Question

8. Fill in the Blanks:

A nerve ____ is generated when a nerve receives a stimulus above ______.

During the depolarization of a nerve cell membrane, ______ ions move into the neuron.

During the repolarization of a nerve cell membrane, _______ ions move out of the neuron.

Following an action potential the short period of time when sodium gates cannot open is called the _____ period. After this time, the ______ pump will ______ transport _____ ions into the neuron and ________ ions out of the neuron to re-establish the ________ potential

A nerve ________ is generated when a nerve receives a stimulus above ________.

During the depolarization of a nerve cell membrane, _______ ions move into the neuron.

During the repolarization of a nerve cell membrane, ________ ions move out of the neuron.

Following an action potential the short period of time when sodium gates cannot open is called the _____ period. After this time, the ______ pump will ______ transport ________ ions into the neuron and _______ ions out of the neuron to re-establish the _______ potential.

9. Explain in a short paragraph why myelinated nerves carry impulses much faster than unmyelinated nerves. Use the following terms in your explanation: Schwann cell, saltatory conduction, Nodes of Ranvier, action potential, myelin sheaths, sensory and motor neurons.

Answer 1

Answer 8:

A nerve impulse is generated when a nerve receives a stimulus above threshold of excitation.

During the depolarization of a nerve cell membrane, Na+ ions move into the neuron.

During the repolarization of a nerve cell membrane, K+  ions move out of the neuron.

Following an action potential the short period of time when sodium gates cannot open is called the refractory period.

After this time, the sodium/potassium pump will not transport Na+ ions into the neuron and K+ ions out of the neuron to re-establish the action  potential

Answer 9: Myelin sheath,which is basically a fatty layer and is made up of schwann cells which covers the neuron's axon. The place where one cell's sheath meets with the next is the unprotected part of axon and these are called Nodes of Ranvier.The Sodium ion channels (which are Voltage gated) are only present in the nodes.The sodium influx created at one node leads to the required depolarization which causes the threshold to reach to next node.The action potential hence travels from one node to other instead of traversing complete axon length. This phenomena is called saltatory conduction. The quick conduction of signal travels from one node to another node and another action potential is created, which refreses the signal. thats how myelinated nerves carry inpulse much faster than unmyelinated nerves