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Cerebellar granule cells form the thick granular layer of the cerebellar cortex and are among the smallest neurons in the brain. (The term granule cell is used for several unrelated types of small neurons in various parts of the brain.) Cerebellar granule cells are also the most numerous neurons in the brain: in humans, estimates of their total ...
These cells are some of the largest neurons in the human brain (Betz cells being the largest), [5] with an intricately elaborate dendritic arbor, characterized by a large number of dendritic spines. Purkinje cells are found within the Purkinje layer in the cerebellum. Purkinje cells are aligned like dominos stacked one in front of the other.
For example, in the rat, the two hippocampi look similar to a pair of bananas, joined at the stems. In humans and other primates, the portion of the hippocampus near the base of the temporal lobe is much broader than the part at the top. Due to the three-dimensional curvature of the hippocampus, two-dimensional sections are commonly presented.
The two types are different appearance and are primarily located on different parts of the neurons under its influence. [20] Receptors with modulatory effects are spread throughout all synaptic membranes and binding of neurotransmitters sets in motion signaling cascades that help the cell regulate its function. [8]
The signaling process is partly electrical and partly chemical. Neurons are electrically excitable, due to the maintenance of voltage gradients across their membranes . If the voltage changes by a large enough amount over a short interval, the neuron generates an all-or-nothing electrochemical pulse called an action potential .
Brain cells make up the functional tissue of the brain. The rest of the brain tissue is the structural stroma that includes connective tissue such as the meninges , blood vessels , and ducts. The two main types of cells in the brain are neurons , also known as nerve cells, and glial cells , also known as neuroglia. [ 1 ]
Pyramidal neurons are also one of two cell types where the characteristic sign, Negri bodies, are found in post-mortem rabies infection. [2] Pyramidal neurons were first discovered and studied by Santiago Ramón y Cajal. [3] [4] Since then, studies on pyramidal neurons have focused on topics ranging from neuroplasticity to cognition.
Iain Davidson summarizes the opposite evolutionary constraints on human brain size as "As large as you need and as small as you can". [29] The human brain has evolved around the metabolic, environmental, and social needs that the species has dealt with throughout its existence. As hominid species evolved with increased brain size and processing ...