Receptors for Light: Functions, Receptors of Vision

Visual receptors and their functions:

Read And Learn More: BDS Previous Examination Question And Answers

Visual pathway:

• It consist of a 6 components.

1. Optic nerve:

• It is formed by the axons of ganglionic cells.
  1. The fibres from the temporal part of retina and present in the lateral half of the nerve.
• They carry impulses from nasal feild of same eye.
  1. The fibres from the nasal part of retina are present in the medial half of the nerve they carry impulses from temporal field of same eye.

2. Optic chiama:

• It is formed by the crossing of medial fibres of both the optic nerve.

3. Optic tract:

• The medial fibers of each optic nerve cross the midline and join the uncrossed lateral fibers of opposite side to form the optic tract.
• The fibers run backwards towards the cerebral peduncle and reach the lateral geniculate nucleus.

4. Lateral geniculate nucleus:

• It is a part of thalamus.
  1. Majority of the fibers synapse and forms subcortical center for visual sensation.
     • From here, the geniculocalcarine tract or optic radiation arises.
     • It is last relay of visual pathway.
  2. Some fibres do not synapse and pass through to terminate in any one of the following centres.
     • Superior colliculus.
     • Pretectal nucleus.
     • Supraoptic nucleus of hypothalamus.

5. Optic radiation:

• Fibers from lateral geniculate body pass through internal capsule and form optic radiation.
• It terminates in primary visual area of visual cortex.

6. Visual cortex:

• It is located on the medial surface of the occipital lobe along the wells and lips of calcarine fissure.
• The macular representation occupies the posterior part while peripheral representation occupies the anterior part of visual cortex.