visual pathways

• What is the function of the suprachiasmic nucleus in the hypothalamus?

  It regulates circadian rhythms.
• How does the suprachiasmic nucleus synchronize intrinsic rhythms?

  It synchronizes with the photoperiod of day length.
• What is the location of the superior colliculus?

  It is located in the midbrain.
• Where do projections from the suprachiasmic nucleus go?

  They project to the superior colliculus.
• What role does the superior colliculus play in sensory integration?

  It integrates vision with other sensory inputs.
• What type of eye movements does the superior colliculus control?

  It controls saccadic eye movements.
• How does the superior colliculus affect head movements?

  It activates neurons controlling neck muscles for head movements in response to visual stimuli.
• What percentage of information from the retina goes to the superior colliculus?

  10%
• Why is the information sent to the superior colliculus important?

  It enables quick responses to images or movement in our vision.
• What is the function of the pretectal nucleus in the midbrain?

  It provides bilateral input to the Edinger-Westphal nucleus.
• What type of input does the Edinger-Westphal nucleus receive from the pretectal nucleus?

  It receives parasympathetic input to control pupil muscles.
• Where is the frontal eye field located?

  It is located in the middle frontal gyrus.
• What is the role of the frontal eye field?

  It coordinates voluntary control of gaze.
• What are the main types of cells found in the retina?

  • Bipolar cells
  • Ganglion cells
  • Horizontal cells
  • Photoreceptor cells
• Where are cones densely packed in the retina?

  In the fovea.
• What happens when photoreceptors synapse with bipolar cells?

  Bipolar cells transmit signals to retinal ganglion cells.
• Which cells in the retina fire action potentials?

  Only retinal ganglion cells.
• What forms the optic nerve in the retina?

  The axons of retinal ganglion cells.
• What is the optic disc known for?

  It is the area where visual information leaves the retina and has no photoreceptors, creating a blind spot.
• What role do horizontal cells play in the retina?

  They allow neighboring cells to influence each other's state.
• What happens to information that reaches the nasal part of the retina?

  It decussates without synapsing.
• How is rod/cone information processed until V1?

  Rod/cone information is kept separate until reaching V1.
• What does the optic nerve become after the optic chiasm?

  The optic tract.
• What are the components involved in visual reflexes?

  • Recruitment of ocular muscles
  • Extrinsic ocular muscles (striated, voluntary control)
  • Controlled by oculomotor, trochlear, and abducens nerves
  • Intrinsic ocular muscles (smooth, involuntary control)
• Which nerve controls the superior rectus muscle?

  The oculomotor nerve.
• What is the function of the inferior rectus muscle?

  It pulls the eyes downwards.
• What does the medial rectus muscle do?

  It adducts the eyes.
• What is the role of the inferior oblique muscle?

  It creates twisting eye movements.
• What does the trochlear nerve control?

  It controls the superior oblique muscle.
• What is the function of the abducens nerve?

  It controls the lateral rectus muscle, which abducts the eyes.
• What is the pupillary light reflex?

  • Change in pupil size in response to light levels
  • Constriction in bright light
  • Dilation in dim light
• What happens to the pupillary constrictor muscles in bright light?

  They contract.
• What happens to the pupillary dilator muscles in dim light?

  They contract.
• What occurs when light shines into one eye?

  Both pupils constrict due to contralateral and ipsilateral pathways.
• What is the anatomical pathway of the pupillary light reflex?

  • 10% of information goes to the superior colliculus
  • Bright light projects to the midbrain and synapses in the pretectal nucleus
  • Pretectal nucleus innervates Edinger-Westphal nucleus
  • E-W nucleus activates the parasympathetic part of the oculomotor nerve
  • Oculomotor nerve projects to ciliary ganglion, innervating constrictor muscles
• What is the accommodation reflex?

  • Change in lens shape when focusing on nearby objects
  • Involves consensual action of muscles in both eyes
• What happens when the eyes view an object up close?

  Convergence of both eyes occurs to prevent diplopia.
• How does pupillary constriction improve optical performance?

  It reduces aberration and increases depth of focus.
• What happens to the ciliary muscles during accommodation?

  They contract reflexively, making the lens convex.
• What is the control of horizontal gaze important for?

  • Reading
  • Tracking stationary/moving objects
  • Quick movements (less than 50 milliseconds)