How Neurons Communicate Part 1 of 2

Once the signal is delivered, excess neurotransmitters in the synaptic cleft drift away, are broken down into

1. inactive fragments 2. or are reabsorbed in a process known as reuptake.

An action potential involves Sodium moving ________ the cell and Potassium moving ________ the cell.

Action potential involves sodium moving inside the cell and potassium moving outside of the cell

Which of the following is the correct order of events describing the movement of an electrical charge through a neuron?

Dendrite, cell body, axon

(2) The neurotransmitters travel across the synapse and bind to receptors on the dendrites of the adjacent neuron, and the process repeats itself in the

New neuron (assuming the signal is sufficiently strong to trigger an action potential)

neuronal membrane

The neuron exists in a fluid environment—it is surrounded by extracellular fluid and contains intracellular fluid (i.e., cytoplasm). The neuronal membrane keeps these two fluids separate

What restricts the movement of these charged molecules (ions)

The semipermeable nature of the neuronal membrane. and, as a result, some of the charged particles tend to become more concentrated either inside or outside the cell.

the peak action potential

a massive influx of Na+ ions and a huge positive spike in the membrane potential,

and positive ions are ready to move to

areas with a negative charge.

At first, it hyperpolarizes,

becoming slightly more negative than the resting potential, and then it levels off, returning to the resting potential.

The electrical charge of the fluids is caused by

charged molecules (ions) dissolved in the fluid

At the peak of the spike, the sodium gates..

close and the potassium gates open.

The input sites of neurons where signals are received from other neurons are known as

dendrites

process of when the cell's charge becomes positive, or less negative, is called

depolarization.

Neuronal communication is often referred to as an

electrochemical event

1. the electrical signal that passes through the neuron depends on the

intra- and extracellular fluids being electrically different

Reuptake

involves the neurotransmitter being pumped back into the neuron that released it, in order to clear the synapse

Ions in high-concentration areas are ready to move to

low-concentration areas

Many additional pores open, causing a

massive influx of Na+ ions and a huge positive spike in the membrane potential

2. the difference in charge across the membrane, called the

membrane potential, provides energy for the signal.

1. In the resting state, sodium (Na+) is at higher concentrations outside the cell, so it will tend to

move into the cell

ions line up on either side of the cell membrane, ready to rush across the membrane when the

neuron goes active and the membrane opens its gates (i.e., a sodium-potassium pump that allows movement of ions across the membrane).

The electrical signal moves down the axon like a wave; at each point, some of the sodium ions that enter the cell diffuse to the next section of the axon, raising the charge past the threshold of excitation and triggering a;

new influx of sodium ions

Clearing the synapse serves both to provide a clear "on" and "off" state between signals and to regulate the

production of neurotransmitter (full synaptic vesicles provide signals that no additional neurotransmitters need to be produced).

As positively charged potassium ions leave, the cell quickly begins

repolarization

Between signals, the neuron membrane's potential is held in a state of readiness, called the

resting potential

ex of an electrical event

the movement of the action potential down the length of the axon is an electrical event

when the action potential arrives at the terminal button, the synaptic vesicles release (1)

their neurotransmitters into the synaptic cleft.

(2.) With this influx of positive ions, the internal charge of the cell becomes more positive. If that charge reaches a certain level, called the

threshold of excitation, the neuron becomes active and the action potential begins.

the inside of the cell is slightly negatively charged compared to the outside. This provides an

additional force on sodium, causing it to move into the cell.

The action potential is an all-or-none phenomenon

an incoming signal from another neuron is either sufficient or insufficient to reach the threshold of excitation there is no turning off an action potential once it starts

the action potential is recreated, or propagated, at its full strength at every point along the

axon

2. Potassium (K+), on the other hand, is more concentrated inside the cell, and will tend to

move out of the cell

ex of the chemical portion of the process.

movement of the neurotransmitter across the synaptic space represents the chemical portion of the process.

When resting, the inside of a cell has a ________ charge. During action potential, the cell briefly has a ________ charge.

negative; positive

When neuron receives signals at the dendrites— (due to neurotransmitters from an adjacent neuron binding to its receptors) (1.)

small pores, or gates, open on the neuronal membrane, allowing Na+ ions. propelled by both charge and concentration differences, to move into the cell. *side note.

The action potential moves all the way down the axon to the

terminal buttons.

This positive spike constitutes the action potential:

the electrical signal that typically moves from the cell body down the axon to the axon terminals.