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Muscular System - Anatomy & Physiology

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  • What are the three main functional groups of muscles?
    Prime mover (agonist): major responsibility for movement; Antagonist: opposes movement; Synergist: assists prime mover and stabilizes.
  • What is the role of a fixator muscle?
    A type of synergist that immobilizes the bone or muscle origin to provide a stable base for the prime mover.
  • How can the action of a muscle be inferred?
    By the position of the muscle relative to the joint it crosses (anterior side produces flexion, posterior side extension, lateral side abduction, medial side adduction).
  • What are the criteria used for naming skeletal muscles?
    Location, shape, size, direction of fibers, number of origins, location of attachments, and muscle action.
  • Give an example of muscle named by shape and by number of origins.
    Shape: deltoid (triangle); Number of origins: biceps (two origins), triceps (three origins).
  • What are the common fascicle arrangements in skeletal muscles?
    Circular, convergent, parallel, fusiform, unipennate, bipennate, multipennate.
  • Describe the circular fascicle arrangement and give an example.
    Fascicles arranged in concentric rings; example: orbicularis oris.
  • What is a convergent muscle fascicle arrangement?
    Broad origin with fascicles converging toward a single tendon; example: pectoralis major.
  • Describe parallel and fusiform fascicle arrangements.
    Parallel: fascicles run parallel to long axis (example: sartorius); Fusiform: spindle-shaped with parallel fibers (example: biceps brachii).
  • What distinguishes pennate muscles and their types?
    Short fascicles attach obliquely to tendon; types: unipennate (one side), bipennate (both sides), multipennate (feather-like).
  • How do fascicle arrangements affect muscle function?
    Fascicles determine range of motion and power; long parallel fibers shorten more but are less powerful; pennate muscles have more fibers, are powerful but shorten less.
  • What are the muscles of facial expression innervated by?
    All are innervated by cranial nerve VII (facial nerve).
  • Name two muscles of mastication and their innervation.
    Masseter and temporalis; both innervated by cranial nerve V (trigeminal nerve).
  • What muscles are involved in inspiration?
    Diaphragm and external intercostals; they enlarge the rib cage during inhalation.
  • Which muscles are responsible for forced expiration?
    Internal intercostals and relaxation of inspiratory muscles decrease rib cage size.
  • List the four paired muscles of the abdominal wall.
    Rectus abdominis, external obliques, internal obliques, transversus abdominis.
  • What are the main actions of the abdominal wall muscles?
    Lateral flexion and rotation of the trunk; assist in urination, defecation, childbirth, vomiting, coughing, and screaming.
  • Name three prime movers of the arm crossing the shoulder joint.
    Pectoralis major, latissimus dorsi, deltoid.
  • What is the function of the rotator cuff muscles?
    Act as synergists and fixators; reinforce shoulder capsule and prevent dislocation.
  • Which muscles flex the forearm at the elbow joint?
    Biceps brachii, brachioradialis, and brachialis.
  • Which muscles extend the forearm at the elbow joint?
    Triceps brachii and anconeus.
  • What are the main muscle groups crossing the hip and knee joints?
    Anterior (flex femur, extend leg), posterior (extend thigh, flex leg), and medial (adduct thigh).
  • Name the prime mover of thigh flexion at the hip.
    Iliopsoas (iliacus and psoas major).
  • What muscles make up the hamstring group?
    Biceps femoris, semitendinosus, semimembranosus; prime movers of thigh extension and leg flexion.
  • Which muscles are responsible for adduction of the thigh?
    Adductor magnus, adductor longus, adductor brevis, pectineus, and gracilis.
  • What is the function of the quadriceps femoris group?
    Powerful knee extensors; also assist in thigh flexion.
  • Name the gluteal muscles and their general actions.
    Gluteus maximus (extends, laterally rotates, abducts thigh), gluteus medius and minimus (abduct and medially rotate thigh).