Muscle Tissue Flashcards
What is the Sliding Filament Hypothesis and 3 main features
Sarcomere shortens and becomes thicker-myofilaments remain the same
1. **A band **remains constant
2. HI goes BYE (H and I bands)
3. Z lines are drawn closer to the ends of the A bands
What are the five stages of the contraction cycle?
- Attachment
- Release
- Bending
- Force Generation
- Reattachment
Actin filaments things to know (4)
- Covered in tropomyosin in a resting state
- Plus end is bound to the Z-line by alpha-actin and nebulin
- Minus end towards M line-protected by tropomodulin (actin capping protein)
- G-actin polymerizes to form F-actin
Myosin II (thick filament) things to know
- Binds to actin subunits to produce movement
- Has a head and tail region
- 2 Globular heads (1 for ATP, 1 for actin)
- “Bare zone” has no globular heads and is in the middle
Important of the Sarcoplasmic Reticulum (SER)?
- Forms a network around myofibrils
- Extends from A-I junction to the next A-I junction in the same sarcomere* (T-tubules are invaginations at this same location)*
- Houses Ca2+ ions
What is/does Dystrophin do in Skeletal muscles?
- Rod-shaped cytoskeletal protein
- Links muscle fiber to ECM protein laminin
- Forms a complex with Dystroglycans/Sarcoglycans (Transmembrane proteins)
Type 1 skeletal muscle
Also known as slow oxidative, red
1. Small
2. Many mitochondria
3. Lots of myoglobin, Fe2+
4. Aerobic respiration, slow twitch/fatigue resistant
5. Used in marathon runners
Location: limb muscles
Type II A skeletal muscles
Fast oxidative glycolytic/intermediate
1. High myoglobin and glycogen content
2. Anaerobic glycolysis
3. Fast twitch, fatigue resistant
4. Common in 400-800m sprinters
Type 2 B skeletal muscles
Fast glycolytic
1. Large
2. Less mitochondria
3. Low level of oxidative enzymes-fatigue easy (lactic acid)
4. Large glycogen stores
Location: extraocular muscles, digits
Sensory Innervation: Muscle Splindle
Senses changes in muscle length/stretch
Located: in the muscle belly
Sensory Innervation: Golgi tendon organ
Senses tension in the muscle
Location: near the tendon
What is the purporse and structure of intercalated discs?
Found in cardiac muscle
1. Transverse component (T):
-Fascia adherens (adhering junctions): serves as attachment site for thin filaments in terminal sarcomeres.
-Maculae adherens (desmosomes): bind to individual muscle cells. Reinforce fascia adherens and found in both T and L parts
2. Lateral component (L)
-Gap junctions
Purkinje Fibers
- Special modified cell found in cardiac tissue
- Conduct impulses of the A-V bundle and allow synchonization of ventricular contraction
- Abundant in mitochondria
- Pale staining-large amt of glycogen
In a relaxed state of Smooth Muscle Contraction where is calcium ions sequestered?
Sarcoplasmic Reticulum
Outline nerve stimulation for smooth muscle contraction
- Free calcium released from SR
- Binds to calmodulin (MLCK complex)
- Phosphoylates myosin
- Myosin binds to actin
- Contraction of muscle
Trompomysin
Considered a regulatory protein
Covers the myosin binding site on the actin filament in the resting muscle
Tropomodulin
Capping protein on actin
Troponin complex (C, T, I)
C: binds to Calcium
T: binds to Tropomyosin
I: Inhibits actin-myosin interaction
Nebulin
Stabilizes actin filaments
Smallest to largest muscle naming
1.Myofilament
2. Myofibril
3. Myofiber
4. Fascile
Types of Striated Muscle: Skeletal
- Under voluntary control
- Multinucleated with nuclei just beneath sarcolemma
- Uniform in length
Epi/Peri/Endomysium
Epi: dense connective tissue encasing multiple fasicles. Contains major BV/nerves
Peri: Around each fasicle. Also contains BV/nerves
Endo: around each myocyte-small BV and neuronal branches
Types of Striated Muscle: Cardiac
- Involuntary control
- Branched
- Single-centrally located nuclei (some bi-nucleated)
- Arranged end-to-end (held in place by intercalated discs)
- Numerous and large mitochondria/glycogen stores
Smooth Muscle
- Central nucleus
- Elongated fusiform cells with tapered ends
- Sarcoplasm: pinocytotic vesicles, Dense bodies which form attachment sites for thin and intermediate filaments (desmin/vimentin)
What do Smooth Muscles secrete?
- Connective tissue matrix
- Synthesize both Type III/IV collagen
- Vascular/Uterine secrete Type 1 collagen/elastin
Calponin
Smooth Muscle
Block myosin binding sites
Caldesmon
Smooth Muscle
Block myosin binding sites
Caveolae
Invaginations in the sarcolemma of Smooth muscle
-resembles T-Tubules of striated muscle
Skeletal Muscle Response to Injury
Limited capacity of regeneration
No regen capacity for cardiac tissue
Smooth Muscle response to injury
Lots of differentiation and divinding from mesenchymal stem cells
