Myelin Sheath and Multiple Sclerosis Quiz

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Questions and Answers

What is the primary role of oligodendrocytes in the central nervous system?

To produce myelin sheaths around axons (correct)

To regulate blood flow to nerve fibers

To facilitate neurotransmitter release

To provide structural support to neurons

Which component contributes to the structure and appearance of the myelin sheath?

Neurotransmitters and receptors

Collagen and elastic fibers

Phospholipids and proteins (correct)

Blood vessels and connective tissue

What is the function of Schwann cells in the peripheral nervous system?

To form myelin sheaths around individual axons (correct)

To generate electrical impulses in neurons

To demyelinate axons during injury

To encapsulate nerve endings for sensory reception

What role do the nodes of Ranvier play in the conduction of nerve impulses?

They allow for saltatory conduction, enhancing speed Signup and view all the answers

What is the primary content of the endoneurium surrounding individual nerve fibers?

Collagen and proteoglycans Signup and view all the answers

What role do oligodendrocytes play in the nervous system?

They myelinate axons in the CNS. Signup and view all the answers

What is the primary function of the myelin sheath?

To increase the speed of nerve impulse conduction. Signup and view all the answers

What are Nodes of Ranvier responsible for in nerve impulse conduction?

They allow for saltatory conduction of impulses. Signup and view all the answers

What type of cells form the myelin sheath in the peripheral nervous system (PNS)?

Schwann cells Signup and view all the answers

A disorder characterized by the destruction of myelin in the CNS is known as what?

Multiple sclerosis Signup and view all the answers

What primarily distinguishes gray matter from white matter in the brain?

Gray matter is richer in cell bodies, while white matter is composed mainly of axons. Signup and view all the answers

What cell types are predominantly involved in forming synapses in gray matter?

Multipolar neurons Signup and view all the answers

In which part of the nervous system is myelin sheath formed by oligodendrocytes?

Central nervous system Signup and view all the answers

What is one of the primary functions of oligodendrocytes in the central nervous system?

To form myelin sheaths around multiple axons Signup and view all the answers

Which statement correctly describes the structure of the myelin sheath in the peripheral nervous system?

It is created by Schwann cells that wrap around individual axons multiple times. Signup and view all the answers

What role do the Nodes of Ranvier play in neuron function?

They facilitate saltatory conduction. Signup and view all the answers

What is a common effect of multiple sclerosis on the nervous system?

Damage to the myelin sheaths surrounding axons Signup and view all the answers

Which type of glial cell in the central nervous system assists with structural support for neurons?

Astrocytes Signup and view all the answers

What distinguishes Schwann cells from oligodendrocytes in terms of myelination?

Schwann cells myelinate single axons, while oligodendrocytes myelinate multiple axons. Signup and view all the answers

What is the main purpose of neurotransmitters in the synapse?

To convert electrical signals from presynaptic cells into chemical signals for postsynaptic cells Signup and view all the answers

Which of the following best describes a key feature of neuroglia compared to neurons?

Neuroglia provide support but do not conduct impulses. Signup and view all the answers

Study Notes

Myelin Sheath and Myelination

Myelin sheath is a lipid-rich insulating layer that wraps around axons in the nervous system.
It increases the speed of nerve impulse conduction along the axon, provides protection and support for axons.
Schwann cells form the myelin sheath in the peripheral nervous system (PNS).
Oligodendrocytes form the myelin sheath in the central nervous system (CNS).
Nodes of Ranvier are spaces in the myelin sheath between individual cells that myelinate the axons.
These gaps allow for saltatory conduction, where the nerve impulse jumps rapidly between nodes, speeding up transmission.

Multiple Sclerosis

It is a disease in which the myelin sheaths surrounding axons are damaged by an autoimmune mechanism.
This interferes with the activity of the affected neurons, producing various neurological problems.
The destructive actions of the immune cells exceed the capacity of oligodendrocytes to produce myelin.

Synapse

It is the junction between neurons where nerve impulses are transmitted.
Transmission is unidirectional.
Synapses convert an electrical signal from a presynaptic cell into a chemical signal in the postsynaptic cell.
This happens through the release of neurotransmitters.

Components of a Synapse

Presynaptic axon terminal: The end of the axon of the presynaptic neuron.
Postsynaptic cell membrane: The membrane of the next neuron (postsynaptic cell).
Synaptic cleft: The narrow gap between the presynaptic and postsynaptic cell membranes.

Types of Synapse

Axodendritic - Axon to dendrite
Axosomatic - Axon to soma
Axoaxonic - Axon to axon

Neuroglia: The Supporting Cells of the CNS

Neuroglia are highly branched, supportive, non-neuronal cells in the CNS and PNS.
They surround neurons, dendrites, and axons.
They are smaller in size than neurons and have a dark-staining nucleus.
They outnumber neurons by a ratio of 9:1.

Types of Neuroglia

CNS:
- Astrocytes
- Oligodendrocytes
- Microglia
- Ependymal cells
PNS:
- Satellite cells
- Schwann cells

Classification of Neurons

Multipolar: One axon, 2 or more dendrites. Most common.
Bipolar: One axon, one dendrite. Found in the sensory organs.
Unipolar: One process extending from the cell body that divides into two branches. Found in sensory neurons.
Anaxonic: Many dendrites but with no true axon. Does not produce action potentials.

White Matter vs. Gray Matter

Gray matter contains abundant neuronal cell bodies, dendrites, and unmyelinated axons.
White matter contains abundant myelinated axons.
Gray matter is located in the cortex of the brain and cerebellum, while white matter is located deeper within the brain and spinal cord.

Meninges

Dura mater: Outermost layer, tough and fibrous.
Arachnoid mater: Middle layer, thin and delicate.
Pia mater: Innermost layer, thin and transparent. Adheres closely to the brain and spinal cord.
Subarachnoid space: Space between the arachnoid mater and pia mater. Contains cerebrospinal fluid (CSF).

Nerve Organization

Nerve fibers are grouped into bundles called fascicles to form nerves.
These bundles are surrounded by connective tissue fibers.

Layers of Connective Tissue Around Nerve Fibers

Endoneurium: Innermost layer, surrounds individual nerve fibers.
Perineurium: Surrounds each fascicle of nerve fibers. Forms a selective barrier, regulating the exchange of substances between the blood vessels and the nerve fibers.
Epineurium: Outermost layer, surrounds the entire nerve.

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Description

Test your knowledge on the structure and function of the myelin sheath, its role in nerve impulse conduction, and the implications of diseases such as multiple sclerosis. This quiz covers essential concepts in neurobiology and the types of cells that contribute to myelination in the nervous system.