Chapter 2.3 The Nerve Impulse

Question 1

______ is a tiny, brief “spike” of electricity traveling through a neuron.

Answer 1

Nerve impulse

Question 2

proteins embedded in the cell membrane of
an axon that serve many functions such as ______

Answer 2

channels, gates, and pumps to permit ion movement

Question 3

What are the 2 kinds of ions that move in and out the membrane?

Answer 3

sodium ions and potassium ions

Question 4

What are the 4 major mechanism of nerve impulse conduction?

Answer 4

Resting Potential, Action Potential, Saltatory Conduction, Refractory Period

Question 5

In the absence of any stimulation or when the neuron is not currently
receiving or sending messages, the membrane potential is at rest. Using a microelectrode
recording that measures electrical charges in the membrane, one tip of electrode is attached
inside the neuron and the tip of another electrode outside the neuron in the extracellular fluid.

Answer 5

Resting Potential

Question 6

It is more negative inside than outside. Specifically, there are more Na+
ions outside the cell than inside and more K+ ions inside than outside, tis is also called____

Answer 6

polarization

Question 7

In the presence of stimulation or when a neuron is receiving
messages sent by the axon, it decreases the negativity of charge inside the membrane,
reducing its polarization toward zero (Depolarization), or from negative to positive. The action potential travels at
a velocity of less than 1 meter/second and is independent of the intensity of the stimulus that
initiated it. Meaning, once started, the nerve impulse cannot be stopped, says the All-or-None
Law.

Answer 7

Action Potential

Question 8

After an action potential occurs at a node, sodium ions enter the axon
and diffuse, pushing a chain of positive charge along the axon to the next node, or the action
potential “jump” from node to node where they regenerate it. Saltatory conductions are fastest
in myelinated axons.

Answer 8

Saltatory Conduction

Question 9

At the peak of action potential, an absolute refractory period occurs where
the axon resists the production of further action potentials regardless of the stimulation, and
the sodium ion channel is shut up. It is followed by a relative refractory period, when a
stronger- than-usual stimulus is necessary to initiate an action potential. Patients with multiple
sclerosis have vision, arm or leg movement, sensation or balance problems caused by a
damage in the myelin sheath.

Answer 9

Refractory Period