Motor end-plate

Motor End-Plate

The Motor end-plate, also known as the neuromuscular junction or myoneural junction, is a specialized synapse where a motor neuron communicates with a skeletal muscle fiber. It plays a crucial role in the conversion of electrical signals from the motor neuron into chemical signals to stimulate muscle contraction.

Structure

The motor end-plate is composed of two main parts: the presynaptic terminal of the motor neuron and the postsynaptic membrane of the muscle fiber. The presynaptic terminal contains synaptic vesicles that store neurotransmitters, specifically acetylcholine. The postsynaptic membrane, also known as the motor end-plate, contains acetylcholine receptors that bind to the acetylcholine released from the presynaptic terminal.

Function

The primary function of the motor end-plate is to transmit signals from the motor neuron to the muscle fiber. This process begins when an action potential reaches the presynaptic terminal, triggering the release of acetylcholine into the synaptic cleft. The acetylcholine then binds to the acetylcholine receptors on the postsynaptic membrane, causing an influx of sodium ions and generating an end-plate potential. If this potential reaches the threshold, it triggers an action potential in the muscle fiber, leading to muscle contraction.

Clinical Significance

Dysfunction of the motor end-plate can lead to various neuromuscular disorders. For example, myasthenia gravis is an autoimmune disease characterized by the production of antibodies against acetylcholine receptors, leading to muscle weakness and fatigue. On the other hand, Lambert-Eaton syndrome is a condition where antibodies are produced against voltage-gated calcium channels in the presynaptic terminal, reducing the release of acetylcholine and causing muscle weakness.

See Also

• Neuron
• Muscle contraction
• Synapse
• Neurotransmitter
• Acetylcholine