Neurons and Glial Cells: Structure, Function, and Neural Signaling

Who established the neuron doctrine?

Ramon y Cajal

What is the primary assertion of the neuron doctrine?

The brain is made of many small, discrete cells.

Approximately how many neurons are in the human brain?

Almost 100 billion neurons.

What are the four important regions of a neuron?

Dendrites, Soma (Cell Body), Axon, Axon terminals.

What is the function of dendrites?

To collect information through branching projections.

What does the soma (cell body) contain?

The nucleus and integrates information.

What is the role of the axon?

To conduct the neural signal across long distances.

What are axon terminals?

Small swellings that release signals to affect other neurons.

What are neurotransmitters?

Chemical signals that cross small gaps known as synapses.

How many synapses are estimated to be in the adult brain?

About 500 trillion synapses.

What are the three main types of neurons?

Sensory neurons, motor neurons, and interneurons.

What is a unipolar neuron and where is it typically located?

A neuron near the spinal cord that transmits information about touch, skin, temperature, and pain.

Where are bipolar neurons found?

In the retina, cochlea, olfactory bulb, and tongue.

What is the function of multipolar neurons?

To carry commands to muscles and glands.

What roles do glial cells play in the nervous system?

Speeding up neuronal signaling, regulating extracellular chemicals, and enabling neurons to modify their connections.

What is the function of astrocytes?

Provide structural and nutritional support for neurons, isolate synapses, clean up debris, and participate in chemical signaling.

What do ependymal cells do?

Line the ventricles and central canal of the spinal cord, move cerebrospinal fluid, and regulate stem cells.

What is the role of oligodendrocytes?

Myelination of axons in the central nervous system.

What do Schwann cells do?

Myelinate axons in the peripheral nervous system.

What is the function of microglia?

Debris cleanup and synapse removal in the central nervous system.

What is the blood-brain barrier?

A semipermeable barrier between the blood and the brain produced by cells in the walls of the brain's capillaries.

What is the area postrema?

A region of the medulla where the blood-brain barrier is weak, allowing detection of poisons that can initiate vomiting.

What is the resting potential of a neuron?

The voltage difference across the resting membrane, which is approximately -70mV.

What initiates the process of neural communication?

An action potential, which is an electrical signal.

What is diffusion in the context of neurons?

The movement of molecules from regions of high concentration to regions of low concentration.

What is saltatory conduction?

The process where action potentials jump from one node of Ranvier to the next, increasing conduction velocity.

What happens at the axon terminal when an action potential arrives?

It causes exocytosis, releasing neurotransmitters into the synaptic cleft.

What is the role of neurotransmitters at the synapse?

They bind to receptors on the postsynaptic target, facilitating communication between neurons.

What is axoplasmic transport?

An active process that propels substances along microtubules in the axon.

What is the difference between anterograde and retrograde transport?

Anterograde transport moves substances from the cell body toward the axon terminal, while retrograde transport moves them from the terminal back to the cell body.

What is the function of tau protein in neurons?

Tau stabilizes microtubules; when dysfunctional, it can lead to neurofibrillary tangles in Alzheimer's disease.

What are the two types of neurotransmitters?

Small-molecular-weight neurotransmitters (like monoamines and amino acids) and large-molecular-weight neurotransmitters (like neuropeptides).

What is the effect of agonists on neurotransmitters?

Agonists enhance the activity of a neurotransmitter.

How are neurotransmitters cleared from the synapse?

Through reuptake into the presynaptic neuron or degradation by enzymes.

What is an EPSP?

An excitatory postsynaptic potential that depolarizes the neuron, increasing its likelihood of firing.

What is an IPSP?

An inhibitory postsynaptic potential that hyperpolarizes the neuron, decreasing its likelihood of firing.

What channels are involved in action potentials?

Voltage-dependent sodium and potassium channels.

What is the duration of an action potential?

1 to 2 milliseconds.

What is the size of an EPSP?

Up to 10mV.

What is the character of an action potential?

All-or-none response.

What is the role of ligand-gated channels?

They open in response to neurotransmitter binding, allowing ions to flow across the membrane.

What is the significance of the axo-axonic synapse?

It modulates the release of neurotransmitters by the target axon.

If a neuron's membrane potential changes from -70mV to -73mV, what type of potential is this?

An IPSP.

If a neuron's membrane potential changes from -70mV to -67mV, what type of potential is this?

An EPSP.

How much depolarization is required for a neuron with a resting potential of -70mV to fire if the threshold is -60mV?

10mV.

What happens to microtubules in Alzheimer's disease?

They collapse due to the dysfunction of tau protein, leading to neural death.

What is the function of neurotransmitter reuptake inhibitors like SSRIs?

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

What is the primary difference between ionotropic and metabotropic receptors?

Ionotropic receptors directly open ion channels, while metabotropic receptors initiate metabolic processes that may lead to channel opening.