Skeletal Muscle Mechanics Quiz

Study Notes

Skeletal muscle comprises connective and muscle tissue.
Connective tissue layers protect and cover muscle fibers, tendons, and the entire muscle.
Three connective tissue layers are:
- Epimysium: Surrounds the entire muscle; dense connective tissue layer.
- Perimysium: Encloses muscle fascicles; contains nerves and blood vessels.
- Endomysium: Encases individual muscle fibers; separates fibers within fascicles.
Tendons also consist of three layers:
- Paratenon
- Epitenon
- Endotenon

First Step: Action potential activates voltage-gated sodium channels along the axon, causing calcium influx at the neuromuscular junction.
Second Step: Calcium influx triggers vesicle fusion with plasma membrane, releasing acetylcholine into the extracellular space.
Third Step: Acetylcholine binds to nicotinic receptors, opening sodium/potassium channels leading to depolarization.
Fourth Step: Action potential spreads through T-tubules, depolarizing muscle fibers.
Fifth Step: Depolarization activates L-Type calcium channels in T-tubule membrane.
Sixth Step: Calcium release channels in the sarcoplasmic reticulum release calcium ions.
Seventh Step: Calcium binds to troponin C, facilitating tropomyosin movement and revealing myosin binding sites.
Eighth Step: Myosin binds to actin, releasing ADP and inorganic phosphate, causing the power stroke and pulling Z-bands together.
Ninth Step: ATP binds to myosin, allowing release from actin, followed by ATP hydrolysis for reconfiguration.
Tenth Step: Steps 8 and 9 repeat as long as ATP and calcium are present.
Eleventh Step: Calcium is actively pumped back into the sarcoplasmic reticulum.

Tarsometatarsal Joints: Arthrodial joints connecting cuneiform and cuboid bones to metatarsals; movements are limited to gliding.
Metatarsophalangeal Joint: A condyloid joint allowing flexion, extension, abduction, adduction, and circumduction; reinforced by plantar and collateral ligaments.
Interphalangeal Joints: Hinge joints between proximal and distal phalanges; movements limited to flexion and extension.

Radiography: Uses electromagnetic radiation to produce images; X-Ray generated through an object captured by a detector.
Computed Tomography (CT): Provides 3D images using X-Rays; eliminates image superimposition and distinguishes between tissues with high contrast.
Sonography: Uses ultrasound to create images; reflects sound waves from tissues to display on a monitor.
Positron Emission Tomography: Produces 3D images of bodily functions; utilizes a radioactive tracer to detect gamma rays.
Magnetic Resonance Imaging (MRI): Employs magnetic fields and radio waves for imaging; safer than other methods despite some contraindications.

Three types of muscle tissue exist: skeletal, cardiac, smooth.
All muscle types convert ATP's chemical energy to mechanical energy.
Skeletal Muscle:
- Voluntary and striated; attached to bones.
- Comprises slow-twitch (Type 1), fast-twitch (Type 2a), and fast-twitch (Type 2b) fibers.
Cardiac Muscle: Involuntary, striated with shorter myocytes (80 micrometers long, 15 micrometers wide).
Smooth Muscle: Involuntary, non-striated; fusiform shape (200 micrometers long, 5 micrometers wide).

Movement: Enables locomotion and movement of internal body contents.
Stability: Maintains posture and supports against gravity.
Control of Openings: Regulates passageways in the body.
Heat Production: Generates body heat, especially during exercise; crucial for glycemic control.

Excitability: Muscle cells respond to stimuli with electrical and mechanical responses.
Conductivity: Local electrical excitation spreads throughout the plasma membrane.
Contractility: Muscle cells shorten substantially upon stimulation.
Extensibility: Muscle cells can stretch up to three times their contracted length.
Elasticity: Muscles recoil to original length after stretching and releasing tension.