Nerve impulses travel at different speeds, depending on the type of fiber throug

Question

Nerve impulses travel at different speeds, depending on the type of fiber through which they move. The impulses for touch travel at 76.2 m/s, while those registering pain move at 0.610 m/s. Assume that person's brain is 1.80 m from his toe and that the impulses travel directly from toe to brain.

If a person stubs his toe, find the time for the impulse for touch to reach his brain.

If a person stubs his toe, find the time for the impulse for pain to reach his brain.

Find the time delay between the pain and touch impulses.

Explanation / Answer

Assume two cars racing along the highway AB. and also assume the first car is Touch-car and the second one is Pain-car.

Given AB = 1.8m : (AB) length of Highway ( or distance from Toe to Brain)
Utc = 76.2m/s : (Utc) speed of Touch-car (or movement of impulse for touch)
Upc = 0.610 m/s : (Upc) speed of Pain-car (or movement of pain registering)

(1)
S = ut : distance travelled is given by the product of speed and time elapsed.
t = S/U
Given: impulse for touch travels =76.2 m/s means in our case (Utc = 76.2m/s)
Ttc = S/Utc ; Ttc is the time elapsed by the impulses
      = 1.8m / 76.2m/s
      = 0.023 s
      = 2.3 mili seconds   : time for impulse for touch to reach the brain. -> answer 1

(2)
Given: registering pain travels = 0.610m/s means in our case (Urp=0.610m/s)
Trp = S/Urp : Trp is the time elapsed by the registers pain
        = 1.8m/0.610m/s
        = 2.95s ; time for impulse of pain to reach the brain. -> answer 2

(3)
Time delay between the pain and touch impulses = Trp-Ttc

= (2.95-0.025)

= 2.93 s -> answer 3

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