A physiology student who spent the night celebrating the successful completion of the first midterm wakes to find himself lying face-down in the gutter. He realizes that the reason he can still detect the pressure of the concrete pressing against his face, despite having been there for hours, is the presence of: a. None of the answers is correct. b. tonic mechanoreceptors. c. phasic chemoreceptors. d. tonic chemoreceptors. e. phasic mechanoreceptors.
The correct answer and explanation is:
The correct answer is: b. tonic mechanoreceptors.
Explanation:
The sensation of pressure, in this case, that the student detects while his face is pressed against the concrete, is mainly due to tonic mechanoreceptors. These receptors are specialized sensory nerve endings that are sensitive to mechanical stimuli such as pressure, stretch, or vibration.
Tonic mechanoreceptors are slow-adapting receptors, meaning they continue to send signals to the brain for as long as the stimulus is present. This is why the student can still perceive the pressure of the concrete even after lying face-down for an extended period of time. These receptors are crucial for detecting prolonged stimuli, such as steady pressure or constant touch, and they provide the brain with continuous information about the ongoing presence of a stimulus. In this scenario, the sustained pressure of the concrete on his face is continuously being registered by these tonic mechanoreceptors.
On the other hand, phasic mechanoreceptors are fast-adapting receptors, meaning they respond to changes in the stimulus. They would detect the initial contact or pressure when the student first hits the ground but would not continue to send signals once the pressure is constant.
Chemoreceptors (both tonic and phasic) are involved in detecting chemical stimuli, such as changes in oxygen, carbon dioxide, or pH levels. They would not play a role in detecting the mechanical pressure of the concrete against the student’s face.
Therefore, tonic mechanoreceptors are the ones responsible for the continuous sensation of pressure in this situation, making them the correct answer.