EXAM 1 Nervous System Koehler's Learning Objectives

List anatomic & physiological factors that make the nervous system different from other systems in terms of how it responds to injury

1. Complex with many divergent parts 2. Limited capacity to regenerate 3. Encased in a bony shell 4. Selective vulnerability related to vascular supply and metabolic needs 5. Disease can be primary or secondary 6. Unique anatomic structures with distinctive responses to injury 7. Unique immune responses due to the BBB and blood-CSF barrier

Explain Wallerian degeneration and differences between CNS and PNS regeneration

Wallerian degeneration is degeneration of the portion of an axon distal to the site of injury. CNS regeneration is limited due to myelin-associated inhibitors, astrocyte extracellular matrix, and glial scarring. PNS regeneration is more successful.

Describe the role of astrocytes in BBB formation and regulation of ions and water

Astrocytes help form the BBB and regulate ions and extracellular water. Damage leads to BBB breakdown and edema.

Types of herniation and causes of brain expansion

Herniation types: subfalcine, transtentorial, cerebellar

Causes of Expansion: edema, hemorrhage, inflammatory cells, neoplasia

Unique features of neuron metabolism

High energy needs, low glucose reserves, sensitivity to oxidative damage, and excitatory neurotransmitters

Cells most sensitive to hypoxia- NOAME

Neurons> Oligodendrocytes> Astrocytes> Microglia> Endothelial cells

Neuron populations most sensitive to hypoxia

Hippocampal neurons, Purkinje cells, pyramidal neocortical neurons

Causes of global hypoxia/ischemia

Anesthetic events, severe anemia

Causes of focal ischemia

Emboli, vascular malformations, atherosclerosis, vasculitis

Brain scarring without fibroblasts

Astroglial scarring (glial scar formation)

Ways genetic defects cause nervous system disease

Impaired metabolism, impaired migration/maturation, impaired waste elimination, tumor formation

Genetic defects affecting maturation/migration

Neural tube defects, migration defects, hemisphere formation defects, abnormal gyri

Unique features of CNS tumors

Can be fatal even if benign, rarely metastasize outside the CNS

How CNS tumors cause injury

Direct compression/invasion and secondary edema, hemorrhage, herniation

Nutritional causes of nervous system injury

Metabolic impairment, competition for binding sites, osmotic imbalance

Thiamine deficiency causes neuronal necrosis how?

Impaired ATP production leading to neuronal necrosis

Hypoxia vs anoxia vs ischemia

Hypoxia: decreased oxygen, anoxia: no oxygen, ischemia: reduced blood flow

Mechanisms of hypoxic/ischemic injury

Energy failure, ion imbalance, cytoskeletal damage, enzyme activation, free radicals

Brain trauma and coup/contrecoup

Direct damage, vascular injury, swelling. Coup: stationary head hit. Contrecoup: moving head hits stationary object

CNS hemorrhage categories

Subdural, subarachnoid, parenchymal

Downstream spinal cord injury concept meaning? (Be prepared to draw a diagram of where you would expect to see lesions in the spinal cord cranial and caudal to a transecting injury)

Wallerian degeneration cranial and caudal to lesion.

PNS trauma processes?

Crushing, traction/avulsion, neoplastic destruction

Poison vs Toxin?

Poison is any harmful substance; toxins are biologic. Endogenous toxins include ammonia.

How do poisons cause cell damage/death?

Disrupt vital cellular functions

Anatomic patterns of poison damage?

Bilateral symmetry, laminar necrosis, selective neuronal loss, spongiosis

How does liver failure lead to brain edema & vacuolation?

Ammonia causes astrocyte swelling and vacuolation

Pathogen injury categories? (3)

Direct damage, vascular damage, immune-mediated damage

Pathogen entry into nervous system routes? (3)

Bloodstream, direct extension, retrograde nerve transport

Immune responses by pathogen? (bacteria, viruses, fungi, algae, protozoa, parasites)- sorry long one...

Bacteria: neutrophils (suppurative), mycobacteria (granulomatous & macrophages), rickettsia (vasculitis & lymphocytes)

Viruses: lymphocytes (nonsuppurative)

Fungi: neutrophils & macrophages (pyogranulomatous), eosinophilic (eosinophils), some primarily cause damage by vasculitis (angiotropic)

Algae: suppurative, pyogranumatous

Protozoa: nonsuppurative, eosinophilic

Non-protozoal parasites (nematodes, arthropods, etc): eosinophilic, granulomatous

Pathogenesis of bacterial meningitis in neonatal animals?

Umbilical infection --> septicemia --> meninges

What does "angiotropic" in relation to fungi mean? How does this cause damage in nervous system?

Invade blood vessels causing hemorrhage and ischemia

How does rabies virus enter the CNS?

Retrograde axonal transport after bite