Term
GENERAL MECHANISMS OF MUSCLE CONTRATION |
|
Definition
u Action potential-motor nerve to muscle fiber
u Nerve secretes acetylcholine into neuromuscular junction
-Activation of multiple acetylcholine-gated Na/K channels
-Influx of Na initiates action potential in muscle cell
-Depolarization of muscle cell releases Ca from SER
-Ca binds to troponin C and allows myosin heads access to actin filaments
- Contraction occurs, sarcomeres shorten
- Resequestration of Ca in the SER, contraction event ends
|
|
|
Term
Energy for muscle contraction |
|
Definition
- cellular ATP (1-2 sec.)
- phosphocreatine (5-8 sec.)
- intramuscular glycogen (1 min.)
- oxidative metabolism (hours)
|
|
|
Term
|
Definition
-Much larger fibers for greater strength of contraction.
-Extensive sarcoplasmic reticulum for the rapid release of calcium.
-Large amounts of glycolytic enzymes.
-Less extensive blood supply.
-Fewer mitochondria.
|
|
|
Term
|
Definition
uSmaller fibers.
-Also innervated by smaller nerves.
-More extensive blood supply to provide large amounts of oxygen.
-Greatly increased numbers of mitochondria.
-Large amounts of myoglobin.
|
|
|
Term
Mechanics of muscle contraction |
|
Definition
-Motor unit-all of the fibers innervated by a single motor neuron are called a motor unit.
-Force summation
–Multiple fiber summation
–Frequency summation and tetanization.
-Skeletal muscle tone.
-Muscle fatigue.
|
|
|
Term
Remodeling of muscle
to match function |
|
Definition
-Muscle hypertrophy
-Muscle atrophy
-Adjustment of muscle length
-Hyperplasia of muscle fibers
|
|
|
Term
Effects of muscle denervation |
|
Definition
-Atrophy begins almost immediately.
-After about 2 months, degenerative changes begin to occur in the muscle fibers themselves.
-In the final stages, most muscle fiber is destroyed and replaced with fibrous and fatty tissues.
-The fibrous tissue will continue to shorten over time unless physical therapy is continued.
|
|
|
Term
Effects of muscle denervation
in poliomyelitis |
|
Definition
-Formation of marcomotor units by the sprouting of new axons from the surviving motor neurons.
-As a result, fine control is lost over the affected muscles.
|
|
|
Term
|
Definition
-Several hours after death, all of the muscle in the body undergo contracture.
-The muscle remain in this state until the muscle proteins are destroyed, usually 15-25 hours later.
|
|
|
