Myelination and Nerve Conduction

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What is the effect of myelination on the conduction of action potentials along the axon?

It decreases the speed of impulse conduction

It has no effect on the conduction of action potentials

It reverses the direction of action potential propagation

It increases the speed of impulse conduction (correct)

What is the primary function of the synaptic cleft in synaptic transmission?

To generate action potentials in the post synaptic neuron

To bind neurotransmitters to receptors on the post synaptic neuron

To act as the site for intraneuronal communication (correct)

To release neurotransmitters from the presynaptic neuron

Where are the voltage-sensitive Na+ and K+ channels located in myelinated nerve fibers?

Absent in myelinated nerve fibers

Clustered in high density at the node of Ranvier (correct)

Located only at the terminal end of the axon

Uniformly distributed along the axon membrane

What is the function of the myelin sheath in the central nervous system?

It insulates the axon, allowing for faster conduction of action potentials Signup and view all the answers

What triggers the release of neurotransmitters from the presynaptic terminal?

The electrotonic invasion of the action potential into the terminal Signup and view all the answers

What is the role of Ca2+ ions in synaptic transmission?

To trigger the release of neurotransmitters from the presynaptic terminal Signup and view all the answers

What is the characteristic of the smallest axons?

They are unmyelinated Signup and view all the answers

What is the effect of the thickness of the myelin sheath on the conduction velocity of the nerve impulse?

The thicker the myelin sheath, the faster the conduction velocity Signup and view all the answers

What is the primary difference between electrical and chemical synaptic transmission?

The direction of transmission Signup and view all the answers

What is the characteristic of the propagation of action potentials in unmyelinated fibers?

It occurs in a continuous manner along the axon Signup and view all the answers

What is the term for the release of neurotransmitters from the presynaptic terminal into the synaptic cleft?

Exocytosis Signup and view all the answers

What is the term for the space between two neurons where chemical transmission occurs?

Synaptic cleft Signup and view all the answers

What is the role of the node of Ranvier in the propagation of action potentials?

It is the site of voltage-gated sodium channel clustering Signup and view all the answers

What is the type of cell that produces myelin in the central nervous system?

Oligodendrocyte Signup and view all the answers

What is the role of synaptic vesicles in synaptic transmission?

To store and release neurotransmitters into the synaptic cleft Signup and view all the answers

What is the term for the process by which neurotransmitters bind to receptors on the post synaptic neuron?

Binding Signup and view all the answers

Where are K+ channels typically localized in a myelinated axon?

Internodal area Signup and view all the answers

What is the term for the mode of conduction of action potential in myelinated axons?

Saltatory conduction Signup and view all the answers

What is the most common type of synapse, representing 80-95% of all synapses?

Axodendritic synapses Signup and view all the answers

What is the primary function of axoaxonic synapses?

Modulating transmitter release by the postsynaptic axon Signup and view all the answers

What is the term for the point of functional contact between axons and skeletal muscle?

Neuromuscular junction Signup and view all the answers

What is the primary direction of information flow in synaptic transmission?

From the presynaptic neuron to the postsynaptic neuron Signup and view all the answers

What type of synaptic transmission is rare in humans and common in invertebrates?

Electrical transmission Signup and view all the answers

What is the term for the specialized complex that allows for the transmission of information between neurons?

Synaptic junction Signup and view all the answers

What is the primary mechanism of neurotransmitter action at the synapse?

Opening or closing of ion channels Signup and view all the answers

What is the primary defect in myasthenia gravis?

Attack on the acetylcholine receptor in the postjunctional folds Signup and view all the answers

What is the primary symptom of myasthenia gravis?

Skeletal muscle weakness and fatigability Signup and view all the answers

What is the effect of antibodies on the acetylcholine receptor in myasthenia gravis?

Structural changes in the postjunctional folds Signup and view all the answers

What is the primary treatment for myasthenia gravis?

Inhibiting acetylcholinesterase to increase acetylcholine in the synaptic cleft Signup and view all the answers

What is the characteristic of Lambert-Eaton syndrome?

Presynaptic disorder affecting neuromuscular transmission Signup and view all the answers

What is the effect of repetitive stimulation on muscle action potentials in myasthenia gravis?

Progressive decrease in muscle action potentials Signup and view all the answers

What is the status of nerve fibers in myasthenia gravis?

Intact nerve fibers Signup and view all the answers

In Lambert-Eaton myasthenic syndrome, muscle weakness and fatigability predominantly affects which musculature?

Proximal limb and trunk musculature Signup and view all the answers

What is the primary site of lesion in demyelinating diseases such as Guillain-Barré syndrome?

CNS oligodendroglia and PNS Schwann cells Signup and view all the answers

What is the characteristic electrophysiologic finding in Guillain-Barré syndrome?

Very slow nerve conduction velocities and reduced compound action potential amplitude Signup and view all the answers

What is the typical pattern of weakness progression in Guillain-Barré syndrome?

Ascending paralysis, starting from the legs Signup and view all the answers

What is the potential complication of Guillain-Barré syndrome?

Respiratory failure Signup and view all the answers

What is the process by which recovery occurs in Guillain-Barré syndrome?

Remyelination Signup and view all the answers