Question

explain a neural circuit

Answer 1

Neurons never function in isolation; they are organized into ensembles orcircuits that process specific kinds of information.

A neural circuit consists of neurons that are interconnected by synapse. Once activated, they carry a specific function. They connect forming a large scale brain network.

. The synaptic connections that define a circuit are typically made in a dense tangle of dendrites, axons terminals, and glial cell processes that together constitute neuropil . Thus, the neuropil between nerve cell bodies is the region where most synaptic connectivity occurs. The direction of information flow in any particular circuit is essential to understanding its function. Nerve cells that carry information toward the central nervous system (or farther centrally within the spinal cord and brain) are called afferent neurons; nerve cells that carry information away from the brain or spinal cord (or away from the circuit in question) are called efferent neurons. Nerve cells that only participate in the local aspects of a circuit are called interneurons or local circuit neurons. These three classes—afferent neurons, efferent neurons, and interneurons—are the basic constituents of all neural circuits.

Neural circuits are both anatomical and functional entities.

A simple example is the circuit that subserves the myotatic (or “knee-jerk”) spinal reflex .The afferent limb of the reflex is sensory neurons of the dorsal root ganglion in the periphery. These afferents target neurons in the spinal cord. The efferent limb comprises motor neurons in the ventral horn of the spinal cord with different peripheral targets: One efferent group projects to flexor muscles in the limb, and the other to extensor muscles. The third element of this circuit is interneurons in the ventral horn of the spinal cord. The interneurons receive synaptic contacts from the sensory afferent neurons and make synapses on the efferent motor neurons that project to the flexor muscles. The synaptic connections between the sensory afferents and the extensor efferents are excitatory, causing the extensor muscles to contract; conversely, the interneurons activated by the afferents are inhibitory, and their activation by the afferents diminishes electrical activity in motor neurons and causes the flexor muscles to become less active .

The result is a complementary activation and inactivation of the synergist and antagonist muscles that control the position of the leg.