The visual pathway

It is divided into a central portion; cones (used in central vision and color vision), and peripheral portion (used in dark adaptation and in the detection of movement)

Retina

Sensitive part of the retina because it has concentration of the cones ( more cones )

Fovea Centralis

It extends from the retina to the optic chiasm and is divided in several parts

Optic nerve

The anatomical path of the optic nerve are:

Intraocular, intraorbital, intracanalicular, and intracranial

It is 1mm in length and subdivided into 3 parts; retinal, choroidal, and scleral; it appears in the eye as optic disc

Intraocular

It is 25mm in length, after leaving the retina through the lamina cribrosa

Intraorbital

It is 4-10mm in length

Intracanalicular

It is 10-23mm in length; the part starting beyond the foramen

Intracranial

It is about 20-30mm in length and the axons from the nasal retina of the opposite side and axons from the temporal retina on the same side from the optic tracts emerge from the posterolateral angle of the optic chiasm as cylindrical bands

Optic tract

It emerges from the posterolateral angles of the optic chiasm as cylindrical bands and the majority of the visual fibers terminate in the lateral geniculate body; some continue to the superior colliculi, and some enter the hypothalamus

Optic tract

A 12-13mm wide transversely oval structure covered by pia mater and represents the junction between the termination of the optic nerves anteromedially and emergence of the optic tracts

Optic Chiasm

The nerve fibers from the nasal half of each retina (including the nasal half of the macula) cross the midline and enter the optic tract of the optic side

Optic Chiasm

The temporal fibers retain their temporal position, with the nasal fibers from the central retina located more posterior than the peripheral fibers

Optic Chiasm

It is small, ovoid swelling on the undersurface of the thalamus where the axons of the ganglion cells of the retina carrying visual impulses synapse

Lateral Geniculate Bodies

It modifies the pattern and strength of the retinal input and may play a fundamental role in color and stereoscopic vision. It contains about 1 million nerve cells, about the same number as the nerve fibers in the optic nerve

Lateral Geniculate Bodies

It is located on the medial aspect of the occipital lobe and may be divided into; (1) The primary visual area (Broadman’s area 17) and (2) The secondary visual area (Broadman’s areas 18 and 19)

Visual Cortex

The storage, metabolism and transport of vitamin A in the visual cycle and its dense pigment serves as to absorb stray light

Retinal Pigment Epithelium

The Retinal Pigment Epithelium utilizes this as a route for the transport of metabolic waste products out of the retinal environment. And it was under of RPE

Bruch’s Membrane

It is composed of rod and cones, contains photopigment-laden discs, and most numerous at the fovea

Photoreceptor Layer

It is responsible for peripheral visual and dark adaptation

Rods

It is responsible for central visual and color vision

Cones

It is not a true membrane but represents the outer limit of the glial Muller cells and thought to be important in maintaining the position of photoreceptors

Outer Limiting Membrane

It contains the nuclei of the rods and cones and it is thickest in the fovea

Outer Nuclear Layer

It contains synaptic terminals of photoreceptors with second order neurons (bipolar and horizontal cells)

Outer Plexiform Layer

It contains the nuclei of the second order neurons (bipolar, horizontal, and amacrine)

Inner Nuclear Layer

It contains processes of bipolar , amacrine and ganglion cell layers, and their synapses

Inner Plexiform Layer

It contains the nuclei of the third order neurons and the sum of the input from the bipolar and amacrine cells, and pass the signal via a long axon to the higher visual centers

Ganglion Cell Layer

It is composed of axons of the retinal ganglion cells and only one that passes through the optic nerve

Nerve Fiber Layer

It represents the termination of glial Muller Cells and in contact with the vitreous 

Inner Limiting Membrane

Scotopic (night-time)

Rods

Photopic (daylight)

Cones

This is the reason why we see a spectrum of colors

Cones

The main second order neurons and comprise of a cell body with two processes that project from the cell body

Bipolar Cells

Receive INPUT from photoreceptors and provide synaptic input to both ganglion and amacrine cells

Bipolar Cells

It spreads dendrites across the retina and receive input from photoreceptors, and also feedback back information to photoreceptors

Horizontal

Acts as intermediary neurons between bipolars and third order neurons

Amacrine Cells

The output neurons of the retina and receives input from bipolar and amacrine cells

Ganglion Cells

It supports cells of the retina, and are crucial for maintaining the normal function of the neurons in the retina

Muller’s Cells

It carries deoxygenated blood coming from the retina

Central Vein of Retina

It supplies the retina with oxygenated blood and nutrients and has central glow in its artery

Central Artery of Retina

The pathological (abnormal) formation of new blood vessels. This process is often uncontrolled and involves the growth of fragile, leaky, and abnormal vessels that can cause significant damage.

Neovascularization

Are small, dark shapes that drift across your vision.

Floaters

It is the largest of the visual areas and clearly very important for vision-so important that it has lots of different names.

Primary Visual Area 17

Also known as striate cortex because it looks kind of stripy under the microscope and located in the occipital lobe

Primary Visual Area 17

It surrounds the primary visual area on the medial and lateral surfaces of the hemisphere and it is non-striate and receives afferent fibers from the primary visual area 17 and other cortical areas, as well as from the thalamus

Secondary Visual Area 18 and 19

Its functions is to relate the visual information received by the primary visual area to past visual experiences, thus enabling the individual to recognize and appreciate what you are seeing

Secondary Visual Area 18 and 19

Integrates the two halves of the visual fields by means of commissural fibers that cross the midline in the splenium of the corpus callosum and possibly involved in sensory-motor eye integration

Corpus Callosum

It is composed of thick bundle of nerve fibers that connect the left and right cerebral hemispheres

Corpus Callosum

Visual cortex that are involved in basic visual features

V1 and V2

Visual cortex that are involved in motion detection, spatial localization, and hand eye movements

V3 and V5

Visual cortex that is involved in color vision

V4

Visual Cortex that is involved in shape perception

V3/VP

The dendrites of it are often sensory receptors, and when they are stimulated the impulse generated travels towards the spinal cord and brain

Sensory Nerves

Receptors that is located in the skin such as touch, temperature and pain

Somatic Sensory Receptors

Receptors that is located throughout the body

Autonomic Nervous System Receptors

Receptors that monitor blood pressure

Baroreceptors

Receptors that monitor blood pH

Chemoreceptors

Receptors that monitor muscle movement, stretch and pain

Proprioceptors

Information from the central nervous system is delivered to the peripheral nervous system via ___

Motor Nerves

Information transmitted through a voluntary somatic nerve may result in skeletal muscle contraction, or the information may be autonomic in nature, traveling via an autonomic nerve, to control smooth muscle contraction or gland secretion.

Motor Nerves

Thin fluid similar to plasma and produced by the choroid plexus in the ventricles of the brain and it is approximately 150mL that is circulating around the brain, in the ventricles, and around the spinal cord. It is also replaced every 8 hours

Cerebrospinal Fluid

It acts as a cushion, supporting the weight of the brain and protecting it from damage and it also helps to maintain a uniform pressure around the brain and spinal cord. There is a limited exchange of nutrients and waste products between neurons and this

Cerebrospinal Fluid

Layers of protective membranes that surround and protect the brain and spinal cord (central nervous system)

Meninges

One of the layer of meninges that is the outermost thickest and toughest layer 

Dura Mater

One of the layer of meninges that is the middle layer which is thin and translucent 

Arachnoid Mater

One of the layer of meninges that is the innermost and very delicate and thin layer

Pia Mater

One of the layer of meninges that is found in between arachnoid mater and pia mater where CSF (cerebrospinal fluid) situated

Subarachnoid space