Lecture 14 Flashcards
Muscle Tissue (24 cards)
List three categories of muscle tissue
- skeletal
- smooth
- cardiac
What are some characteristics of skeletal muscle?
- Multinucleated syncytium
- Peripheral nuclei
- Sarcomeric arrangment
- Single motor axon innervates each fiber
- All-or-none contraction
- Contains tropomyosin-c
What are some characteristics of smooth muscle?
- Single mononucleated cells
- NO sarcomeric arrangement
- Does not respond in an all-or-none contraction
- Gap Junctions connect cells
What are some characteristics of cardiac muscle?
- Single mononucleated cells
- Cells branch to form a network
- Sarcomeric arrangement
- Gap-junction communication
- Intercalated Discs
- Not directly innervated
What are the staining characteristics for the three classes of myofiber types?
Type I - Darker intense staining for oxidative enzymes
Type IIA - Lighter, intermediate staining for oxidative enzymes
Type IIB - Light staining for oxidative enzymes
What are the distinguishing physiological characteristics for each of the three types of myofibers?
Type I - “Dark or red” fibers, many mitochondria, slow contractions, use oxidative phosphorylation
Type IIA - Uses aerobic and anaerobic respiration for ATP, contract rapidly, resistance to fatigue
Type IIB - Anaerobic ATP prod., fatigue quick, rapidly contracts, “white or light” fibers, rich in ATPase
Describe the hierarchy of skeletal muscle
Muscle > Fasicle > Myofiber bundle > Myofibril bundle > linear sarcomeres > filaments > actin (thin), and myosin (thick)
Describe the hierarchy of the connective tissue coverings associated with the muscle
Epimysium (covers muscle) > perimysium (covers fasicle) > Endomysium (covers myofibers)
What is the organization of a myofiber?
Myofibers are made of sarcomeres which are separated by Z bands, there is a middle A band with two I bands on the outside
What is the reason for the banded appearance in the myofibers?
The filaments of the sarcomere is organized in a way that creates the banding pattern.
Describe the changes of the myofiber banding between relaxation and contraction
A-band is equal to length of bundle of myosin filaments and does not change during contraction
I bands become shorter during a contraction
H-band is between the A band, the width decreases and may totally disappear during a contraction
How are actin and myosin filaments organized in a sarcomere?
Myosin or thick filaments make up the A and H bands, actin filaments associate with the end of myosin A band and then attach to Z discs at the ends. The bits of actin not within the myosin bundle make up the I bands.
What is the role of Troponin?
Troponin is a complex of Troponin I, C, and T, that inhibits binding between actin and myosin, binds calcium, and binds tropomyosin, respectively
What is the role of Tropomyosin?
Tropomyosin runs in the groove formed by F-actin strands, and each molecule extends 7 actin monomers and binds to the troponin complex.
List 7 components of the cytoskeleton
- aB-crystallin -Dystrophin
- Dystroglycan complex
- a-Actinin -Nebulin
- Titin -Desmin Intermediate Filaments
- Plectin
How does aB-crystallin interact with other components to help provide structural integrity of a muscle fiber?
aB-crystallin protects desmin from mechanical stress
How does dystrophin interact with other components to help provide structural integrity of a muscle fiber?
- Anchors actin to sarcolemma
- Reinforces sarcolemma during muscle contraction
- Links the a-actinin/desmin complex to cytoplasmic side of sarcolemma
How does the dystroglycan complex interact with other components to help provide structural integrity of a muscle fiber?
Links dystrophin to laminin-2
How does a-actinin interact with other components to help provide structural integrity of a muscle fiber?
Attaches the thin filaments to the Z-line
How does nebulin interact with other components to help provide structural integrity of a muscle fiber?
- Regulates length of actin filament
- Extends from Z disc to end of actin filament
How does titin interact with other components to help provide structural integrity of a muscle fiber?
- Limits displacement range of sarcomere
- Provides myosin with elasticity
- Large fibrous protein
- Connects ends of thick filaments to the Z-line
How does desmin intermediate filaments interact with other components to help provide structural integrity of a muscle fiber?
- Desmin filament framework surrounds the Z-line and extends into each sarcomere
- Links myofibrils together laterally, and links them to the sarcolemma
How does plectin interact with other components to help provide structural integrity of a muscle fiber?
binds the desmin filaments
What roles to satellite cells have in repair, maintenance, and regeneration of skeletal muscle tissue?
Satellite cells function as stem cells, they are quiescent, they can become mitotic in times of stress, and can give rise to myogenic precursor cells.
