Exam 2-2 Flashcards
(268 cards)
3 types of muscle
skeletal, cardiac, muscle
skeletal muscle ells
long multinucleated composed of many myofibrils is striated--from arrangement of protein fibers in cells voluntary contraction
Muscle cell life
born from merging of undifferentiated cells called myoblasts
once matured–no mitosis
Satellite cells
adult muscle stem cells, triggered to divide by injury– can repair some injured muscles (since muscles can’t fix themself–no mitosis)
hypertrophy
swelling of individual muscle cells– happens with exercise
sarcoplasmic reticulum
specialized endoplasmic reticulum that can sequester and store Ca.
It stores it in the ER and is will be used to spread signal throughout the muscle cell
T-tubules
invaginations of the plasma membrane that transmits the membrane depolarization into the cell
sarcoplasm
cytoplasm of a muscle cell
sarcoplasmic reticulum
endoplasmic reticulum of a muscle cell-stores Ca
Sarcolemma
the plasma membrane of a muscle cell
Sarcomere
contractile unit of a muscle cell
is the smallest functional unit of a muscle
consists of thick and thin filaments–myofilaments
1 sarcomere=z line to z line
Myosin
Thick filament
Have heads and tails– the heads are gathered and the tails are wrapped together
have 2 sites: ATP binding site and actin binding sites
What are the 2 sites on myosin
ATP site (binds and cleaves ATP-->ADP) Actin binding site
thin filament
Actin, troponin and tropomyosin
Tropomyosin
long- string like
hides myosin binding site, preventing myosin from binding to actin
Troponin
bound to tropomyosin, binds Ca which triggers a shape change that moves typopmyosin out of the way, revealing the myosin binding site and allowing actin and myosin to interact
During contraction, what is in high conc. in the sarcoplasm?
Ca
Sliding filament theory
filaments fo not get shorter, they slide across each other, shortening the length of the cell
Crossbridges
myosin binds to actin, pulling the actin framework closer together, Z lines get closer together and H and I zones are eliminated.
Requires ATP
Happens multiple times along the actin filament
Sarcomere shortens
Excitation contraction
- AP reaches motor neuron terminal
- AP opens Ca channels, Ach is released
- ACh binds receptors of sarcolemma of muscle cell
- Na channels open
- Na moves in to muscle fiber causing a small local depolarization
- If threshold is reached– a muscle AP occurs
Muscle AP travels along the sarcolemma and down T-Tubules - AP on t-tubules excited receptors on sarcoplasmic reticulum– opening Ca channels
- Ca is released into sarcoplasm
- Ca binds troponin causing s shape change, which moves tropomyosin out of the way.
- Myosin binds to actin– cross bridge
- Cross bridge formation triggers a shape change in myosin, cocking head to an abgle, sliding the filaments past each other
- ADP is released from myosin head, and a new ATP binds and releases the cross bridge
- Myosin binds to next available actin binding site
- ATP breaks down to ADP, energy is transfered to myosin head, cocks again and the filaments slide
- continues as long as intracellular Ca is high, and ATP is available
- In synapse- AChE is degradding ACh
- Chem gated Na channels close
- Ca pump in sarcoplasmic reticulum re-sequesters Ca
- Removal of Ca from troponin restores blocking of actins binding sites
- Cross bridge cycling stops, relaxation occurs
In muscles– do we use intra or extracellular Ca?
Intra cellular, while in normal AP in neurons we use extracellular Ca
What is ATPs role in filament binding?
ATP binds and releases the crossbridge.
Muscle motor units
functionally all the same– can’t contract q/o the others.
Helps control how much of a msucle you need to use– done by fine tuning the number of motor units
Neuromuscular junction overview
Only one NT: ACh
One form of NT clearance: AChE
Only excitatory