Hypolemmal cisternae
Hypolemmal cisternae are specialized structures found within the neurons of the central nervous system (CNS). These cisternae are subtypes of the endoplasmic reticulum (ER), specifically located beneath the neuronal plasma membrane, hence the prefix 'hypo-' meaning under or beneath, and 'lemmal' referring to the cell membrane. They play a crucial role in calcium signaling and homeostasis within the neuron, contributing to the regulation of neurotransmitter release and overall neuronal activity.
Structure[edit | edit source]
Hypolemmal cisternae are characterized by their close proximity to the plasma membrane, separated by a narrow space. They are part of the smooth endoplasmic reticulum (SER), lacking ribosomes on their surface, which distinguishes them from the rough ER. Their structure is crucial for their function in calcium storage and release, as they are strategically positioned to rapidly respond to incoming signals by releasing calcium ions into the cytosol.
Function[edit | edit source]
The primary function of hypolemmal cisternae is to regulate intracellular calcium levels. Calcium ions are pivotal for various cellular processes, including muscle contraction, neurotransmitter release, and gene expression. In neurons, calcium plays a vital role in triggering synaptic vesicle fusion with the plasma membrane, leading to neurotransmitter release into the synaptic cleft. Hypolemmal cisternae release calcium in response to specific signals, such as the influx of calcium through voltage-gated calcium channels, thereby amplifying the calcium signal within the neuron.
Additionally, these structures are involved in the reuptake and storage of calcium, helping to quickly restore basal calcium levels following neuronal activation. This rapid cycling of calcium is essential for the precise control of neuronal signaling and the prevention of calcium toxicity, which can lead to neuronal damage.
Clinical Significance[edit | edit source]
Alterations in the function or structure of hypolemmal cisternae can have significant implications for neuronal health and disease. Dysregulation of calcium homeostasis is associated with various neurological disorders, including Alzheimer's disease, Parkinson's disease, and Huntington's disease. Research into the role of hypolemmal cisternae in these conditions is ongoing, with the hope that understanding these mechanisms may lead to new therapeutic targets.
See Also[edit | edit source]
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