Histology: Muscle (Exam 1) Flashcards
What produces movement in muscles
shortening of muscle fibers
What are the contractile proteins found in muscles
actin and myosin
What are the thin filaments
acin
What are the thick filaments
myosin
Why do muscle cells stain eosinophilic
due to the proteins
What muscles are striated
cardiac
skeletal
What muscles are voluntary
skeletal
What muscles are involuntary
cardiac and smooth
What muscles lack striation
smooth
Where is smooth muscle found
surrounding blood vessels and walls of viscera
What is the function of smooth muscle
viscera movement
How are muscle cells formed
aggregation and fusion of myoblasts
What is a single cell called in muscle
muscle fiber
Describe nuclei in skeletal muscle
multinucleated
peripherally located under sarcolemma
What is muscle strength dependent on
the number of fibers
What are tendons composed of
dense regular connective tissue
What do tendons connect
muscle to bone or bone to bone
What are the three layers of CT around a muscle
epimysium
perimysium
endomysium
Where is endomysium found
surrounding each muscle fiber
Where is perimysium found
surrounding bundles of muscle fibers
Where is epimysium found
on the outside of a muscle
What type of structure does endomysium have
delicate CT
What is a myofibril
structural and function subunit of a muscle fiber
What do collections of muscle fibers form
muscle fasicle
What do collections of muscle fasicles form
Muscle
What is the composition of a myofibril
actin and myosin myofilaments
What is a sarcomere
contractile unit of a muscle fiber
What are thin filaments in a sarcomere
actin
tropomyosin
troponin
What are the thick filaments in a sarcomere
myosin
What are the components called in a sarcomere
I band A band H band M line Z line
What is the I band
range of thin filaments on the end of sarcomeres
What is the A band
range of thick filaments from I band to I Band
What is the H band
range in the center between thick bands, includes the M line
Where is the M line located
middle of the sarcomere
Where is the Z line located
in between actin bands, on the edges of a sarcomere
What are the parts of the sarcomere that will change with contraction
H and I band get shorter
What occurs to the A band during contraction
stays the same length
What is the function of dystrophin
anchors z line to cell membrane
How is myosin anchored to the m-line
through myomesin
What will shorten during skeletal muscle contraction
sarcomere
What remains the same length during contraction
myofilaments
What structures are found around the sarcoplasmic reticulum in sarcomeres in skeletal muscles
mitochondria and glycogen
What regulates contraction of skeletal muscle
calcium
What is required for myosin actin to react
calcium
What is the function of the sarcoplasmic reticulum in skeletal muscle
reservoir for calcium
What does the sarcoplasmic reticulum form to aid in its function
terminal cisternae around myofibrils
What are t-tubules
invaginations of plasma membrane into the muscle fiber
What is the function of t-tubules
carry the action potential into muscle fiber to allow release of Ca2+ in the cell
Do skeletal muscles contain a triad or diad system
triad
What is the arrangement of the triad t-tubule system
Triad:
2 cisternae and T-tubule
What is the reservoir part of the sarcoplasmic reticulum
terminal cisternae
Where do terminal cisternae and t tubules form a triad
at the A-I junction
How many triads are found per sarcomere
2
What leads to excitation of a muscle fiber at the neuromuscular junction
release of acetylcholine from neuron that is taken up by a muscle fiber leading to excitation
How does myasthenia gravis affect muscles
NMJ is blocked by antibodies on the muscle end, leading to muscle weakness
the muscles cannot be stimulated
What type of disease is myasthenia gravis
auto-immune disease
How will botulinum toxin affect muscles
prevent neurotransmitter release
What does the presynaptic axon terminal of a NMJ contain
mitochondria and secretory vesicles containing ACh
What does the muscle fiber plasma membrane of a NMJ contain
infoldings that contain ACh receptors (Na+ channels)
What is a motor unit
motor neuron and all of the muscle fibers it innervates
How does innervation determine coordination
smaller ration = the smoother the movement
What are proprioceptors
special receptors that sense degree of muscle stretch and tension
What do proprioceptors provide info about
feedback about position in space
What are the two types of proprioceptors
Golgi tendon organs
muscle spindles
What is the function of extrafusal fibers
contract to generate force
What are extrafusal fibers innervated by
alpha motor neurons
What is the function of intrafusal fibers
to detect muscle stretch, specialized fibers for proprioception
Where are intrafusal fibers found
in muscle spindles
What are intrafusal fibers innervated by
motor neurons
What is the function of the muscle spindle
responds to changes in muscle length to prevent overstretching
What direction do intrafusal fibers run
parallel with the muscle belly
How will the muscle spindle respond to overstretching of a muscle
detect stretch and send afferent signal through gamma motor neuron to the CNS
effent signal from CNS will travel through alpha motor neurons to extrafusal fibers causing them to contract and shorten the muscle
How many fibers are in a nuclear bag
2-4
How many fibers are in a nuclear chain
6-8
What is the golgi tendon organ
encapsulated receptor found at junction between muscle and tendon
What is the structure of the golgi tendon
afferent nerve endings interwoven between collagen fibrils
What is the function of the golgi tendon organ
monitors muscle load for force of contraction
What type of cells does cardiac muscle have
mononucleated cells centralized nuclei striated intercalated disks branching
What are the three components of the intercalated discs in cardiac muscle
Fascia Adherens
Macula adherens
Gap junctions
What is the fascia adherens do
anchors thin filaments
What component of the intercalated disc does fascia adherens make up
transverse component
What are macula adherens
desmosome
What does the macula adherens do
hold cells together during repetitive contractions
What do gap junctions do
allow cells to communicate
What part of the intercalated disc does gap junctions make up
lateral component
What does the fascia adherens function as
terminal z line
What lines are t-tubules associated with in cardiac muscle
z line
What lines are t-tubules associated with in skeletal msucle
A-I junction
Describe the sarcoplasmic reticulum in cardiac muscle
only diad
not organized well
terminal cisterne and t-tubule
What are purkinje fibers
modified cardiac muscle cells that regulate heartrate
Where are purkinje fibers found
in the ventricular walls of the heart
WHat is heartrate regulated ultimately by
autonomic nervous system
WHere is smooth muscle found
walls of viscera, blood vessels, iris, ciliary body, dartos muscle, erector pili
What type of cells does smooth muscle have
fusiform cells with central cork-screw nuclei
How do smooth muscle cells communicate
through gap junctions
How does smooth muscle contraction differ from other muscle types
prolonged, wave-like contraction
Does smooth muscle have a t-tubule system
no
How is calcium delivered to the smooth muscle
via caveolae
What does calcium do to smooth muscle
cause myosin light chain kinase to phosphorylate myosin
What is unique to smooth muscle
myosin light chain kinase phosphorylates myosin
What is smooth muscle regulated by
ANS
What are dense bodies
proteins located in sarcoplasm of smooth muscle cells
What is the function of dense bodies
attach actin filaments so contraction causes a corkscrew twisting that shortens the cell
Describe muscle repair and renewal in skeletal muscle
does not renew
becomes scar tissue
What in muscle cells show limited capacity for skeletal muscle fiber differentiation
satellite cells
What is necessary for muscle integrity
innervation
Describe muscle repair and renewal of cardiac muscle
does not renew in adults
becomes scar tissue
Describe muscle repair and renewal in smooth muscle
have the ability to proliferate
responds to injury via mitosis