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Anatomy & Physiology: Nervous System and Sensory Systems

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이 집합의 용어 (29)

  • Central Nervous System (CNS) vs Peripheral Nervous System (PNS)
    CNS includes brain and spinal cord, acting as integration and command center. PNS includes cranial and spinal nerves, serving as communication lines linking body parts to CNS.
  • Neuron Anatomy: Dendrites
    Dendrites receive signals from other neurons and serve as the input region of the neuron.
  • Neuron Anatomy: Axon Hillock
    The axon hillock is the trigger zone where graded potentials are summed and converted into an action potential if threshold is reached.
  • Functions of Astrocytes in CNS
    Astrocytes support neurons, form the blood-brain barrier, and mop up excess ions and neurotransmitters.
  • Role of Oligodendrocytes vs Schwann Cells
    Oligodendrocytes form myelin sheath in CNS; Schwann cells form myelin sheath in PNS.
  • Resting Membrane Potential
    Established at about -70 mV mainly by the sodium-potassium pump pumping 3 Na+ out and 2 K+ in, plus K+ leak channels.
  • Action Potential Threshold
    Threshold is around -55 mV at the axon hillock; if reached, an all-or-none action potential fires.
  • Voltage-Gated Sodium Channel States
    Three states: Resting (closed), Activated (open) allowing Na+ influx, and Inactivated (blocked) during repolarization.
  • Steps of Synaptic Transmission
    1. Action potential arrives; 2. Ca2+ influx; 3. Neurotransmitter exocytosis; 4. Neurotransmitter binds postsynaptic receptors; 5. Postsynaptic graded potential.
  • Methods of Neurotransmitter Clearance
    Cleared by enzymatic degradation, reuptake into presynaptic neuron or astrocytes, and diffusion away from synaptic cleft.
  • EPSP vs IPSP
    EPSP is a graded depolarization pushing membrane potential closer to threshold; IPSP is a graded hyperpolarization pushing it further away.
  • Spatial vs Temporal Summation
    Spatial summation: multiple presynaptic neurons fire simultaneously; Temporal summation: one neuron fires rapidly in succession.
  • Absolute vs Relative Refractory Period
    Absolute: no action potential possible due to Na+ channel inactivation. Relative: action potential possible but requires stronger stimulus due to hyperpolarization.
  • Receptive Field Size and Sensitivity
    Small receptive fields (e.g., fingertips) allow fine discrimination and high sensitivity; large fields (e.g., back) have low sensitivity and poor localization.
  • Tonic vs Phasic Receptors
    Tonic receptors are always active and slow-adapting; Phasic receptors are fast-adapting and respond quickly then stop.
  • Five Receptor Types by Modality
    Mechanoreceptors, Chemoreceptors, Thermoreceptors, Photoreceptors, and Nociceptors detect mechanical, chemical, temperature, light, and pain stimuli respectively.
  • Olfactory Signal Transduction Pathway
    Odorant binds GPCR on olfactory cilia → cAMP opens Na+/Ca2+ channels → depolarization → action potential → olfactory bulb → primary olfactory cortex.
  • Cranial Nerves Involved in Taste
    CN VII (Facial) anterior 2/3 tongue, CN IX (Glossopharyngeal) posterior 1/3, CN X (Vagus) epiglottis and pharynx.
  • Taste Transduction Mechanisms
    Salty and sour use direct ion influx; sweet, umami, bitter use GPCRs triggering second messenger cascades.
  • Retina Layers from Back to Front
    Pigment epithelium → photoreceptors (rods and cones) → bipolar cells → ganglion cells (form optic nerve).
  • Phototransduction in the Dark
    High cGMP keeps Na+ channels open (dark current), depolarizing rods (~-40 mV) and causing continuous glutamate release inhibiting bipolar cells.
  • Phototransduction in the Light
    Light bleaches rhodopsin → activates transducin → PDE breaks down cGMP → Na+ channels close → rod hyperpolarizes (~-70 mV) → glutamate release stops → bipolar cells activated.
  • Rhodopsin Cycle Steps
    1. Bleaching/dissociation; 2. Transport of all-trans retinal to pigment epithelium; 3. Enzymatic isomerization to 11-cis retinal; 4. Recombination with opsin.
  • Why Dark Adaptation Takes Time
    Rhodopsin must be regenerated via the rhodopsin cycle, which takes 20-30 minutes to restore night vision after bright light exposure.
  • Endolymph vs Perilymph Composition
    Endolymph is high in K+ and low in Na+ (inside scala media); Perilymph is low in K+ and high in Na+ (scala vestibuli and tympani).
  • Sound Transduction in Cochlea
    Sound vibrates tympanic membrane → ossicles → oval window → pressure waves in perilymph → basilar membrane moves → hair cells bend → K+ channels open → depolarization → neurotransmitter release.
  • Pitch Perception in Cochlea
    High pitch detected at stiff, narrow base; low pitch detected at flexible, wide apex of cochlea.
  • Equilibrium Sensory Structures and Functions
    Macula (utricle & saccule) detects static equilibrium and linear acceleration; Ampulla (semicircular canals) detects angular acceleration.
  • Key Rule for Motion Perception
    Motion is only perceived during acceleration or deceleration; constant speed causes endolymph to move with the body, so hair cells are not bent.