Module 3 (Skeletal Muscles) Flashcards
What is each skeletal muscle composed of
Skeletal muscle tissue, epithelial, connective and nervous tissue
Functions of skeletal muscles
Contracts to move parts of the body
Maintain posture and stabilizes joints
Control excretion and swallowing
Produce heat
Support and protect internal organs
What happens when skeletal muscles attach to 2 bones across a joint
When contracted, the muscle brings parts of those bones closer together
Organization of skeletal muscle tissue
Consists of muscle tissue and CT
CT surrounds the muscle and attaches the ends of each muscle to bone
What are the 3 layers of CT
Epimysium
Perimysium
Endomysium
What is epimysium
Outermost layer of CT that surround the entire muscle and is continuous with the tissue that becomes the tendon
What is perimysium
Middle layer of CT surrounding a bundle of muscle fibers within a muscle
What is a bundle of muscle fibers called
Fascicle
What is endomysium
Innermost layer of CT that surrounds the individual muscle cells within a muscle bundle
Features of a muscle cell
Sarcolemma
Nuclei
Myofibril
Myofilaments
Sarcoplasmic reticulum
T-Tubules (transverse tubules)
What is sarcolemma
Cell membrane surrounding a muscle cell
How is sarcolemma different from endomysium
Beneath the sarcolemma are the nuclei, myofibrils, and sarcoplasm
Nuclei of muscle cells
Multinucleated and located towards the outside of the myofiber
What is myofibril
Structural units of the muscle cell and contain contractile myofilaments
What are myofilaments
Contractile units of the muscle cell
What is sarcoplasmic reticulum
Surrounds each myofibril and is where the muscle cell stores calcium
Needed for muscle function
What are T-Tubules (Transverse tubules)
Extensions of the sarcolemma that surround the myofibrils and transmit nerve stimulation to the sarcoplasmic reticulum within the cell
Organization of myofilaments
Organized into repeating structural units knows as sarcomeres
What happens sarcomeres shorten
It causes contraction of the muscle
What does each unit consist of
Actin and mysoin and one sarcomere spans from one z-line to the next
What is actin and myosin
Thin (actin) and thick (myosin) filaments
What is sarcomere banding
Refers to the distinct lines and bands that create the striated appearance
Due to the arrangement of actin and myosin
What is the A-band
Made up of think and thin filaments
Appears darker when viewed histologically
What is the Z-line
Composed of protein that makes a “zig-zag” line marking the beginning and end of each sarcomere
Where can the Z-line be found
Lies in the middle of the I-band and is where the thin filaments attach
What is the M-line
Composed of protein down the centre of the sarcomere “mid-line” and where thick filaments attach
What is the I-band
Made up of thin filaments and appears lighter in colour
How do muscles contract
Actin and myosin filaments slide over each other, which shortens the sarcomere
This increases muscle tension
Why do sarcomere appear to have light and dark bands
Because of the overlap of thick and thin filaments
Why is the I-band light in colour
It is only area that consists thin filaments
Why is the Z-line dark in colour
It contains an abundance of structural proteins
Why is the A-band dark in colour
It consists of thick filaments and is even darker towards the sides because it overlaps with thin filaments
How is the M-line similar to the Z-line
It also has an abundance of structural proteins that create a dark line
Organization of skeletal muscles
The muscles of the body are generally organized as being superficial, intermediate, or deep
