Ca1 hippocampus anatomy
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those cells nearest to the CA1 - Sb junction are connected, and those furthest apart are connected. The distal end of the CA1 region projects to the proximal end of the Sb, i.e. The connection from CA1 - Sb follows a strict anatomical layout. However, it is not a straightforward uni-directional pathway. The pathway from CA1 to Subiculum (Sb) and on to the entorhinal cortex forms the principal output from the hippocampus. This pathway is utilised very extensively exhibits to study NMDA receptor-dependent LTP and LTD.
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These latter fibres are termed commissural fibres, as they cross from one hemisphere of the brain to the other. The axons either come from neurons in the same hippocampus (ipsilateral) or from the other hippocampus ( contralateral). This pathway is derived from axons that project from the CA3 region of then hippocampus to the CA1 region. Schaffer Collateral/Associational Commissural Pathway For instance, LTP is NMDA receptor-independent in this pathway, but instead appears to involve pre-synaptic kainate receptors. This pathway is studied extensively as a model for the functional roles of kainate receptors in synaptic plasticity. Multiple granule cells can synapse onto a single CA3 pyramidal cell. MF synapses on CA neurons are large aggregations of termini, with multiple transmitter release sites and post-synaptic densities. They extend from the dendate gyrus to CA3 pyramidal cells, forming their major input. The mossy fibres are the axons of DG granule cells. These neurons in turn send the main hippocampal output back to the EC, forming a loop. CA1 neurons also receive inputs direct from the Perforant Path and send axons to the Subiculum (Sb). They send axons to CA1 pyramidal cells via the Schaffer Collateral Pathway (SC), as well as to CA1 cells in the contralateral hippocampus via the Associational Commisural (AC) Pathway. CA3 neurons also receive input from the DG via the Mossy Fibres (MF). The hippocampal Network: The hippocampus forms a principally uni-directional network, with input from the Entorhinal Cortex (EC) tht forsms connections with the Dentate Gyrus (DG) and CA3 pyramidal neurons via the Perforant Path (PP - split into lateral and medial). Iit was in this pathway that long-term potentiation (LTP) was first discovered. The perforant path can be segregated into lateral and medial pathways ( LPP and MPP, respectively), depending on whether the fibres arise from the lateral or medial entorhinal cortex. Axons from layers II/IV project to the granule cells of the dentate gyrus (DG) and pyramidal cells of the CA3 region, while those from layers III/V project to the pyramidal cells of the CA1 and the subiculum. The axons of the perforant path arise principally in layers II and III of the entorhinal cortex (EC), with minor contributions from the deeper layers IV and V.
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The perforant path is the major input to the hippocampus. The main pyramidal cell layers are the CA1-4 regions (principally CA1 and CA3) and the dentate gyrus.
#Ca1 hippocampus anatomy series
The different cell layers and sections are defined by the series of connections made. Thus there are defined routes for information flow making the hippocampus a very popular target for the study of synaptic function. They form well-characterised closed loops that originate mainly in the adjacent entorhinal cortex. The connections within the hippocampus generally follow this laminar format and, as a rule, are uni-directional. The hippocampus is formed by two interlocking sheets of cortex and in cross-section has a very defined laminar structure with layers visible where rows of pyramidal cells are arranged. It is critical to spatial learning and awareness, navigation, episodic/event memory, associational recollection. together with the adjacentĪmygdyla, it forms the central axis of the Neural pathways Hippocampal Pathways Introduction The hippocampus is perhaps the most studied structure in the brain.