Nervous System Organization: Neurons, Populations, and Synaptic Connectivity

Vocabulary flashcards covering key concepts about neurons, populations, and synaptic connectivity from the lecture notes.

Population of neurons

A group of neurons that functioning together expresses behavior; the population, not a single neuron, determines the nervous system output; behavior can continue despite some loss due to redundancy and group dynamics.

Input (population level)

The process by which a population receives information from external sources or other neurons, forming the first step in sharing information across the network.

Integration

The process of combining inputs from multiple neurons to influence a neuron's overall excitability and potential to fire.

Output

The signal produced by a neuron or neuronal population that acts to influence other cells or muscles.

Excitatory input

A input that increases a neuron’s activity or probability of firing.

Inhibitory input

A input that decreases a neuron’s activity or probability of firing.

Baseline excitability

The resting electrical state of a neuron, which changes as inputs are integrated and determines how it will vote (fire) in response to inputs.

Neural information

A change in neuronal activity that carries information across a network.

Knee-jerk reflex

A simple reflex example used to illustrate population-level neural processing; involves sensory input, a relay in the spinal cord, and motor output to produce movement.

Sensory input

Information about the external environment captured by sensory receptors; considered the entry point into the nervous system.

Sensory (afferent) neuron

Neuron that carries information from the periphery toward the CNS.

Motor (efferent) neuron

Neuron that carries signals from the CNS to muscles or glands to produce movement or secretion.

Interneuron

A neuron that connects other neurons within the CNS; often modulatory, capable of changing the activity of other neurons and linking networks.

Multipolar neuron

A common neuron shape (often motor in function) with many dendrites surrounding the soma and a single axon, suited to integrate a lot of information.

Pseudo-unipolar neuron

A sensory neuron with a soma and an axon that bifurcates into two branches—one input (dendritic side) and one output (axonal side)—common in touch and proprioception pathways.

Bipolar neuron

A sensory neuron with two processes (one input/dendrite side and one output/axon side), often involved in vision pathways.

Dendrites

Input branches of a neuron that receive signals; dendritic spines are small protrusions that form synapses.

Axon

The output pathway of a neuron, which may have collateral branches and ends in presynaptic terminals to transmit signals to other neurons.

Axon collateral

Branches of an axon that allow a single neuron to influence multiple target cells.

Presynaptic terminal

The end of an axon or collateral where neurotransmitters are released to transmit a signal to the postsynaptic cell.

Postsynaptic cell

The neuron or cell that receives the signal at a synapse.

Dendritic spine

A tiny protrusion on a dendrite that anchors a presynaptic terminal and forms a site of synaptic contact; can be damaged in traumatic brain injury.

Synapse

The contact point where information is transferred from the presynaptic neuron to the postsynaptic neuron; can be axodendritic, axosomatic, or axoaxonic.

Axodendritic synapse

Synapse from an axon terminal to a dendrite; typically excitatory.

Axosomatic synapse

Synapse from an axon terminal to the soma (cell body); often inhibitory.

Axoaxonic synapse

Synapse from an axon terminal to another axon; typically modulatory.

Serial transmission

One-to-one transmission where one neuron connects to the next in a linear chain.

Convergent transmission

Many neurons connect to a single neuron, funneling information into one target.

Divergent transmission

One neuron connects to multiple neurons, distributing its signal and potentially amplifying it.

Arborization

Dendritic branching pattern of a neuron; higher density (more arborization) generally indicates more input and greater processing capacity.

Interneuron modulation

Interneurons can alter the flow of information between other neurons, enabling complex processing and changes in population activity.