Khan Academy on a Stick

Advanced nervous system physiology

There are billions and billions of neurons in your brain (about 85 billion), and they’re all sending electrical signals throughout your body right now! They tell your eyes to move across this page, how to interpret the words that you read, how to maintain your posture, your heart rate, and your breathing...all of it in a fraction of a second. In this section, we’ll explore the nature of this vast, complex system, from the cellular level to how it operates at a sensory level. A common misconception is that we only have 5 senses (see, smell, taste, hear, and feel), but we have many more that are nuanced but equally important. Learn more about how our bodies are designed to interact with the world.

Health and medicine

Neurotransmitter release
Neurotransmitter removal
Neuroplasticity
Astrocytes
This video describes the structure and function of astrocytes. By Matt Jensen.
Microglia
This video describes the structure and function of microglia. By Matt Jensen.
Ependymal cells
This video describes the structure and function of ependymal cells. By Matt Jensen.
Oligodendrocytes
This video describes the structure and function of oligodendrocytes. By Matt Jensen.
Schwann cells
This video describes the structure and function of Schwann cells. By Matt Jensen.

Neural cells and neurotransmitters

Get an overview of the structure and function of neurons, and learn about the many other important cells needed to help our nervous system function optimally! By Matt Jensen.

Neuron membrane potentials

Learn the causes and functions of neuron membrane potentials, including resting, graded, and action potentials.

Perceptual organization
Sensory adaptation
Weber's law and thresholds
Somatosensation
Explore our ability to sense the environment through our body. By Ron.
Signal detection theory - part 1
Signal detection theory - part 2
Bottom-up vs. top-down processing
Gestalt principles

Sensory perception

Learn about how we perceive our various senses, including the theories, laws, and organizational principles that underly our ability to make sense of the world around us.

The structure of the eye
In this video, I review the structure of the eye. By Ronald Sahyouni.
Visual sensory information
In this video, I explore our sense of vision. By Ronald Sahyouni.
The phototransduction cascade
This explains phototransduction cascade which is critical to our sense of vision. By Ronald Sahyouni.
Photoreceptors (rods vs cones)
In this video, I explore the similarities and differences between rods and cones. By Ronald Sahyouni.
Photoreceptor distribution in the fovea
In this video, I explore how photoreceptors (rods and cones) are distributed in the fovea. By Ronald Sahyouni.
Visual field processing
In this video, I review how we process our visual field, and how information from the right and left visual field is broken down and sent to the brain. By Ronald Sahyouni.
Feature detection and parallel processing
In this video, I review our ability to break down an image into its component "features" such as color, form, and motion. This is known as feature detection, and since the detection of various features happens simultaneously, or in parallel, it is referred to as parallel processing. By Ronald Sahyouni.

Sight (vision)

Photons are hitting your eye as you read this! Learn about our sense of sight, including the cells responsible for converting light into a neural impulse, the structure of the eye, and how we break down images to make sense of them.

Sound (Audition)

Learn about how we hear, including the structure of the outer, middle, and inner ear, as well as the basics of auditory processing & cochlear implants.

Somatosensation
Explore our ability to sense the environment through our body. By Ron.
Sensory adaptation and amplification
Sensory adaptation and amplification are discussed in this video to differentiate the two. By Ronald Sahyouni.
Somatosensory homunculus
In this video, I review the somatosensory homunculus, which is basically a "topological" representation of the body in the brain. By Ronald Sahyouni.
Proprioception and kinesthesia
The differences between propioception (sense of body position) and kinesthesia (sense of body movement) are discussed. By Ronald Sahyouni.
Pain and temperature
Explore our senses of pain & temperature. By Ron.

Somatosensation

We perceive the environment through our bodily senses, including our sensation of pain, temperature, pressure, balance, and movement. Discover how our body gathers this information and processes it so that we can make sense of the world.

Taste (gustation) and smell (olfaction)

Learn about our senses of smell (olfaction) and taste (gustation), including the anatomy and underlying molecular basis behind these important senses.