4.1 Neurons Glia

Who is considered the founder of modern neuroscience?

Santiago Ramón y Cajal (1852–1934), an anatomist and artist.

What is cell theory?

The theory that all living things are composed of cells.

Who proposed cell theory in 1839?

Theodor Schwann (animals) and Matthias Schleiden (plants).

What technological improvement helped scientists discover cells?

Improvements in microscopy.

What was Camillo Golgi's black reaction?

A staining method developed in 1873 using silver nitrate on fixed tissue that stained a few random cells completely.

Why was Golgi's black reaction important?

It allowed scientists to see the detailed structures of individual neurons.

What was Golgi's contribution to neuroscience?

He developed the black reaction and described many neural structures.

What was Santiago Ramón y Cajal's contribution to neuroscience?

He improved Golgi's staining method and created detailed drawings of neurons and neural circuits.

What was the main disagreement between Golgi and Cajal?

Golgi supported reticular theory, while Cajal supported the neuron doctrine.

What is reticular theory?

The idea that the brain is one continuous network of interconnected fibers.

Who supported reticular theory?

Camillo Golgi.

What is the neuron doctrine?

The idea that the brain consists of separate, individual cells called neurons that communicate with one another.

Who supported the neuron doctrine?

Santiago Ramón y Cajal.

Which scientist's view of brain organization became widely accepted?

Cajal's neuron doctrine.

What did Golgi and Cajal receive the Nobel Prize for?

They shared the 1906 Nobel Prize in Physiology or Medicine for their work on the nervous system.

What is the relationship between systems neuroscience and molecular neuroscience?

Systems neuroscience studies large-scale circuits and behavior, while molecular neuroscience studies molecules and cellular mechanisms.

What are the two main classes of cells in the nervous system?

Neurons and glia.

What are neurons?

The principal signaling cells of the nervous system that transmit information over distances.

What are the main functions of neurons?

Receive, integrate, and transmit signals; they are essential for sensation, movement, thought, and behavior.

What are glial cells?

Non-neuronal cells that support and actively regulate the nervous system.

What are the major functions of glial cells?

Support neurons, regulate neurotransmitters, help maintain the blood-brain barrier, provide myelin, and perform immune functions.

Why are glial cells important beyond simply supporting neurons?

They actively influence synaptic signaling, neuronal function, and the brain's chemical environment.

What is dynamic polarization?

The principle that information flows in a preferred direction through distinct neuronal input and output structures.

Who proposed the law of dynamic polarization?

Santiago Ramón y Cajal.

What is the typical direction of information flow through a neuron?

Dendrites and soma → axon hillock → axon → axon terminals → synapses.

What is the cell body, or soma?

The main part of a neuron that contains the nucleus and maintains cellular functions.

What is the function of the soma?

It contains the nucleus and cellular machinery needed to maintain the neuron.

What are dendrites?

Usually short, branching neuronal extensions that receive incoming signals.

What are dendritic spines?

Small protrusions on dendrites that commonly receive synaptic inputs.

What is the axon?

A long, thin neuronal extension that carries electrical signals away from the cell body.

What is the axon hillock?

The region near the soma where incoming signals are integrated and action potentials are typically initiated.

What are axon terminals?

The endings of an axon that release neurotransmitters to communicate with target cells.

What is a synapse?

A junction where one neuron communicates with another cell.

Who hypothesized the existence of synapses, and when?

Charles Sherrington in 1906.

When were synapses visualized using electron microscopy?

In the 1950s.

When was synaptic vesicle release experimentally measured?

In the 1950s.

What are the three major types of glial cells covered in this lecture?

Astrocytes, oligodendrocytes/Schwann cells, and microglia.

What are astrocytes?

Star-shaped glial cells that regulate the neuronal environment and support synaptic and blood-brain barrier function.

What are astrocytic end feet?

Extensions of astrocytes that contact blood vessels and help regulate the blood-brain barrier.

What is the blood-brain barrier?

A selective barrier that regulates which substances can move from the blood into brain tissue.

How do astrocytes help maintain the blood-brain barrier?

They interact with blood vessels and help regulate the exchange of substances between blood and brain tissue.

Where are astrocytes often found in relation to synapses?

Closely associated with synapses.

What is a tripartite synapse?

A synapse involving a presynaptic neuron, a postsynaptic neuron, and an associated astrocyte.

What do astrocytes absorb and release?

Important biological compounds that support neuronal and endothelial function and help regulate the synaptic environment.

What are oligodendrocytes?

Glial cells in the central nervous system that form myelin around axons.

What are Schwann cells?

Glial cells in the peripheral nervous system that form myelin around axons.

Where are oligodendrocytes found?

In the central nervous system (CNS).

Where are Schwann cells found?

In the peripheral nervous system (PNS).

What is myelin?

A fatty insulating sheath around axons that improves the speed and reliability of electrical signal transmission.

How does myelin improve neuronal signaling?

It allows action potentials to travel faster and more reliably along axons.

What are nodes of Ranvier?

Gaps between adjacent myelin segments along an axon.

What is multiple sclerosis (MS)?

An autoimmune disease in which the immune system attacks myelin in the central nervous system.

How can damage to myelin affect neuronal communication?

It can slow, disrupt, or block electrical signal transmission.

What are microglia?

Immune cells of the brain and central nervous system.

What do microglia do?

Remove protein clumps, dead or dying cells, and other cellular debris while helping monitor brain health.

How are neurons and glia different?

Neurons primarily transmit information, while glia regulate, protect, insulate, and support the nervous system; glia also actively influence signaling.

Why are Cajal's drawings important?

They revealed the detailed shapes, connections, and organization of neurons and neural circuits.

What does the neuron doctrine imply about brain function?

Brain function can be understood by studying individual neurons and how they communicate.

What is the difference between cellular and molecular neuroscience?

Cellular neuroscience studies individual cells and their functions; molecular neuroscience studies the molecules and mechanisms underlying those functions.

What is the difference between circuit neuroscience and behavioral neuroscience?

Circuit neuroscience studies how neurons and circuits interact; behavioral neuroscience studies how nervous system activity produces behavior.