Cortical Plasticity and Pain Pathways

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Questions and Answers

What phenomenon is illustrated by the feeling of touch in a missing limb when stimulating facial areas in amputees?

Neurotransmitter depletion

Peripheral nerve regeneration

Nociceptive pain response

Cortical plasticity (correct)

Which neurotransmitter is primarily associated with the termination of C fibers in the dorsal horn during pain transmission?

Dopamine

Substance P (correct)

Serotonin

Glutamate

What effect do endogenous opioids have on nociceptor action potentials?

Enhance nociceptor activity

Promote depolarization of the membrane

Increase the calcium influx

Decrease the amplitude of excitatory post-synaptic potential (correct)

Which peptide is NOT part of the family activated by opioid receptors in the brain?

Substance P Signup and view all the answers

What anatomical structure is primarily involved in the spinothalamic tract related to pain processing?

Laminae I and V of the dorsal horn Signup and view all the answers

What is the primary event that occurs during Wallerian degeneration?

Axonal and myelin damage is cleared distally from the injury Signup and view all the answers

Which receptors are implicated in mediating oligodendrocyte apoptosis after spinal cord injury?

FAS and P75 death receptors Signup and view all the answers

What role do microglia play in the context of oligodendrocyte apoptosis?

Microglia activate and induce apoptosis in oligodendrocytes Signup and view all the answers

What therapeutic mechanism can be employed to prevent apoptosis in acute spinal cord injury?

Targeting upstream events of the caspase cascade Signup and view all the answers

Where does apoptosis predominantly occur in relation to the lesion epicenter during acute spinal cord injury?

In both ascending and descending white matter tracts Signup and view all the answers

Which part of the central nervous system is affected by multiple sclerosis?

Spinal cord Signup and view all the answers

What is the primary effect of multiple sclerosis on oligodendrocytes?

Demyelination Signup and view all the answers

What type of immune cells are primarily involved in the inflammatory response seen in multiple sclerosis?

T and B lymphocytes Signup and view all the answers

Which structure is primarily affected by the inflammatory demyelinating lesions in multiple sclerosis?

White matter Signup and view all the answers

What is the functionality of the nodes of Ranvier?

Enhance neural conduction Signup and view all the answers

Which of the following is NOT a component of myelin mentioned in relation to multiple sclerosis?

Neurotransmitter receptors Signup and view all the answers

What is the main uncertainty regarding the immune response in multiple sclerosis?

Whether it primarily targets myelin or oligodendrocytes Signup and view all the answers

What is a potential consequence of chronic inflammatory demyelination in multiple sclerosis?

Progressive neurologic disability Signup and view all the answers

Study Notes

Cortical Plasticity and Somatosensory Representation

Cortical plasticity allows for changes in somatosensory representation in the cortex.
Example: Stimulation of facial regions in an amputee can lead to sensations where the missing arm used to be.

Pain Pathways

Pain transmitted via the anteriorlateral (spinothalamic) tract.
Aδ fibers terminate in laminae I and V of the dorsal horn, releasing glutamate as the synaptic transmitter.
C fibers terminate in laminae I and II, using substance P for neurotransmission.

Endogenous Analgesic System

Endogenous opioids function as neurotransmitters and neuromodulators.
Opioid receptors in the brain respond to peptides such as enkephalins, dynorphins, and endorphins.
Activation of opioid receptors decreases calcium influx, lowering nociceptor action potentials.
Opioid action results in hyperpolarization of the membrane and reduces excitatory post-synaptic potential (EPSP) amplitude.

Spinal Cord Injury (SCI) and Apoptosis Mechanisms

Wallerian degeneration and axonal demyelination trigger oligodendrocyte apoptosis.
Microglia activation may induce apoptosis in oligodendrocytes due to inflammation.
FAS and P75 neurotrophin receptors mediate oligodendrocyte death post-spinal cord injury.
Apoptosis occurs in both ascending and descending white matter tracts surrounding the lesion.

Multiple Sclerosis (MS)

MS is an autoimmune disease characterized by chronic inflammatory demyelination and axonal damage within the central nervous system (CNS).
Affects brain, spinal cord, and optic nerves, but spares the peripheral nervous system (PNS).
Presents with inflammatory demyelinating lesions (plaques) that can be acute, chronic, active, or silent.
Inflammatory infiltrates in lesions include T cells, B cells, macrophages, and activated microglia.
The primary target of MS pathology is oligodendrocytes, the myelinating cells of the CNS.

Myelin Structure in MS

Myelin consists of a lipid bilayer with key proteins such as myelin-associated glycoprotein (MAG), myelin basic protein (MBP), proteolipid protein (PLP), and myelin oligodendrocyte glycoprotein (MOG).
During demyelination, oligodendrocytes become damaged, although it's unclear whether the immune response specifically targets myelin or oligodendrocytes.

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Description

Explore the fascinating topic of cortical plasticity, particularly how the somatosensory representation changes in the brain. This quiz involves concepts related to the spinothalamic tract and its implications in pain perception, illustrated through examples like limb amputation.