Aksonipäätteet

Aksonipäätteet, also known as synaptic boutons or terminal boutons, are specialized structures found at the end of neuronal axons. These small, bulbous protrusions play a crucial role in intercellular communication within the nervous system. Their primary function is to transmit signals from one neuron to another, or to an effector cell like a muscle or gland. This transmission occurs through the release of chemical messengers called neurotransmitters.

When an electrical signal, an action potential, travels down the axon and reaches the aksonipääte, it triggers a cascade of events. Voltage-gated calcium channels open, allowing calcium ions to flow into the terminal. This influx of calcium is the key signal that initiates the release of neurotransmitters stored in small sacs called synaptic vesicles. These vesicles fuse with the presynaptic membrane of the aksonipääte, releasing their neurotransmitter contents into the synaptic cleft, the small space between the two cells.

The released neurotransmitters then diffuse across the synaptic cleft and bind to specific receptors on the postsynaptic membrane of the adjacent neuron or effector cell. This binding initiates a new electrical or cellular response in the receiving cell, thus propagating the nerve impulse. Aksonipäätteet are therefore essential components of neural circuits, enabling the complex processing and transmission of information that underlies all nervous system functions.