====== Excitatory Neuron ======

{{:icons:neuron_excitation.png?direct&50 |}} **Excitatory neurons** are neurons that depolarize the postsynaptic membrane, increasing the likelihood of an action potential.

~~TAG:neuron,excitatory,neurotransmitter,glutamate~~

===== 🧠 Overview =====

  * Main neurotransmitter: **Glutamate**
  * Effect: **Depolarization** (Excitatory postsynaptic potential — EPSP)
  * Typical receptors: **AMPA, NMDA, kainate, mGluRs**
  * Synapse type: **Asymmetric (Gray’s Type I)**
  * Common example: **Pyramidal neurons** in the cortex

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==== 🔬 Characteristics ====

^ Feature ^ Description ^
| Neurotransmitter | Glutamate |
| Synapse Type     | Asymmetric (Gray’s Type I) |
| Postsynaptic Effect | Excitatory (depolarization) |
| Location         | Cortex, hippocampus, thalamus |
| Receptors        | AMPA, NMDA, kainate, mGluRs |
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==== 🧪 Functional Role ====

Excitatory neurons are crucial for:

  * Sensory processing
  * Learning and memory
  * Long-range projections (e.g., corticospinal tract)
  * Shaping neural circuit output

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==== 🧬 Example: Cortical Pyramidal Neuron ====

Pyramidal neurons are:

  * **Multipolar** cells with a pyramid-shaped soma
  * Located in **layers 3 and 5** of the neocortex
  * The **main output** cells of the cerebral cortex
  * Their axons project to other brain regions or spinal cord

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The basic excitatory neurons of the cerebral cortex, the [[pyramidal cell]]s, are the most important signal integrators for the local circuit. They have quite characteristic morphological and electrophysiological properties that are known to be largely constant with age in the young and adult [[cortex]]. However, the brain undergoes several dynamic changes throughout life, such as in early development phases and cognitive decline in the aging brain. 
Barzó et al. set out to search for intrinsic cellular changes in supragranular pyramidal cells across a broad age range: from birth to 85 years of age, and they found differences in several biophysical properties between defined age groups. During the first year of life, subthreshold and suprathreshold electrophysiological properties changed in a way that shows that [[pyramidal cell]]s become less excitable with maturation, but also become temporarily more precise. According to the findings, the morphological features of the three-dimensional reconstructions from different life stages showed consistent morphological properties, and systematic dendritic spine analysis of an infantile and an old pyramidal cell showed clear, significant differences in the distribution of spine shapes. Overall, the changes that occur during development and aging may have lasting effects on the properties of pyramidal cells in the cerebral cortex. Understanding these changes is important to unravel the complex mechanisms underlying brain development, cognition, and age-related [[neurodegenerative disease]]s
((Barzó P, Szöts I, Tóth M, Csajbók ÉA, Molnár G, Tamás G. [[Electrophysiology]] and [[morphology]] of human cortical supragranular pyramidal cells in a wide age range. Elife. 2025 Mar 28;13:RP100390. doi: 10.7554/eLife.100390. PMID: 40152903.))