2-Minute Neuroscience: The Retina

  • 🎬 Video
  • ℹ️ Published 6 years ago

In my 2-Minute Neuroscience videos I explain neuroscience topics in 2 minutes or less. In this video, I cover the retina. I discuss the five major types of neurons found in the retina: photoreceptor cells (i.e. rods and cones), bipolar cells, ganglion cells, horizontal cells, and amacrine cells. I also briefly describe the fovea, our area of highest visual acuity, and the optic disc, which creates a natural blind spot in our visual field.


Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss the retina.

The retina contains the neural component of the eye. When light reaches the back of the eye, it enters the cellular layers of the retina.

The cells of the retina that detect and respond to light, known as photoreceptors, are located at the very back of the retina. There are two types of photoreceptors: rods and cones. Rods allow us to see in dim light, but don't allow for the perception of color. Cones, on the other hand, allow us to perceive color under normal lighting conditions. Throughout most of the retina, rods outnumber cones. In one area called the fovea, however, there are no rods but many cones. The fovea represents the area of the retina that provides our highest acuity vision, and thus is at the center of our gaze.

When light hits photoreceptors, it interacts with a molecule called photopigment, which begins a chain of events that serves to propagate the visual signal. The signal is transmitted to cells called bipolar cells, which connect photoreceptors to ganglion cells. Bipolar cells pass the signal on to ganglion cells, which leave eye in a large cluster at an area called the optic disc. The optic disc doesn't contain any photoreceptors, and so represents an area on the retina that can't process visual information, creating a natural blind spot. However, we normally don't notice our blind spot. The brain uses information from surrounding photoreceptors and the other eye to fill in the gaps in images that are processed by the retina. After leaving the retina, the ganglion cell fibers are called the optic nerve. The optic nerve carries visual information toward the brain to be processed.

There are two other cell types in the retina that should be mentioned: horizontal and amacrine cells. Horizontal cells receive input from multiple photoreceptor cells. They integrate signaling from different populations of photoreceptor cells, make adjustments to the signals that will be sent to bipolar cells, and regulate activity in photoreceptor cells themselves. Amacrine cells receive signals from bipolar cells and are involved in the regulation and integration of activity in bipolar and ganglion cells.


Nolte J. The Human Brain: An Introduction to its Functional Anatomy. 6th ed. Philadelphia, PA. Elsevier; 2009.

💬 Comments

You must start your own "khan Academy" this 2 minute idea is genius!

Author — AmhCharts


This helped me a lot I am coming back to this channel next time I need to revise mammalian nervous systems thanks!!!

Author — Warfare Messiah


thank you very much!! could you please explain the auditory, supraspinal, somatomotor and somatosensory systems.

Author — bella


Based on what I have heard about the Retina, the amacrine cells receive information before the horizontal cells. Can you try to look that up?
I think you have switched those two by mistake :)

Author — Nick Larsen


Could someone explain in a little more detail what horizontal and amacrine cells do?

Author — Vasco Gamero


Studying for my perception test in 4 hours and this helped. My professor is great but the diagram he gave made it confusing to how the radiation got to the back of the eye.

Author — Jessica Rabbit


This helped me a lot
Thank you very much

Author — Hamda Khalfan


When it comes to afterimages, is that because of photopigment bleaching in photoreceptors or adaptation of neurons in the visual cortex? or both?

Author — who isthis


So does light travel through the retinal ganglion cells and bipolar cells to get to the photoreceptors and then get processed starting from photoreceptors going down or does light just have to pass the other cells to get to the photoreceptors?

Author — Ragavi Gobiraj


What would happen if you could direct an electric charge back along the optic nerve to the photoreceptors? Would they emit light?

Author — ryan alving


"no rods" in the fovea. Oh... so that's why, when it's dark, you can see things in your peripheral, but not when looking straight at them.

Author — JNCressey


This helped me alot to understand the eye better👍

Author — Hayden Supple


at 0:13 the light should not go in a straight line, rather be refracted due to the lens

Author — Mike Keefe


Sooo my question at this point: If Glutamat normally is excitatory why does it work as inhibitor on bipolar cells? And aditionally, why is GABA on biopolar cells an excitator but works normally as inhibitory neuro transmitter? I totally don't understand it every time, I watch something about the function of eyes.

Author — Alienvjj


at 0:14 the way you drew the cell layers of the retina is backwards in respect to your drawing of the entire eye ball... just to make sure not to confuse everyone

Author — Anna Pleet


Rods and cones are electrically active or inactive?

Author — surya subash


hey which aap u use for editing? its awesome ..



Yo does anyone know what kind of level in science this is pls??

Author — Tim Andrieux


Ingest oils to enhance contrast in vison.

Author — Jeremy Cornwell


I think I'm gonna stop going to my classes and just study from youtube.

Author — Sebastien Lewis