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69 Cards in this Set

  • Front
  • Back
Muscle Tissue is specialized for what
Contraction and relaxation
Muscle tissue comes from what germ layer
mesoderm
What are the three types of muscle tissue
skeletal, cardiac and smooth
Skeletal Muscle is derived from what mesoderm origin
Mesenchyme
What is skeletal muscle composed of
Fasciculi, bundles of muscle fibers
Describe three layers of skeletal muscle CT organization
1. Epimysium
2. Perimysium
3. Endomysium
Def epimysium
External sheath of dense ct surrounding the entire muscle
Def perimysium
Septa (partition) of ct surrounding each fasciculus
Def endomysium
Delicate layer of ct surrounding each muscle fiber (cell)
Def muscle fiber
a muscle cell
# of nuclei in skeletal muscle
multinucleated of various diameter
Where are the nuclei located in muscle fibers
periphery
Each muscle fiber is filled with structural subunits called ________
Myofibrils
Myofibrils are composed of what
Contractile subunits called sarcomeres
Each saromere is composed of what?
Each sarcomere is composed of thick and thin filaments
Skeletal muscle fibers have striations of ______ and _____ bands
Skeletal muscles have cross striations of dark and light bands
Dark bands of skeletal muscle are ______?
A Bands
Light bands of skeletal fibers are ____?
I bands
charac of A band
The A band is the central portion of the sarcomere
Consists mainly of myosin filaments
Portion overlap by actin filaments
def I band
I Band is the segment composed of actin filaments bisected in the midle by the z line
def z line
actin filament insert
a segment between the two z lines is a sarcomere
def h band
central rgion of the a band consisting only of the myosin molecules
def m line
center of the a band wher two thick filaments are connected to each other
What are the four main proteins of the muscle?
1. Actin
2. Tropomyosin
3. Troponin
4. Myosin
What are the two types of actin?
1. G-actin (globular monomers)
2. F-actin (Filamentous polymers, double helix of g-actin wrapped around each other
define tropomyosin
long, thin, homodimer
What are the three subunits of Troponin?
TnT (strongly attaches to tropomyosin
TnC (binds Ca2+)
TnI (inhibits actin-myosin interaction)
Define myosin
Large complex protein with heavy and light chains
What does the haevy chain consist of?
2 thin rod like proteins twisted together with a globulaar head at one end
composition of light of myosin?
4 small proteins associated with the head
Describe the sliding filament hypothesis
increase in the amount of overlap between the thick and thin filaments. Thin filaments are pulled into the a band, resulting in shortening of the sarcomere
During contraction, which bands shorten?
I and H bands
define stage 1 contraction
myosin head is tightly bound to the actin (rigor configuration)
Define stage 2
ATP binds to the myosin head conformation change uncouples myosin head from actin
Define stage 3
Myosin head bends as ATP is hydrolized to ADP
Define stage 4
Myosin head binds to actin, releases adp, returns to original unbent conformation and forces movement of the thin filament along the thick filament (POWER STROKE)
Define stage 5
Myosin head tightly binds to actin (rigor configuration)
What regulates contraction
Ca2+ mus be present for contraction and removed after the contraction
Define sarcoplasmic reticulum
Networks around the myofibrils extending from one A-I junction to the next within the a sarcomere, includes terminal cisternae
Define Terminal cisternae
Ring like SR channel at the junction between A&I bands
Define Transverse tubular system (T system)
1.Numerous tubular invaginations of the the sarcolemna (T tubule)
2.Located between terminal cisternae
3. Contain voltage-sensor proteins
Define voltage sensor proteins
They depolarize adjacent terminal cisternae to release Ca2+
Define Triad
Complex of T tubule and two adjacent terminal cisternae
What do you find at the end on individual muscle fibers
Axons of motor neurons originated from spinal chord or brainstem
Define motor end plate (neuromuscular junction)
Axon terminal covered by thin schwan cell membrane & contains numerous mitochondria and synaptic vessicles contraining neurotransmitters (mostly acetalcholine) has synaptic clegt and junction folds
Define junction fold
Fold of the sarcolemma
Describe process of innervation
!. action potential reaches motor end plate
2. acetylcholine is released from the axon terminal into the synaptic cleft
3. Neurotransmitters bind the sacrolemma and initiate membrane depolarization
4.Depolarization is propagated along the entire muscle fiber via t-tubule system
5. at Each triad, depolarization stimulates SR to release Ca2+
6. Initiation of the contraction cycle
7. Cessation of depolarization Ca2+ is actively transported back into SR
8. Muscle relaxes
What is a motor unit?
All the muscles fibers innervated by a single neuron
Define small motor unit?
Fine, delicate, fast, movements
Define large motor unit?
Coarser, stronger movements
Define muscle spindle
Specialized receptor unit in muscle. It is a ct capsule surrounding a fluid filled space.
Define intrafusal fibers
A few long, thick fibers and short, thin fibers and have several sensory nerve fibers that are innervated and send information
Define Golgi tendon organs
Collagen fibers of the tendon innvervated by sensory nerves
How many types of skeletal muscle fibers are there and name them
Three
1. Type I fiber
2. Type II and
3. Intermediate fibers
Define type 1 fibers
Slow twitch fibers
Rich in sarcoplasm and myoglobin
dark red color
continuous contraction, most of energy is derived from oxidative phosphorilation of fatty acids
Define type 2 fibers
fast twitch fibers
Less myoglobin
light red color
rapid, discontinuous contraction
Define intermediate fibers
Morphologically and functionally in the middle between type 1 and type II fibers
Describe cardiac muscle
Come from splanchnic mesoderm cells

one or two central nuclei

numerous mitochondria

cells are smaller in atria than in the ventricles
What is the difference in the cardiac muscle and skeletal muscle?
Cross striation is identical in both
SR and T tubules aren't arranged in as regularly in cardiac
Diad: one T tubule and one SR terminal cisernae
Define intercalated discs
Junctional complexes at the interface between adjacent cardomyocytes
What two regions can be distinguished from each other at transverse portion
1. Fasciae Adherens (anchoring sites for actin filaments
2. Desmosomes or maculae adherentes (bind cells together)
What on the lateral portion of the intercalated discs provides ionic continuity between adjacent cells
Gap junctions
Describe smooth muscle
Elongated,non striated fusiform cells
Single central nuclei
Bundles of myofilaments form a lattice network
How does smooth muscle and skeletal muscle differ
Contraction differs. NO tropomyosin
Calmodulin: binds Ca2+ & activates myosin light chain kinase, phosphorylates myosin, allows it to interact with actin filaments
No T tubules
Rich desmin and vimentin
Dense bodies: on membrane and cytoplasm
Similar to z lines and function as an anchor for actin filaments
What type of innervation does smooth muscle
Autonomic. both sympathetic and parasympathetic
What is visceral smooth muscle and what are abundant in them
A large sheet of smooth muscle cells, found in the intestines, uterus , ureter.

Abundant gap junctions, relatively poor nerve supply
Define multiunit smooth muscle
rich innervation. precise and graded contractions
Do cardiomyocytes/ skeletal fibers/smooth muscle undergo regeneration
cardiomyocytes haveAlmost no regeneration
Skeletal fibers have limited regeneration
Smooth muscles have active regeneration
Satelite cells defined
inactive myoblast in the basal lamina of mature muscle fiber