Biophysics - Synaptic Transmission

Flashcards covering key vocabulary and concepts related to nervous system biophysics and synaptic transmission.

Nervous System

The body’s communication network with two main parts: The central nervous system (CNS) and the peripheral nervous system (PNS). Made up of neurons (nerve cells), which send and receive electrical signals.

Central Nervous System (CNS)

The brain and spinal cord.

Peripheral Nervous System (PNS)

All the nerves and small clusters of nerve cells (called ganglia) outside the CNS.

Neuron

Nerve cells that send and receive electrical signals.

Regulation

Controls body functions and helps the body respond to changes.

Coordination

Keeps the organs working together in sync.

Integration

Makes sure the whole body acts as one unit.

Soma (Cell Body)

Contains the cell's DNA, controls the cell’s metabolism, gathers small electrical signals, and makes neurotransmitters.

Dendrites

Short branches that receive signals from other neurons through synapses.

Axon

A long branch that sends signals to other neurons or target cells.

Axon Hillock

The starting point of the axon where incoming signals are summed up, triggering an action potential if strong enough.

Action Potential

An electric pulse that travels down the axon.

Myelin Sheath

A fatty layer that wraps around the axon to help electrical signals travel faster and more efficiently.

Schwann Cells

Cells that make myelin in the PNS.

Oligodendrocytes

A type of glial cell that makes myelin in the CNS.

Nodes of Ranvier

Small gaps in the myelin along the axon that allow the electrical signal to “jump” from node to node (saltatory conduction).

Saltatory Conduction

The process where the electrical signal “jumps” from node to node, making the signal travel much faster.

Continuous Conduction

Action potential moves step by step along the entire length of the nerve; occurs in unmyelinated nerves and muscles.

Depolarization

Occurs when sodium ions (Na⁺) flow into the cell, making the inside of the cell more positive.

Repolarization

Occurs when potassium (K⁺) channels open, and K⁺ leaves the cell, making the inside negative again.

Hyperpolarization

When K⁺ channels stay open a bit longer, making the cell even more negative than usual.

Refractory Period

A short period where sodium channels are inactive, preventing the signal from going backward.

Synaptic Transmission

How information is passed from one neuron to another, a neuron to a muscle, or a neuron to a gland at a synapse.

Synapse

A special connection point where communication happens between neurons, neurons and muscles, or neurons and glands.

Synaptic Cleft

The tiny gap between the presynaptic and postsynaptic cells.

Neurotransmitters

Chemical messengers released into the synaptic cleft that bind to receptors on the postsynaptic membrane.

Exocytosis

The process where vesicles fuse with the presynaptic membrane and release neurotransmitters into the synaptic cleft.

Ligand-Gated Ion Channels

Receptors on the postsynaptic membrane that open when neurotransmitters bind to them, allowing ions to flow into the cell.

Excitatory Neurotransmitters

Increase the chance of an action potential by depolarizing the membrane (e.g., glutamate).

Inhibitory Neurotransmitters

Decrease the chance of an action potential by hyperpolarizing the membrane (e.g., GABA).

Ionotropic Receptors

Fast, direct receptors where the neurotransmitter binds directly to a receptor that also acts as an ion channel.

Metabotropic Receptors

Slower, indirect receptors that activate a G-protein on the inside of the cell membrane, starting a signaling pathway.

Electrical Synapses

Use direct physical connections (gap junctions) between two neurons, allowing signals to go both directions (bidirectional) and very fast.

Chemical Synapses

Use neurotransmitters to send signals across a synaptic cleft, moving in one direction only (from presynaptic to postsynaptic) and slower than electrical synapses.

Electro-Chemical (Mixed) Synapses

Combine features of both electrical and chemical synapses, mainly found in lower vertebrates.

Excitatory Synapses

Increase the chance of an action potential; common neurotransmitters include glutamate and acetylcholine.

Inhibitory Synapses

Decrease the chance of an action potential; common neurotransmitters include GABA and glycine.

Postsynaptic Potential (PSP)

A small change in the membrane’s electrical charge caused by a neurotransmitter binding to a receptor on the postsynaptic membrane.

Excitatory Postsynaptic Potential (EPSP)

Depolarization: the inside of the cell becomes more positive, increasing the chance of an action potential.

Inhibitory Postsynaptic Potential (IPSP)

Hyperpolarization: the inside becomes more negative, decreasing the chance of an action potential.

Spatial Summation

Many different synapses activate at the same time, and their combined PSPs add up.

Temporal Summation

One synapse sends signals repeatedly in a short period, and the effects build up over time.

Integration

The process of combining all excitatory and inhibitory inputs at the postsynaptic neuron.