3.5 Muscle II Flashcards
Thin filaments contain
Actin, troponin, and tropomyosin
Thick filaments contain
Myosin
Z-line contains
Alpha-actin and desman (IF)
- holds sarcomere together
A band consists of
Thick and thin filaments
I band consists of
Thin filaments and attached Z line
H band consists of
Myosin rods (no heads)
What is a triad and what kind of muscle is it in?
- T-tubule and sarcoplasmic reticulum
- Ca2+ release channel
- Only in skeletal muscles
What surrounds the T tubules?
Terminal cisternae of SR
Endomysium is made of what type of CT?
Dense irregular CT
The axon terminal is at the level of the
Endomysium and sarcolemma
An action potential causes the release of
Calcium
What lines the axon that is on a muscle?
External lamina (basal lamina)
Junctions folds are located on the
Muscle (that’s receiving a signal from axon)
Define motor-end-plate and what is it made of?
- The myoneural junction
- Contains the terminal bouton, synaptic cleft and junctional folds
Define synaptic cleft
Depression in sarcolemma occupied by axon terminal
Steps for muscle contraction
- Nerve impulses arrive at neuromuscular junction
- Acetylcholine released into synaptic cleft
- Na+ channels open
- Depolarization spreads through T tubules
- Proteins change conformation in T tubules
- Ca+ released from triad
- Ca+ released from SR
- Ca+ binds TnC of Troponin
- Contraction and Ca+ returns to terminal cisternae
Define muscle spindle
Stretch receptor within the skeletal muscle
- sends sensory into CNS
Define tendon organs
Sense tension
Satellite cells do what for the muscle?
Repair and increase the size of the muscle
What’s the specialized cell junction in cardiac muscles?
Intercalated discs
- muscle fibers are attached through intercalated discs
What junctions are associated with intercalated discs in cardiac muscles?
Adherence junctions, gap junctions, and desmosomes
Mitochondria are larger and longer in cardiac or skeletal muscles?
Cardiac
The sarcoplasmic reticulum is more developed in cardiac or skeletal muscle?
Skeletal
Diads are what?
- Present in cardiac muscle
- have mostly T tubules and little SR
The T tubules are located where in cardiac muscle?
Z line
What junction is associated with actin in cardiac muscles?
Zonula adherens
Pigment in cardiac muscle
Lipofuscin
What intercalated discs are on the transverse of cardiac muscles?
Zonula adherens and macula adherens
What intercalated disc is on the longitudinal portion of cardiac muscles?
Gap junctions
Medulla adherens function in cardiac muscle
Cell attachment
Cell-to-cell junctions allow for
Muscles to stay together
Describe atrial myofibers
- T-tubules are sparse or absent
- membrane-limited granules
Smooth muscle nuclei location
Centrally located
- there’s a narrow space around each cell
Describe the SR of smooth muscles
Rudimentary (simple)
Do smooth muscles have T tubules?
No
Describe myofilaments in smooth muscles
- not organized into sarcomere
- arranged parallel to long axis of cell
Actin in smooth muscles
- tropomyosin present
- NO troponin
- calmodulin present
Myosin in smooth muscles
- Have no bare central region
- contraction and relaxation is regulated by hormones via cAMP
Describe myofilaments in smooth muscles
Crisscross obliquely through the cell like network
Alpha-actin function
Attached actin to the membrane
Smooth muscle intermediate filament location and example
- Throughout cytoplasm
- Ex: Desmin (skeletin) and vimentin
Describe dense bodies in smooth muscle
- anchoring site for actin and intermediate filaments
- contain alpha-actin
- cytoplasm/membrane associated
Smooth muscle cell contraction steps:
- Ca2+ (released through gap junctions) binds calmodulin which binds to myosin light chain kinase to phosphorylation myosin light chains
- This binds to actin + ATP causes actin contraction
2 ways smooth muscles can contract
single cell can contract
OR
Contraction wave
Is smooth muscle contraction long or short?
Long w/o fatigue
Smooth muscle organelles
Golgi, ER and polyribosomes
Type of junction in smooth muscles
Gap junctions
