What is neuromuscular junction and its function?
The neuromuscular junction (NMJ) is a highly specialized synapse between a motor neuron nerve terminal and its muscle fiber that are responsible for converting electrical impulses generated by the motor neuron into electrical activity in the muscle fibers.
What neurotransmitter is released at the neuromuscular junction?
Acetylcholine (ACh) is the principal neurotransmitter at the vertebrate neuromuscular junction (NMJ), however since the discovery that motoneurons and presynaptic terminals of rodent endplates from the hindlimb muscles extensor digitorum longus (EDL) and soleus are positive for glutamate labelling [1,2], it has been …
What is synaptic gutter?
Figure 7-1C shows the junction between a single axon terminal and the muscle fiber membrane. The invaginated membrane is called the synaptic gutter or synaptic trough, and the space between the terminal and the fiber mem- brane is called the synaptic space or synaptic cleft.
Is motor end plate same as neuromuscular junction?
Neuromuscular junctions, also called motor end plates, are specialised chemical synapses formed at the sites where the terminal branches of the axon of a motor neuron contact a target muscle cell.
What are neuromuscular junction disorders?
Neuromuscular junction disorders (dysfunction at location where nerves connect with muscles): Myasthenia gravis – communication problem between nerves and muscles results in muscle weakness and muscle fatigue. Lambert-Eaton Syndrome – often coincides with cancer, causing muscle weakness.
What events take place at the neuromuscular junction?
A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. Muscles require innervation to function—and even just to maintain muscle tone, avoiding atrophy.
What is MEPP and EPP?
Acetylcholine is released in bursts, or quanta. A single quantum causes only a slight depolarization, called a miniature end-plate potential (MEPP). One hundred to 200 quanta, released simultaneously or in rapid series by a nerve impulse, cause multiple MEPPs, which summate, or combine, to produce an EPP.
How does acetylcholine cause depolarisation?
The nicotinic acetylcholine receptors are ligand-gated cation channels, and open when bound to acetylcholine. The receptors open, allowing sodium ions to flow into the muscle’s cytosol. The electrochemical gradient across the muscle plasma membrane causes a local depolarization of the motor end-plate.
What does an endplate contain?
transmission of nerve impulse This receptor, called the end plate, is a glycoprotein composed of five subunits. Other neurotransmitter receptors do not have the same structure, but they are all proteins and probably have subunits with a central channel that is activated by the neurotransmitter.
What is the most common neuromuscular junction disorder?
The most common pathology is antibody mediated damage or down regulation of ion channels or receptors, resulting in myasthenia gravis (MG), Lambert-Eaton myasthenic syndrome (LEMS), and acquired neuromyotonia (Isaac’s syndrome). Not surprisingly these three conditions share many common features (table 1).
What will happen if any damage occurs in the neuromuscular junction?
Neuromuscular junction disorders typically decrease nerve cell activity and cause muscle weakness. But they do not affect sensation (that is, they do not cause loss of sensation or abnormal sensations, such as tingling or a pins-and-needle sensation).