SLP 491 Neurons and Synapses

Comprehensive vocabulary flashcards covering neuron anatomy, ion exchange, and the stages of the action potential based on the SLP 491 worksheet.

Functions of neurons

To receive, process, and transmit signals.

Dendrites

Structures that receive information from other neurons.

Nucleus

Located in the soma or cell body; its function is to process signals and make the decision on whether to fire.

Axon

The structure along which the signal travels.

Myelin

A covering on the axon that provides protection (insulation and prevention of cross communication) and speeds up the signal along the axon.

Nodes of Ranvier

Gaps in the myelin sheath where ion gates are found.

Axon terminals (Boutons)

Structures located at the end of the axon.

Synapse

The transmission of a signal from one neuron to the next.

Vesicle

A bubble in the axon terminal containing neurotransmitters.

Presynaptic neuron

The neuron sending the signal, located before the synapse.

Postsynaptic neuron

The neuron receiving the signal, located after the synapse.

Two main types of neurotransmitters

Excitatory and inhibitory.

Main intracellular ions

$A^-$ and $K^+$ (found inside the neuron).

Main extracellular ions

$Na^+$ and $Cl^-$ (found outside the neuron).

“Salty banana”

A mnemonic meaning salt ($NaCl$) is outside the cell and Potassium ($K$) is inside the cell.

Membrane permeability

How readily various ions can cross the cell walls to enter or exit the cell.

Concentration gradient

The principle that ions travel from high concentration to low concentration.

Resting potential

The state where the cell is not firing but has the potential to send a signal, typically at a voltage of $-70\,mV$.

Action potential

The state where the cell fires and sends a signal down the axon, triggered at $-55\,mV$.

Depolarization

When the cell moves away from extreme negative towards zero; occurs when sodium gates open at $-55\,mV$ and $Na^+$ pours in.

“All-or-nothing event”

The rule that at $-55\,mV$, the cell will fire no matter how much more $Na^+$ is received.

Repolarization

When the cell moves back past zero towards extreme negative; begins at $+30\,mV$ when sodium gates close and potassium gates open for $K^+$ to exit.

Hyperpolarization

When the cell undershoots past $-70\,mV$ down to $-90\,mV$ because potassium gates close slowly, allowing too much $K^+$ to leave.

Refractory period

The period where the cell recovers and moves back to the resting potential of $-70\,mV$, during which it cannot fire.

Homeostasis

When the cell goes back to equilibrium or resting potential, achieved by the sodium-potassium pump.

Excitatory neurotransmitters

Neuromitters that make the cell receptive to $Na^+$.

Inhibitory neurotransmitters

Neurotransmitters that make the cell block $Na^+$.

Spatial summation

Simultaneous input from several presynaptic terminals.

Temporal summation

Repeated input from the same presynaptic terminal.