Name: chemical and electrical synapses
Uploaded: 2026-08-26T08:19:40.596Z
Duration: 1 min 22 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Life Science

SC.912.L.14

SC.912.L.14.24

Synaptic Signaling

Neurons communicate with each other and with other cells mainly through chemical signaling at synapses.These specialized regions are where the axon terminal of the presynaptic cell, which sends the message, comes into close proximity to the postsynaptic cell, which receives it.The signal consists of neurotransmitter molecules, which are stored in membrane-bound organelles called synaptic vesicles within the axon terminal.When an electrical signal, known as an action potential, happens in the presynaptic neuron, it causes these vesicles to fuse with the cell membrane.As the vesicles fuse, they release neurotransmitters into the synaptic cleft, the narrow space between cells.The neurotransmitters then diffuse across the cleft and bind to receptors on the postsynaptic cell. This binding triggers a response in the postsynaptic cell, which, in this case, is a neuron. As a result, an action potential may be produced.Together, these synaptic signals allow neurons to pass information through neural circuits across the body.

synaptic signaling

Neurons communicate at synapses, or junctions, to excite or inhibit the activity of other neurons or target cells, such as muscles. Synapses may be chemical or electrical.Most synapses are chemical. That means that an electrical impulse&#x2014;or action potential&#x2014;spurs the release of chemical messengers. These chemical messengers are also called neurotransmitters. The neuron sending the signal is called the presynaptic neuron. The neuron receiving the signal is the postsynaptic neuron.The presynaptic neuron fires an action potential that travels through its axon. The end of the axon, or axon terminal, contains neurotransmitter-filled vesicles. The action potential opens voltage-gated calcium ion channels in the axon terminal membrane. Ca2+ rapidly enters the presynaptic cell (due to the higher external Ca2+ concentration), enabling the vesicles to fuse with the terminal membrane and release neurotransmitters.The space between presynaptic and postsynaptic cells is called the synaptic cleft. Neurotransmitters released from the presynaptic cell rapidly populate the synaptic cleft and bind to receptors on the postsynaptic neuron. The binding of neurotransmitters instigates chemical changes in the postsynaptic neuron, such as opening or closing ion channels. This, in turn, alters the membrane potential of the postsynaptic cell, making it more or less likely to fire an action potential.To end signaling, neurotransmitters in the synapse are degraded by enzymes, reabsorbed by the presynaptic cell, diffused away, or cleared by glial cells.Electrical synapses are present in the nervous system of both invertebrates and vertebrates. They are narrower than their chemical counterparts and transfer ions directly between neurons, allowing faster transmission of the signal. However, unlike chemical synapses, electrical synapses cannot amplify or transform presynaptic signals. Electrical synapses syncronize neuron activity, which is favorable for controlling rapid, invariable signals such as the danger escape in squids.Neurons can send signals to, and receive them from, many other neurons. The integration of numerous inputs received by postsynaptic cells ultimately determines their action potential firing patterns.

Neurons communicate at synapses, or junctions, to excite or inhibit the activity of other neurons or target cells, such as muscles. Synapses may be ...

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Education

JoVE Core

Biology

Cellular Processes

Cell Signaling

KEY TERMS AND CONCEPTS

chemical and electrical synapses

Neurons send signals across synapses, which are junctions between cells. These signals can excite or inhibit other neurons or target cells such as muscles. Most synapses are chemical. Some are electrical.

Chemical synapses use action potentials, which are electrical impulses, to trigger the release of neurotransmitters. The sending neuron is the presynaptic neuron, and the receiving neuron is the postsynaptic neuron. An action potential travels along the axon and reaches the axon terminal, where neurotransmitter-filled vesicles are stored. The action potential opens voltage-gated calcium ion channels, calcium enters the presynaptic cell, and the vesicles fuse with the terminal membrane to release neurotransmitters into the synaptic cleft, the gap between the two cells. The neurotransmitters then bind to receptors on the postsynaptic neuron and cause chemical changes, such as opening or closing ion channels. These changes alter the postsynaptic membrane potential and can make the cell more or less likely to fire its own action potential. Signaling ends when neurotransmitters are broken down by enzymes, taken back up by the presynaptic cell, diffused away, or cleared by glial cells.

Electrical synapses also occur in the nervous systems of invertebrates and vertebrates. They are narrower than chemical synapses and pass ions directly from one neuron to another. This makes transmission faster. However, electrical synapses cannot amplify or transform the presynaptic signal. They help synchronize neuron activity, which is useful for rapid, steady responses such as the escape behavior of squid. Neurons can receive input from many other neurons and also send signals to many others. The combined input that a postsynaptic cell receives helps determine its firing pattern in the end.

Chemical and Electrical Synapses

what is cell signaling?

How Cells Send and Receive Signals

Cell signaling lets cells send and receive messages from the environment and from other cells. Even with a protective membrane, cells need to detect changes and respond to them. Unicellular and multicellular organisms use signaling to stay coordinated and to react to outside cues. Cells often rely on receptor proteins in the membrane to sense information. Skin cells can respond to touch, and photoreceptors in the retina can detect light. Most cells respond to chemical signals such as hormones,...

internal receptors

Steroid Hormones and Intracellular Receptors

Steroid hormones and other small signaling molecules can pass through the cell membrane and bind to intracellular receptors inside the cell. These receptors are also called internal receptors. Many hydrophilic signals cannot cross the plasma membrane, so this pathway is used by signals that are small or hydrophobic. Nitric oxide, or NO, also uses this type of signaling. When a ligand, which is a signaling molecule, binds to a receptor in the cytoplasm or nucleus, the receptor changes shape.

contact-dependent cell communication

Cell-to-Cell Signaling via Channels

Cell-to-cell signaling can happen when neighboring cells are in direct contact. In this kind of communication, cells use receptor-ligand interactions or special cytoplasmic channels to move small molecules between them. In animal cells, these channels are called gap junctions. They form when six proteins called connexins assemble into a cylindrical structure in the plasma membrane called a connexon. When connexons from two adjacent cells line up, a channel opens between the cells. Enzymes help...

autocrine signaling

Self-Signaling Cells in Immunity and Cancer

Autocrine signaling is a cell communication method in which a cell sends a signal to itself. The same cell releases an extracellular signaling molecule and also has receptors that can bind to that molecule. This lets the cell respond to its own message. In the immune system, this process is important for homeostasis, or keeping body conditions stable. A well-studied example is the macrophage, an immune cell that secretes cytokines such as interleukin-1, or IL-1. Macrophages also have membrane...

paracrine signaling

Local Cell Signaling in Blood and Healing

Local cell signaling helps cells communicate with nearby neighbors using released signaling molecules. These molecules act only over a short distance because they break down quickly or are inactivated if they are not taken up. This type of signaling supports processes such as nitric oxide signaling in blood vessels, neuron-to-neuron communication at synapses, blood clotting, tissue repair, and local allergic skin reactions. A clear example is nitric oxide signaling in blood vessels. The...

Neurons send signals across synapses, which are junctions between cells. These signals can excite or inhibit other neurons or target cells such as muscles. Most synapses are chemical. Some are electrical. Chemical synapses use action potentials, which are electrical impulses, to trigger the release of neurotransmitters. The sending neuron is the presynaptic neuron, and the receiving neuron is the postsynaptic neuron. An action potential travels along the axon and reaches the axon terminal,...

endocrine signaling

Hormones Travel to Distant Target Cells

Endocrine signaling uses hormones to send messages to target cells in other organs. Endocrine cells release these hormones into the circulatory system, which carries the signal through the body. Because the hormone reaches the whole organism, only cells with the right receptors respond. This kind of signaling usually acts slowly, but its effects last longer. Endocrine cells can use cell surface receptors or intracellular receptors, depending on the hormone. Cell surface receptors are...

bacterial signaling

Quorum Sensing in Bacteria

Quorum sensing lets bacteria coordinate behavior by sensing how many cells are nearby. Bacteria can signal inside the cell or between cells. When many bacteria act together, they can behave like a community and change gene expression as a group. This signaling starts with autoinducers, or AIs. Individual bacteria make AIs and release them across the cell membrane into the surrounding space. Some AIs diffuse out passively along a concentration gradient, while others are moved out by active...

yeast signaling

Yeast Cell Communication in Mating

Yeast cell communication helps control mating, colony growth, and other cell responses. Yeasts are single-celled organisms, but unlike bacteria, they are eukaryotes with a nucleus. Their signaling works much like cell signaling in other eukaryotic cells. A signal often begins when a ligand, such as a protein or small molecule released from a yeast cell, binds to a receptor on the cell surface. This binding activates second-messenger kinases, which then switch transcription factors on or off.

g protein-coupled receptors

GPCR Signaling Through G Proteins

G-protein coupled receptors, or GPCRs, start cell signaling after a ligand binds to the receptor. The receptor is a single polypeptide that crosses the cell membrane seven times. These membrane loops create an outside pocket that fits a specific ligand, such as a neurotransmitter or hormone. The inside loops connect to a G-protein.

enzyme-linked receptors

Trk Receptors in Cell Signaling

Trk receptors are enzyme-linked receptors that help cells respond to growth factors and some hormones. They belong to the receptor tyrosine kinase, or RTK, family. These receptors can trigger several signals inside a cell after they are activated. Neurotrophin receptors are one RTK group and include TrkA, TrkB, and TrkC, which are tropomyosin-related kinase receptors. TrkA binds nerve growth factor, neurotrophin-6, and neurotrophin-7. TrkB binds brain-derived neurotrophic factor, or BDNF, and...

ion channels

Ion Channels in Cells and Membranes

Ion channels are membrane proteins that help cells move ions across the plasma membrane. Ions such as sodium, potassium, and calcium move into and out of cells to maintain the electrochemical gradient. This gradient supports cell size and volume, nerve signaling, and gas and nutrient exchange. Ion channels are specialized integral membrane proteins that let specific ions pass down their electrochemical gradient. Their main job is to help keep the membrane potential, which is needed for cell...

what are second messengers?

Cell Signals That Use Second Messengers

Cell signals often use second messengers to carry messages inside the cell. Many receptor-binding ligands are hydrophilic, so they do not cross the cell membrane. Instead, the signal is relayed to an internal messenger that can spread the message farther. G-protein coupled receptors can activate the phosphoinositol pathway and the cyclic AMP, or cAMP, pathway. In the phosphoinositol pathway, the receptor activates phospholipase C. This enzyme hydrolyzes phosphatidylinositol biphosphate, or...

intracellular signaling cascades

Cell-Surface Receptor Signal Cascades

Cell-surface receptor signal cascades move information from outside the cell into the cytoplasm. This process is called signal transduction. It happens only with cell-surface receptors, because they cannot interact with most cell parts, such as DNA. Internal receptors are different. They can interact directly with DNA in the nucleus and help start protein synthesis. When a ligand binds to a receptor, the receptor changes shape. That shape change affects the receptor’s intracellular domain or...

key terms and concepts

Learn how neurons pass signals across synapses, from calcium-triggered neurotransmitter release to fast electrical synapses and signal ending.

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SC.912.L.14.6

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D. Most multicellular organisms are composed of organ systems whose structures reflect their particular function.

Chemical and Electrical Synapses

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