Neurons

Question 1

Name the anatomical structure that contains the cell bodies (somata) of primary somatosensory neurons, and state how these neurons are classified in terms of their morphology (2)

Answer 1

Spinal/dorsal root ganglion; pseudo-unipolar

Question 2

Briefly describe the structure and function of the cell type after which the “Substantia Nigra” is named, give a unique diagnostic feature of these cells and state in what neurological disorder these cells play a key role (4)

Answer 2

Multipolar, dopamine-releasing neurons; modulate the activity of the direct and indirect pathways involved in motor control in the basal nuclei; contain neuromelanin pigment inclusions; Parkinson’s disease

Question 3

List the four (4) most common types of support cells in the CNS and for each name its principal function (4) [x3]

Answer 3

Astrocytes (metabolic support), oligodendrocytes (myelination), microglia (immune defense), ependyma (interface between CSF and brain tissue/movement of CSF)

Question 4

Briefly describe the structure and function of the cell type after which the “Substantia Nigra” is named (2) [x2]

Answer 4

Multipolar, dopaminergic neurons, modulate the activity of the direct and indirect pathways involved in motor control in the basal nuclei

Question 5

Give a unique diagnostic feature of these cells and state in what neurological disorder these cells play a key role (1)

Answer 5

Contain neuromelanin pigment inclusions; Parkinson’s disease

Question 6

List the three (3) most common types of support cells in the CNS and briefly summarize how they affect axon regeneration after traumatic injury (6)

Answer 6

Astrocytes, reactive gliosis/glial scar; oligodendrocytes, neurite growth inhibitory proteins block axon regrowth; microglia, clear cell debris but may further damage neurons by releasing cytotoxic factors

Question 7

Name the cell types that will be primarily affected by de-myelinating diseases (2)

• of the CNS
• of the PNS
• state the principal structural difference between these cell types (1)

Answer 7

Oligodendrocytes
Schwann cells

Schwann cells myelinate only one axon segment, oligodendrocytes many

Question 8

What cell type resident in CNS tissue has a primary function in immune defence? (½)

Answer 8

Microglia

Question 9

Given that the cell type (above) is difficult to demonstrate in tissue using classic histological staining, outline a technique that allows cell type-specific labelling (1)

Answer 9

Immunohistochemistry: antibodies against cell type-specific markers are used to label cells

Question 10

Name the structures that contain the cell bodies of primary sensory neurons

Answer 10

Spinal/dorsal root ganglia

Question 11

Classify the primary sensory neurons in terms of their morphology (½)

Answer 11

Pseudo-unipolar

Question 12

List two (2) major functions of the neuronal cytoskeleton (2)

Answer 12

Maintaining cellular structure; axonal transport

Question 13

List the three (3) most common types of supporting cells in the CNS and briefly outline how they contribute to the failure of axon regeneration after injury (4½)

Answer 13

Astrocytes: become reactive, form glial scar and express axon-growth inhibiting proteoglycans; oligodendrocytes: up regulate and release axon growth inhibiting proteins (e.g. Nogo-A); microglia: remove debris, but may further damage neurons through release of cytotoxic agents