Exam 1 Flashcards
What does Titin connect the myosin filament to?
The z-disk
What is Titin connected to?
The z-disk and the I band
What type of stabilizer is Titin?
Longitudinal
What is a possible property of Titin?
Elastic ability
What is hyperplasia?
An increase in muscle fibers
What is hypertrophy?
An increase in myofibrils within a muscle fiber
What makes up the I-band?
Actin which is supported by nebulin and insertion to z-disks
What are the proteins that form intermediate filaments? What do these make up? Are these contractile?
desmin, vimentin and synemin
The Z-disk
No these are not contractile
What purpose do desmin, vimentin and synemin serve?
They attach the z-disk to the cytoskeleton and keep myofibrils “in register” within the muscle fiber.
Are the actin attachments staggered or straight on either side of the z-disk?
Yes
What is the order of the following from inside out: fasicle/muscle fiber/sarcomere/muscle/myofibril
sarcomere- myofibril- muscle fiber- fasicle(grouping of fibers)- muscle
How many nuclei per myofibril?
Many! They are multinucleated
Where are the nuclei located in muscle cells? What structure do they trend towards?
Dispersed along inner surface(periphery) of the plasmalemma. Trend towards motor end-plate region.
What organelle the endoplasmic reticulum associated with?
The nuclei
What is the function of the endoplasmic reticulum?
Transportation and modification of cellular proteins outside of the cell
What coordinates protein synthesis and is involved with the ER?
Ribosomes
Analogy) Protein synthesis: Amino Acids
Words: Letters
What do mitochondria create?
Adenosine Tri-Phosphate (ATP)
What substrates are associated with mitochondria?
Various enzymes, NADH, FADH2, Electron Transport Chain
What type of metabolism is the mitochondria associated with?
Aerobic
Where are mitochondria typically located?
Between myofibrils in Z-line region and in relation to nuclei and motor end-plate
The mitochondria form a network, what is this called?
Mitochondrial reticulum
The inner membrane of mitochondria are folded, forming ___.
Cristae
Between mitochondrial Cristae, there is a matrix which houses ___
Krebs cycle enzymes and mitochondrial DNA(mtDNA)
Can mitochondrial networks split and fuse?
Yes
What locations can mitochondria be located?
Subsarcolemmal and Intermyofibrillar
Subsarcolemmal mitochondria are positioned to receive what?
O2 from nearby arteries
What function do subsarcolemmal mitochondria provide in regards to integrity?
Believed to provide energy required to maintain sarcolemmal integrity(ion and metabolite exchange)
Where are a significant portion of the mitochondria located?
Subsarcolemmal
What mitochondria are located within the contractile elements?
Intermyofibrillar
Which mitochondria have higher activity per unit mass?
Intermyofibrillar
What role do intermyofibrillar mitochondria have?
Maintaining ATP supply for energy transduction during contraction
What type of metabolism are the cytoplasmic components associated with?
anaerobic
What makes up the cytoplasmic components?
soluble proteins
cytoskeletal components
glycogen granules
glycolytic enzymes
What primary proteins make up the filamentous components?
myosin and actin
What action do myofibrils perform?
Contract and relax
What structures/organelles are intertwined with the myofibrils?
mitochondria, SR and T-tubule system
What are the two primary protein filaments?
Actin and myosin
The protein filaments connect to the endomysial connective tissue which connects to the tendon with these attachment proteins:
vinculin, talin, paxillin and tensin
The A band is located ___ and consists of ____?
at the center of the sarcomere
myosin
The I band is located ___ and consists of ___?
from Z-disk to A-band
contains Actin
In the resting sarcomere, do actin and myosin overlap?
Yes
The H zone is located ___ and consists of ___?
the center of the A band
only, myosoin(no overlap)
The M region is located ___ and consists of ___?
the very center of the sarcomere
filaments cross connecting myosin
Where is alpha actinin located?
The z disk, providing support and connecting actin proteins to z disk
List the myofilaments:
Troponin(I, C and T), Tropomyosin and Nebulin
What size protein is Nebulin? What function does it serve?
It is large
It holds Actin in place
What is the largest protein in the body?
Titin
What function do the intermediate fibers serve for the z-disk.
They (desmin, vimentin and synemin) attach the Z-disk to the cytoskeleton
What membrane components are there in skeletal muscle?
SR and T-Tubules
What is the main function of the SR?
Release and store Ca++
Where does the SR release Ca++ into?
cytosol
Where does the Ca++ primarily bind to once in the cytosol?
TnC on troponin complex
What SR membrane components are responsible for release/uptake of Ca++?
The Ryanodine receptors release Ca++ into cytosol
The SERCA pump sequesters Ca++
Where do the T-tubules exist in skeletal muscle?
They lie perpendicular to muscle fiber long axis and extend into the myofilaments at junctions of A and I bands
What are terminal cisternae?
These are the lateral sacs of the SR near the T-tubules
What makes up the triad?
TC of SR/T/TC of SR
What purpose do the T tubules serve?
A place for ion exchange between extracellular and intracellular spaces.
What is the plasmalemma?
A plasma membrane allowing the cytosol to have vastly different chemical composition from the fluid surrounding the cell
___ and ___ are embedded in the two lipid bi layers
protein channels and pumps
Plasmalemma embedded proteins can be both ___ and ___
extrinsic (peripheral) and intrinsic(transmembrane- exposure to both in/out)
Where are junctional folds in the plasmalemma concentrated?
Near motor end plate
What functions can embedded plasmalemma proteins serve?
Transport system for nutrients, ion channels, adenylate cyclase, kinases, hormone receptors
The cytoskeleton reinforces what? What does the cytoskeleton hold in place?
the plasmalemma
Organelles such as the nuclei and mitochondria
What are satellite cells?
Undifferentiated myonucleated cell which is used to repair/recover from injury
Where do satellite cells exist?
beneath basement membrane and outside plasma membrane
What is the order of connective tissue surrounding different parts of the muscle?
Epimysium surrounds the muscle , perimysium surrounds the fasicles and endomysium surrounds the muscle fibers
What function does the connective tissue serve?
Scaffolding for muscle development and resists excessive passive stretch and distributes force
What proteins are utilized for attachment of myofibrils near the tendon?
Vinculin, Talin, Paxillin, and Tensin
What is the basement membrane?
The glycoprotein complex surrounding muscle fiber lying between plasmalemma and endomysisum
What makes up the sarcolemma?
The basement membrane(out) and plasma membrane(in)
What enzymatic action occurs in basement membrane? What is the function of this?
acetylcholinesterase
Synaptic transmission termination
What trophic functions does the basement membrane provide?
development and innervation
What three layers make up the basement membrane?
Outward-in: reticular lamina, lamina densa and lamina lucida
What are the components of the basement membrane?
acetylcholinesterase, collagen, fibronectin and tenascin
What major regeneration function is associated with being just below the basement membrane?
satellite cells
What are the four phases of muscular development?
Axonal outgrowth, myogenesis, synaptogenesis and synapse elimination
What is the first step in muscle formation?
mesoderm is induced from ectoderm
What is gastrulation?
The blastula invaginating itself to form the gastrula
In terms of dorsal mesoderm and dorsal ectoderm, where do each stay? What Does the inner form?
Dorsal mesoderm lies beneath dorsal ectoderm and forms the CNS
What is the second step in muscle formation?
A portion of the mesoderm forms somites, then develops into skeletal muscle
During step two of muscle formation, where does the skeletal muscle develop?
Along the length of the embryo out of small clusters along the spine
During embryonic development, what factors play a role and where?
Determination is the first half, which includes myoD and myf5. Differentiation is the second half, which includes mrf4 and Myogenin.
What is the third step in muscle formation?
The myogenic cells proliferate and then differentiate
Where does proliferation start during muscle formation?
Somites
During stage 3 of muscular development, how are myoblasts classified?
Embryonic myoblast are primary
Fetal myoblast are secondary
Adult myoblast are satellite cells
What comes first, proliferation or differentiation?
Proliferation then differentiation
What extracellular signals are directing muscle development?
Sonic Hedgehog and WNT, Noggin, and bone morphogenic proteins
When are myoblast formed and when do they fuse into myotubes?
Stage 3 of muscular development
Name the events during and following myoblast fusion into myotube.
Nuclei align in center»>Synthesis of special proteins»>Formation of myofibrils»>Increased mitochondria»>Rudimentary T-tubule system»>SR from outer nuclear envelope
Does a developing myotube plasmalemma have the to stimulate an AP?
Yes
What type of receptors does the plasma membrane gain first?
ACh and cholinesterase
What is stage 4 of muscular formation?
Homeotic genes define the shape of the embryo and appearance of major body features and Morphogenes are secreted based on the embryo position.
What is stage 5 of muscular formation?
Division of muscle masses to form individual muscles
What stage is fiber type determined?
5
How is fiber typing determined during stage 5?
The myotubes can have slow or fast MHC (myosin heavy chain) types
What are the 6 stages to development of muscle innervation?
1) Inductive signals from mesoderm->ectoderm
2) Neural tube forms
3) Nerve cells proliferate, then migrate
4) Axons grow out from the spinal cord
5) Axons establish connections with muscle fibers
6) Redundant synapse and motoneurons are eliminated
When the NMJ is developing, what receptor type density increases?
ACH in post synaptic membrane
