Muscle 3 Flashcards
T/F Cardiac muscle has a single nucleus at the end of the muscle fiber.
False. At the MIDDLE of the muscle fibers
where are intercalated discs
at the connections between cells
Desmosomes
mechanical connections
Gap junctions
eletrical connections
Cardiac muscle works as a __.
functional syncytium
T/F Cardiac muscle tissue contracts with neural stimulation.
FALSE. without
Timing of contractions in cardiac muscle tissue are determined by these type of cells.
Pacemaker cells
The Autonomic nervous system can do what do that cardiac muscle (2)
1) alter the rhythmicity established by the pacemaker
2) adjust the contractility of the cardiac muscle
cardiac muscle cell contraction last how much longer than do those of skeletal muscle fibers.
10 times
What type of muscle is under control of ANS
Smooth
T/F Smooth muscle cells are longer than cardiac muscle cells.
TRUE
T/F Cells contain sarcomeres.
FALSE
What type of muscle is present in hollow organs and tube structures
Smooth
Are smooth muscle cells have a direct connection with neurons?
Not exactly. There are places where the plasma membrane is close enough to nerve endings that it can still receive the neurotransmitter and bind to change the activation site
What muscle types behave as a functional syncytium?
unitary smooth muscle and cardiac muscle
Cell-to-cell communication occurs through what, as with cardiac muscle?
Gap-junction
Where does calcium availability for smooth muscle come almost entirely from?
extracellular calcium
Smooth muscle is MYOSIN/ACTIN regulated.
MYOSIN
You need MORE/LESS ATP contraction for smooth muscle to occur?
LESS
What in smooth muscle allows for sustained contractions without much energy consumption?
Latch bridges
When does relaxation take place in smooth muscle?
when Ca++ is taken back up from the cytoplasm and phosphate enzyme inactivates the myosin molecule
What activates the myosin light chain kinase?
when Ca++ binds to calmodulin
What activates the catalytic form of myosin to interact with actin and perform crossbridge cycling? What is needed to keep the cycling occuring?
Phosphorylation of myosin light chain kinase;ATP
Phasic muscle contraction
smooth muscle: twitch like contraction in response to single stimuli or brief bursts of stimuli (occurs in the muscles that propel contents of the organ)
What are phasic muscle contractions associated with? (2)
1) action potentials
2) slow waves are associated with periodic depolarization and generation of action potentials
Tonic muscle contraction
smooth muscle: sustained contractions over time
Where do tonic muscle contractions occur?
In sphincters and blood vessels
Why are tonic muscle contractions dissociated with action potentials?
Contraction is modulated by external stimuli that modulate membrane potential and calcium availability.
T/F Mechanical activity of smooth muscle is constantly modulated by load or length.
FALSE. it is not modulated by this, allowing the metabolic demand to be relatively constant.
