System (CNS)

The CNS includes the brain and the spinal cord, which are protected by the bones of the skull and vertebral column. During its embryonic development, CNS develops from the ectoderm. Can you state why some areas of the brain and spinal cord are grey and some are white? .

. Brain The brain acts as the command and control system. It is the site of information During this, K + ion gates are more permeable to K + even after reaching the threshold level as it closes slowly; hence called Lazy gates . The membrane potential returns to its original resting state when K + ion channels close completely.

During hyperpolarization the Na + voltage gate ­remains closed (Figure . ). Conduction Speed of a nerve impulse The conduction speed of a nerve impulse depends on the diameter of axon. The greater the axon’s diameter, the faster is the conduction.

The myelinated axon conducts the impulse faster than the non - myelinated axon . The voltage-gated Na + and K + channels are concentrated at the nodes of Ranvier . As a result, the impulse jumps node to node, rather than travelling the entire length of the nerve fibre. This mechanism of conduction