Ch. 10 - Muscular Tissue Flashcards
C/C the appearances of skeletal, cardiac, and smooth muscle tissues
SK - multi-nucleated, striated
C - one nucleus, striated, intercalated discs
SM - one nucleus, no striations
What are 5 functions of muscle tissue?
- movement
- stabilization
- regulating organ volumes
- movement of substances w/i bodies (smooth, cardiac)
- generating heat (involuntary contraction of skeletal muscles)
What are 4 properties of muscle tissue?
- electrical excitability
- contractility
- extensibility
- elasticity
What are skeletal muscles formed of?
thousands of myocytes (muscle fibres!)
3 layers of CT; subcutaneous (adipose, areolar), fascia
blood cells, nerves
What is fascia?
dense sheets of irregular CT that supports and surrounds muscles
What are the 3 layers to help organize muscles?
- endomysium: separates individual myocytes from each other
- perimysium - surrounds fasciles (10-100 myocytes)
- epimysium - surrounds whole muscle
What is the difference between a tendon and aponeurosis?
T - CT layers extending beyond muscle bully, attaching to periosteum
A - extends as broad flat sheet
What are the sarcoplasm, sarcolemma, and sarcoplasmic reticulum??
sarcoplasm = cytoplasm
sarcolemma = plasma membrane
SR = smooth ER; stores Ca2+ ions and encircles each myofibril
What are transverse tubules?
invaginations of sarcolemma that spread the action potential to all parts of myocyte
What are myofibrils?
consist of thick and thin filaments; contractile structures
What causes the striation pattern in skeletal muscle cells?
the arrangement (overlap)of thick and thin filaments; filaments do not change length!
What are the 3 kinds of proteins that make up myofibrils?
contractile - myosin, actin
regulatory - troponin, tropomyosin
structural - titin, myomesin
Describe composition and shape of thick filaments
- made of myosin
- resembles 2 golf clubs twisted together, myosin heads extend towards thin F
- held in place by M line (myomesin)
Describe composition and shape of thin filaments
- made of actin, with some trop/tropomyosin
- actin filaments bind to myosin
- held in place by Z discs
What occurs prior to a contraction cycle?
- myosin binding sites on actin are covered by tropomyosin
- onset of contraction: SR releases Ca2+ into sarcoplasm
- Ca2+ bind to troponin and cause trop-tropom compolexes to move away from m-binding sites on actin
- once binding sites are free, contraction cycle begins
What are the steps of the contraction cycle?
- ATP binds to myosin head hydrolyzes atp
- attachment of activated M to A, forming crossbridge
- powerstroke (movement of thin F to M line via myosin head pivoting)
- ATP binds to myosin head, detachment of myosin from actin
What is rigor mortis?
rigidity of muscles after death bc muscle cant contract/stretch due to lack of ATP synthesis
- after death, calcium leaks out of SR, allowing binding of M heads to actin, but myosin cannot detach from actin due to lack of ATP
What causes the Ca2+ to be released? What is this phenomenon?
muscle action potential - rapid change in membrane potential that involves depolarization followed by repolarization
What is excitation-contraction coupling?
excitation - muscle action potential along sarcolemma, into T tubules
contraction - sliding of filaments
How does a muscle contraction begin?
motor neurons send NT acetylcholine to trigger an action potential in muscle sarcolemma
What is a neuromuscular junction (NMJ)?
a type of synapse where communication occurs bt neuron and muscle cell
What are the components of a NMJ?
- synaptic end bulbs (end of axon terminal) containing synaptic vesicles filled with ACh
- motor end plate membrane (part of muscle cell) containing ACh receptors
What is the process of a neuron action potential?
- ACh is released from synpatic vesicle (in axon)
- ACh binds to ACh receptor (on muscle cell)
- Muscle action potential is produced
- AChE breaks down ACh on receptors on motor end plate, causing action potential to cease, and muscle cell to relax
What role do muscle proteins play in muscle contractions?
contractile prot (myosin and actin)