Chapter 9 - The Eye (Slide Notes)

Neuroscience Notes: Neuroanatomy and Vision

Functionally Related Structures: The Limbic System

  • The limbic system is crucial for emotions and memory.
  • Key structures and their roles:
  • Medial Prefrontal Cortex:
    • Responsible for social behavior, cognition, impulsivity, and emotional regulation.
    • Example: Damage illustrated by Phineas Gage, who suffered personality changes due to brain injury.
  • Hippocampus:
    • Essential for memory formation.
    • Damage can lead to memory impairment.
    • Key cases: Patient HM, Clive Wearing.
  • Amygdala:
    • Involved in processing emotions, particularly fear.
    • Damage results in lack of fear in dangerous situations.
    • Notable conditions: Kluver-Bucy syndrome, Urbach-Wiethe disease.

Types of Amnesia Associated with the Hippocampus

  • Two main types:
  • Retrograde Amnesia: Loss of pre-existing memories.
  • Anterograde Amnesia: Inability to create new memories (e.g., Clive Wearing).

Life Without an Amygdala

  • Urbach-Wiethe Disease:
  • Rare genetic disorder resulting in lesions of the amygdala, affecting emotional responses.
  • Patients may display inappropriate social behaviors and lack of fear responses.

Monoamine Transmitter Systems

  • Core System:
  • Made up of a small number of neurons primarily from the brainstem.
  • One neuron can influence many others, having extensive axonal projections.
  • Volume Transmission:
  • Neurotransmitters can be released broadly, not strictly at synapses, leading to diffuse effects.

Introduction to Vision

  • Vision Components:
  1. Light
  2. Parts & Functions of the Eye
  3. Retina and its functions
  4. Visual pathway
  5. Color and pattern vision

Light and the Human Eye

  • Visible Spectrum:
  • Human eyes can detect light wavelengths from 400 nm to 700 nm.
  • This range represents only a fraction of the electromagnetic spectrum.
  • Dogs experience red-green color blindness similarly to 8% of human males and 0.5% of females.

Structure and Function of the Eye

  • Key Structures:
  • Sclera:
    • Tough outer wall of the eye, provides structure.
  • Cornea:
    • Transparent covering that bends light for refraction.
  • Iris:
    • Pigmented muscle ring that adjusts light entry through the pupil.
  • Pupil:
    • Adjustable opening in the iris.
  • Lens:
    • Focuses light on the retina; shape can change for accommodation (via ciliary muscles).
  • Aqueous Humor:
    • Nourishes cornea and lens; maintains intraocular pressure.
  • Vitreous Humor:
    • Fills the space between lens and retina.
  • Retina:
    • Contains photoreceptors (rods and cones) that transduce light into electrical signals.
  • Fovea:
    • Area of detailed vision, with only cones for color sensitivity.

Retina Functionality

  • Photoreceptors:
  • Rods (light sensitivity) and cones (color sensitivity) convert light into neural signals.
  • Blind Spot:
  • Area without photoreceptors where the optic nerve exits; the brain compensates for this gap in vision.
  • Pigmented Epithelium:
  • Absorbs excess light to improve vision sharpness, nourishes photoreceptors, and facilitates light absorption to enhance vision clarity.