Neuroscience cheat sheet

Neuron structure

Dendrites commonly receive signals, the cell body integrates inputs, and an axon carries signals towards other cells.

Structure varies across neuron types.

Action potentials

An action potential is a rapid change in membrane potential propagated along an excitable membrane.

Its occurrence depends on membrane conditions and reaching threshold.

Synapses

At a chemical synapse, transmitter release influences receptors on a receiving cell. Synaptic effects can increase or decrease activity.

A chemical signal crosses the gap between cells.

Nervous-system divisions

The central nervous system includes brain and spinal cord. Peripheral nerves connect it with the rest of the body.

Sensory input and motor output travel through different pathways.

Resting membrane potential

Ion concentration differences and selective membrane permeability create a voltage across a cell membrane. Pumps maintain gradients; ion channels determine much of the immediate electrical behaviour.

A membrane potential is a difference between two locations, not an isolated charge stored in one point.

All-or-none spikes

Once threshold is reached in a suitable membrane region, an action potential is regenerated. Stimulus strength is often represented by firing patterns and recruitment rather than a larger individual spike.

A stronger stimulus need not produce a taller action potential in the same axon.

Excitation and inhibition

Synaptic inputs can make a postsynaptic neuron more or less likely to fire. Their effects depend on receptors, ionic gradients, timing and location.

The effect of a transmitter is not determined by its name alone.

Plasticity

Neural connections and their effectiveness can change with activity, development and experience. Plasticity has mechanisms and limits; it does not mean any brain function can be instantly reassigned.

Practice-related changes are studied through behaviour and neural measurements together.

Worked example: conduction

In a simplified model, a signal travels 0.6 m along an axon at 30 m/s. Travel time is 0.6/30 = 0.02 s, or 20 ms, excluding synaptic delays.

Convert seconds to milliseconds only after completing the distance/speed calculation.

Common mistake: one region, one behaviour

Brain regions participate in interacting networks. A correlation between a task and a measured signal does not prove that one region is the sole cause or location of a complex behaviour.

Use converging evidence from more than one method when evaluating a functional claim.

Check your understanding

Why is a larger action potential not the usual code for a stronger stimulus?

Spikes in a given axon are approximately all-or-none; firing rate, timing and the number of recruited neurons can carry intensity information.

Curriculum connections

Sources