In-Depth Notes on Sensory Systems

Sensory Systems Notes

Learning Objectives

  1. Sensory Processing and Transduction

    • Describe events in sensory processing and actions involved in transduction: stimulus detected by receptors, followed by action potentials generated in response to that stimulus.

  2. Post Transduction Terms

    • Transmission: Signal travels along afferent pathways to the CNS.
    • Projection: Information arrives in specific brain regions.
    • Interpretation and Perception: The brain modifies stimuli based on familiarity and context.

  3. Location of Sensory Receptors

    • Receptors can be free nerve endings (unencapsulated) or encapsulated, and may be standalone structures differentiated based on their location.

  4. Graded Potentials

    • Graded potentials vary in magnitude with stimulus strength; their amplitude determines action potential frequency.

  5. Sensory Receptors Classification

    • By Location:
      • Exteroceptors: Respond to external stimuli.
      • Interoceptors: Respond to internal stimuli.
      • Proprioceptors: Indicate body orientation and position.
    • By Modality (Stimulus Type):
      • Mechanoreceptors: Detect mechanical changes like pressure or touch.
      • Chemoreceptors: Respond to chemical stimuli.
      • Photoreceptors: Respond to light.
      • Thermoreceptors: Detect temperature changes.

  6. Frequency Code vs. Population Code

    • Frequency Code: The frequency of action potentials encodes stimulus strength.
    • Population Code: The number of activated receptors contributes to signal strength.

  7. Sensory Adaptation

    • Tonic Receptors: Adapt slowly; maintain consistent response to a stimulus.
    • Phasic Receptors: Adapt quickly; respond to changes in stimuli.
    • Sensory adaptation allows ignoring of non-critical stimuli.

  8. Mechanoreceptors

    • Free Nerve Endings: Detect touch, pressure, pain.
    • Encapsulated Receptors: Include:
      • Meissner Corpuscles: Light touch.
      • Pacinian Corpuscles: Deep pressure and vibration.
      • Ruffini Endings: Detect heavy pressure and stretching.
    • Muscle Spindles: Monitor muscle length.
    • Golgi Tendon Organs: Monitor muscle tension.

  9. Human Ear Structures

    • Outer Ear: Collects sound waves (Pinna).
    • Middle Ear: Amplifies sound (malleus, incus, stapes); pressure regulation via auditory tube.
    • Inner Ear: Contains structures for hearing and equilibrium (cochlea, semicircular canals).
    • Cochlea: Converts sound waves into fluid pressure waves. Contains the Organ of Corti for mechanotransduction.

  10. Pitch Detection

    • Pitch is determined by the frequency of sound waves (Hz).
    • Loudness is dictated by the amplitude of these waves.

  11. Gustation Process

    • Taste buds consist of 50-150 receptor cells in different regions of the tongue and are involved in detecting sweet, sour, bitter, and umami flavors.
    • Communicated via cranial nerves.

  12. Olfaction Process

    • Involves olfactory epithelium and receptor cells (bipolar) that connect to the olfactory bulb, interfacing with the brain to localize smells.

  13. Photoreceptor Comparison

    • Differences exist between eyespots, compound eyes, and camera eyes in terms of structure and function.
    • Compound Eyes: Composed of multiple units (ommatidia) focused toward movement detection rather than fine shape resolution.

  14. Human Eye Structures

    • Cornea: Initial focus of light.
    • Lens: Focuses light onto retina, can change shape for accommodation.
    • Retina: Contains rods (sensitive to light) and cones (color detection).
    • Differences in accommodation are also noted (myopia, hyperopia).

  15. Vision Types

    • Monocular Vision: Wide field, but less depth perception.
    • Binocular Vision: Provides depth perception through simultaneous input from both eyes.
    • Distinction between optic nerve, optic tract, and optic chiasm is vital for understanding visual signal processing.