Bibliographic record
Abstract
In general terms, neurons communicate with each other through chemical messengers called neurotransmitters. Given the complexity of the brain, it should not be surprising that there are more than 100 known neurotransmitters (Purves et al . 2008). Neurotransmitters are synthesized in nerve cells, sometimes using precursors from the diet (e.g. tyrosine; see Figure 5.8), and are released into the synapse where they bind to specific receptors located on the postsynaptic cell. As discussed in the present chapter, this simple view conceals the many fascinating ways in which neurons communicate with each other. This chapter focuses on the different categories of neurotransmitters, the synthesis, storage, transport and release of neurotransmitters, their action at receptors and their deactivation. The influence of drugs on neurotransmitter function will also be discussed. Chapter 6 examines the specific effects of neurotransmitters in the neuroendocrine system, and Chapter 10 covers the actions of neurotransmitters at their receptors on postsynaptic cells. The neuron and the synapse A typical neuron is shown in Figure 5.1. Neurons possess a cell body, which contains the nucleus, and the characteristic dendrites plus an axon. The dendrites receive messages from other cells onto their spines and shafts, while the axon transmits information to other cells. Although each nerve cell has only one axon, this axon may have a number of branches and the nerve terminals at the end of each branch can form synapses with other neurons. Nerve cells communicate with each other by the release of neurotransmitters from the nerve terminals of the axon into the synapse, the space that separates the presynaptic and postsynaptic cells. Neurotransmitters released into the synapse then bind to their receptors on the postsynaptic cell. As shown in Figure 5.1, synapses can form between the axon of the presynaptic cell and a number of different sites on the postsynaptic cell, including the shafts and/or spines of dendrites (axodendritic synapses), the cell body (axosomatic synapses) and the axons (axoaxonic synapses).
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.098 | 0.069 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".