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Anatomy & Physiology: Muscle and Nervous Systems

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Terms in this set (29)

  • What are the three types of muscle tissue and their key characteristics?
    Skeletal muscle: attached to bones, voluntary, striated, multinucleate, fast contraction.
    Cardiac muscle: heart wall, involuntary, striated, branched, uninucleate, non-fatigable.
    Smooth muscle: hollow organs, involuntary, nonstriated, spindle-shaped, slow contraction.
  • What are the connective tissue wrappings in skeletal muscle from outermost to innermost?
    Epimysium: surrounds entire muscle.
    Perimysium: surrounds fascicles (groups of fibers).
    Endomysium: surrounds individual muscle fibers.
  • What is the sarcomere and its main structural components?
    The sarcomere is the functional contractile unit of skeletal muscle, defined by Z discs. Key parts: Z disc, A band (thick filaments), I band (thin filaments), H zone (thick filaments only), M line (anchors thick filaments).
  • How do the sarcomere bands change during muscle contraction?
    Z discs move closer.
    I band narrows.
    H zone narrows and disappears.
    A band width remains constant.
  • What proteins compose thick and thin filaments in muscle fibers?
    Thick filaments: myosin molecules with ATPase and actin-binding sites.
    Thin filaments: actin (F-actin and G-actin), tropomyosin (blocks myosin sites), troponin (binds Ca2+).
  • Describe the neuromuscular junction (NMJ) and its role in muscle excitation.
    NMJ includes axon terminal, synaptic cleft, and motor end plate. Action potential triggers Ca2+ influx, releasing ACh, which binds receptors causing depolarization and muscle AP propagation.
  • What causes malignant hyperthermia during anesthesia?
    Mutation in ryanodine receptors causes uncontrolled Ca2+ release from sarcoplasmic reticulum, leading to sustained muscle contraction, ATP depletion, heat production, and rigidity.
  • Explain excitation-contraction coupling in skeletal muscle.
    AP travels down T-tubules, DHP receptors activate RyR channels on SR, releasing Ca2+. Ca2+ binds troponin, shifting tropomyosin to expose actin binding sites for myosin.
  • Outline the four steps of the cross-bridge cycle in muscle contraction.
    1. Attachment: myosin head binds actin.
    2. Power stroke: myosin pivots, pulling actin.
    3. Detachment: ATP binds myosin, releasing actin.
    4. Cocking: ATP hydrolyzed, myosin resets.
  • What causes rigor mortis after death?
    ATP production stops, Ca2+ leaks out, myosin binds actin but cannot detach without ATP, causing muscle stiffness.
  • Define a motor unit and its significance in muscle control.
    A motor unit is one somatic motor neuron and all muscle fibers it innervates. Controls muscle contraction strength and precision.
  • What are the three phases of a muscle twitch?
    1. Latent period: AP propagation and Ca2+ release.
    2. Contraction: cross-bridge cycling and tension rise.
    3. Relaxation: Ca2+ reuptake and tension decline.
  • Describe temporal summation and tetanus in muscle contraction.
    Temporal summation occurs when stimuli arrive before relaxation ends, increasing tension. High-frequency stimuli cause unfused or fused tetanus (sustained contraction).
  • What is the length-tension relationship in muscle fibers?
    Muscle force depends on initial fiber length; optimal length (~70%-130% resting) allows maximal cross-bridge overlap and force.
  • Differentiate isometric and isotonic muscle contractions.
    Isometric: tension increases, muscle length constant.
    Isotonic: tension constant, muscle length changes (concentric shortens, eccentric lengthens).
  • List the three pathways for ATP regeneration in muscle and their characteristics.
    1. Direct phosphorylation: creatine phosphate transfers phosphate to ADP, 1 ATP, 10-15 sec.
    2. Anaerobic glycolysis: glucose to lactic acid, 2 ATP, 30-60 sec.
    3. Aerobic respiration: glucose/fatty acids with O2, ~32 ATP, hours.
  • What is Excess Postexercise Oxygen Consumption (EPOC)?
    Elevated oxygen intake after exercise to restore muscle ATP, creatine phosphate, glycogen, myoglobin, and metabolize lactic acid.
  • Compare the three skeletal muscle fiber types.
    Slow oxidative (Type I): slow contraction, aerobic, fatigue resistant, red.
    Fast oxidative (Type IIa): fast contraction, aerobic/anaerobic, intermediate fatigue.
    Fast glycolytic (Type IIx): fast contraction, anaerobic, fatigues quickly, white.
  • How does smooth muscle contraction differ from skeletal muscle?
    Ca2+ binds calmodulin, activating MLCK which phosphorylates myosin heads for cross-bridge cycling; no troponin or T-tubules.
  • What are the main functions of astrocytes and oligodendrocytes in the CNS?
    Astrocytes: support neurons, regulate ions, form blood-brain barrier.
    Oligodendrocytes: produce myelin sheaths around CNS axons.
  • Describe the structure and function of a neuron.
    Neurons have a soma (cell body), dendrites (input), and axon (output). They transmit electrical signals via action potentials.
  • What establishes the resting membrane potential (RMP) in neurons?
    RMP (~−70 mV) is due to ionic concentration differences (high K+ inside, Na+ outside), membrane permeability (K+ leak channels), and Na+/K+ pump activity.
  • Explain depolarization and hyperpolarization in neuronal membranes.
    Depolarization: membrane potential becomes less negative, increasing excitability.
    Hyperpolarization: membrane potential becomes more negative, decreasing excitability.
  • Outline the stages of an action potential and associated ion channel activity.
    1. Resting: channels closed.
    2. Depolarization: Na+ channels open, Na+ influx.
    3. Repolarization: Na+ channels inactivate, K+ channels open, K+ efflux.
    4. Hyperpolarization: K+ channels close slowly.
  • What are absolute and relative refractory periods?
    Absolute: no new AP possible (Na+ channels inactivated).
    Relative: strong stimulus can trigger AP during hyperpolarization.
  • How does myelination affect nerve conduction velocity?
    Myelination enables saltatory conduction, where APs jump between Nodes of Ranvier, increasing speed up to 150 m/s.
  • Compare electrical and chemical synapses.
    Electrical synapses use gap junctions for rapid bidirectional ion flow.
    Chemical synapses use neurotransmitter release across a synaptic cleft for unidirectional signaling.
  • What is the difference between EPSPs and IPSPs?
    EPSPs depolarize the postsynaptic membrane, increasing AP likelihood.
    IPSPs hyperpolarize the membrane, decreasing AP likelihood.
  • How do temporal and spatial summation contribute to neuronal integration?
    Temporal summation: rapid repeated signals from one synapse.
    Spatial summation: simultaneous signals from multiple synapses combine to reach threshold.