Muscle Tissue Flashcards
What are skeletal muscles called?
myocytes or muscle fibers
What does groups of muscle fibers form?
fascicles
What are muscle fibers separated by?
endomysium
What are fascicles separated by?
perimysium
what surrounds the entire muscle?
epimysium
What is the cytoplasm of myofibers primarily occupied with?
myofibrils
Where is the nuclei located in skeletal muscle?
In the periphery
What are myofibrils composed of?
thin (actin) and thick (myosin) filaments
What is the basic functional unit of a myofibril?
sarcomere
What is the group of myofibrils surrounded by?
sarcolemma
What are the invaginations of the sarcolemma?
transverse(t)-tubules
What are the dilated ends of the sarcoplasmic reticulum that release Ca2+
terminal cisternae
anchor site for actin (thin) microfilaments?
Z-line
Anchor site for thick myosin filaments?
M-line
only contains actin thin filaments?
I-band
only contains myosin thick filaments?
H-zone
overlap of thick and thin filaments plus the H-zone?
A-band
When a muscle cell contracts what occurs with the filaments?
the thin filaments slide past the thick filaments toward the center of the sarcomere bringing Z-lines closer together
What are the regulatory proteins found in thin filaments?
tropomyosin and troponin
Runs in groove formed by F-actin strands
tropmyosin
what does tropomyosin bind to?
to the troponin complex
Troponin is a complex composed of what?
3 proteins, troponin I, troponin C, and troponin T
What is the role of troponin T?
it binds tropomyosin to the complex
What is the role of troponin I?
it inhibits the binding of myosin to actin
what is the role of troponin C?
it binds Ca2+ and is only found in striated muscle
What is the regulatory protein that permits cross-bridge formation when it binds Ca2+
troponin
What carries the depolarization from the sarcolemmal membrane to the cell interior
T-tubules
What is the site of Ca2+ storage and release for excitation-contraction coupling?
sarcoplasmic reticulum
What does depolarization of of the T tubules cause?
a conformational change in its dihydropyridine receptor (DHPR)
what does a conformation change in the DHPR cause?
opens Ca2+ release channels in the nearby sarcoplasmic reticulum
What happens when Ca2+ binds to troponin C on the thin filaments?
it causes a conformational change in troponin that moves tropomyosin out of the way
When does the cross-bridge cycle begin?
once calcium binds to troponin c and moves tropomyosin out of the way
What happens when ATP binds to myosin?
it produces a conformational change in myosin that causes myosin to be released from actin
What causes myosin to be displaced toward the plus end of actin?
hydrolysis of ATP to ADP and inorganic phosphate
sites of special cell adhesions and low electrical resistance
intercalated discs
ribbon- like adhesions found at the ends of terminal sarcomeres and anchored to actin filaments
fascia adherens
spot-like adhesions between cells anchored to intermediate filaments of the cell
desmosome
small channel-like connections between cells allowing excitation/contraction wave to pass from one cell to the next connected cell
gap junctions
How does cardiac muscle contract?
rhythmically without innervation
What is the most predominant junction in cardiac muscle?
fascia adherens
Which junction transmits contractile forces between cells in cardiac muscle?
fascia adherens
What are dense bodies of smooth muscle comprised of?
desmin and vimentin intermediate filaments
