Sensation and Perception Quiz

Sensation and Perception

• Sensation: Changes in the sensory system in response to the environment.
• Perception: Interpretation of these sensory changes.
• Transduction: Conversion of physical energy to nervous (electrochemical) energy.

Vision

• Light enters the eye through the cornea and lens, focusing on photoreceptors at the back of the eye.
• Photoreceptors: Convert light into neural signals.
• Two types: Rods and cones.
  • Rods: Sensitive to low light levels, located outside the fovea (peripheral vision).
  • Cones: Sensitive to bright light, perceive color, located in the fovea (central vision).
• Rods use rhodopsin; cones use opsin.
• Rods are more numerous than cones.
• Ganglion cells (M and P cells) receive input from bipolar cells, which receive inputs from rods and cones.
• M cells (parasol): Motion detection; connected to rods.
• P cells (midget): Color processing; connected to cones.
• Ganglion cell axons form the optic nerve.

Audition and Somatosensation

• Audition: Vibration frequency converts sound to neural signals.
• Somatosensation: Mechanical pressure converts touch to neural signals.

Remote Sensing

• Remote sensing: Receiving sensory information without physical contact with the stimulus.

Neurological Assessment

• Alert and Oriented x3 (A+O x3): Patient knows person, place, and time.

Visual Pathway

• Light passes through layers of translucent cells in the retina. These cells are shifted aside in the fovea for better light access.
• The fovea is the central region of the retina with the highest density of cones.
• Retinal neurons transmit information through bipolar to ganglion cells, and then onto optic nerve.
• Optic nerve axons project to the Lateral Geniculate Nucleus (LGN) of the thalamus.
• Ipsilateral (same side) projects to layers 2, 3, and 5 of LGN, Contralateral (opposite side) projects to layers 1, 4, and 6 of LGN.

Receptor Adaptation

• Rapidly adapting receptors: Detect changes and then adapt (return to baseline firing).
• Slowly adapting receptors: Respond continuously as long as the stimulus is present.

Receptive Fields

• Receptive field: Portion of the external world that a receptor responds to.
• Sensitivity is related to receptor density.
• Two-point sensitivity: How close two stimuli can be before they're perceived as one.

Receptive Field Organization (Center-Surround)

• On-center, off-surround: More APs when the center is stimulated, less when the surround is stimulated.
• Off-center, on-surround: Less APs when the center is stimulated, more when the surround is stimulated.

Cortical Processing

• Simple cells: Detect basic patterns.
• Complex cells: Detect shapes and movement.
• Primary sensory areas: Process initial information.
• Secondary (higher) areas: Perform more elaborate processing.

Optic Chiasm and Retinotopic Map

• Optic nerves from both eyes combine at the optic chiasm.
• The retinotopic map in the visual cortex is inverted, upside down, and reversed.