Neurobiology - Cells of the Nervous System (Lecture Notes)

Flashcards covering neuron structure, neuroglia, regeneration, and classification based on the provided lecture notes.

Approximately how many neurons are in an adult brain?

About 87 billion.

What are the three basic features that all neurons share?

Cell body (soma), dendrites, and an axon.

Which part of the neuron receives signals from other neurons?

Dendrites.

Which part of the neuron transmits impulses away from the cell body?

The axon.

What is the region at the beginning of the axon where an impulse is initiated?

The axon hillock.

What is the gap between myelin sheath segments called?

Nodes of Ranvier.

Which glial cells produce myelin in the central nervous system?

Oligodendrocytes.

Which glial cells produce myelin in the peripheral nervous system?

Schwann cells.

True or False: All axons are myelinated.

False—not all axons are myelinated.

What is the outermost wrapping around a myelinated peripheral nerve fiber formed by Schwann cells?

Neurilemma.

Which glial cells nourish neurons and help form the blood-brain barrier?

Astrocytes.

Which glial cells perform phagocytosis and provide immune defense in the CNS?

Microglia.

Which cells line the ventricles and help regulate cerebrospinal fluid composition?

Ependymal cells.

Which glial cells wrap around CNS axons to form the myelin sheath?

Oligodendrocytes.

Which PNS cells support clusters of neuron cell bodies in ganglia?

Satellite cells.

Do mature neurons divide?

No — they are amitotic.

What usually happens if a neuron’s cell body is injured?

The neuron usually dies.

In the PNS, what enables a damaged axon to regenerate?

Schwann cells and the neurilemma form a guiding sheath for regrowth.

Why is regeneration in the CNS unlikely?

CNS axons lack neurilemma; oligodendrocytes do not proliferate after injury; no guiding sheath.

What are the four major CNS neuroglia and a primary function of each?

Astrocytes (nourish neurons, BBB, ion regulation, scar tissue); Oligodendrocytes (myelinate CNS); Microglia (phagocytosis/immune defense); Ependymal cells (line ventricles/Central canal, regulate CSF).

Name the three structural classifications of neurons.

Multipolar, Bipolar, Unipolar (pseudounipolar).

What is a multipolar neuron and how common is it?

A neuron with many processes; about 99% of neurons; most CNS neurons.

What is a bipolar neuron and where are they typically located?

Two processes; typically in eyes, ears, and nose.

What is a unipolar (pseudounipolar) neuron and where are they usually found?

One process; cell bodies mainly in ganglia; usually sensory.

Name the functional classes of neurons and their primary roles.

Sensory (afferent) neurons carry impulses to the CNS; Interneurons (association) connect neurons in the CNS; Motor (efferent) neurons carry impulses from the CNS to effectors.

What is the direction of impulse flow for sensory (afferent) neurons?

From the peripheral nervous system toward the CNS.

What is saltatory conduction and which structures enable it?

The jumping of action potentials from node to node, enabled by myelin sheath and Nodes of Ranvier.

What are the main components of neuroglia’s job in development and maintenance?

Provide structural support, guide neuron positioning, stimulate specialization, remove ions/neurotransmitters, and secrete growth factors.

What is the outcome if a peripheral axon regenerates and reconnects with its target?

Function may return; otherwise, function may be lost.