Studied by 14 peopleWhat causes movement of skeletal muscle?
contraction
What do flexion and extension of skeletal muscle have in common?
both caused by muscle contraction
What do skeletal muscle cell nuclei look like?
Long, tube-shaped, multi-nucleiated, nuceli in perpiphery
What is a sarcomere?
contractile unit of skeletal muscle fiber made of actin and myosin
How many nerves innervate one skeletal muscle fiber?
ONE
What is the Z disc of a sarcomere?
end unit that anchors actin
What is the A band of the sarcomere?
dark area of BOTH actin and myosin
What is the M line of the sarcomere?
the middle of the sarcomere
What is the H zone of the sarcomere?
the zone of only myosin (thick letter, thick filament)
What is the I band?
only actin (thin filament)
Which muscle types have striations?
skeletal and cardiac
What does myosin look like?
intertwined helices
What does actin look like?
beaded string with tropomyosin string intertwined and troponin pearls at points of contact between the two
What does troponin bind to in order to pull tropomyosin off?
Calcium
What happens when calcium binds to troponin?
It pulls tropomyosin off the actin to reveal a myosin head binding site
What muscle fibers can be innervated by more than one nerve?
smooth muscle fibers
What muscle fibers can only be innervated by ONE nerve?
cardiac and skeletal
How can you increase contraction in skeletal muscle?
spatial or temporal summation
What is a type 1 skeletal muscle fiber also known as?
Slow-twitch
What is a type 2 skeletal muscle fiber also known as?
fast-twitch
What is a slow-twitch skeletal muscle fiber?
less powerful muscle fiber that fatigues slowly
What is a fast-twitch skeletal muscle fiber?
more powerful muscle fiber that fatigues quickly
How are fast-twitch skeletal muscle fibers more powerful?
extensive sarcoplasmic reticulum for increased calcium release
What are the two subclasses of type 2 (fast-twitch) skeletal muscle fibers?
2a and 2b
What is a type 2a skeletal muscle fiber?
in-between a slow and fast twitch
What is a type 2b skeletal muscle fiber?
classic fast-twitch
What kind of blood supply does a type 1 skeletal muscle fiber have?
rich blood supply
What kind of blood supply does a type 2 skeletal muscle fiber have?
less extensive blood supply
What neurotransmitter is released at the neuromuscular junction?
Acetylcholine
What happens to a muscle fiber when acetylcholine is released at the NMJ?
causes NA+ to enter the muscle cell and depolarize the cell which starts an action potential
What does an initial action potential in a muscle fiber cause?
T-tubercles to release calcium from the sarcoplasmic reticulum
What happens when calcium is released from the sarcoplasmic reticulum?
calcium binds to troponin to lift tropomyosin
What happens after tropomyosin is removed from myosin head binding sites on actin?
enzymes cause ATP to be hydrolyzed while the myosin head is unattached
What happens after ATP is hydrolyzed in a sarcomere?
myosin head binds to the actin
What causes the myosin head to pull the actin filament?
The release of ADP+P
What causes the ADP+P to be released from the myosin head?
The myosin head binding to the actin filament causing a conformational change
How does myosin release from the actin?
when a new ATP binds
What are the four additional mechanisms by which smooth muscle is stimulated?
mechanical pressure
blood pH
Oxygen
Extracellular ion concentration
Do smooth muscles have actin and myosin?
Yes, just not as organized so no striations are formed
What are the cell characteristics of smooth muscle?
spindle-shaped with single, central nucleus
Compare/contrast the cell nuclei of skeletal, smooth, and cardiac muscle
skeletal- multiple nuclei in periphery
smooth- single, central nucleus
cardiac- single, central nucleus
What are the two types of smooth muscle cells?
multi-unit
single unit
What is a multi-unit smooth muscle cell?
has several autonomic neuronal axons spread like a network in between al of the cells for fine movement (being able to signal one cell at a time)
What is a single unit smooth muscle cell?
has one autonomic neuronal axon running near all the muscle cells and gap junctions for communication of ONE big uniform contraction
What special characteristic do cardiac muscle cells have?
intercalated discs
What are intercalated discs for?
communication
How is smooth muscle contraction initiated?
Calcium levels increase and bind to CaM (calmodulin)
How is skeletal/cardiac muscle contraction initiated?
Acetylcholine released at NMJ
What happens once calcium binds to calmodulin?
The calcium-calmodulin complex activated MLCK
What is MLCK?
myosin light chain kinase
What is the job of MLCK?
phosphorylate light chains of myosin heads to increase myosin ATPase activity (add ADP+P to myosin head)
What step is the first step to be the same in skeletal/cardiac and smooth muscle contraction?
ATP is hydrolyzed and cross-bridging begins
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