Chapter 1-8 Neurophysiology: Nervous System, Neurons, Glia, Resting Membrane Potential, and Action Potentials

A comprehensive set of Q&A flashcards covering the major concepts from the lecture notes on nervous system structure, neuron and glial cell biology, resting membrane potential, ion channels, graded potentials, action potentials, and synaptic transmission.

What are the two main divisions of the nervous system?

Central nervous system (brain and spinal cord) and peripheral nervous system (nerves outside the CNS).

What are the three primary functions of the nervous system described in the notes?

Sensory input, integration/processing, and motor output.

What is the afferent division and which direction does it carry information?

Sensory division; carries information toward the central nervous system.

What is the efferent division and which direction does it carry information?

Motor division; carries information away from the central nervous system to effectors.

What are the two main cell types of nervous tissue?

Neurons and glial cells.

Approximately what percentage of brain cells are glial cells?

About 90%.

Name the three special characteristics of neurons.

Longevity (they live a long time), amitotic (do not divide), and high metabolic demand (need lots of oxygen and glucose).

What is the basic functional unit that conducts nerve impulses?

Neuron.

What is the soma in a neuron?

The cell body that contains the nucleus and organelles.

What are dendrites?

Smaller processes off the soma that receive information from other neurons.

What is the axon?

The long process that conducts action potentials away from the soma.

What is the axon hillock?

The cone-shaped region where the axon originates from the soma; initiation site of an action potential.

What are axon terminals?

Distal endings of the axon where neurotransmitter release occurs.

How many axons does a typical neuron have?

One axon per neuron; multiple dendrites may be present.

What are oligodendrocytes and Schwann cells?

Oligodendrocytes form myelin in the CNS; Schwann cells form myelin in the PNS.

What is the function of myelin?

Insulates axons to speed signal conduction.

What are ependymal cells?

Ciliated cells that circulate cerebrospinal fluid (CSF) in the CNS.

What are microglial cells?

CNS immune cells that phagocytose debris and pathogens.

What are astrocytes?

Glial cells that support neurons, regulate the ionic and chemical environment, guide development, and help maintain synapses.

What are satellite cells?

PNS glia analogous to astrocytes; support neurons at ganglia and help maintain the chemical environment around synapses.

What does the banana in the ocean mnemonic remember about ion distribution?

Potassium is higher inside the cell; sodium, chloride, and calcium are higher outside.

What is the typical resting membrane potential (RMP) of a neuron?

Approximately -70 millivolts (often cited as -65 to -70 mV).

Which four ions are central to resting membrane potential in the notes?

Sodium (Na+), potassium (K+), chloride (Cl−), and calcium (Ca2+).

What is the role of the Na+/K+ ATPase pump?

Primary active transporter that moves 3 Na+ out and 2 K+ in using ATP, helping maintain ionic gradients and contributing to the negative inside of the cell.

Why is the RMP closer to the potassium equilibrium potential than the sodium equilibrium potential?

Because the membrane is more permeable to K+ (more K+ leak channels) than to Na+ at rest.

What is the equilibrium potential for potassium (E_K)?

About -94 mV.

What is the equilibrium potential for sodium (E_Na)?

About +60 mV.

What does the Nernst equation conceptually relate?

It relates ion concentration differences across the membrane to the equilibrium potential for that ion.

What is the function of leak channels?

They are always open and contribute to the resting membrane potential by setting the membrane’s baseline permeability.

What are ligand-gated channels and where are they typically located?

Channels that open or close in response to binding of a chemical ligand; located mainly on dendrites and soma; mediate postsynaptic potentials.

What are voltage-gated channels and which ions do they involve in neurons?

Channels that open/close in response to changes in membrane potential; voltage-gated Na+ and K+ channels along the axon; voltage-gated Ca2+ channels at axon terminals.

What are gap junctions?

Direct cytoplasmic connections between adjacent cells that allow ions and small molecules to pass, enabling fast electrical coupling.

What are mechanically gated channels?

Channels that open or close in response to mechanical deformation (e.g., hair cell potassium channels opened by bending).

What are the structural classifications of neurons?

Multipolar (most common), bipolar, and unipolar/pseudo-unipolar.

What are the three functional classifications of neurons?

Afferent (sensory) neurons, interneurons (integration inside CNS), and efferent (motor) neurons.

What is the primary function of glial cells?

To support, protect, and insulate neurons and to maintain the neuronal environment; they outnumber neurons.

What is the all-or-none principle in action potentials?

An action potential occurs fully or not at all; once threshold is reached, the amplitude is the same regardless of stimulus strength.

Where do graded potentials occur, and how do they behave over distance?

Occur in dendrites and soma; small, variable changes that decay with distance from the stimulus.

Where do action potentials occur, and what channels initiate them?

In the axon, starting at the axon hillock; initiated by voltage-gated Na+ and K+ channels.

What occurs during phase 1 of an action potential?

Rapid opening of voltage-gated Na+ channels leading to depolarization.

What occurs during phase 2 and phase 3 of an action potential?

Phase 2 (repolarization) due to Na+ channel inactivation and opening of K+ channels; Phase 3 (hyperpolarization) as K+ channels stay open longer than needed.

What ions are involved in the depolarization and repolarization phases of the action potential?

Depolarization: Na+ influx via Na+ channels; Repolarization: K+ efflux via K+ channels.

What is the role of Ca2+ channels at the axon terminal?

Voltage-gated Ca2+ channels open in response to depolarization, allowing Ca2+ influx that triggers neurotransmitter release.

What triggers neurotransmitter release at the synapse?

Calcium influx through voltage-gated Ca2+ channels at the presynaptic terminal.

What is a synapse and what are the two main cells involved?

A junction where a presynaptic neuron communicates with a postsynaptic cell (neuron or effector); presynaptic and postsynaptic cells.

What happens during temporal summation?

Graded potentials summing over time from the same location to reach threshold.

What happens during spatial summation?

Graded potentials from different locations arrive at the same time and add together to reach threshold.

What is a collateral in the context of neurons?

An axon collateral is a branch of the axon that can contact multiple targets.

What is the difference between tract and nerve?

Tract is a bundle of axons in the CNS; nerve is a bundle of axons in the PNS.

What is the role of astrocytes during development?

They help migrate developing neurons to the correct locations and help form proper synaptic connections.

What is the resting membrane potential relative to threshold, and what is the typical threshold depolarization amount?

RMP around -70 mV; threshold is about -55 mV (roughly 15 mV depolarization from resting potential).