Question

1. Explain how size of a local sensory potential affects afferent action potentials.

2. Describe an experimental technique to assess the sensitivities to different frequencies of sound (Hz) OR to different wavelengths of light.

Answer 1

Explanation:

1. Size of local sensory potential affects afferent action potential

A local potential is also called as gradient potential. It occurs as a small change in the resting membrane potential of a neuron. This potential can occur in plasma membrane of neurons or membranes that are involved in receiving sensory stimuli. A graded potential occurs for shorter duration and depends on the received stimulus. The amplitude is very small for a local potential which is approximately 10mV and for action potential is 100 mV. The amplitude of a local potential is proportional to strength of the stimulus and that based on the stimulus it can either depolarize or hyperpolarize a membrane. A local potential is created by an external stimuli which is carried by sensory neurons to be released at the synapse. The graded potentials at the post-synaptic cell produce depolarization. The ligand gated sodium gate pushes more sodium ions into the neuron membrane causing it to depolarize. This local depolarization potentials sums up to reach the threshold potential that initiates action potential in that cell. The voltage measured as potential energy and current which is the difference in ionic charges are important factors that is essential for conversion of local to action potential. Therefore, the size of the local potential is essential to creating an action potential.

2. Experiment to evaluate sensitivity

a. Different sound frequencies: The experiment to evaluate sensitivity to different frequency of sounds in an individual is termed as auditory threshold. This is a psychophysical method. The human ear is an organ that can identify sound vibrations. The ear can perceive sounds from range of 20 to 20,000 Hz. The auditory threshold detects both amplitude and frequency of sounds that are sensitive to the ear. The amplitude is measured as decibels (dB) and the frequency is measured as hertz (Hz).

b. Different light wavelengths: The experiment to measure different wavelengths at different intensities is called as spectral sensitivities. It is an electrophysiological study where different wavelength produce different electrical response which can be measured by flash methods recorded by means of an electrode. Currently sensor methods or quantum efficiency methods are used for measurement. In sensor systems, the output of wavelength is quantified as spectral input–output data via standard linear methods. In quantum efficiency the quantum of light is captured as electrons is measured as the function of wavelengths.