Chapter 3 | Body, Meet World

Chapter Subheadings

Sensory Receptors • Sensory Organs • What Is Meant by “Heightened” Senses?


How do the matter and energy of sensation interact with out bodies? And, how do our sensory organs, and the cells and proteins they consist of, detect this stuff of sensation. How would you go about making the senses better, and what are their physical limits? We also look at the impossibility of using temperature to sense remote object, as seen on the Daredevil television show.

Chapter Excerpt: “The size of the receptive field matters a great deal to how much detail can be resolved by a particular sensory system. The reason we can see in such fine detail at the very center of the visual field is because the photoreceptors here, exclusively cones in this case, sit very close together, with each photoreceptor relaying its information to a single neuron in the optic nerve. Meanwhile, the neurons that receive input from the rods are hooked up to many rods each, around one hundred on average. So, while the density of cones and rods is roughly the same, an individual cone can pass along much more detailed information. The way the retina is “wired” means that cone input is like the latest HD video game graphics, while input from rods is more like an 8-bit Nintendo.”

Helpful videos

A (detailed) look at the G-protein coupled receptor

This video offers an introduction to cell signaling with G-proteins and the GPCR. It also illustrates how the receptor is embedded in the cell layer.

A further look at ion pumps and channels

This video is further illustration of some of the types of proteins mentioned in the chapter. 

A brief introduction to the evolution of the eye

The video also mentions important concepts touched on in the chapter, such as eyespots, and pinhole eyes.

A look at “heat vision” in pit vipers

Do note that the visualization of the (larger) world in infrared is not what the snakes see. In reality, these snakes can only detect prey this way at short range.