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The action potential travels from the soma down the axon to the axon terminal. The action potential is initiated when a signal from the soma causes the soma-end of the axon membrane to depolarize. The depolarization spreads down the axon. Meanwhile, the membrane at the start of the axon repolarizes. Because potassium channels are open, the membrane cannot depolarize again. The action potential continues to spread down the axon this way.
The action potential is conducted down the axon as the axon membrane depolarizes, then repolarizes.

Synaptic transmission

The synapse or “gap” is the place where information is transmitted from one neuron to another. Synapses usually form between axon terminals and dendritic spines, but this is not universally true. There are also axon-to-axon, dendrite-to-dendrite, and axon-to-cell body synapses. The neuron transmitting the signal is called the presynaptic neuron, and the neuron receiving the signal is called the postsynaptic neuron. Note that these designations are relative to a particular synapse—most neurons are both presynaptic and postsynaptic. There are two types of synapses: chemical and electrical.

Chemical synapse

When an action potential reaches the axon terminal it depolarizes the membrane and opens voltage-gated Na + channels. Na + ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated Ca 2+ channels to open. Calcium ions entering the cell initiate a signaling cascade that causes small membrane-bound vesicles, called synaptic vesicles , containing neurotransmitter molecules to fuse with the presynaptic membrane. Synaptic vesicles are shown in [link] , which is an image from a scanning electron microscope.

The axon terminal is spherical. A section is sliced off, revealing small blue and orange vesicles just inside.
This pseudocolored image taken with a scanning electron microscope shows an axon terminal that was broken open to reveal synaptic vesicles (blue and orange) inside the neuron. (credit: modification of work by Tina Carvalho, NIH-NIGMS; scale-bar data from Matt Russell)

Fusion of a vesicle with the presynaptic neuronal plasma membrane causes neurotransmitter to be released into the synaptic cleft , the extracellular space between the presynaptic and postsynaptic cells, as illustrated in [link] . The neurotransmitter diffuses across the synaptic cleft and binds to receptor proteins on the postsynaptic cell's plasma membrane.

Illustration shows a narrow axon of a presynaptic cell widening into a bulb-like axon terminal. A narrow synaptic cleft separates the axon terminal of the presynaptic cell from the postsynaptic cell. In step 1, an action potential arrives at the axon terminal. In step 2, the action potential causes voltage-gated calcium channels in the axon terminal open, allowing calcium to enter. In step 3, calcium influx causes neurotransmitter-containing synaptic vesicles to fuse with the plasma membrane. Contents of the vesicles are released into the synaptic cleft by exocytosis. In step 4, neurotransmitter diffuses across the synaptic cleft and binds ligand-gated ion channels on the postsynaptic membrane, causing the channels to open. In step 5, the open channels cause ion movement into or out of the cell, resulting in a localized change in membrane potential. In step 6, reuptake by the presynaptic neuron, enzymatic degradation and diffusion reduce neurotransmitter levels, terminating the signal.
Communication at chemical synapses requires release of neurotransmitters. When the presynaptic membrane is depolarized, voltage-gated Ca 2+ channels open and allow Ca 2+ to enter the cell. The calcium entry causes synaptic vesicles to fuse with the membrane and release neurotransmitter molecules into the synaptic cleft. The neurotransmitter diffuses across the synaptic cleft and binds to ligand-gated ion channels in the postsynaptic membrane, resulting in a localized depolarization or hyperpolarization of the postsynaptic neuron.

The binding of a specific neurotransmitter causes particular ion channels on the postsynaptic membrane to open. Unlike the sodium channels which respond to a change in the membrane voltage (i.e., voltage-gated channels), these ion channels are classified as ligand-gated , since they open the gates in response to binding of the ligand (neurotransmitter). Neurotransmitters can either have excitatory or inhibitory effects on the postsynaptic membrane, as detailed in [link] . For example, when acetylcholine is released at the synapse between a nerve and muscle (called the neuromuscular junction) by a presynaptic neuron, it causes postsynaptic Na + channels to open. Na + enters the postsynaptic cell and causes the postsynaptic membrane to depolarize.

Questions & Answers

show that the set of all natural number form semi group under the composition of addition
Nikhil Reply
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Lukman Reply
_3_2_1
felecia
⅗ ⅔½
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_½+⅔-¾
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The denominator of a certain fraction is 9 more than the numerator. If 6 is added to both terms of the fraction, the value of the fraction becomes 2/3. Find the original fraction. 2. The sum of the least and greatest of 3 consecutive integers is 60. What are the valu
SABAL Reply
1. x + 6 2 -------------- = _ x + 9 + 6 3 x + 6 3 ----------- x -- (cross multiply) x + 15 2 3(x + 6) = 2(x + 15) 3x + 18 = 2x + 30 (-2x from both) x + 18 = 30 (-18 from both) x = 12 Test: 12 + 6 18 2 -------------- = --- = --- 12 + 9 + 6 27 3
Pawel
2. (x) + (x + 2) = 60 2x + 2 = 60 2x = 58 x = 29 29, 30, & 31
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Ifeanyi
on number 2 question How did you got 2x +2
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combine like terms. x + x + 2 is same as 2x + 2
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x*x=2
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2+2x=
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Mark and Don are planning to sell each of their marble collections at a garage sale. If Don has 1 more than 3 times the number of marbles Mark has, how many does each boy have to sell if the total number of marbles is 113?
mariel Reply
Mark = x,. Don = 3x + 1 x + 3x + 1 = 113 4x = 112, x = 28 Mark = 28, Don = 85, 28 + 85 = 113
Pawel
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find the value of 2x=32
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divide by 2 on each side of the equal sign to solve for x
corri
X=16
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Want to review on complex number 1.What are complex number 2.How to solve complex number problems.
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use the y -intercept and slope to sketch the graph of the equation y=6x
Only Reply
how do we prove the quadratic formular
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Tric Reply
4
Trista
x-2y+3z=-3 2x-y+z=7 -x+3y-z=6
Sidiki Reply
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Mark
Solve for the first variable in one of the equations, then substitute the result into the other equation. Point For: (6111,4111,−411)(6111,4111,-411) Equation Form: x=6111,y=4111,z=−411x=6111,y=4111,z=-411
Brenna
(61/11,41/11,−4/11)
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x=61/11 y=41/11 z=−4/11 x=61/11 y=41/11 z=-4/11
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Need help solving this problem (2/7)^-2
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x+2y-z=7
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what is the coefficient of -4×
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-1
Shedrak
A soccer field is a rectangle 130 meters wide and 110 meters long. The coach asks players to run from one corner to the other corner diagonally across. What is that distance, to the nearest tenths place.
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Jeannette has $5 and $10 bills in her wallet. The number of fives is three more than six times the number of tens. Let t represent the number of tens. Write an expression for the number of fives.
August Reply
What is the expressiin for seven less than four times the number of nickels
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how do you translate this in Algebraic Expressions
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why surface tension is zero at critical temperature
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Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
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. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
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Source:  OpenStax, Principles of biology. OpenStax CNX. Aug 09, 2016 Download for free at http://legacy.cnx.org/content/col11569/1.25
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