39 terms


Muscle cells in resting state just before stimulation; contraction mechanism in a skeletal muscle cell.
There is a greater concentration of ______ outside the cell.
Na+ or Sodium
There is a greater concentration of ______ inside the cell.
K+ or potassium
When the stimulus is delivered, the permeability of the membrane at that point is changed; and ______, initiating the depolarization of the membrane.
Na+ diffuses into the cell
Almost as soon as the depolarization wave has begun, a repolarization wave follows it across the membrane. This occurs as _________.
K+ diffuses out of the cell
Repolarization restores the ________ of the resting cell membrane.
electrical conditions
The relative ionic concentrations are reestablished by ______.
Activatiion of the sodium-potassium pump, which moves K+ into the cell and Na+ out of the cell.
Describe in order the contraction mechanism in a skeletal muscle cell.
-Depolarization occurs; and the action potential is generated
-The action potential, carried deep into the cell by the T Tubules, triggers the release of calcium ions from the sarcoplasmic reticulum.
-Calcium Ion concentrations at myofilaments increase; myofilaments slide past one another, and the cell shortens
-The concentration of the calcium ions at the myofilaments decreases as they are actively transported into the sarcoplasmic reticulum
-Muscle cell relaxes and lengthens
Name the 3 layers of connective tissue that are part of each muscle.
Epimysium, Perimysium, and Endomysium
dense collagen fibers that separate the muscle from surrounding tissues and organs
surrounds fasicles and contains blood vessels and nerves that maintain blood flow and innervate the muscle fibers within the fasicles
Within a fascicle, surrounds individual skeletal muscle cells, or muscle fibers, and loosely interconnects adjacent muscle fibers.
Skeletal Muscles are comprised of:
Skeletal muscle tissue, connective tissue, nerves, and blood vessels.
Name the six functions of skeletal muscle
Produce skeletal movement
Maintain posture and body position
Support Soft Tissues
Guard entrances and exits
Maintain body temperature
Store Nutrient Reserves
A bundle of muscle fibers
The 3 types of muscle tissue are:
At each end of the muscle collagen fibers of the epimysium, perimysium, and endomysium come together to form either a bundle known as a ______ or a broad sheet called an _________.
Attach skeletal muscle to bones
Tendons and aponeuroses
Large, multinucleate group of cells
Skeletal muscle fibers
Plasma membrane of a muscle fiber
Specialized cytoplasm of a muscle fiber with varying calcium concentration
1st step in muscle contraction
A sudden change in the transmembrane potential
Narrow tubes that are continuous with the sarcolemma and extend into the sarcoplasm at right angles to the cell surface, filled with extracellular fluid, distribute contraction signals quickly throughout the interior of the cell.
T-Tubules (Transverse Tubules)
The triggers for muscle fiber contraction
Action Potentials
Cylindrical structures encircled by transverse tubules consisting of bundles of protein filaments (myofilaments) and titin.
Composed primarily of Actin
Thin filaments
Composed primarily of myosin
Thick Filaments
Cell membrane of muscle cell
Stores calcium and forms a tubular network around each individual myofibril
Sarcoplasmic Reticulum
Combination of a pair of terminal cisternae, and a transverse tubule
A muscle contraction begins when:
Stored calcium ions are released into the sarcoplasm, then diffusing into individual contractile units called sarcomeres
Dark staining proteins that help stabilize the positions of the thick filaments
M Line
Contains thick filaments but no thin filaments
H Band
Region where each thin filament is surrounded by 3 thick filaments and each thick filament is surrounded by six thin filaments
Zone of overlap
Contains thin filaments but not thick filaments and extends from the A band of one sarcomere to the A band of the next sarcomere
The I band
Mark the boundary between adjacent sarcomeres consisting of the protein actinin, which interconnect thin filaments of adjacent sarcomeres
Z lines
Strands of the elastic protein _______extend from thick filaments to attachment sites at the Z line and aids in thick and thin filament alignment, restoring resting sarcomere length, and resistance of extreme muscle fiber stretching.
Triads are located at:
The zone of overlap
Encircle each sarcomere
2 T tubules
A single __________ contains 4 proteins: F-actin, nebulin, tropomyosin, and troponin.
Thin Filament