Alerting is readiness in preparation for an impending stimulus.  This includes tonic effects and phasic effects. 


Alerting

Tonic sensory input adapts slowly to stimuli and continues to produce action potentials over the duration of the stimui. It conveys information about the duration of the stimulus. Tonic effects result from spending time on a task (vigilance).


University of Georgia

Sensory receptors are specialized neurons that are uniquely responsive to specific types of stimuli from the environment. Their function is to detect sensory information, such as light, sound, or pressure, and initiate the process of sensation.

Sensory Receptors

Tang, YY., Hölzel, B. & Posner, M. The neuroscience of mindfulness meditation. Nat Rev Neurosci 16, 213–225 (2015). https://doi.org/10.1038/nrn3916.

The Neuroscience of Mindfulness Meditation

Wikipedia

Transduction is the process by which, upon exposure to a stimulus, a receptor cell converts that energy or substance into a change in the electrical potential across its membrane. Receptor cells are transducers that convert energy around us into neural activity that leads to sensory perception.

Transduction

Sensory adaptation is the process by which conscious perception of a stimulus decreases over time due to constant exposure. By demonstrating that continuous sensory input does not always reach awareness, it serves as a key concept to help explain the difference between what is merely sensed and what is actually perceived.

Sensory Adaptation

Also known as top-down processes, neural connections descend from the brain to lower stations in the sensory pathway, in some cases as far as the receptor surface. In this top-down process, the upper brain regions modulate the activity of lower centers.

Control of Receptor Cells from Upper Levels

The receptive field of a sensory neuron consists of a region of space in which a stimulus will alter that neuron's firing rate. To determine a receptive field of a receptor cell, one must record the neuron's electrical responses to a variety of stimuli to see what makes the activity of the cell change from its resting rate. 

Receptive Fields

Tonic Receptor Cells

Phasic receptors rapidly adapt to a stimulus. The response of the cell diminishes very quickly and then stops. It conveys information on rapid changes in stimulus intensity and rate. Phasic effects result from brain changes induced by warning signals or targets.


Phasic Receptor Cells

Based on the following scenario, identify the specific type of environmental information that the auditory sensory receptors are specialized to detect, and explain the fundamental role these receptors play in the process of hearing.

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