Anatomy LE 1: Muscle and Nervous Tissue
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Questions and Answers

What is the function of the ATP binding sites in the myosin II heads?

  • To release acetylcholine
  • To bind to calcium ions
  • To bind to troponin
  • To bind to ATP and facilitate muscle contraction (correct)

    • What triggers the release of acetylcholine from the presynaptic cleft?

  • Calcium ions binding to troponin
  • Nerve action potential (correct)
  • Muscle action potential
  • Muscle contraction

    • What is the function of the T-tubules in muscle fibers?

  • To store calcium ions
  • To facilitate the spread of muscle impulse (correct)
  • To release acetylcholine
  • To bind to troponin

    • What is the result of tropomyosin moving on the actin filaments?

    <p>Exposure of active sites on actin molecules</p> Signup and view all the answers

    What is the characteristic of muscle tissue that allows it to respond to stimuli?

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

    What is the function of troponin in muscle contraction?

    <p>To change shape and move tropomyosin</p> Signup and view all the answers

    What is the result of the binding of myosin heads to active sites on actin filaments?

    <p>Creation of cross bridges</p> Signup and view all the answers

    What is one of the functions of skeletal muscle in the body?

    <p>All of the above</p> Signup and view all the answers

    What is the function of the triad component in skeletal muscle?

    <p>To allow depolarization of the sarcolemma</p> Signup and view all the answers

    Which type of muscle has rudimentary sarcoplasmic reticulum and no T-tubules?

    <p>Smooth muscle</p> Signup and view all the answers

    What is the function of Purkinje fibers?

    <p>To transmit contractile impulses</p> Signup and view all the answers

    What is found in the center portion of Purkinje fibers?

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

    What is unique about the nucleus of Purkinje fibers?

    <p>It is larger and rounder than regular cardiac muscle cells</p> Signup and view all the answers

    What type of fibers are involved in the contraction of thick filaments?

    <p>Calcium-binding non-muscle cells</p> Signup and view all the answers

    Aside from cardiac muscle, what is also known as visceral muscle?

    <p>Smooth muscle</p> Signup and view all the answers

    What is composed of desmin and vimentin?

    <p>Intermediate filaments</p> Signup and view all the answers

    What happens to the RER when an axon is injured?

    <p>It is greatly reduced initially</p> Signup and view all the answers

    What happens to the nerve fiber distal to the injury?

    <p>It degenerates along with the myelin sheath</p> Signup and view all the answers

    What happens to the muscle fibers after injury?

    <p>They show denervation atrophy</p> Signup and view all the answers

    What happens to the Schwann cells after injury?

    <p>They proliferate to form a compact chord</p> Signup and view all the answers

    What is the result of successful nerve regeneration?

    <p>Muscle is restored</p> Signup and view all the answers

    What undergoes conformational changes after binding with Calcium?

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

    Which of the following is not a characteristic of cardiac muscle?

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

    What is the function of Schwann cells in the PNS?

    <p>To form myelin sheaths in the PNS for electrical insulation</p> Signup and view all the answers

    Visceral smooth muscle is found in the following organs except:

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

    What is the result of phagocytosis of injured cells by microglia in the CNS?

    <p>Space liberation and glial scar formation</p> Signup and view all the answers

    What type of changes occur in the site of damage during nerve regeneration?

    <p>Location changes</p> Signup and view all the answers

    What is the role of microglia in the CNS?

    <p>Phagocytosing injured cells</p> Signup and view all the answers

    What is the result of glial scar formation in the CNS?

    <p>Permanent damage to the CNS</p> Signup and view all the answers

    What is the characteristic of fibrous astrocytes?

    <p>Hundreds of processes to cover and provide regulated microenvironments</p> Signup and view all the answers

    What is the difference between CNS and PNS in terms of nerve regeneration?

    <p>PNS has a higher rate of regeneration</p> Signup and view all the answers

    Which type of muscle lacks a neuromuscular junction?

    <p>Smooth muscle</p> Signup and view all the answers

    Which of the following cells is responsible for myelin sheath formation in the CNS?

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

    What is the term for a group of muscle fibers?

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

    What type of muscle has fusiform shaped cells and are centrally located?

    <p>Smooth muscle</p> Signup and view all the answers

    Which nerves control smooth muscle contraction?

    <p>Autonomic nervous system</p> Signup and view all the answers

    What is another name for smooth muscle and cardiac muscle?

    <p>Visceral muscle</p> Signup and view all the answers

    During contraction, what part of a sarcomere shortens?

    <p>More than one of the choices.</p> Signup and view all the answers

    Which of the following is not found in the thick filament?

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

    What type of neurons make up the majority of neurons in the body?

    <p>Multipolar Neurons</p> Signup and view all the answers

    What type of cells are the macrophages of the CNS?

    <p>Microglial cells</p> Signup and view all the answers

    Study Notes

    Muscle and Nervous Tissue

    • Muscle tissue has three main functions: movement of bones or fluids, maintaining posture and body position, and stabilizing joints.
    • Muscle tissue also has four special characteristics: excitability, contractility, extensibility, and elasticity.

    Characteristics of Muscle Types

    • Skeletal muscle:
      • Has numerous and larger T-tubules to compensate for lesser sarcoplasmic reticulum.
      • Has a well-developed sarcoplasmic reticulum.
      • Found in muscles attached to bones.
    • Cardiac muscle:
      • Has a less developed sarcoplasmic reticulum.
      • Has fewer and smaller T-tubules.
      • Found in the heart.
    • Smooth muscle:
      • Lacks T-tubules and has a rudimentary sarcoplasmic reticulum.
      • Found in the walls of internal organs such as the intestines, ureter, and uterus.

    Muscle Contraction

    • Muscle action potential is initiated in the sarcolemma of the muscle fibers.
    • Calcium ions are released from the terminal cisternae into the sarcoplasm as the muscle impulse spreads along the T-tubules.
    • Calcium ions bind to troponin, causing a conformational change that exposes active sites on actin molecules.
    • Myosin heads bind to these active sites, creating cross-bridges that lead to muscle contraction.

    Sarcoplasmic Reticulum and T-Tubule Relationship

    • The sarcoplasmic reticulum is a type of smooth endoplasmic reticulum that stores and releases calcium ions.
    • The T-tubule (transverse tubule) is a deep invagination of the sarcolemma that allows the depolarization of the sarcolemma to affect the sarcoplasmic reticulum and trigger the release of calcium ions.

    Purkinje Fibers

    • Located in the subendocardial layer of the cardiac muscle.
    • Generate and rapidly transmit contractile impulses to various parts of the myocardium.
    • Have a larger, round nucleus.
    • Terminate by joining cardiac myocytes, permitting direct passage to the cardiac muscle cells.

    Nerve Regeneration

    • In the PNS, Schwann cells form myelin sheaths around axons, and when an axon is injured, the Schwann cells proliferate to form a compact chord that guides the regrowing axon.
    • In the CNS, injured cells are phagocytosed by microglia, and the space is occupied by the proliferation of glial cells, forming a glial scar that hinders the process of repair.

    Glial Cells

    • Schwann cells:
      • Form myelin sheaths in the PNS.
      • Enclose all axons in nerves of the PNS.
      • Function: electrical insulation.
    • Astrocytes:
      • Most common cell of the CNS.
      • Produce hundreds of processes to cover and provide regulated microenvironments for neuronal perikarya, capillaries, and synapses.
      • Types: fibrous astrocyte and protoplasmic astrocyte.
    • Microglia:
      • Special macrophages that phagocytose injured cells in the CNS.
      • Function: phagocytosis.

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