Skeletal muscle Flashcards
Tree types of muscle
skeletal muscle
cardiac muscle
smoot muscle
What are the characteristics of cardiac muscle?
- branching
- one/two nuclei per cell
- straited
- involuntary
- medium speed contractions
what are the characteristics of a smooth muscle?
- fusiform cells
- one nucleus per cell
- nonstraited
- involantary
- slow wave-like contractions
what are the characteristics of a skeletal muscle?
- long cylindrical cells
- many nuclei per cell
- striated
- VOLUNTARY
- rapid contractions
What organelles do “sarco” refer to?
Skeletal muscle
order the advance muscular system
Epimysium perimysium fascicle endomysium myofiber myofibrill
Order the skeletal muscle structure
skeletal muscle (organ) muscle fascicle (bundle of cells) Muscle fiber (cell)
Order the skeletal muscle fiber
sarco sarcolemma = plasma membrane sarcoplasm =cytoplasm sarcopasmic reticulum: ER sarcosomes :mithochondria
What is a muscle cell?
a muscle cell (myocyte) is packed with myofibrils. myofibrils is composed of THIN filaments protein ACTIN and thick filaments MYOCIN
what is sarcolemma
plasma membrane
what is sarcoplasm
cytoplasm,
what is sarcosome?
mitochondria
What is tropomyosin?
a double-stranded protein that prevents actin-myosin interaction
What is troponin
a protein that binds tropomyosin to G-actin controlled by Ca++
what is nebulin?
it’s a protein that holds F-actin strands together
What is sarcomere?
Space between Z- Structures to which the actin myofilaments are anchored.
Sarcomere: Packet of microfilaments with their regulatory proteins:troponinandtropomyosin
The sarcomere is bundled within the myofibril that runs the entire length of the muscle fiber and attaches to the sarcolemma (membrane) at its end.
ACTIN arethin filamentsof the sarcomere and have the proteins tropomyosin and troponin.
The filaments that are thicker, are called MYOSIN
Function of T-tube?
For the action potential first to reach the membrane of the SR, T- Tubules in the sarcolemma
These T-tubules ensure that the membrane can get close to the SR in the sarcoplasm. The arrangement of a T-tubule with the membranes of SR on either side is called atriad. The triad surrounds the cylindrical structure called amyofibril, which contains actin and myosin.
The T-tubules carry action potential into the interior of the cell, which triggers the opening of calcium channels in the membrane of the SR, causing Ca++to diffuse out of the SR and into the sarcoplasm.
It is the arrival of Ca++in the sarcoplasm that initiates contraction of the muscle fiber by its contractile units, or sarcomeres.
Muscle contracts
Summary
After the AP arrive, Ca is released from the SR
Ca bind to Troponin on that thin fiber, what moves the tropomyosin out of the way, uncovering the biding sites for myosin
ADP and P (phosphate) are attached to the myosin head
The myosin heads now move, attaching to the Actin, the moment the head attaches, the P leaves the head
The energy of the ADP is now used to move the head, what causes the sliding of actin and myosin. The is released while in movement
The bond between myosin and actin is broken when ATP bind to the head
ATP is broken down to ADP and a phosphate group, releasing energy that is stored in the head and will be used on the next contraction
If Ca ions are still present, the sequence is repeated
What is Actin?
thin filament
what is myosin
thick filament
What is the function of T-tuble?
t. tubls carry the action potential into the interior cell which triggers the opening of calcium channels in the membrane or SR (sarcoplasmic reticulum) causing ca++ to diffuse out of the SR and into the sarcoplasm.
- it is the arrival of Ca++ in the sarcoplasm that initiates contraction in the muscle-fiber by its contractile units (sarcomere)
what is epimysium?
Dense fibrous I.R connective tissue that surrounds the skeleton muscle
what is a fascicle?
a bundle of muscle fibers
what is perimysium?
dense fibers I.R connective tissue that covers each bundle (fascicle) of single muscle fibers
What is tropomyosin
It’s a protein that blocks myosinhead to attache to the actin
What is troponin
Calcium binds to troponin that moves tropomyosin away - myoinhead can bind to actina and the muscle can contract
What’s the function of the T-tubule?
Transmit AP through the cell
What is sarcolemma?
Plasma membrane
What is sarcoplasm?
Cytoplasm
What is sarcosomes?
Mithokondria
What’s the function of sarcroplasmic reticulum?
Concentrate ca++, (via ion pumps) and release ca++ inte sarcomeres to begin muscle contractions
What’s the thin filament fibers?
F-actin 2 twisted rows of globular G-actin the active sites on G-actin strands bind to myosin
Tropomyosin a duble strand prevents acrin-myosin interactions
Troponin a globular protein , binds tropomyosin to G-actin controlled by ca++
Nebulin holds F-actin stands together
