Question

Compare the auditory and visual projections from the sense organ to the cortex.

How are they similar?

How are they different?

Include information about the sense organs and cranial nerves, the number of relays in the brain and where they are located, and where they terminate in the cortex.

Do both systems have modularity? Explain.

Answer 1

	Similarities	Differences
Auditory projections	They perform the same operations on different input signals The specificity of the cortical areas for one function or another is organized along processing streams that are manifested neuroanatomically as well as physiologically.	Auditory cortex focuses on the frequency of the impulses It is one dimensional
Visual projections	visual cortex focuses on the reflexes on the lense It is two dimensional

Sense organs -

Eye -

• More than half the sensory receptors in the human body are located in the eyes, and a large part of the cerebral cortex is devoted to processing visual information.
• The accessory structures of the eye include the eyelids, eyelashes, eyebrows, the lacrimal apparatus and the extrinsic eye muscles
• Anatomical parts of eye are cornea, iris, pupil, lens, retina, macula, optic nerve, choroid and vitreous.

Ear -

• The ear can transduce sound vibrations with small amplitudes in to electrical signals 1000 times faster than photoreceptors can respond to light
• Besides the receptors for sounds waves, the ear also contains receptors for equilibrium
• The ear is divided into three main regions :
• the external ear - auricle or pinna and external auditory meatus
• the middle ear- Auditory ossicles : malleus, incus, stapes ; auditory muscles ; eustachian tube
• the internal ear - consists of the sense organs of hearing and equilibrium. Sense organ for hearing is the cochlea and sense organ for equilibrium is the vestibular apparatus.

Cranial nerves

cranial nerves supporting eyes

Optic -

• Component - sensoryComponent
• function - vision
• origin - back of the eye ball
• opening to the skull - optic canal

Occulomotor nerve -

• Component - Motor
• Functions - raises upper eyelid, turns eyeball upward, downward and medially , constricts pupil , accomadates the eye.
• origin - Anterior surface of the midbrain
• Opening to the skull - superior orbital fissure

Trochlear -

• Component - Motor
• Function - Assisting in turning eyeball downward and laterally
• Origin - Posterior surface of the brain
• Opening to the skull - superior orbital fissure

Abducent -

• Component - Motor
• Function - Lateral rectus muscle turns eyeball laterally
• Origin - Anterior surface of hindbrain between pons and medulla
• Opening to the skull - Superior orbital fissure

Cranial nerve for hearing

• Vestibulocochlear Nerve VIII - special sensory nerve, provides hearing ( cochlear branch ) and sense of balance ( vestibular branch)

The Thalamus is called the relay station because it sorts incoming sensory information to the appropriate part of the brain.

The medial geniculate bodies

• Relay station of the auditory pathway
• Medial geniculate body recieves fibres of lateral leminiscus
• Fibres arising in the medial geniculate bodies constitue the accoustic radiation

The lateral geniculate bodies

• Relay station for visual pathway
• Recieves fibres from retinae of both the eyes
• Efferent fibres arising in the body constitute optic radiation
• Lateral geniculate body also recieves fibres from primary visual cortex, superior colliculus and from the reticular formation of pons and medulla.

Modularity refers to the ability of a system to organize descrete individual units that can overall increase the efficiency of a network activity.

Both the systems have modularity, because they with the help of different suborgans that help for the proper recognition and interpretation of the images / sounds makes the process of sensory perception an effective one. The sensory organs starts reacting when the impulse is recognised, and is transmitted to the receptor site at the brain and then after interpretation is transmitted to the respective effector site.