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Muscle Tissue
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69
Histology
09/03/2011

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Term
Muscle Tissue is derived from which tissue?
Definition
Mesoderm
Term
Muscle Cells are known as....
Definition
Fibers
Term
Three Types of fibers
Definition
Type I - Slow Oxidative
Type IIA - Intermediate
Type IIB - Fast glycolitic
Term
True/False Muscle fibers types vary in amount of mitochondria, myoglobin, and other enzymes?
Definition
True
Term
Lists the three layers that muscle cells are organized into?
Definition
Epimysium
Perimysium
Endomysium
Term
Perimysium divides muscles into _____ and is highly ______
Definition
Fasicles/vascularized
Term
Characteristics of endomysium
Definition
- pathway for capillaries
- contains extrafusal and intrafusal cells
- rich in collagen and retiular fibers
- divides muscle into individual fibers
Term
Function of Alpha Actinin?
Definition
Binds actin to the Z-disk
Term
Myofibrils are composed of?
Definition
Actin and Myosin
Term
Sarcomere associated proteins can be found attached where?
Definition
at the Z disk
Term
True/False Tropomyosin is a globular protein?
Definition
False - Filamentous
Term
Muscle tissue can be broken down to below the cellular level, describe breakdown
Definition
Muscle - muscle fiber - myofibrils (sarcomeres) - myofilaments
Term
An actin molecule is a polymer of?
Definition
Two intertwined molecules of filamentous actin.... each filamentous actin strand is composed of polymers of G-actin
Term
A polymer of myosin is composed of around how many subunit molecules?
Definition
200
Term
What is the function of myomesin?
Definition
To cross link myosin filaments, apparent at the M-line
Term
True/False each muscle cell contains only one type of muscle fiber?
Definition
False
Term
True/False the A band does not shorten during contraction?
Definition
True - The A band contains BOTH actin and myosin, since filaments never shorten, only slide past one another, the A band will not shorten
Term
True/False none of "bands" associated with the sarcomere shorten during contraction?
Definition
False - The I bands (Actin only), H bands (only myosin), and Z disk shorten/drawn closer
Term
The Z Disk of the sarcomere is found where?
Definition
Bisecting the I Band
Term
Describe the relationships between A and H bands with M line
Definition
The H band bisects the A band, in turn the M line bisects the H band
Term
Explain Afferent fibers of muscle spindles
Definition
Two types
1.)Anulospiral - composed of type I neuron fibers and consists of nuclear bag and chain fibers, respond to stretch rate
2.)Flower Spray - type IIA nerve fibers and are found on either side of annulospiral, monitor duration of stretching
Term
In terms of myofibrils a sarcomere is measured....
Definition
From Z-disk to Z-disk
Term
True/False Myosin is the principal contractile protein of myofibrils?
Definition
False - Actin
Term
Motor unit
Definition
A neuron and all of the muscle cells that it innervates
Term
Function of Titan
Definition
Found connected to the Z-disk and spans all the way to the M line (half the length of a sarcomere) gives the sarcomere its elastic properties
Term
sER in muscle cells is known as? what is its function?
Definition
Sarcoplasmic Reticulum / Sequesters Calcium (in skeletal muscle) and releases calcium into cytoplasm (other muscle types)
Term
Which myofilament is the thick/thin filament?
Definition
Myosin/Actin
Term
What role does calcium play in actin myosin binding in skeletal muscle?
Definition
ca binds to troponin C, which interrupts TnI/actin interaction and slides tropomyosin out of the way
Term
Efferent fibers of muscle spindles are composed of what type of neuron fiber?
Definition
gamma 2/3
Term
True/False the sarcoplasmic reticulum in cardiac cell leaks at a constant rate?
Definition
True - allows for autonomic rhythyms
Term
True/False a Triad is found in cardiac muscle cell
Definition
False - dyads are found in cardiac, triads in skeletal
Term
Five Steps of the contraction cycle
Definition
1.)Attachment - No ATP
2.)Release - ATP binds to myosin
3.)Bending - ATP hydrolyzed but still bound (head pivots)
4.)Force Generation -(ADP and P released)power stroke occurs
5.)Reattachment - myosin head undergoes conformational change and attaches to another actin
Term
If cardiac muscle is damaged it is replaced by....
Definition
A Connective tissue scar
Term
How is ATP generated in type IIB fibers?
Definition
Glycolysis Type IIB = slow glycolytic/white
Term
Sarcolemma is depolarized at the....
Definition
Motor end plate
Term
Primary function of ANS on cardiac muscle cells?
Definition
To speed up/slow down contraction rates
Term
The T- Tubules are found where in skeletal muscle cells?
Definition
At the AI Junction
Term
ANP is found where? and what is its fxn?
Definition
In Atrial granular cell (have ANP precursor) and raises BP
Term
Glycogen, lipid, and mitochondria are found where in cardiac cells?
Definition
mainly in the poles, known as the sarcoplasmic cone
Term
Troponin is a globular protein composed of...
Definition
Tnc - binds calcium
TnI - Binds actin
TnT _ binds to tropomyosin
Term
Skeletal muscle contraction will continue as long as.....
Definition
There is unbound free calcium in the cytoplasm
Term
True/False Calcium is removed in skeletal muscle cytoplasm via Calcioesterase?
Definition
False - pumps on sER membrane
Term
Strength of muscle contraction depends on?
Definition
The Number of motor units involved
Term
True/False fibers of the same muscle unit will contract in unison
Definition
True
Term
Dense Plaques are similar to what structure?
Definition
Z Disk
Term
The plasma membrane of a muscle cell is known as the...
Definition
Sarcolemma
Term
T Tubule system in cardiac vs skeletal
Definition
Larger, sER less developed, arranged into diads vs triads, found at Z disk vs AI junction
Term
True/False SMC contraction will stop when there is no more calcium in the cytosol
Definition
False - although calcium is responsible for reaction cascade, contraction will not stop until myosin is dephosphorylated
Term
True/False Smooth muscle has the slowest contraction rate of all muscles?
Definition
True - 10x slower
Term
True/False Muscle Spindles contain both afferent and efferent innervation
Definition
True - Knee jerk reflex
Term
traits of myoepithelial cells and myofibroblasts
Definition
both are non contractile muscle cells

Myoepi - b/w epithelium and basal lamina of certain glands ducts - mammary glands, similar in shape and contraction mechanism to SMCs but from ectoderm (SMCs from mesoderm)

2.)Myofibroblasts - resemble fibroblasts but have high amounts of actin and myosin - wound healing
Term
True/False Type I fibers generate ATP via Glycolysis
Definition
False - Type I = slow oxidative (red) ATP is generated via Oxidative phosphorylation, takes longer but more ATP generated, therefore fatigues slower than white fibers
Term
True/False myofilaments are organized into myofibrils in all muscle cell types?
Definition
False - does not arrange like that in smooth muscle
Term
other names for a motor end plate?
Definition
myoneural/neuromuscular jxn
Term
function of efferent nerve fibers found in muscle spindles?
Definition
depolarized muscle spindles to contract to counteract muscle stretching
Term
Muscle Tissue composes how much of your total body weight?
Definition
35-45%
Term
Function of dystrophin
Definition
an extra-sarcomere protein, connects the sarcoplasm to the ECM via actin
Term
What is the name of the protein that sequesters calcium in skeletal muscle?
Definition
Calsequestrin
Term
True/False cardiac muscle is regenerative
Definition
False - only skeletal and smooth
Term
True/False Skeletal muscle cells have more glycogen, lipid, and mitochondria than cardiac muscle
Definition
False - Consider contraction rates
Term
Purkinje Fibers are modified __________ and are found in the _______
Definition
cardiac muscle cells/AV bundle of HIS
Term
Two Types of Smooth muscle cells?
Definition
1.)Unitary/visceral
gap jxns found in between cells for depolarization propogation
2.)Multiunit
found in Iris and large arteries, ANS precisely controls contraction, poor/no gap jxns
Term
What effects electrical properties of Multiunit SMCs?
Definition
hormones and ANS neurotransmitters epi and norepi
Term
most of a SMCs sarcoplasm is occupied by what?
Definition
actin fillaments inserting into dense plaques (cytoplasmic densities)
Term
Describe Intercalated discs
Definition
Found in cardiac muscle, two portions
1.)transverse - across fibers contains fascia adherents (zonula adherens) and maculae adherents (prevent seperation from contraction)
2.)lateral - parallel to fibers
contains gap jxns for electrical coupling
Term
Intermediate Filaments contained in SMCs?
Definition
Desmin - non vascular
Vimentin - Vascular
Term
True/False muscle spindles are known as extrafusal cells?
Definition
False - Intrafusal
Term
Sarcolemmal Vesicles
Definition
function in uptake and release of Ca in SMCs found in periphery
Term
Myosin Activation in SMCs
Definition
- Ca binds to calmodulin
- ca/calmodulin complex activates MLCK
- phosphorylates MLC which interacts with actin
- MLC is dephosphorylated preventing actin binding