In all these cases, the effect of the stimulus is to produce an electrical signal in the receptors and consequently a modification in the rate of neurotransmitter release at their terminals. Outside information can take the form of light entering our eyes of mechanical deformation to cells in the cochlea or vestibule due to sound or pressure waves or of chemicals, as in our sense of smell or taste. These cells are modified to respond to “outside information” rather than to synaptic inputs from other nerve cells. Stimulus on the nervous system exerts its effects on special cells called receptors. Now that we understand neural transmission and synapses involved in basic reflexes, we can begin to ask how nerve cells are assembled into more complex structures like pools, circuits, and pathways. Visual and Auditory Reflexes & Reaction Times One example of such a complex response is the flexion withdrawal reflex, where a noxious stimulus to one leg causes withdrawal of the stimulated leg and extension of the other. Thus, more neurons and synapses are involved, which usually results in a longer delay between stimulus and response and often a more complex response. More complex reflexes usually involve additional (inter-) neurons and more than one population of motor neurons. Sensory information also ascends to higher centers, but the brain is not necessary or required to perform the reflex. The required circuitry for this reflex is confined to the spinal cord, as shown in Figure 1. Image by Marta Aguayo CC BY 3.0.Ī simple reflex like the myotactic reflex is produced via single synapses between sensory axons and motor neurons. A cross-section of the spinal cord showing the single synapse between the sensory and the motor neurons involved in a myotactic reflex. A loud sound or something flying at your eye makes you blink, while a tap on the tendon under the knee cap produces the knee-jerk (or myotactic) reflex.
A reflex is the most simple stimulus-response reaction.
Auditory nerve pathway series#
If a motor response is initiated, it usually involves a series of action potentials which produce muscle contraction and movement in one or more parts of the body. An external stimulus is detected by a receptor, which sends sensory information to the central nervous system, where it is processed. The nervous system allows us to detect changes in the environment and react to them.
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