Neurons, Glial Cells, and the Blood-Brain Barrier

Fifty vocabulary flashcards covering neuron structure, glial cells, and blood-brain barrier concepts discussed in the lecture.

Axon Terminal

The frayed end of an axon that forms multiple branches and serves as the output region communicating with other cells.

Dendrite

A cell process that receives information from neighboring cells; distinguished by its input function rather than shape.

Action Potential

The electrical wave that travels along an axon, initiating communication between neurons.

Sensory Neuron

A neuron that carries information from sensory receptors toward the brain, without receiving input from another neuron.

Pseudo-unipolar Neuron

A sensory neuron type with one axon and no true dendrites, commonly involved in touch sensation.

Bipolar Neuron

A neuron with the cell body located centrally between two processes; found in special senses like smell and vision.

Olfaction

The sense of smell; transmitted by specialized bipolar neurons.

Retina

Light-sensitive layer at the back of the eye containing bipolar neurons for vision.

Cell Body (Soma)

The central part of a neuron containing the nucleus; location varies among neuron types.

Axon

The long projection of a neuron that conducts action potentials toward axon terminals.

Touch Receptor

Specialized endings on sensory neuron branches in the skin that initiate action potentials when stimulated.

Branching

The splitting of neuronal processes, giving dendrites or axon terminals their characteristic tree-like shape.

Blood Vessel

A structure wrapped by astrocyte end-feet to regulate substances entering brain tissue.

End-feet

Astrocyte processes that physically contact blood vessels and neurons, mediating nutrient transfer.

Astrocyte

Star-shaped glial cell in the CNS that forms the blood-brain barrier and delivers nutrients to neurons.

Myelin

Insulating sheath around axons that speeds electrical conduction; produced by specific glial cells.

Oligodendrocyte

CNS glial cell that produces myelin around multiple axons.

Central Nervous System (CNS)

Composed of the brain and spinal cord; contains astrocytes, oligodendrocytes, microglia, and ependymal cells.

Peripheral Nervous System (PNS)

All neural tissue outside the CNS; contains satellite cells and Schwann cells as glial counterparts.

Satellite Cell

PNS glial cell functionally similar to an astrocyte, supporting neurons in peripheral ganglia.

Schwann Cell

PNS glial cell that produces myelin around a single axon; named after Dr. Schwann.

Microglia

Resident immune cells of the CNS serving as the first line of immunologic defense inside the brain.

Blood-Brain Barrier (BBB)

Selective barrier formed partly by astrocyte end-feet that restricts passage of substances from blood into brain tissue.

Immune Privilege of Brain

The concept that white blood cells and antibodies are normally excluded from the brain by the BBB.

Pathogen

An infection-causing agent, such as a bacterium or virus, barred from entering the brain by the BBB.

White Blood Cell

Immune cell that can carry hidden pathogens; normally prevented from entering the brain to avoid Trojan-horse infections.

Trojan Horse Strategy

Mechanism by which pathogens hide inside white blood cells and could invade the brain if not blocked by the BBB.

Washington DC Police Analogy

Lecture metaphor illustrating that only specialized ‘police’ (microglia) are allowed inside the ‘restricted area’ (brain).

First Physical Defense

Role of the BBB in preventing unwanted substances from entering the brain before immune action is needed.

First Immune Defense

Role of microglia as the initial immunologic responders within brain tissue.

Ependymal Cell

CNS glial cell lining ventricles that produces cerebrospinal fluid; has no PNS equivalent.

Cerebrospinal Fluid (CSF)

Fluid produced by ependymal cells that surrounds and cushions the brain and spinal cord.

Transport Channel

Protein pathway that permits regulated entry of specific molecules like glucose and amino acids through the BBB.

Diffusion through BBB

Passive movement of small or lipid-soluble molecules, such as oxygen, carbon dioxide, caffeine, and nicotine, directly across the barrier.

Oxygen (O₂)

Small gas that freely diffuses across the BBB to support brain metabolism.

Carbon Dioxide (CO₂)

Gas that freely diffuses out of the brain across the BBB as a metabolic waste product.

Caffeine

Lipid-soluble stimulant molecule that readily crosses the BBB by diffusion, affecting brain alertness.

Nicotine

Fat-soluble compound from tobacco that diffuses across the BBB and acts on neuronal receptors.

Electrolytes

Charged ions such as Na⁺ and K⁺ that require transport channels to enter the brain because of their charge.

Glucose

Primary energy source for neurons; crosses the BBB through specific transporter proteins.

Amino Acids

Building blocks of proteins; enter the brain via regulated transport across the BBB.

Large and Charged Molecules

Substances that cannot freely cross the BBB and must be transported or are excluded entirely.

Insulation (of Axon)

Function of myelin to prevent current loss and increase action-potential speed.

Uber Eats Analogy

Lecture image describing astrocytes delivering nutrients from blood vessels to neurons.

Symmetrical Neuron

Neuron whose two ends appear mirror-image of each other, as seen in some bipolar neurons.

Action Potential Direction

In sensory neurons, the electrical signal starts in the skin and travels toward the brain along the axon.

Sensory Pathway

Route by which touch receptors in skin trigger action potentials that ascend to the brain.

Restricted Molecules

Toxins, pathogens, and immune cells that are entirely barred from brain entry by the BBB.

End-feet Regulation

Astrocyte control of what exits blood vessels and reaches neurons through their vascular contacts.

Neuron

Primary cell type of nervous tissue specialized for electrical signaling, composed of dendrites, a soma, an axon, and terminals.

Glial Cell

Supportive nervous-system cell type that includes astrocytes, oligodendrocytes, microglia, and others, each with specialized functions.