Muscle cell structure. Flashcards
Skeletal muscle tissue [long cylindrical]:
Located in voluntary muscle.
They are multi-nucleated.
They are striated.
The release of acetylcholine induces an action potential.
Contractions of skeletal muscle tissues are dependent on:
Stimulation by somatic motor neurons, which form a chemical synapse called the neuromuscular junction.
One motor end plate per:
Muscle fiber.
Cardiac muscle tissue [long irregularly shaped cells]:
Striated & found in the heart.
Uni-nucleated.
Connected by gap junctions.
Autorhythmicity:
Action potential arises within the muscle tissue.
You don’t need nervous stimulation for contractions in cardiac tissue.
Intercalated disks:
Where gap junctions are located.
The intercalated disks are located between cells.
Action potential in skeletal muscle cells are:
Transmitted from cell to cell via electrical synapses.
Skeletal muscle cells are called:
Muscle fibers.
Smooth muscle tissue [spindle shaped]:
Located in the viscera, involved in the reflex response.
Smaller than muscle fiber.
Contains a single nucleus.
types of smooth muscle tissue:
Single unit.
Multi-unit.
Single unit (smooth muscle tissue):
The cells are connected by electrical synapses.
They also have autorhythmicity.
Ex: GI Tract, uterus.
Multi-unit (smooth muscle tissue):
They have no electrical synapses.
They respond to neurotransmitters or hormones.
They do not produce an action potential.
What does smooth multi-unit muscle tissue produce:
Depolarizing postsynaptic potential that stimulates contraction.
Sarcolemma:
Plasma-membrane of the skeletal muscle.
Sarcoplasm:
Cytosol [ICF].
Myofibril:
Cylindrical structures that extends the length of the muscle fiber and contain sarcomeres.
Contraction of sarcomeres causes contraction of the muscle fiber.
Myofibril can also contract.
Sarcoplasmic reticulum:
Calcium ion storage organ.
Transverse tubules:
Propagate action potentials from the sarcolemma to the interior of the muscle fiber.
Myofilament arrangement produces:
A & I bands.
Types of filaments:
Thick filament.
Thin Filament.
Thick filaments are attached to:
The M line.
___ thin filaments surrounds ____ thin filament.
6 thin surrounds 1 think.
Z-Disk:
Protein that holds the thin filament in place.
Located at the center of each I band.
Sarcomere:
Contractile unit of a myofibril.
Each sarcomere contracts.
It is the area between two adjacent z-disks.
Titin:
Gives elasticity to the myofibrils.
Nebulin:
Assemble & stabilizes the thin filaments.
Thin filaments are made up of:
G-actin.
Tropomyosin.
Troponin.
G-actin:
Each G-actin contains 1 myosin-binding site.
Globular protein that can polymerize to form a long chain.
Myosin binding site:
Where thick filaments meets the thin filaments.
In a thin filament, two:
Two G-actin are coiled together to form an F-actin.
Tropomyosin:
A filamentous protein that lies along F-actin, and which has the ability to block myosin-binding sites.
At rest, Tropomyosin lies:
Over the myosin binding site.
Troponin:
A protein that consists of three subunits.
Troponin T.
Troponin I.
Troponin C.
What subunits of troponin interacts with tropomyosin:
Troponin T & I.
Troponin T:
Holds tropomyosin in place.
Troponin I:
Ensures myosin remains over the myosin binding site.
Troponin C:
Can bind to calcium ions and regulates the activity of troponin I & T.
In the presence of ca, it moves tropomyosin away from myosin binding site.
Thick filaments:
Made primarily of the protein myosin.
Myosin:
Made up of six subunits.
2 heavy chains & 4 light chains.
In the presence of calcium ions, troponin C:
Moves tropomyosin away from myosin binding site.
Heavy chain of myosin:
The 2 head & tail.
The light chain of myosin:
Flexible hinge region.
Each myosin head has:
One G-actin binding site.
One ATPase site.
The head of the myosin is also called:
Cross-bridges.
One thick filament consists of:
200-400 myosin molecules.
The middle of the thick filament lacks:
cross-bridges.
Barezone:
The middle of the thick filament that lacks cross-bridges.
Barezones are attached to the M-line in the sarcomere.
