Visual Pathways Lecture

Question 1

unconscious roles of vision

Answer 1

PLR, orient head and eyes to visual stimuli, influences circadian and seasonal rhythms

Question 2

Explain the pathway from the retina to the diencephalon

Answer 2

axons from ganglion cell alyer converge from all regions of retina onto the optic disk, exit the globe through the area cribrosa of the sclera to become the optic nerve, as they leave they acquire myelin created by oligodedrocytes, axons of right and left optic nerve approach one another on ventral aspect of the diencephalon and converge at the optic chiasm and become the otpic tract.

Question 3

what is the thalamic relay nucleus for vision

Answer 3

lateral geniculate nucleus (LGN)

Question 4

Destinations for axons of the optic tract

Answer 4

• Lateral geniculate nucleus (LGN) [labeled number 1 in photo] axons sent here, synapse here, relays info to visual cortex for conscious proception
  Thalamic relay nucleus for vision
  80% of axons terminate here
• ** Pretectal nuclei ** (rostral midbrain) [labled number 2 in photo] some synapse in midbrain here to coordinate pupillary light reflexes, can be cortically blind and still have PLRs
  Control of pupillary light reflexes
• Rostral colliculus [3] visual information that projects here are being used to drive the visual grasp reflex, turning the head to some sort of stimulus
• Hypothalamus [4] just above the optic chiasm which is how hypothalamus gets its name (nucelus name is suprachiasmatic nucleus), light there is to set circadian rhythms. How nature has reproductive system work.

In the horse industry, benefit to have horses birth earlier, put horses in light to trick the horse into breeding.

Question 5

the pretectal nuclei is control of PLRs, name the neurons involved and its pathway

Answer 5

receptor = Retina
afferent = optic n
interneuron = pretectal nuclei
efferent = occulomotor n, occulomotor nucleus (parasympathetic)
target = pupillary sphincter m.

Question 6

Rostral colliculi (mickey’s eyes)

Answer 6

coordinating visual grasp reflex, visual input strong driver
Visual stimulus activates motor pathways
Orient head and eyes toward stimulus
Other sensory modalities too

Question 7

Hypothalamus (suprachiasmitc nucleus (describes location))

Answer 7

Regulator of 24 hr internall clock
Change in day length dictates reproductive cycles