AP PSYCHOLOGY

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BIOLOGICAL BASES OF BEHAVIOR

THE NERVOUS AND ENDOCRINE SYSTEMS

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Which of the following are the characteristics of an impulse? I It follows the all or nothing law II Speed of impulse transmission is faster in myelinated axonIII Speed of impulse transmission is faster in unmyelinated axon with a smaller diameter IV In the absolute refractory period, a new impulse cannot be generated even if a strong stimulus is received
A
I, II and III
B
I, II and IV
C
I, III and IV
D
II, III and IV
Explanation: 

Detailed explanation-1: -The characteristic properties of the nerve impulse are: electrical excitability; non-decremental or uniform conduction rate of impulse under uniform conditions; all-or-none response; and absolute refractoriness during response.

Detailed explanation-2: -By acting as an electrical insulator, myelin greatly speeds up action potential conduction (Figure 3.14). For example, whereas unmyelinated axon conduction velocities range from about 0.5 to 10 m/s, myelinated axons can conduct at velocities up to 150 m/s.

Detailed explanation-3: -Myelin can greatly increase the speed of electrical impulses in neurons because it insulates the axon and assembles voltage-gated sodium channel clusters at discrete nodes along its length.

Detailed explanation-4: -Nerve impulse flows more rapidly in Myelinated nerve fiber than in the Non-nucleated fibers. In myelinated fibers the nerve impulse jumps from one node of Ranvier to another, thus it is faster.

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