Structure
The axon hillock has a number of specialized properties that make it capable of action potential generation, including adjacency to the axon and a much higher density of voltage-gated ion channels than is found in the rest of the cell body. In electrophysiological models, the axon hillock is lumped in with the initial segment of the axon where membrane potentials propagated from synaptic inputs to the dendrites or cell body are summed. In dorsal root ganglion cells, the cell body is thought to have approximately 1 voltage-gated sodium channel per square micrometre, while the axon hillock and initial segment of the axon have about ~100-200 voltage-gated sodium channels per square micrometre; in comparison, the nodes of Ranvier along the axon are thought to have ~1000-2000 such channels per square micrometre. This clustering of voltage-gated ion channels is a consequence of plasma-membrane and cytoskeletal associating proteins such as ankyrin.
Read more about this topic: Axon Hillock
Famous quotes containing the word structure:
“Women over fifty already form one of the largest groups in the population structure of the western world. As long as they like themselves, they will not be an oppressed minority. In order to like themselves they must reject trivialization by others of who and what they are. A grown woman should not have to masquerade as a girl in order to remain in the land of the living.”
—Germaine Greer (b. 1939)
“If rightly made, a boat would be a sort of amphibious animal, a creature of two elements, related by one half its structure to some swift and shapely fish, and by the other to some strong-winged and graceful bird.”
—Henry David Thoreau (1817–1862)
“A structure becomes architectural, and not sculptural, when its elements no longer have their justification in nature.”
—Guillaume Apollinaire (1880–1918)