Senses and Perception Study Guide

The Cerebral Cortex

  • The outside layer of tissue surrounding the brain.
  • Divided into two hemispheres (right and left) by the Corpus Callosum.

Key Concepts Related to Vision

  • Transduction: The process of converting molecules or signals in the environment into action potentials.
  • Cornea: The protective transparent membrane over the eye.
  • Pupil: The opening in the iris that allows light to enter the eye.
  • Iris: The colored part of the eye that dilates the pupil to change the volume of light exposure to the retina.
  • Lens: A part of the eye behind the pupil that expands and thins to focus light on the retina.
  • Optic Nerve: The neuron in the back of the eye that sends processed retinal data to the Lateral Geniculate Nucleus and then the Primary Visual Cortex.

Brain Facts: Chapter 2 Senses and Perception

  • Photoreceptors: The first layer of the retina consisting of rods and cones.
    • Rods: A type of photoreceptor that allows one to see in dim to bright light.
    • Cones: Another type of photoreceptor that uses red, green, and blue to form 16,777,216 different colors.
    • Fovea: The center of the retina where cones are most closely packed, resulting in sharper vision.
    • Macula: The area directly bordering the fovea key for reading and driving. Visual acuity is highest here.
    • Macular Degeneration: A disease where photoreceptors die in the macula; a main cause of vision loss in adults over 55.
  • Lateral Geniculate Nucleus: A part of the thalamus visual data from the eyes travels through.
  • Primary Visual Cortex: Located at the back of the brain in the Occipital Lobe; processes scenes and objects hierarchically.

Visual Processing Pathways

  • Optic Chiasm: The point where data from both eyes crosses over.
  • Dorsal Stream: One of the visual system's processing paths to the Parietal lobe that computes visual motion and timing; helps ascertain spatial location of objects.
  • Ventral Stream: Another processing route to the Temporal Lobe; fuses color into images utilizing memories and overlaps past memories.

Other Visual Concepts

  • Astrocyte: A star-shaped cell of the myelin sheath.
  • Binocular Vision: The sensation of visual data obtained from two eyes, improving overall visual angles, volume, and peripheral vision.
  • Strabismus: A defect (cross-eyed) often causing blindness in one eye due to favoring of the other.
  • Ophthalmologist: A doctor specializing in the eyes.

The Somatosensory System

  • The bodily touch system that responds to stimuli such as pressure, pain, temperature, etc.
  • Somatosensory Cortex: Translates and categorizes skin sensory neuron signals into different touch perceptions (pain, tickling, impact, etc.).
  • A-Beta Fiber: Type of neuron with a myelin sheath allowing quick transmission and responsible for sharp pain transmission.
  • C-fiber: Type of thin neuron without a myelin sheath passing sensory information slowly; associated with dull pain.
  • Nociceptors: Sensory fibers that respond to tissue damage (high-level pain).
  • Capsaicin: The chemical in peppers causing spiciness, which registers as pain to the somatosensory system.
  • Prostaglandins: Nerve impulses that make receptors more reactive to tissue damage increasing pain sensitivity.
  • Allodynia: Pain due to malfunctioning prostaglandins causing intense pain from minor stimuli.
  • Neuropathic Pain: Pain caused by issues in the somatosensory system, not by an actual ailment (e.g. diabetic neuropathy).
  • Periaqueductal Grey Matter: A brainstem region that activates pain-abatement pathways.
  • Endorphins: Endogenous opioids suppressing pain.
  • Analgesic: A substance that decreases pain without causing loss of consciousness (e.g. Aspirin, Tylenol).
  • Cognitive Behavioral Therapy: Therapy aimed at changing thoughts and behaviors for improved functioning.

The Auditory System

  • Tympanic Membrane: Also known as the eardrum; vibrates to sound pressure, sending vibrations to amplification bones.
  • Amplification Bones: Malleus (hammer), Incus (anvil), Stapes (stirrup) transmit vibrations to the Oval Window.
  • Oval Window: Membrane separating middle ear and cochlea, converting vibrations to pressure waves sent to the cochlea.
  • Cochlea: Fluid-filled, spiral structure in the inner ear that transduces pressure waves into electrical potentials using hair cells.
  • Basilar Membrane: Cells in the cochlea differentiating between sound frequencies (high pitch to low pitch).
  • Hair Cells: Lining the Basilar Membrane transduce frequencies into electrical potentials; have stereocilia that facilitate ion migration in response to fluid movement.
  • Thalamus: Main sensory hub in the brain for processing sensor data.
  • Primary Auditory Cortex: First processing center for hearing handling attributes like intensity and frequency.
  • Wernicke's Area: Brain area responsible for the interpretation of heard language.

The Sensory Systems

  • Gustation: The sensation of taste; Olfaction: The sensation of smell.
  • Olfactory Neurons: Transduce scent molecules into smell-related electrical potentials; one of the only regenerating neuron types.
  • Cranial Nerves: Transmit gustation data to the brain, including the facial, glossopharyngeal, and vagus nerves.
  • Gustatory Cortex: Located in the Frontal Lobe, identifies taste.
  • Olfactory Bulb: Transmits olfactory data to the brain.
  • Neurogenesis: The ability of neurons to reproduce throughout an organism’s lifespan.
  • Insula: Cerebral region categorizing taste.
  • Primary Olfactory Cortex: Area linked to memory of scents.
  • Inferior Temporal Lobe: Contains neurons responsive to olfactory and taste combinations.

Brain Function: Vision, Hearing, and Touch

  • Vision: Involves 30% of the human cerebral cortex; light processing journey: Cornea -> Pupil -> Lens -> Retina.
  • Hearing: Sound transmitted via eardrum to the amplification bones, sends to cochlea.
  • Touch: Somatosensory paths process pressure, temperature and pain messages to enable bodily perception.

Conclusion

These concepts illustrate key functions and processes in human sensory systems, highlighting the complexity of our perceptual experiences. The implications of understanding sensory pathways extend to areas like treatment of disorders, enhancing rehabilitation methods, and improving our knowledge of human cognition and behavior.