Exam Three PDF

1. Most of the muscle tissue in the body is skeletal muscle. 2. Remaining muscle is smooth muscle that makes the walls of hollow organs and cardiac muscle forms walls of the heart. 3. Smooth muscle- found around the viscera, regulates lumen size 4. Cardiac- Constitutes the heart muscle(myocardiu...

1. Most of the muscle tissue in the body is skeletal muscle. 2. Remaining muscle is smooth muscle that makes the walls of hollow organs and cardiac muscle forms walls of the heart. 3. Smooth muscle- found around the viscera, regulates lumen size 4. Cardiac- Constitutes the heart muscle(myocardium) 5. Character of skeletal muscle: voluntary control, striated, multi nucleic, and cylindrical. 6. Smooth and cardiac muscle move materials within the body 7. Skeletal muscle is also known as voluntary muscle 8. Skeletal muscles is made up of relatively large cells called muscle fibers 9. Skeletal muscle is made up of muscle fibers 10. These muscle fibers can range from 10 to 100 um. 11. Hundreds of embryonic cells fuse to produce each muscle cell 12. Plasma membrane = sarcolemma 13. Nucleus of the muscle cell is found under sarcolemma. 14. Each mylofaments is made up of myosin and actin, which are arranged into subunits called Sarcomeres(the functional contractile unit of the muscle cell). 15. Each thick filament is surrounded by six thin filaments 16. Each thin filament is surrounded by three thick filaments. 17. Myofibrils are made up of even smaller than like structures called myofilament 18. myofilament are made up of proteins- actin and myosin 19. Thousands of muscle fibers are bundled together with connective tissue to form the organs we referred to as skeletal muscles 20. Each muscle fiber is surrounded by a areoler connective tissue sheath called the endomysium. 21. Several sheathed muscle fibers are wrapped by collagenic membrane called perimysium, forming a bundle of muscle fibers called fascicle. 22. Sarcoplasmic reticulum- tubal system that surrounds each myofibril and contains Ca++. 23. 24. 1. Muscle fibers are delicate and easily damaged. They’re bundled together with connective tissue to form skeletal muscles, which we use for movement. 25. 2. Each muscle fiber (an individual muscle cell) is wrapped in a thin, protective layer called the endomysium. Think of it like a cushion for each fiber. 26. 3. Several muscle fibers grouped together form a bundle, which is then wrapped in another layer called the perimysium. This bundle of fibers is called a fascicle. 27. 4. Multiple fascicles are then bundled together to form a whole muscle. This whole muscle is covered by a thicker layer called the epimysium. 28. 5. All three layers of connective tissue (endomysium, perimysium, and epimysium) come together to form tendons or aponeuroses (flat, sheet-like structures). These connect muscles to bones or to other muscles. 29. Epimysium of many muscle combine into denser Deep Fascia, which then combine into tendons or aponeurosis, which bind muscles to bones. 30. 6. A muscle attaches to bones in two places: 31. Insertion: The more movable attachment point. 32. Origin: The fixed or less movable attachment point. 33. 2 important functions of tendons: durability and conserve space 34. Larger, powerful muscle= more connective tissue 35. As we age, the mass of muscle fiber decreases, and the amount of connective tissue increases 36. Each axon of Motor neuron usually divides into many branches called terminal branches 37. The voluntary skeletal muscle cells must be stimulated by motor neurons via nerve impulses. 38. 39. Muscles that are responsible for producing a particular movement are called prime movers or agonists. 40. Muscles that oppose or reverse a moment are called antagonists. 41. When prime mover is active, fiber of the antagonist stretched and in the relaxed state. 42. Synergists helps the action of agonists by assisting with the same moment or by reducing unnecessary moment. 43. Synergists are muscles that help the main muscles (called agonists) do their job. They do this by either: Assisting with the movement, or Reducing unwanted or unnecessary movement. 44. Muscles Crossing Multiple Joints: When a muscle crosses two or more joints, contracting it would normally cause movement at all those joints. Synergists help by stabilizing some of these joints so that movement only happens where it’s needed. Example: The muscles that flex your fingers also cross the wrist joint. Synergist muscles stabilize the wrist so you can make a fist without bending your wrist at the same time. 45. Fixators or flexion muscles are specialized synergist that in mobilize the origin of a prime mover so that all the tension is at the insertion. Example, muscles that help maintain posture are fixators. 46. 1. Three Groups: Muscles in the upper limb are divided into three groups: 47. Muscles that move the arm 48. Muscles that move the forearm 49. Muscles that move the hand and fingers 50. 2. First Group - Moving the Arm: 51. These muscles cross the shoulder joint and attach to the humerus (upper arm bone). 52. Examples: Subscapularis, supraspinatus, infraspinatus, deltoid. 53. They mainly originate from the axial skeleton or shoulder girdle. 54. These are considered trunk muscles. 55. 3. Second Group - Moving the Forearm: 56. These muscles cross the elbow joint and make up the muscles around the humerus. 57. They start from the humerus and insert into the forearm bones. 58. They control movements like flexion, extension, pronation, and supination (bending and rotating the forearm). 59. 4. Third Group - Moving the Hand and Fingers: 60. These muscles form the main muscles of the forearm. 61. They cross the wrist and attach to the fingers and hand. 62. Their job is to control movements of the hand and fingers. 63. 64. Here’s a short and simple explanation: 65. 1. Signal Starts: An action potential (nerve impulse) travels down a motor neuron to the axon terminal, where it releases acetylcholine (a chemical messenger). 66. 2. Acetylcholine Release: Acetylcholine enters the synaptic cleft and binds to receptors on the sarcolemma (muscle cell membrane). 67. 3. Depolarization: This binding makes the sarcolemma let in sodium ions, causing a depolarization wave that travels down T-tubules (channels linked to the sarcolemma). 68. 4. Calcium Release: The depolarization wave reaches the sarcoplasmic reticulum (near the T-tubules), which then releases calcium. 69. 5. Contraction Trigger: Calcium enters the sarcomere (the muscle unit), starting a series of events that lead to muscle contraction. 70. The plasma membrane is more permeable to K+ then Na+. 71. The resting membrane potential is of particular interest in excitable cells, such as muscle fibers, and neurons because changes in that voltage underline their ability to do work (contract or issue signals) 72. When muscle fiber is stimulated, the sarcolemma becomes temporarily more permeable to NA plus, which enters a cell 73. Action potential - nerve impulses 74. 1. All-or-None Principle: A muscle fiber (cell) either fully contracts or doesn’t contract at all—there’s no partial contraction for a single fiber. 75. 2. Graded Response: While a single muscle fiber contracts fully, the whole muscle can vary how strongly it contracts. This depends on how many muscle fibers are activated at the same time. 76. 3. Threshold vs. Subthreshold Stimulus: 77. A threshold stimulus is strong enough to make the muscle fiber contract. 78. A subthreshold stimulus is too weak, so the fiber doesn’t contract. 79. 4. Maximal Stimulus: This is the smallest stimulus strong enough to make all the muscle fibers in a muscle contract. 80. 5. Multiple Motor Unit Summation (Recruitment): When a muscle needs to contract more strongly, the brain activates (or recruits) more motor units (groups of muscle fibers controlled by a single nerve). This is how the muscle increases its strength to match the task. 81. 82. Here’s the simplified explanation of all the points from your document and the graphs. I’ve broken it down into manageable parts for you: 83. 84. 1. Muscle Twitch 85. 86. A muscle twitch is a single, brief contraction of a muscle. It has three phases: 87. Latent phase: The time between the stimulus and when the muscle starts contracting. No visible contraction happens here. 88. Contraction phase: The muscle shortens and produces force. 89. Relaxation phase: The muscle returns to its original resting state. 90. 91. 2. Treppe (Staircase Effect) 92. 93. When the same stimulus is applied repeatedly, the muscle contractions get stronger over time. 94. Why? The repeated stimuli increase heat and calcium levels in the muscle, improving its efficiency. 95. Think of this like warming up before exercise—your muscles work better after a few tries. 96. 97. 3. Wave Summation 98. 99. If stimuli are applied to the muscle before it fully relaxes, the contractions build on each other. 100. This happens because the muscle is still partially contracted when the next stimulus arrives, so it generates more force. 101. Result: A stronger contraction overall. 102. 103. 4. Tetanus 104. 105. When stimuli come very quickly and repeatedly, there’s no time for the muscle to relax. 106. The muscle stays in a state of sustained contraction: 107. Complete tetanus: The contraction is steady and powerful, with no relaxation at all. 108. 109. 5. Muscle Fatigue 110. 111. Fatigue happens when the muscle can’t contract anymore because it runs out of energy. 112. Causes: 113. Lack of oxygen (leading to lactic acid buildup). 114. Accumulation of waste products like phosphate or potassium. 115. Depletion of ATP, the muscle’s energy source. 116. Result: The muscle force decreases, and the contractions weaken. 117. 118. What the Graphs Show 119. 120. 1. Twitch Graph (Top Left): 121. Shows one muscle contraction and its three phases (latent, contraction, relaxation). 122. 2. Treppe Graph (Top Right): 123. Demonstrates the “staircase effect,” where repeated contractions grow stronger with the same stimulus. 124. 3. Wave Summation Graph (Bottom Left): 125. Displays overlapping contractions. Each one starts before the previous one ends, increasing the overall strength. 126. 4. Complete Tetanus and Fatigue Graph (Bottom Right): 127. Shows a sustained contraction (flat line at the top during tetanus). 128. The force eventually decreases as the muscle fatigues. 129. 130. Key Terms to Remember 131. 132. 1. Latent Phase: Delay before the muscle starts contracting. 133. 2. Contraction Phase: Muscle shortens and exerts force. 134. 3. Relaxation Phase: Muscle relaxes and returns to rest. 135. 4. Treppe: Gradual increase in contraction strength with repeated use. 136. 5. Wave Summation: Adding up contractions for more force. 137. 6. Tetanus: Maximum, continuous contraction. 138. 7. Fatigue: Muscle weakness due to energy depletion. 139. 140. 141. Primary Function of Muscles: 142. Muscles convert chemical energy (from nutrients) into mechanical energy. 143. This allows muscles to shorten or contract, enabling movement. 144. 3. How Muscles are Stimulated: 145. Somatic motor nerves (nerves that control voluntary movements) send signals from the brain or spinal cord to the muscles. 146. These signals trigger muscle contractions. 147. 148.