Muscular System Overview

About 40%.

Contractility is the ability of a muscle to shorten with force.

Excitability.

<p>Extensibility allows muscles to stretch to their normal resting length and beyond to a limited degree.</p> Signup and view all the answers

<p>Elasticity refers to the ability of muscle to recoil to its original resting length after being stretched.</p> Signup and view all the answers

<p>Skeletal muscle.</p> Signup and view all the answers

<p>Contraction of the stomach.</p> Signup and view all the answers

<p>Muscle tissues serve functions such as movement, posture maintenance, and heat generation.</p> Signup and view all the answers

<p>The shortening of myofibrils is caused by the shortening of the sarcomeres as the distance between Z lines is reduced.</p> Signup and view all the answers

<p>Myosin cross bridges produce asynchronous power strokes that pull the thin filaments (actin) over the thick filaments (myosin).</p> Signup and view all the answers

<p>The A bands remain the same length, while the adjacent I bands shorten as they are pulled closer together.</p> Signup and view all the answers

<p>The neuromuscular junction transmits signals from motor neurons to muscle fibers, initiating muscle contraction.</p> Signup and view all the answers

<p>Action potentials travel over the sarcolemma and descend into the muscle via T tubules.</p> Signup and view all the answers

<p>The release of ACh leads to large depolarizing end-plate potentials and generates action potentials in the muscle.</p> Signup and view all the answers

<p>APs in T tubules are linked to Ca2+ release from the SR, as channels in both structures interact mechanically.</p> Signup and view all the answers

<p>This phenomenon is known as electromechanical coupling.</p> Signup and view all the answers

<p>H bands shorten as the thin filaments on the sides of the sarcomeres are pulled toward the center.</p> Signup and view all the answers

<p>The A bands retain their length during contraction, which is significant because it indicates that the thick filaments do not change in size even as muscle fibers contract.</p> Signup and view all the answers

<p>Calcium ions are pumped back into the sarcoplasmic reticulum by Ca2+-ATPase pumps, leading to no more calcium available to bind to troponin C.</p> Signup and view all the answers

<p>A motor unit consists of a single motor neuron and all the muscle fibers it innervates.</p> Signup and view all the answers

<p>Finer muscle control requires smaller motor units, which have fewer muscle fibers.</p> Signup and view all the answers

<p>Motor unit recruitment increases contraction strength by activating more motor units to coordinate muscle fibers.</p> Signup and view all the answers

<p>When a motor neuron is activated, all muscle fibers in its motor unit contract simultaneously.</p> Signup and view all the answers

<p>The eye muscles, which may have about 20 muscle fibers per motor unit, allow for precise control of eye movement.</p> Signup and view all the answers

<p>Fine control muscles have smaller motor units with fewer fibers, while larger muscles have motor units with thousands of fibers.</p> Signup and view all the answers

<p>Ca2+ binding to troponin C is essential for forming cross bridges that lead to muscle contraction.</p> Signup and view all the answers

<p>When action potentials cease, calcium is pumped back into the sarcoplasmic reticulum, ending muscle contraction.</p> Signup and view all the answers

<p>The trade-off is that finer muscle control generally comes from smaller motor units, while larger motor units provide greater strength.</p> Signup and view all the answers

<p>Muscle tone is the tension at rest in muscles, established by weak, involuntary contractions of motor units, regulated by neurons in the brain and spinal cord.</p> Signup and view all the answers

<p>Hypotonia is characterized by decreased muscle tone leading to flaccid muscles, while hypertonia involves increased muscle tone causing stiffness and spasticity.</p> Signup and view all the answers

<p>Isometric contractions occur without changing muscle length while generating force, whereas isotonic contractions involve changes in muscle length during contraction.</p> Signup and view all the answers

<p>Type I fibers, known as slow twitch fibers, are adapted for aerobic metabolism, have a high resistance to fatigue, and appear red due to rich myoglobin content.</p> Signup and view all the answers

<p>Satellite cells are stem cells located near muscle fibers that play a crucial role in muscle repair and regeneration following injury.</p> Signup and view all the answers

<p>Type II A fibers use aerobic metabolism and are intermediate in characteristics, while Type IIX fibers rely on anaerobic metabolism for fast, powerful contractions.</p> Signup and view all the answers

<p>The alternating activation of motor units maintains muscle firmness and helps prevent fatigue by distributing the workload among different muscle fibers.</p> Signup and view all the answers

<p>Skeletal muscle.</p> Signup and view all the answers

<p>It directs the actions of involuntary muscles.</p> Signup and view all the answers

<p>Myofibril.</p> Signup and view all the answers

<p>Endomysium.</p> Signup and view all the answers

<p>Cardiac muscle has striations and intercalated disks, while smooth muscle is not striated and has a centrally located nucleus.</p> Signup and view all the answers

<p>It stores calcium ions necessary for muscle contraction.</p> Signup and view all the answers

<p>Smooth muscle cells have a single, centrally located nucleus and lack striations.</p> Signup and view all the answers

<p>Epimysium.</p> Signup and view all the answers

<p>Sarcomere.</p> Signup and view all the answers

<p>Through the arrangement of myofibrils and the alternating patterns of the thick and thin filaments.</p> Signup and view all the answers