Neurons & Glia: Structure, Function, and Neural Signaling in the Nervous System

What are the two types of cells that make up the nervous system?

Neurons and glia.

What is the primary function of neurons?

Info processing and communication.

What role do glia play in the nervous system?

They are the primary support cells.

What are the four distinct structural components of a neuron?

Dendrites, soma (cell body), axon, and axon terminal.

What is the function of dendrites in a neuron?

They serve as the input component for receiving information.

What is the role of the soma (cell body) in a neuron?

Signal integration and processing.

What does the axon do?

It transmits signals away from the cell body.

What is the function of the axon terminal?

It serves as the output component for sending signals to other neurons.

What is the composition of the neural membrane?

A two-molecule-thick layer of phospholipids.

What is selective permeability in neurons?

The regulation of the direction and type of chemicals allowed in or out of the neuron.

What is the difference between transmitter-gated channels and voltage-dependent channels?

Transmitter-gated channels open in response to neurotransmitter binding, while voltage-dependent channels open in response to specific intracellular voltage.

What is the function of the sodium-potassium pump?

It maintains the differences in chemical composition between the intracellular and extracellular environments.

What does the calcium pump do?

It moves calcium ions out of the cell.

What is anterograde transport?

Movement along microtubules away from the cell body.

What is retrograde transport?

Movement toward the cell body from the periphery.

How do certain pathogens enter the nervous system?

They hitchhike via the retrograde transport system.

What are neurofilaments responsible for?

Providing structural support to neurons.

What role do microfilaments play in neurons?

They participate in changing the length and shape of axons and dendrites in response to learning.

What organelles are found in the cell body of a neuron?

Nucleus, nucleolus, ribosomes, endoplasmic reticulum, Golgi apparatus, and mitochondria.

What is the function of the nucleus in a neuron?

It contains the DNA that directs the functioning of the cell.

What is the role of mitochondria in neurons?

They construct ATP, the major energy source of neurons.

What are dendritic spines and their significance?

They provide additional locations for synapses and can change shape based on activity, contributing to learning and memory.

What is the axon hillock?

The junction of the axon to the cell body, responsible for initiating the electrical signal.

What is the function of myelin in axons?

It insulates the axon and speeds up signal transmission.

What are the nodes of Ranvier?

Spaces between myelin where the electrical signal is regenerated.

What role does myelin play in neurons?

Myelin reduces the energy requirements of neurons by decreasing the work done by sodium-potassium pumps, with ion channels located only at the nodes of Ranvier.

How are neurons classified structurally?

Neurons are classified as unipolar (one process), bipolar (two processes), or multipolar (many processes).

What are unipolar neurons and where are they found?

Unipolar neurons have a single process and are found in sensory systems and the autonomic nervous system, involved in touch, temperature, or pain.

What are bipolar neurons and where are they located?

Bipolar neurons have two processes and are found in the retina, cochlea, olfactory bulb, and tongue, transmitting information in several sensory systems.

What characterizes multipolar neurons?

Multipolar neurons, the most common type, have many processes and are found in the thalamus, cerebral cortex, and cerebellum, acting as bridges between sensory and motor neurons.

What are the functional classifications of neurons?

Neurons can be classified as sensory neurons (receive sensory info), motor neurons (transmit commands from CNS to muscles), or interneurons (connect sensory and motor neurons).

What are macroglia and what types are included?

Macroglia are the largest glial cells, including astrocytes, oligodendrocytes, and Schwann cells.

What functions do astrocytes perform?

Astrocytes provide structural support, transfer nutrients, contribute to the blood-brain barrier, isolate synaptic gaps, gather molecules from the synapse, and respond to CNS damage by cleaning up and forming scar tissue.

What is the role of oligodendrocytes in the CNS?

Oligodendrocytes myelinate the CNS and form a network that is not conducive to regeneration after neural damage, linked to conditions like Multiple Sclerosis.

How do Schwann cells differ from oligodendrocytes?

Schwann cells myelinate the peripheral nervous system and help guide the regrowth of damaged axons, while oligodendrocytes do not have this capacity.

What is the function of microglia?

Microglia remove debris from damaged neurons and help form the blood-brain barrier, but uncontrolled activation can lead to inflammation and damage to healthy cells.

What initiates the action potential in a neuron?

The action potential is initiated when the cell body is depolarized to threshold at the axon hillock of the presynaptic neuron.

What is the ionic composition of a resting neuron?

In a resting neuron, intracellular fluid has high potassium and low sodium and chloride, while extracellular fluid has high sodium and chloride and low potassium.

What maintains the concentration gradients in neurons?

The sodium-potassium pump maintains the concentration gradients essential for neural signaling.

What happens during the depolarization of a neuron?

During depolarization, the membrane potential becomes more positive, leading to the initiation of an action potential if the threshold is reached.

What is the role of the sodium-potassium pump?

The sodium-potassium pump helps maintain the resting potential by moving sodium out of the neuron and potassium into the neuron.

What occurs at the threshold of depolarization?

At threshold, an action potential is produced in the axon, similar to pulling the trigger of a gun.

What is remyelination?

Remyelination is the process of regrowing the myelin sheath around neurons, which can be aided by stem cells.

How do diffusion and electrical forces contribute to neural signaling?

Diffusion moves molecules from high to low concentration, while electrical forces move like-signed ions apart and opposite-signed ions together, both contributing to the action potential.

What is the significance of the resting potential in neurons?

The resting potential is crucial for maintaining the ability of neurons to signal; if potassium levels increase in the extracellular fluid, it can disrupt this potential.

What triggers the opening of voltage-dependent sodium channels in a neuron?

Reaching the threshold voltage.

What happens to the charge inside a neuron at the peak of an action potential?

The inside becomes positively charged.

What is the difference between the absolute refractory period and the relative refractory period?

The absolute refractory period is when no action potential can be generated, while the relative refractory period allows for action potentials but requires a stronger stimulus.

How do action potentials propagate down unmyelinated axons?

Through passive conduction, requiring replication of the action potential at each segment.

What is saltatory conduction?

The rapid propagation of action potentials along myelinated axons, occurring only at the nodes of Ranvier.

What are the two forms of synapses?

Electrical synapses and chemical synapses.

What characterizes electrical synapses?

They have very tiny synaptic gaps and allow fast excitatory signals.

What is the process by which neurotransmitters are released into the synaptic gap?

Exocytosis.

What role does calcium play in neurotransmitter release?

Calcium influx stimulates vesicles to fuse with the membrane and release neurotransmitters.

What is the function of auto receptors in the presynaptic neuron?

They provide feedback regarding the amount of neurotransmitter present in the synapse.

How do SSRIs (Selective Serotonin Reuptake Inhibitors) help in treating depression?

They inhibit the reuptake of serotonin, increasing its availability in the synapse.

What are ionotropic receptors?

Receptor proteins that directly open selective ion pores when activated by neurotransmitters.

What are metabotropic receptors?

Receptor proteins that release G proteins upon activation, leading to various intracellular effects.

What are EPSPs and how do they affect the postsynaptic neuron?

Excitatory postsynaptic potentials (EPSPs) produce slight depolarizations, increasing the likelihood of an action potential.

What are IPSPs and their effect on the postsynaptic neuron?

Inhibitory postsynaptic potentials (IPSPs) produce slight hyperpolarizations, reducing the likelihood of an action potential.

What is spatial summation in neuronal signaling?

The addition of inputs from many synapses to determine if an action potential will be produced.

What is temporal summation?

The accumulation of input from a single active synapse over a short period to produce an action potential.

What is presynaptic facilitation?

When a presynaptic neuron increases the amount of neurochemical released by the target axon.

What is presynaptic inhibition?

When a presynaptic neuron decreases the amount of neurochemical released by the target axon.

What is the role of astrocytes in neurotransmitter diffusion?

They influence the speed of diffusion away from the synaptic gap.

What is the effect of monoamine oxidase in relation to neurotransmitters?

It breaks down monoamines like serotonin, dopamine, and norepinephrine, potentially leading to depression if overactive.

What is the function of neurotransmitter transporters?

They recapture neurotransmitters for reuse by the presynaptic neuron.

What is the significance of receptor sites on postsynaptic cells?

They respond specifically to certain neurotransmitters, allowing for selective activation.

What happens when neurotransmitters bind to postsynaptic receptors?

They can produce either excitatory or inhibitory effects on the postsynaptic neuron.

What is the average number of synapses formed by each neuron in the human brain?

About 1,000 synapses.

What is the estimated number of synapses in one human brain compared to stars in the galaxy?

There are more synapses in one human brain than stars in the galaxy.