C2.2 Neural Signaling Flashcards

Flashcards about neural signaling, covering topics from neuron structure to synaptic transmission and action potentials.

Neurons

The functional cells of the nervous system responsible for electrical signaling and communication of information within the body.

Glial cells

Supporting cells that help neurons carry out their functions.

Soma

Main part of a neuron, also known as the cell body, which contains the nucleus and major organelles within the cytoplasm.

Dendrites

Highly branched and short extensions of the plasma membrane (fibers) that receive signals from other neurons.

Axons

Long singular fibres that emerge from the cell body and propagate the action potential (neural signal) from the soma unidirectionally towards the axon terminal.

Membrane potential

The electrical state of a cell, a measure of the distribution of positive and negative ions across the cell membrane, measured in millivolts (mV).

Resting membrane potential

When a neuron is at rest (not transmitting a signal), its resting membrane potential is around -70mV.

Sodium-potassium pump

Moves 3 sodium ions out and 2 potassium ions in by active transport to maintain a negative charge inside the cell.

Action potentials (nerve impulses)

Very rapid changes in the membrane potential of a cell caused by ions moving in and out of the cell.

Depolarization

The cell membrane becomes depolarized (a decrease in the voltage difference between the inside and outside of the cell), reaching a final membrane potential of around +40mV.

Repolarization

Restores the membrane potential back to its resting state of -70mV immediately after complete depolarization (at the action potential peak).

Hyperpolarization

For a short moment in time, the neural membrane is hyperpolarized at around -80mV, at which point the potassium ion channels close and the membrane potential is slowly brought back to -70mV by the sodium-potassium pump.

Refractory period

The cell enters a refractory period in which another action potential cannot be produced until resting potential is restored; this prevents an action potential from traveling backwards, maintaining its unidirectionality.

Myelin sheath

Some types of glial cells – oligodendrocytes in the CNS and Schwann cells in the PNS – produce a lipid-rich substance that surrounds the axon.

Nodes of Ranvier

Small sections of the axon that are not covered with myelin.

Coefficient of Determination (R2)

Evaluates the degree to which variation in the independent variable explains the variation in the dependent variable.

Synapses

Junctions between neurons (sensory, interneural, motor) and between neurons and effector cells (muscles, glands).

Synaptic transmission

A signal can only pass in one direction across a typical synapse.

Acetylcholine

An excitatory neurotransmitter used between neurons and muscle cells (neuromuscular junctions) to stimulate muscle contraction.

Threshold potential

Needs to be reached in order for voltage-gated sodium ion channels to depolarize/open (around -50mV).

Local currents

Sodium ions diffuse into the nearby areas of the membrane, causing the threshold potential to be reached and depolarization to occur at the neighboring membrane area.

Nodes of Ranvier

Gaps in myelin coverage along an axon and about one micrometer long.

Saltatory conduction

The action potential ‘jumps’ or ‘skips’ the membrane area wrapped in myelin and cause depolarization only at nodes of Ranvier.

Neonicotinoids

Insecticides that bind to acetylcholine receptors in the CNS’s cholinergic synapses (synapses that use acetylcholine as a neurotransmitter), preventing synaptic transmission which leads to paralysis and eventual death.

Cocaine

A stimulant psychoactive drug that prevents dopamine reuptake into the presynaptic neuron, causing it to accumulate in the synaptic cleft and leading to continuous excitation of the postsynaptic neuron, giving false feelings of euphoria and pleasure.

Inhibitory neurotransmitters

Neurotransmitters that inhibit depolarization bind to the postsynaptic membrane and cause the opening of chloride ion channels, leading to the influx of Cl- ions into the cytoplasm, causing the membrane potential to become even more negative (hyperpolarization).

Summation

Multiple presynaptic neurons interact with all-or-nothing consequences in terms of postsynaptic depolarization.

Receptors in skin nerve endings

Detect the specific sensation (for example, pain receptors detect the chemical within hot spices) and open in response to the stimulus, allowing positively charged ions to flow into the neuron causing the threshold potential to be reached and nerve impulses then pass through the neurons to the brain, where pain is perceived.

Consciousness

A property of the human body that emerges from the interaction of all individual neurons in the brain