor unit but are all the same fiber type.
By the addition of motor neurons, the force of contraction within a skeletal muscle can be increased.
What does summation in a single muscle fiber mean?
Fiber increases force and frequency of contraction.
Why do isometric contractions occur?
Series elastic elements allow the fibers to maintain constant length even though the sarcomeres are shortening and creating tension.
How does the body uses its bones?
As levers and joints as fulcrums. This system maximizes distance and speed but also requires muscles to do more work.
When is contraction fastest?
When the load on the muscle is zero. Speed depends on muscle fiber type and load.
Although smooth muscle is slower than skeletal muscle, smooth muscle can...
Sustain contractions longer without fatiguing.
Single-unit smooth muscle
Contracts as a single unit when depolarizations pass from cell to cell through gap junctions.
What happens during smooth muscle relaxation?
Ca2+ is pumped out of the cytosol and myosin light chains are dephosphorylated by MYOSIN PHOSPHATASE.
What happens during smooth muscle contraction?
Ca2+ enters the cell through Ca2+ channels in the cell membrane. Additional Ca2+ is released from the sarcoplasmic reticulum.
Ca2+ entry causes smooth muscle contraction without a significant change in membrane potential.
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