Neuroscience: Synapses Overview

A junction between a neuron and another cell, allowing communication.

The neuron sending the signal across the synapse.

The neuron receiving the signal across the synapse.

A synapse where the signal is transmitted directly through channels connecting the two cells.

A synapse where the signal is transmitted through chemical messengers.

A synapse between a neuron and a muscle cell.

A type of chemical synapse where the neurotransmitter binds to receptors on the postsynaptic neuron, generating a new electrical signal.

A type of chemical synapse where the neurotransmitter binds to receptors on the postsynaptic neuron, preventing the neuron from firing.

The arrival of an action potential (AP) at the presynaptic terminal triggers the release of neurotransmitters into the synaptic cleft.

Voltage-gated calcium (Ca+2) channels open in the presynaptic terminal when it depolarizes. This allows Ca+2 to flow into the terminal, increasing its concentration.

Synaptic vesicles containing neurotransmitters fuse with the presynaptic membrane, releasing their contents into the synaptic cleft.

The amount of Ca+2 entering the presynaptic terminal determines the number of vesicles that fuse and release neurotransmitters.

Neurotransmitters like acetylcholine (Ach) bind to receptors on the postsynaptic membrane, triggering a change in the postsynaptic cell's membrane potential.

The binding of neurotransmitters to receptors can either depolarize (excite) or hyperpolarize (inhibit) the postsynaptic cell, depending on the type of receptor.

Glutamate is the most common excitatory neurotransmitter in the central nervous system (CNS). It plays a key role in learning and memory by transmitting excitatory signals.

Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the CNS. It helps regulate anxiety and reduces overstimulation of nerve cells.

A neurotransmitter that initiates muscle contractions and is also involved in learning and memory in the CNS.

Proteins found on the surface of vesicles that help guide them to their target membranes.

Proteins located on the target cell or organelle membrane that bind with V-SNAREs during exocytosis.

The complex formed by the interaction of V-SNAREs and T-SNAREs, allowing for the merging of vesicles with the target membrane.

A powerful neurotoxin produced by Clostridium botulinum that blocks the release of neurotransmitters, leading to muscle paralysis.

Conditions or diseases that affect the neuromuscular junction.

A chemical messenger released by a presynaptic neuron that binds to receptors on the postsynaptic neuron.

A type of neurotransmitter that makes the postsynaptic neuron more likely to fire an action potential.

A type of neurotransmitter that makes the postsynaptic neuron less likely to fire an action potential.

The change in the membrane potential of the postsynaptic neuron that makes it more likely to fire an action potential.

The change in the membrane potential of the postsynaptic neuron that makes it less likely to fire an action potential.

When multiple presynaptic neurons send signals to a single postsynaptic neuron.

When a single presynaptic neuron sends signals to multiple postsynaptic neurons.

The combined effect of multiple EPSPs and IPSPs on the postsynaptic neuron.

Botulinum toxin, also known as Botox, acts by blocking the release of acetylcholine from nerve endings, preventing muscle contraction.

Botulinum toxin specifically targets and destroys proteins involved in the release of neurotransmitters at the synapse, like SNAP-25, syntaxin, and synaptobrevin.

Tetanus toxin, produced by Clostridium tetani, selectively destroys synaptobrevin in inhibitory interneurons, leading to an overactivity of motor neurons, causing severe muscle contraction and spastic paralysis.

Lambert-Eaton syndrome is an autoimmune condition where antibodies attack voltage-gated calcium channels, reducing calcium-dependent acetylcholine release at the neuromuscular junction, leading to muscle weakness.

Myasthenia gravis is an autoimmune disease where antibodies target acetylcholine receptors at the neuromuscular junction, leading to a decrease in muscle function.

Curare is a natural compound with muscle relaxant properties that blocks the action of acetylcholine at the neuromuscular junction, preventing muscle contraction.

Botulinum toxin is produced by the bacterium Clostridium botulinum, found naturally in soil, water, and some food products, particularly thriving in oxygen-free environments.

Botulism can occur through the consumption of contaminated food, especially homemade canned foods, low-acid foods, and rarely commercial canned foods. Honey can also contain botulinum spores, making it unsafe for infants.