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Anatomy & Physiology: Nervous System and Neurons

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  • Difference between endocrine and nervous system responses
    Endocrine system responses are slower, longer lasting, and widespread; nervous system responses are faster, shorter, and targeted to specific organs.
  • Main subdivisions of the nervous system
    CNS: brain and spinal cord; PNS: nerves and ganglia outside CNS.
  • Functional divisions of the PNS
    Sensory (afferent): carries signals to CNS; Motor (efferent): carries signals from CNS to muscles and glands.
  • Subdivisions of the motor division
    Somatic motor: voluntary control of skeletal muscles; Autonomic nervous system (ANS): involuntary control of cardiac, smooth muscles, and glands.
  • Sympathetic vs Parasympathetic divisions
    Sympathetic: fight or flight, increases heart rate and respiration, decreases digestion; Parasympathetic: rest and digest, decreases heart rate and respiration, increases digestion.
  • Three physiological properties of neurons
    Excitability: respond to stimuli; Conductivity: transmit electrical signals; Secretion: release neurotransmitters.
  • Structural classification of neurons
    Multipolar: many dendrites, one axon; Bipolar: one dendrite, one axon; Unipolar: single process with soma off to side.
  • Functions of dendrites and axon
    Dendrites: receive signals toward soma; Axon: sends nerve impulses away from soma.
  • Role of axon hillock and initial segment
    Form the trigger zone where action potentials originate if threshold is reached.
  • Types of axonal transport
    Anterograde: away from soma (kinesin); Retrograde: toward soma (dynein).
  • Neuroglial cells in CNS and their functions
    Astrocytes: blood-brain barrier; Oligodendrocytes: myelin sheath; Ependymal cells: produce CSF; Microglia: immune defense.
  • Neuroglial cells in PNS
    Schwann cells: myelinate axons; Satellite cells: support neuron soma.
  • Myelin sheath characteristics
    Insulating layer around axons; speeds conduction; formed by oligodendrocytes in CNS and Schwann cells in PNS.
  • Nodes of Ranvier
    Gaps in myelin sheath where voltage-gated ion channels are concentrated; enable saltatory conduction.
  • Factors affecting conduction speed
    Presence of myelin and axon diameter; myelinated and thicker axons conduct faster.
  • Resting membrane potential (RMP)
    Typically -70mV; inside of neuron is negative relative to outside due to ion distribution.
  • Local (graded) potentials
    Short-range, variable strength changes in membrane potential; reversible and decremental.
  • Action potentials
    All-or-none, nondecremental electrical impulses that propagate along axons when threshold is reached.
  • Phases of action potential
    Depolarization (Na+ influx), repolarization (K+ efflux), hyperpolarization (overshoot), then return to RMP.
  • Absolute vs relative refractory periods
    Absolute: no new AP possible; Relative: stronger stimulus can trigger AP.
  • Saltatory conduction
    APs jump between nodes of Ranvier in myelinated axons, increasing conduction speed.
  • Types of synapses
    Axodendritic, Axosomatic, and Axoaxonic based on connection points.
  • Acetylcholine (ACh) synaptic transmission steps
    AP triggers Ca2+ influx, ACh released by exocytosis, binds postsynaptic receptors, opens Na+ channels causing depolarization.
  • Inhibitory GABAergic synapse
    Uses GABA neurotransmitter; opens Cl- channels causing hyperpolarization and inhibition.
  • Neural integration and summation
    EPSPs and IPSPs combine; if EPSP > IPSP and threshold reached, neuron fires.
  • Temporal vs spatial summation
    Temporal: repeated signals from one synapse; Spatial: simultaneous signals from multiple synapses.