Muscular System Overview
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Questions and Answers

All movement requires...?

muscles

What is the muscular system?

the organ system that enables the body to have flexibility and movement.

Name the three types of muscles.

skeletal muscle, smooth muscle, cardiac muscle

What is skeletal muscle?

<p>A muscle that is attached to the bones of the skeleton and provides the force that moves the bones.</p> Signup and view all the answers

What is smooth muscle?

<p>Involuntary muscle found inside many internal organs of the body.</p> Signup and view all the answers

What is cardiac muscle?

<p>Found only in the heart, involuntary control, contracts to propel blood into the circulatory system.</p> Signup and view all the answers

What is fascia?

<p>A fibrous membrane covering, supporting and separating muscles.</p> Signup and view all the answers

What is a tendon?

<p>Attaches muscle to bone.</p> Signup and view all the answers

Define aponeuroses.

<p>Connective tissue that forms broad fibrous sheets which may attach to the covering of adjacent muscles.</p> Signup and view all the answers

What is epimysium?

<p>Connective tissue that closely surrounds a skeletal muscle.</p> Signup and view all the answers

What is perimysium?

<p>Layer of connective tissue that extends inward from the epimysium &amp; separates the muscle tissue into small sections.</p> Signup and view all the answers

What are fascicles?

<p>Bundles of skeletal muscle fibers.</p> Signup and view all the answers

What is endomysium?

<p>Connective tissue surrounding a muscle fiber.</p> Signup and view all the answers

What is deep fascia?

<p>Fibrous covering that surrounds deeper organs, even epimysium of muscles.</p> Signup and view all the answers

What is subcutaneous fascia?

<p>Layer of tissue that is under the skin and connects the skin to muscles and underlying tissues.</p> Signup and view all the answers

What are myofibrils?

<p>Bundles of protein filaments within the muscle fiber.</p> Signup and view all the answers

What is myosin?

<p>A protein that makes up nearly half of the proteins in muscle cells.</p> Signup and view all the answers

What is actin?

<p>A contractile protein that is part of the thin filaments in muscle fibers.</p> Signup and view all the answers

What are sarcomeres?

<p>Striations that form a repeating pattern of units along each muscle fiber.</p> Signup and view all the answers

What is the sarcoplasmic reticulum?

<p>Organelle of the muscle fiber that stores calcium.</p> Signup and view all the answers

What are transverse tubules?

<p>System of tubules that provides channels for ion flow throughout the muscle fibers to facilitate the propagation of an action potential.</p> Signup and view all the answers

What is a muscle strain?

<p>Overstretching, overexertion, or overuse of soft tissue, less severe than a sprain.</p> Signup and view all the answers

Why do skeletal muscles appear striated?

<p>Because muscle cells only contract not extend; skeletal muscles work in pairs.</p> Signup and view all the answers

What is a synapse?

<p>A junction where information is transmitted from one neuron to the next.</p> Signup and view all the answers

What are neurotransmitters?

<p>Chemical messengers that cross the synaptic gaps between neurons.</p> Signup and view all the answers

What are motor neurons?

<p>Neurons that carry outgoing information from the brain and spinal cord to the muscles and glands.</p> Signup and view all the answers

What are neuromuscular junctions?

<p>Region where a motor neuron comes into close contact with a skeletal muscle cell.</p> Signup and view all the answers

What is a synaptic cleft?

<p>A small gap that separates the membrane of the neuron &amp; the membrane of the muscle fiber.</p> Signup and view all the answers

What is acetylcholine (ACh)?

<p>A neurotransmitter that enables learning and memory and also triggers muscle contraction.</p> Signup and view all the answers

What is rigor mortis?

<p>A fixed muscular contraction after death.</p> Signup and view all the answers

What is tendonitis?

<p>Inflammation of a tendon.</p> Signup and view all the answers

What is tenosynovitis?

<p>Inflammation of the sheath surrounding a tendon.</p> Signup and view all the answers

What is poliomyelitis?

<p>Acute, contagious viral disease of the central nervous system that can lead to paralysis.</p> Signup and view all the answers

What is Duchenne Muscular Dystrophy?

<p>A human genetic disease caused by a sex-linked recessive allele; characterized by progressive weakening and a loss of muscle tissue.</p> Signup and view all the answers

The function of the skeletal muscle unit is...?

<p>sarcomere</p> Signup and view all the answers

Both muscle relaxation and contraction require...?

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

What is botulism?

<p>Rare poisoning caused by toxins produced by Clostridium botulinum bacteria.</p> Signup and view all the answers

What is a myogram?

<p>A chart of the timing and strength of a muscle's contraction.</p> Signup and view all the answers

What makes up a motor unit?

<p>A muscle fiber or cell and motor neuron that connects to it.</p> Signup and view all the answers

What is Myasthenia Gravis?

<p>A disease in which acetylcholine receptors on muscle cells are destroyed so that muscles can no longer respond to the acetylcholine signal to contract.</p> Signup and view all the answers

What are the steps of Muscle Contraction & Relaxation?

<p>Step 1: A nerve impulse travels down an axon and causes the release of acetylcholine. Step 2: Acetylcholine causes the impulse to spread across the surface of the sarcolemma. Step 3: The nerve impulse enters the T Tubules and Sarcoplasmic Reticulum, stimulating the release of calcium ions. Step 4: Calcium ions combine with Troponin, shifting troponin and exposing the myosin binding sites on the actin. Step 5: ATP breaks down ADP + P. The released energy activates the myosin cross bridges and results in the sliding of thin actin myofilament past the thick myosin myofilaments. Step 6: The sliding of the myofilaments draws the Z lines towards each other, the sarcomere shortens, the muscle fibers contract and therefore muscle contracts. Step 7: ACh is inactivated by Acetylcholinesterase, inhibiting the nerve impulse conduction across the sarcolemma. Step 8: Nerve impulse is inhibited, calcium ions are actively transported back into the Sarcoplasmic Reticulum, using the energy from the earlier ATP breakdown. Step 9: The low calcium concentration causes the myosin cross bridges to separate from the thick actin myofilaments and the actin myofilaments return to their relaxed position. Step 10: Sarcomeres return to their resting lengths, muscle fibers relax and the muscle relaxes.</p> Signup and view all the answers

What are the steps of Muscle Relaxation?

<ol> <li>ACh rapidly decomposes the remaining ACh in the synapse. 2. Muscle impulses stop. 3. Stimulus to sarcolemma &amp; muscle fiber membrane ceases. 4. Calcium moves back into sarcoplasmic reticulum (SR). 5. Myosin &amp; actin binding prevented. 6. Muscle fiber relaxes.</li> </ol> Signup and view all the answers

What is Cross Bridge Cycling?

<ol> <li>Myosin head attaches to actin binding sites, forming cross-bridges. 2. Myosin cross-bridge pulls thin filament. 3. ADP &amp; phosphate released from myosin. 4. New ATP binds to myosin. 5. Linkage between actin &amp; myosin cross-bridge breaks. 6. ATP splits. 7. Myosin cross-bridge goes back to original position.</li> </ol> Signup and view all the answers

What is creatine phosphate?

<p>An energy storage molecule used by muscle tissue; can be removed and attached to an ADP to generate ATP quickly.</p> Signup and view all the answers

Muscle cells are a major source of...?

<p>heat</p> Signup and view all the answers

What is oxygen debt?

<p>The amount of oxygen required after physical exercise to convert accumulated lactic acid to glucose.</p> Signup and view all the answers

What are thick myofilaments?

<p>Composed of myosin protein; forms cross bridges.</p> Signup and view all the answers

What are thin myofilaments?

<p>Composed of actin protein; associated with troponin &amp; tropomyosin proteins.</p> Signup and view all the answers

What is myoglobin?

<p>Oxygen-storing pigment in muscle tissue.</p> Signup and view all the answers

What is lactic acid threshold?

<p>The value of exercise intensity at which lactic acid production increases.</p> Signup and view all the answers

What is threshold stimulus?

<p>Stimulation level that must be reached to elicit an action potential in a neuron or muscle fiber.</p> Signup and view all the answers

What is muscle fatigue?

<p>Inability of a muscle to maintain its strength of contraction or tension.</p> Signup and view all the answers

What is a cramp?

<p>A painful and involuntary muscle contraction.</p> Signup and view all the answers

What is a refractory period?

<p>Period of time during which the neuron cannot generate another action potential.</p> Signup and view all the answers

What is the all-or-none response?

<p>When a muscle fiber responds completely or not at all to a stimulus.</p> Signup and view all the answers

What is a twitch?

<p>A single quick, jerky muscular contraction from a single nerve impulse followed by relaxation.</p> Signup and view all the answers

What is muscle tone?

<p>Normal state of balanced muscle tension.</p> Signup and view all the answers

What is summation?

<p>Increase force of contraction by a skeletal muscle fiber when a twitch occurs before the previous twitch relaxes.</p> Signup and view all the answers

What is tetanic contraction?

<p>A sustained contraction that lacks partial relaxation.</p> Signup and view all the answers

What is recruitment?

<p>An increase in the number of motor units being activated.</p> Signup and view all the answers

What is isotonic concentric contraction?

<p>When skeletal muscles develop tension and shorten when an external force is applied.</p> Signup and view all the answers

What is eccentric contraction?

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

What is isometric contraction?

<p>When a skeletal muscle develops tension but does not shorten.</p> Signup and view all the answers

What are Type I fibers?

<p>Dark muscle fibers for long sustained or continued contractions.</p> Signup and view all the answers

What are Type IIa fibers?

<p>Fibers characterized as inefficient and fatiguable with low aerobic power.</p> Signup and view all the answers

What are Type IIb fibers?

<p>White, fast twitch, rapid contraction fibers.</p> Signup and view all the answers

What is visceral smooth muscle?

<p>A smooth muscle tissue that forms sheets or layers in the walls of visceral organs.</p> Signup and view all the answers

What is rhythmicity?

<p>Spontaneous repeated contractions.</p> Signup and view all the answers

What is peristalsis?

<p>Involuntary waves of muscle contraction that keep food moving along in one direction through the digestive system.</p> Signup and view all the answers

What are the two major types of smooth muscle?

<p>Multiunit smooth muscle and visceral smooth muscle.</p> Signup and view all the answers

What is multiunit smooth muscle?

<p>Muscle fibers that are less well organized and function as separate units.</p> Signup and view all the answers

Cardiac muscle is similar to skeletal muscle due to...?

<p>via intercalated disks (gap junctions)</p> Signup and view all the answers

What is the function of intercalated discs?

<p>To protect the brain and spinal cord from trauma and provide a fluid for diffusion.</p> Signup and view all the answers

What is the origin of a muscle?

<p>Less movable end of a muscle.</p> Signup and view all the answers

What is the insertion of a muscle?

<p>More movable end of a muscle.</p> Signup and view all the answers

What is an agonist?

<p>A muscle that causes an action.</p> Signup and view all the answers

What is a synergist?

<p>A muscle functioning in cooperation with another muscle.</p> Signup and view all the answers

What is a prime mover?

<p>Muscle responsible for a particular body movement.</p> Signup and view all the answers

What is an antagonist?

<p>Chemicals that block the action of a particular neurotransmitter.</p> Signup and view all the answers

What is smooth muscle contraction?

<p>Lack troponin; use calmodulin to bind calcium; slower to contract &amp; relax.</p> Signup and view all the answers

What is cardiac muscle contraction?

<p>Only in the heart, composed of striated cells, forming fibers that are interconnected.</p> Signup and view all the answers

What are skeletal muscle contractions?

<p>Generate a great variety of body movements; bones and muscles act as levers.</p> Signup and view all the answers

What are the four basic components of a lever system?

<ol> <li>rigid bar 2. fulcrum 3. resistance 4. force</li> </ol> Signup and view all the answers

What is a first-class lever system?

<p>Parts are arranged 1. resistance 2. fulcrum 3. force</p> Signup and view all the answers

What are examples of a first-class lever system?

<p>Seesaws &amp; scissors.</p> Signup and view all the answers

What is a second-class lever system?

<p>Parts are arranged 1. fulcrum 2. resistance 3. force</p> Signup and view all the answers

What is an example of a second-class lever system?

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

What is a third-class lever system?

<p>Parts are arranged 1. resistance 2. force 3. fulcrum</p> Signup and view all the answers

What is an example of a third-class lever system?

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

What is pectoralis major?

<p>A muscle of large size in the pectoral region.</p> Signup and view all the answers

What is the deltoid?

<p>Shaped like a delta or triangle.</p> Signup and view all the answers

What is the extensor digitorum?

<p>Extends digits (fingers).</p> Signup and view all the answers

What is the extensor digitorum (toes)?

<p>Extends digits (toes).</p> Signup and view all the answers

What is biceps brachii?

<p>A muscle with two heads in the brachium (arm).</p> Signup and view all the answers

What is the sternocleidomastoid?

<p>Attached to the sternum, clavicle, &amp; mastoid process.</p> Signup and view all the answers

What is the external oblique?

<p>Located near the outside, with fibers that run obliquely.</p> Signup and view all the answers

What is the epicranius?

<p>Covers the upper part of the cranium &amp; consists of two muscular parts: the frontalis &amp; occipitalis.</p> Signup and view all the answers

What is the orbicularis oculi?

<p>A ring-like band of muscle that surrounds the eye.</p> Signup and view all the answers

What is the orbicularis oris?

<p>A sphincter muscle that encircles the mouth.</p> Signup and view all the answers

What is the buccinator?

<p>Located in the wall of the cheek on the outer surface of maxilla and mandible.</p> Signup and view all the answers

Study Notes

Muscular System Overview

  • All movement in the body requires muscles to function effectively.
  • The muscular system is an organ system essential for flexibility and movement.

Types of Muscle Tissue

  • Three muscle types:
    • Skeletal muscle: attached to bones, voluntary control.
    • Smooth muscle: involuntary control found in internal organs (e.g., intestines, blood vessels).
    • Cardiac muscle: only in the heart, involuntary, propels blood circulation.

Muscle Structure and Components

  • Fascia: Fibrous membrane that covers, supports, and separates muscles.
  • Tendons: Connect muscles to bones for movement.
  • Aponeuroses: Broader connective tissue sheets attaching adjacent muscles.
  • Epimysium: Connective tissue surrounding an entire skeletal muscle.
  • Perimysium: Connective tissue that divides muscle into smaller sections.
  • Fascicles: Bundles of skeletal muscle fibers.
  • Endomysium: Connective tissue around individual muscle fibers.
  • Deep fascia: Surrounds deeper organs and muscles.
  • Subcutaneous fascia: Connects skin with muscles and underlying tissues.

Muscle Cell Components

  • Myofibrils: Protein filament bundles within muscle fibers.
  • Myosin: Major protein in muscle cells, primarily involved in contraction.
  • Actin: Contractile protein forming thin filaments in muscle.
  • Sarcomeres: Structural units of muscle fibers, giving striations.
  • Sarcoplasmic reticulum: Calcium storage organelle in muscle fibers.
  • Transverse tubules: Channels for ion flow aiding in action potential propagation.

Muscle Function and Physiology

  • Muscle contraction and relaxation require ATP for energy.
  • Synapse: Junction where nerve impulses transmit signals to muscles.
  • Neurotransmitters: Chemical messengers like acetylcholine (ACh) that enable muscle contractions.
  • Rigor mortis: Post-mortem muscular contraction, indicative of energy depletion.

Muscle Disorders

  • Muscle strain: Overexertion or overstretching of muscle tissue.
  • Tendonitis: Inflammation of a tendon; tenosynovitis is inflammation of the tendon sheath.
  • Poliomyelitis: Viral disease affecting the nervous system, can lead to paralysis.
  • Duchenne Muscular Dystrophy: Genetic disease leading to progressive muscle weakening.
  • Myasthenia Gravis: Disease where muscle response is impaired due to destroyed receptors.

Muscle Contraction Process

  • Initiation involves ACh release, propagating nerve impulse and triggering calcium ion release.
  • Calcium interacts with troponin to expose myosin binding sites on actin, leading to muscle contraction.
  • Relaxation occurs when ACh is inactivated, calcium returns to sarcoplasmic reticulum, and muscle fibers relax.

Muscle Fatigue and Recovery

  • Oxygen debt: Extra oxygen required post-exercise to clear lactic acid.
  • Muscle fatigue stems from various factors: decreased blood flow, ion imbalances, lactic acid buildup.
  • Muscle cramps: Involuntary muscle contractions, causing pain.

Muscle Classification

  • Striated muscles: Skeletal muscles appear striped; allow for complex movements via paired contraction and relaxation.
  • Smooth muscle: Lacks striations; characterized by slower contractions, regulated by calcium binding with calmodulin.
  • Cardiac muscle: Contains intercalated discs enhancing synchronized contractions in the heart.

Lever Systems in Muscles

  • Four components required for a lever system: rigid bar, fulcrum, resistance, force.
  • Types of lever systems:
    • First-class: Fulcrum between resistance and force (e.g., seesaws).
    • Second-class: Resistance between fulcrum and force (e.g., wheelbarrows).
    • Third-class: Force between fulcrum and resistance (e.g., tweezers).

Muscle Fiber Types

  • Type I fibers: Dark, endurance-focused fibers for prolonged contractions.
  • Type II fibers: Fast-twitch fibers, differentiated into:
    • Type IIa: Versatile, less fatigue-resistant.
    • Type IIb: Rapid contractions, fatigue quickly, found in fine movement muscles.

Key Muscle Functions

  • Muscle tone: Balanced state of contraction potential.
  • Twitch: Brief, quick contraction resulting from a single nerve impulse.
  • Tetanic contraction: Sustained contraction with no relaxation.
  • Recruitment: Activation of more motor units to increase force of contraction.

Muscle Anatomy Highlights

  • Origins and insertions: Less movable (origin) versus movable (insertion) ends defining muscle action.
  • Agonist and antagonist muscles: Agonist causes movement, antagonists relax in opposition.

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Description

Explore the essential components of the muscular system, including the types of muscle tissue such as skeletal, smooth, and cardiac muscles. Understand the structure and function of muscles, fascia, tendons, and connective tissues that support movement in the body.

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