A&P 2 Midterm Study Guide
Ch. 10
Characteristics of smooth and cardiac muscle tissue
• Cardiac Muscle
o Involuntary, intrinsically controlled,
... [Show More] striated, branched, and single nucleated.
• Smooth Muscle (Visceral)
o Involuntary, not striated, not branched, and singly nucleated. Functions of the 3 types of muscle tissue
• Skeletal Muscle
o Moves bones and other structures
• Smooth Muscle
o Contractions and relaxation of the autonomic nervous system, and walls of organs
• Cardiac Muscle
o Pump blood
Characteristics of skeletal muscle: excitability, elasticity
• Voluntary, striated, not branched, and multinucleated
• Excitability: ability to respond to a stimulus, delivered from a motor neuron or a hormone.
• Elasticity: ability to return to its original length & shape after contraction or extension.
Components of a skeletal muscle cell
• Myofibrils: cylindrical structures that extend along the complete length of the cell. Twitch contraction
• Brief contraction of all muscle fibers in a motor unit in response to a single action potential in its motor neuron.
Layers of connective tissue holding skeletal muscle organs together (3 types)
• Epimysium: outer layer, dense irregular connective tissue, surrounds muscle organs
• Perimysium: middle layer, dense irregular connective tissue, contains nerves and vasculature; surrounds muscle fascicles.
• Endomysium: interior layer, loose/elastic connective tissue, contains capillaries, nerves and stem cells, surround muscle fibers.
Parts of the sarcomere
• Z Discs: narrow, plate-shaped regions of dense material that separate one sarcomere from the next.
• A Band: dark, middle part of sarcomere that extends entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments.
• I Band: lighter, less dense area of sarcomere that contains remainder of thin filaments but no thick filaments. A Z-disc passes through center of each I-Band.
• H Zone: narrow region in center of each A Band that contains thick filaments but no thin filaments
• M Line: region in center of H zone that contains proteins that hold thick filaments together at center of sarcomere.
SR function
• Store calcium ions (Ca2+) T tubule function
• conduct the signal to contract throughout the entire fiber, are part of sarcolemma.
Acetylcholine
• ACh – neurotransmitter released at the Neuromuscular Junction. Functions in memory, waking up, attention and learning.
The sliding mechanism theory
• Myosin pulls on actin, causing thin filament to slide inward
• Consequently, Z discs move toward each other and the sarcomere shortens
• Whole muscle shortens > transfers force to tendon > movement Role of ATP in muscle contraction
• ATP binds to myosin, moving myosin to its high-energy state, releasing the myosin head from the actin active site.
• ATP can then attach to myosin, which allows the cross-bridge cycle to start again, hence muscle contraction can occur.
The steps of muscle contraction (start at NMJ, ending with sarcomere shortening)
• Action potential in a motor neuron triggers the release of Ca2+ ions from the sarcoplasmic reticulum
• Calcium ions bind to troponin (on actin) and cause tropomyosin to move, exposing binding sites for the myosin heads
• The actin filaments and myosin heads form a cross-bridge that is broken by ATP
• ATP hydrolysis causes the myosin heads to swivel and change orientation
• Swiveled myosin heads bind to the actin filament before returning to their original conformation (releasing ADP + Pi)
• The repositioning of the myosin heads move the actin filaments towards the center of the sarcomere
• The sliding of actin along myosin therefore shortens the sarcomere, causing muscle contraction [Show Less]