Name: neuron signaling and synapses
Uploaded: 2025-05-22T09:05:36.000Z
Duration: 1 min 30 s
Channel: JoVE

Neurons are cells of the nervous system that transmit electrical signals. Typically a neuron has a cell body or soma - containing the nucleus, highly branched structures called dendrites, and an axon that extends from the cell body.
Dendrites receive signals from other neurons at junctions called synapses. The axon hillock, where the cell body meets the axon, generates the action potential, the primary form of electrical signaling in the nervous system. The axon then transmits the action potential to other neurons and cells.
Axons are often wrapped in a fatty myelin sheath made by supporting cells called glia, which insulates them, helping to maintain the electrical signal as it is transmitted along. The nodes of Ranvier, gaps in the myelin sheath, are regions where the action potential is repeatedly regenerated down the axon.
The axon terminal contains synaptic vesicles filled with neurotransmitter molecules. When an action potential reaches the terminal, neurotransmitters are released into the synaptic cleft, a region of space between cells at a synapse.
Different neurotransmitters can have varying effects on the target cell, namely excitatory - initiating an action potential, or

neuron structure

Neuron Structure

Neurons are the main type of cell in the nervous system that generate and transmit electrochemical signals. They primarily communicate with each other using neurotransmitters at specific junctions called synapses. Neurons come in many shapes that often relate to their function, but most share three main structures: an axon and dendrites that extend out from a cell body.
Structure and Function of Neurons
The neuronal cell body&#8212;the soma&#8212; houses the nucleus and organelles vital to cellular function. Extending from the cell body are thin structures that are specialized for receiving and sending signals. Dendrites typically receive signals while the axon passes on the signals to other cells, such as other neurons or muscle cells. The point at which a neuron makes a connection to another cell is called a synapse.
Neurons receive inputs primarily at postsynaptic terminals, which are frequently located on spines&#8212;small bumps protruding from the dendrites. These specialized structures contain receptors for neurotransmitters and other chemical signals. Dendrites are often highly branched, allowing some neurons to receive tens of thousands of inputs. Neurons most commonly receive signals at their dendrites, but they can also have synapses in other areas, such as the cell body.
The signal received at the synapses travels down the dendrite to the soma, where the cell can process it and determine whether it should send the message forward or not. The action potential is the main electrical signal generated by neurons. It carries the information forward onto the next cell. It is first generated at the axon hillock&#8212;the junction between the soma and the axon.
Axons vary in length but can be quite long. For example, some extend from the spinal cord all the way to the foot. Longer axons are usually wrapped in a fatty myelin sheath that insulates the axon, helping to maintain the electrical signal. The myelin sheath is created by glia&#8212;another type of cell in the nervous system. In myelinated axons, the action potential is regenerated at each node of Ranvier&#8212;repeated gaps in the myelin&#8212;until it reaches the terminal at the end of the axon or presynaptic terminal.
The presynaptic terminal has vesicles that contain pools of neurotransmitters. Action potentials trigger the vesicles to undergo exocytosis by fusing to the cell membrane and releasing neurotransmitters into the synaptic cleft&#8212;the gap between cells at a synapse. Different neurotransmitters can have varying effects on the postsynaptic cell. An excitatory synapse increases the chances of initiating an action potential on the postsynaptic cell, while an inhibitory synapse decreases the chances of an action potential.
Neuronal Morphology
The overall shape of neurons&#8212;their morphology&#8212;can vary dramatically and often relates to their function. Some neurons have few dendritic processes and a single axon; others have very convoluted dendritic arbors, while others have axons that can span the length of the organism. The diverse morphologies are often used to define the type of neuron. The number of inputs&#8212;synaptic connections&#8212;can influence how a cell responds to signals. Therefore, the morphology of the dendrites, and the number of synapses they contain, is an important features that can determine the type of neuron. In the peripheral nervous system, the dendrites can also define the receptive field of a cell&#8212;the physical space on the body that they are sensitive to.
The Art of Visualizing Neuronal Structures
The Spanish anatomist Santiago Ramon y Cajal, working in the late 19th and early 20th century, pioneered the tracing of individual neurons and provided fundamental insights into their very nature. He produced stunning depictions of cells that still offer a considerable amount of detail. Using the staining technique developed and named after the Italian biologist Camillo Golgi, he was able to trace the structure of many different kinds of cells in the brain. He also sketched some of the basic connections of neuronal circuits&#8212;networks of neurons that are activated together to process specific information.

Neurons are the main type of cell in the nervous system that generate and transmit electrochemical signals. They primarily communicate with each other ...

Education

JoVE Core

Cell Biology

Unit 1

Channels and the Electrical Properties of Membranes

channels-and-the-electrical-properties-of-membranes

KEY TERMS AND CONCEPTS

neuron signaling and synapses

Neurons are the main cells of the nervous system that generate and pass along electrochemical signals. They communicate with one another mainly through neurotransmitters at special connections called synapses. Neurons can have different shapes, and those shapes often match their function. Most, however, share three main parts: a cell body, dendrites, and an axon.

The cell body, or soma, contains the nucleus and the organelles needed for cell activity. Dendrites extend from the soma and usually receive signals. The axon carries signals to other cells, such as other neurons or muscle cells. The point where a neuron connects with another cell is called a synapse.

Inputs are received mainly at postsynaptic terminals. These are often found on dendritic spines, which are small bumps on dendrites. Spines contain receptors for neurotransmitters and other chemical signals. Because dendrites are often highly branched, some neurons can receive tens of thousands of inputs. Neurons can also receive synapses in other places, including the cell body.

The signal from a synapse travels down the dendrite to the soma. There, the cell processes the information and decides whether to pass the message on. The main electrical signal made by neurons is the action potential. It starts at the axon hillock, the junction between the soma and the axon.

Axons can vary in length, and some are very long. For example, an axon may extend from the spinal cord all the way to the foot. Longer axons are often wrapped in a fatty myelin sheath that insulates the axon and helps keep the signal strong. Glia, which are another type of nervous system cell, create the myelin sheath.

In myelinated axons, the action potential is renewed at each node of Ranvier. These are repeated gaps in the myelin. The signal continues this way until it reaches the axon terminal, also called the presynaptic terminal. This terminal contains vesicles filled with neurotransmitters.

When an action potential reaches the terminal, the vesicles fuse with the cell membrane and release neurotransmitters. This process is called exocytosis. The neurotransmitters enter the synaptic cleft, which is the gap between cells at a synapse. Some synapses are excitatory and make an action potential more likely in the next cell. Others are inhibitory and make it less likely.

Neuron shape, or morphology, can vary a great deal and often reflects function. Some neurons have only a few dendritic processes and one axon. Others have very complex dendritic branches, and some have axons that stretch across the whole organism. These differences are often used to identify neuron types. In the peripheral nervous system, dendrites can also help define the receptive field, which is the body area a cell responds to.

The study of neuron structure was advanced by Santiago Ramon y Cajal, a Spanish anatomist who worked in the late 19th and early 20th century. He traced individual neurons and made detailed drawings that still show important features today. Using a staining method developed and named after Camillo Golgi, he was able to trace many different cell types in the brain. He also drew early neuronal circuits, which are networks of neurons activated together to process specific information.

Neuron Signaling and Synapses

aquaporins

Aquaporins and Membrane Transport

Aquaporins are membrane proteins that move water across cell membranes. Some aquaporins, called aquaglyceroporins, also transport glycerol. A few aquaporins may also help move volatile substances such as carbon dioxide and ammonia. These channels are found in many different tissues. Water-selective aquaporins are important in the kidneys, exocrine glands, and central nervous system. Aquaporins that may act as gas channels are often highly expressed in red blood cells, epithelial cells, and...

non-gated ion channels

Leak Channels in Resting Membranes

Leak channels are ion channels that let charged ions move across the plasma membrane without a gate. These proteins help maintain membrane potential, which is essential for cell survival. They can move more than a thousand ions in milliseconds during a cellular event. Unlike gated ion channels, non-gated channels have no opening trigger. They are also called leakage or passive channels. Instead, they switch between open and closed states at an intrinsic rate, so ions keep “leaking” through...

ligand-gated ion channels

How Ligand-Gated Ion Channels Work

Ligand-gated ion channels are membrane proteins that open when a chemical signal binds to them. They have a channel for ions to pass through and a ligand-binding site. When the ligand attaches, the channel opens and ions can move across the cell membrane. These channels are grouped into three subfamilies. The Cys-loop group includes nicotinic acetylcholine receptors, gamma-aminobutyric acid (GABA) receptors, glycine receptors, and 5-hydroxytryptamine receptors. The pore-loop group includes...

voltage-gated ion channels

How Voltage Gated Channels Control Signals

Voltage-gated ion channels control electrical signals in neurons, heart cells, and muscle cells. These transmembrane proteins open and close when the membrane potential changes. They sit in the cell membrane of electrically excitable cells and help ions move across it. Each channel includes a voltage-sensing domain that spans the lipid bilayer. Charged residues in this sensor shift when the membrane potential changes. That movement opens the channel and allows ions to pass through. Different...

mechanically-gated ion channels

Touch and Heat Sensors in Cell Membranes

Mechanically-gated ion channels are membrane proteins that open when cells experience physical stress. Tension, compression, swelling, and shear stress can change the shape of the protein. That change opens a transmembrane pore and lets ions pass to help transmit signals. In eukaryotes, these channels are found in several body regions, including neurons, lungs, skin, bladder, and heart. They support many normal physiological processes. They are also involved in disease when their function...

Neurons are the main cells of the nervous system that generate and pass along electrochemical signals. They communicate with one another mainly through neurotransmitters at special connections called synapses. Neurons can have different shapes, and those shapes often match their function. Most, however, share three main parts: a cell body, dendrites, and an axon. The cell body, or soma, contains the nucleus and the organelles needed for cell activity. Dendrites extend from the soma and usually...

resting membrane potential

How Neurons Keep a Negative Voltage

Neurons keep a negative voltage across their membrane when they are at rest. This membrane potential is the voltage difference between the inside and outside of a cell. In a resting neuron, it is usually around -70 millivolts, which means the inside is more negative than the outside and the cell is polarized. This negative charge depends on two main factors. The membrane is selectively permeable, so most ions and molecules cannot cross the lipid bilayer without help from ion channel proteins.

resting potential decay

Resting Membrane Potential Maintenance

The resting membrane potential stays near -70 mV in a neuron because the membrane allows ions to move in a selective way. At rest, the membrane is slightly permeable to sodium ions (Na+) and chloride ions (Cl-) and highly permeable to potassium ions (K+). Ion channels and pumps keep the concentration differences between the inside and outside of the cell in place. Potassium leak channels let K+ move out of the cell at rest. This outward movement makes the inside of the cell more negative. A...

action potential

How Nerve Signals Travel Down Axons

Nerve signals travel down axons as action potentials, which are electrochemical pulses that let neurons communicate. This signal moves to the axon terminals and triggers neurotransmitter release, passing information through the nervous system. An action potential is an all-or-none change in membrane potential that produces a fast spike in voltage. Neurons usually rest at about -70 millivolts. When they receive input from neurotransmitters or sensory stimuli, the membrane potential can become...

channel rhodopsins

Light-Gated Ion Flow in Channel Rhodopsins

Channel rhodopsins are light-sensitive ion channels found in some organisms. They belong to the rhodopsin family, which also includes photoreceptors in bacteria, plants, and the vertebrate retina. These proteins use bound chromophores, such as retinal in rhodopsins and bilin in phytochromes, to respond to light. Rhodopsins are a group of cell surface proteins called G-protein coupled receptors. These proteins help move signals across biological membranes. Over evolution, the rhodopsin family...

patch clamp

Recording Ion Channel Currents with Patch Clamp

Patch clamp is a lab method used to record electrical currents across a cell membrane. It helps scientists study how ions move through channels in the membrane. These electrical signals are important for functions such as muscle contraction and nerve transmission. The method uses a glass micropipette filled with electrolyte solution. The pipette is sealed tightly to a small part of the cell membrane. This creates an electrically isolated patch, so ions moving through the channels flow into the...

electrical synapses

Gap Junctions in Electrical Signaling

Electrical synapses use gap junctions to pass signals directly between neurons and other cells. The presynaptic and postsynaptic membranes sit very close together, about 3.5 nm apart. Channel proteins connect the two cells and create a direct path for current. Unlike a chemical synapse, an electrical synapse does not rely on neurotransmitters crossing a synaptic cleft. The gap junction is built from two hexameric connexin hemichannels, also called connexons. Each adjacent cell contributes one...

chemical synapses

How Neurons Signal at Synapses

Chemical synapses let neurons pass signals to another neuron, a muscle cell, a gland cell, or a sensory cell. They use neurotransmitter molecules released from synaptic vesicles to carry the message. Because of that process, there is a short delay of about one millisecond between the arrival of the action potential and the opening of ion channels on the postsynaptic cell. Chemical synapses also send information in one direction only. A synaptic cleft separates the presynaptic and postsynaptic...

excitatory and inhibitory effects of neurotransmitters

excitatory-and-inhibitory-effects-of-neurotransmitters

How Neurotransmitters Trigger or Block Signals

Neurotransmitters can either trigger or block signals at a chemical synapse. When an action potential reaches the presynaptic axon terminal, it causes the neuron to release neurotransmitters into the synaptic cleft. The released molecule then binds to specific receptors on the postsynaptic cell membrane. A molecule is usually identified as a neurotransmitter when it is present in the presynaptic neuron, released in response to strong presynaptic depolarization, and matched with receptors on...

muscle contraction

How Muscles Receive Signals to Contract

Muscle contraction begins when a nerve signal reaches a skeletal muscle fiber. At the motor endplate, a motor neuron releases acetylcholine, a neurotransmitter that carries the signal to the muscle cell. Acetylcholine binds to receptors on the sarcolemma, the muscle cell membrane, and lets sodium ions enter the cell. This starts an action potential in the muscle fiber and helps pass electrical signals from the brain to the muscle. The signal must also be controlled so the muscle does not stay...

the role of ion channels in neuronal computation

the-role-of-ion-channels-in-neuronal-computation

How Ion Channels Shape Neuron Firing

Ion channels help neurons decide when to fire an action potential. A postsynaptic neuron often receives signals from many presynaptic neurons, and the axon hillock adds those inputs together to judge whether firing is likely. In some cases, one strong EPSP, or excitatory postsynaptic potential, is enough to trigger a spike. In many cases, several EPSPs must arrive close together for the cell to reach threshold. This signal adding process is called summation. It can be temporal when one...

long-term potentiation

How Synapses Strengthen During Learning

Long-term potentiation, or LTP, is a way the brain strengthens synapses over time. A synapse is the chemical connection between neurons. LTP is one form of synaptic plasticity, which means changes in synapse strength. It works opposite to long-term depression, or LTD, which weakens synapses. Together, LTP and LTD are major mechanisms behind learning and memory. LTP can happen when a presynaptic neuron repeatedly fires and stimulates a postsynaptic neuron. This is called Hebbian LTP. It follows...

long-term depression

Synaptic Weakening in Memory Circuits

Long-term depression, or LTD, is a form of synaptic weakening in the brain. It is one way synaptic plasticity, or changes in the strength of chemical synapses, can occur over time between presynaptic and postsynaptic neurons. LTD works opposite long-term potentiation, or LTP, which strengthens synapses. Together, LTD and LTP help support learning and memory. LTD also helps keep the brain flexible. If synapses stayed maximally strengthened for too long, the brain would become less efficient and...

key terms and concepts

Explore how neurons send signals through dendrites, axons, myelin, and synapses, and see how neuron shape and Cajal’s drawings reveal nervous system function.

Neuron Signaling and Synapses | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Neuron Signaling and Synapses

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