Lecture 12: Visual System

• Why are two eyes necessary for wider peripheral vision?

  They provide depth perception and wider vision
• How do animals differ from humans in terms of peripheral vision?

  Animals have less overlapping visual fields
• What are the main components of the eye that focus light?

  Pupil and lens
• What role does the retina play in vision?

  It converts images into nerve impulses
• What additional function does the retina perform besides converting images?

  It facilitates feature analysis of images
• Where does visual information processing occur after the retina?

  Thalamus, rostral colliculus, visual cortex
• What are the three concentric layers of the eye wall?

  1. Fibrous tunic
  2. Vascular tunic
  3. Neuroepithelial (inner) tunic
• What maintains pressure within the eyeball?

  Vitreous body and aqueous humor
• What does the fibrous tunic consist of?

  Sclera and cornea
• What is the function of the fibrous tunic?

  Provides mechanical support and protection
• What is the sclera's role in the eye?

  It provides rigidity and maintains shape
• What is the cornea's function?

  It helps bend light toward the retina
• What structures make up the vascular tunic?

  Iris, ciliary body, choroid
• What muscles are found in the iris?

  Dilator and sphincter muscles
• What happens when the sphincter muscle contracts?

  Pupillary size decreases (miosis)
• What does pupillary dilation indicate?

  Sympathetic tone and certain emotions
• What does the ciliary body consist of?

  Ciliary processes and ciliary muscles
• What is the role of ciliary processes?

  They secrete aqueous humor
• How do ciliary muscles assist in vision?

  They alter the lens shape for accommodation
• What occurs when ciliary muscles contract?

  The lens becomes more convex for near vision
• What is the choroid's composition?

  Loose connective tissue with vasculature
• What is the function of the choroid?

  It provides nutrition to ocular tissue
• What is the tapetum lucidum?

  An additional layer in some animal choroids
• What effect does the tapetum lucidum have on animal eyes?

  It causes eyes to glow in low light
• What are the two layers of the retina?

  Outer pigmented layer and inner neural layer
• What is the function of the pigmented layer of the retina?

  It stores vitamin A and acts as phagocytes
• What are the three major layers of the neural layer of the retina?

  Photoreceptor layer, bipolar cell layer, ganglion cell layer
• How does light travel through the retina?

  It passes through ganglion and bipolar cell layers first
• What types of neurons are found among the retinal cells?

  Horizontal cells and amacrine cells
• What is the role of horizontal and amacrine cells?

  They modify signals along the photoreceptive pathway
• What are the two types of photoreceptor cells?

  • Rod cells
  • Cone cells
• What are the two portions of photoreceptor cells?

  Outer segment and inner segment
• What is the function of the outer segment of photoreceptor cells?

  It contains photopigments for light conversion
• What is the function of the inner segment of photoreceptor cells?

  It is the metabolic region of the cell
• What percentage of photoreceptor cells are rod cells?

  95%
• What is the photochemical in rod cells?

  Rhodopsin
• What is the role of rhodopsin?

  It perceives shades of gray
• Why are rod cells essential for night vision?

  They have a low threshold of excitability
• How do cone cells differ from rod cells?

  They have a higher threshold of excitability
• What do cone cells provide that rod cells do not?

  Color perception