PHSI2005 Study Guide - Final Guide: Neocortex, Motor Cortex, Central Sulcus

You step onto a hot beach with your bare feet. A nerve impulse, generated in your foot, travels through your nervous system at an average speed of 118 m/s. How much time does it take for the impulse, which travels a distance of 1.58 m, to reach your brain?

Experiments have shown that the nervous system of the human eyeeffectively takes 30 "frames" per second (like a movie camera) andthat when the eye is fully dark-adapted, it needs to receive onlyabout 500 photons per frame from an object to register it. Our sunradiates a power of about 3.9x10²⁶ at all wavelengths,peaking in the yellow region of the spectrum (only about one-halfof this energy is in the visible range, however).

Estimate how far away a star like the sun could be and still bevisible.

Neurons are components of the nervous system of the body that transmit signals as electric impulses travel along their length. These impulses propagate when the charge suddenly rushes into and then out of a part of the neuron called an axon. Measurements have shown that, during the inflow part of this cycle, approximately 5.6×10^{11}Na+ (sodium ions) per meter, each with charge +e, enters the axon. How many coulombs of charge enters a 1.5-cm length of the axon during this process?