What Is a Cone Cell?

Pyramidal cells are the main projection neurons in the cerebral cortex and are divided into large, medium and small types. Pyramidal cells are named for their cone-like shape. Pyramid cells are bright-sighted cells and contain sensory pigments. They have certain selectivity in their perception, for example, they are more sensitive to the yellow-green domain in the spectrum, but less sensitive to the red-violet domain ^[1] . Pyramidal cells are cone-shaped. A thicker protrusion from the cone-shaped tip is called the main dendrite, which protrudes to the surface layer of the cortex and continuously emits many small dendritic branches along the way. There are also some basal dendrites at the bottom of the cone cells, which expand in the horizontal direction. There are a large number of dendritic spines on all dendrites. The number of dendritic spines increases as the cell body distance increases. The axons are emitted from the center of the bottom of the cell opposite the main dendrites. They are thin and uniform, with varying lengths. The short ones travel within the cortex and form synaptic connections with neighboring cells, while the elders leave the cortex to participate Projection fibers that descend to the brainstem and spinal cord, or travel to different cortical areas on the ipsilateral and contralateral sides to form commissural fibers.

Pyramidal cells are also called "visual cones". One of two types of photoreceptors in the retina. There are about 7 million pyramidal cells in the human eye, and they are most concentrated in the central fossa of the macula. It is far less sensitive to light than cylindrical cells, but its ability to resolve image details is much stronger than cylindrical cells. Under bright conditions where the brightness level is above 0.001cd / , only pyramidal cells produce vision, which is called bright vision. In the visual process, pyramidal cells can not only provide brightness information, but more importantly, they can provide color information. Therefore, they can clearly distinguish the difference between light and dark of the viewed object, and can distinguish their color differences sharply. Pyramidal cells are the physiological basis for color vision ^[2]

KATP channels in cells

The cortex is a layer of gray matter on the surface of the cerebral hemisphere, with an average thickness of 2 to 3 mm. There are many depressed "grooves" and raised "backs" on the surface of the cortex. The total area of the adult cerebral cortex can reach 2200 square centimeters. There are about 14 billion neurons in the cerebral cortex, mainly pyramidal cells, granulosa cells, and spindle cells. Nerve cells are arranged in layers, generally divided into 6 layers from shallow to deep:

(1) Molecular layer, few cells, but many nerve fibers parallel to the surface.

(2) The outer granular layer is mainly composed of many small pyramidal cells and stellate cells.

Pyramidal cells

(3) Pyramid cell layer, mainly medium and small pyramidal cells.

(4) The inner granular layer is composed of dense stellate cells.

(5) Ganglion cell layer, which mainly contains medium and large pyramidal cells: the pyramidal cells in the central anterior gyrus are particularly large. The main component of the cone bundle.

(6) Polymorphic cell layer, mainly spindle cells, except for a part of their axons and axons of layer 5 cells, the efferent nerve fibers reach the brainstem and spinal cord, and some of them go to the same side or contralateral side of the hemisphere , Forming the joint fibers that connect the various areas of the cortex.