Skeletal Muscle Flashcards
What are the Functions of Skeletal Muscle?
- To move!
- Venous return of blood to the heart
- Breathing (diaphragm)
- Communication
- Thermogenesis (body temp regulation, produce Heat)
- Metabolic homeostasis
What are Myofibres?
- AKA muscle fibres
- Named for their elongated shape
- One fibre can be 10-100um in diameter and up to 2.5 feet in length
What is Myostatin?
Myostatin is a protein that acts as a negative regulator of muscle growth, inhibiting muscle development and promoting muscle atrophy.
Where is Muscle Tissue Found in the body?
Properties of Muscle Tissue:
Function: specialized to contract (shorten) and create the force required for movement
Properties:
- Excitable – muscle responds to nervous stimulation
- Contractile – muscles contracts (shortens) to create movement
- Extensible – muscle can be stretched
- Elastic – muscle recoils to its original size and position after being stretched
What would increase the diameter of a muscle fiber?
Excersize, lifting weights
What are the 3 layers of Muscle Fiber?
Sacrrolemma - Cell Membrane
Sacroplasma - Cytoplasm of Muscle Cell
Myofibrils - Contractile proteins
What are Fasicles?
- Groups of muscle fibres bundled together
- Fascicles are bundled together to form the muscle
What are Tendons?
Tendons Connect Muscles to Bone
What are Aponeurosis?
flat extensions of tendon
What are Fascia?
sheet/band of fibrous connective tissue that lies deep to the skin and surrounds muscles/other organs of the body, made primarily of collagen
What is Superficial Fascia?
(subcutaneous)
- Separates skin from muscle, insulates and provides protection
- Contains: adipose tissue, blood vessels and lymph vessels
What is Deep Fascia?
- Holds similar muscles together, occupies space between muscles
- Contains: nerves and blood vessels
What are the 3 Extensions of the Deep Fascia?
Epimysium: surrounds the entire muscle
Perimysium: deep to the epimysium, wraps muscle fascicles
Endomysium: deepest layer, wraps each individual myofibre
Muscle layers from deep to superficial:
How does Skeletal Muscle change as we age?
More connective and adipose tissue between muscle fibers (mostly collagen) (therefore fat increases)
What are Satellite Cells?
- Specialized muscle stem cells important for muscle adaptation and regeneration
- Reside in a quiescent state in the satellite cell niche between the sarcolemma and the basal lamina
- Have their own nucleus
What are the arrows pointing too?
Nuclei
Satellite Cell Location:
on periphery of muscle fiber in satellite cell niche
What is The Fate of Satellite Cells?
Once a stimulus activates the SC on the Muscle Fiber, the SC is activated and leaves its niche
The Satellite cells begin to proliferate and differentiate to other neccessary cells. (remember its a STEM cell)
Now they can either:
Become a Myotube for muscle repair or regenaration or
Fuse with injured Muscle fibers to help repair by producing proteins.
T-tubules and the Sarcoplasmic reticulum (SR)
T-tubules allow the action potential, an electrical signal, to rapidly penetrate deep into the muscle fiber. This penetration ensures that the entire muscle fiber contracts simultaneously.
The sarcoplasmic reticulum (SR) is a specialized type of endoplasmic reticulum (ER) found in muscle cells
What are myofibrils?
What are they Composed of?
Myofibres contain organelles called myofibrils
Myofibrils are composed of myofilaments:
What are Myofilaments?
actin (the thin filament) and
myosin (the thick filament)
What is the Sacromere?
Actin and myosin are the key components of the sarcomere, the functional unit of skeletal muscle (allow for muscle contraction!!)
Myofibril
Green = Actin
Purple = Myosin
Sacromere
What are the Bands of the Sarcomere? Zones? Disks? Lines?
A Band: the zone covering the length of the myosin filaments
I Band: the zone covering the thin filaments only
H Zone: the light area in the middle of the A Band where the thin filaments do not reach (myosin filaments only)
M Line: runs down the middle of the H Zone
Z Disk: the middle of the I Band, contains proteins that connect thin filaments together and keep them in their vertical position
What is Z-Line Streaming?
Z-line streaming refers to the movement of Z-lines (structures in muscle cells) during muscle contractions, enabling efficient force generation.
