Monosynaptisiin

Monosynaptisiin refers to a monosynaptic reflex arc. This is the simplest type of neural pathway that mediates a reflex. It involves a single synapse between a sensory neuron and a motor neuron. When a sensory receptor is stimulated, the sensory neuron transmits an impulse to the spinal cord. In the spinal cord, this sensory neuron directly synapses with a motor neuron. The motor neuron then carries the impulse to an effector, such as a muscle, causing a rapid response. This direct connection between the sensory and motor neuron is what characterizes a monosynaptic reflex.

The most well-known example of a monosynaptic reflex is the stretch reflex, commonly observed in the patellar reflex or knee-jerk reflex. When the patellar tendon is tapped, the quadriceps muscle is stretched. This stretch is detected by muscle spindles, which are sensory receptors within the muscle. The sensory neuron from the muscle spindle sends an impulse to the spinal cord, where it directly excites a motor neuron. This motor neuron then sends an impulse back to the quadriceps muscle, causing it to contract and extend the lower leg. The speed of the response is crucial for maintaining posture and balance, as it occurs before conscious processing by the brain. The monosynaptic nature of this reflex allows for a very quick reaction time.