96 Questions
What type of protein uses chemical energy from adenosine triphosphate hydrolysis to generate mechanical force and bind to microtubules?
Kinesin
Which part of the brain has a mixture of gray and white matter?
Thalamus
What is the primary component of gray matter?
Cell bodies of neurons
What is the term for the network of intermingled thinly myelinated axons, dendrites, and glial cell processes in gray matter?
Neuropil
What type of cells are responsible for myelination in the central nervous system?
Oligodendrocytes
Which structure is involved in the transport of vesicles and effete neurofilament proteins?
Dynein
What is the name of the structure that connects the two hemispheres of the brain?
Corpus callosum
What is the term for the white matter areas that border the lateral and ventral surfaces of the thalamus?
Internal capsule
What is the clear space surrounding large axons an artifact of?
The dissolution of lipid components of myelin lamellae by solvents
Which of the following stains identifies microglia within a section of brain?
IHC stain for ionized calcium binding adapter molecule 1 (Iba1)
What is the main function of neurons in the CNS?
To modulate and transmit chemical and electric signals
What is the estimated number of neurons in the human brain?
1 × 10^11
What is the process of nerve impulse conduction dependent on?
The establishment of an electric potential across the cell membrane of the neuron/axon
What is the function of the glial cells in the CNS?
To maintain CNS homeostasis and play an important role in the immune response and healing
What is the main difference between the dorsal, lateral, and ventral funiculi in the spinal cord?
The type of axons they contain
What is the name of the outermost layer of the meninges?
Dura mater
What is the function of astrocytes in the nervous system?
To regulate the ionic balance around neurons
What is the name of the space enclosed by the arachnoid and pia mater?
Subarachnoid space
What is the term for the gap between the terminal end of one neuron and the beginning of another?
Synapse
What is the function of oligodendrocytes in the nervous system?
To form myelin sheaths around axons
What is the approximate ratio of glial cells to neurons in the mammalian CNS?
10:1
What is the name of the cells that line the ventricular system?
Ependymal cells
What is the function of the axon in a neuron?
To transmit signals to other neurons
What is the term for the site where the axon terminates and forms a connection with another neuron?
Synapse
What is the term for inflammation of the meninges?
Meningitis
What is the term for inflammation restricted to the dura mater?
Pachymeningitis
What occurs in response to irritation in the inner dura mater, arachnoid membrane, and pia mater?
Proliferation of cells
What is the most common location of dural ossification in older dogs?
Ventral, cervical, and lumbar dura mater
What type of cells form glial nodules in viral and protozoal encephalitides?
Reactive microglial cells and infiltrating macrophages
What is the term for the space enclosed by the arachnoid and pia mater?
Subarachnoid space
How do infectious agents typically spread to the meninges?
Hematogenously, by direct extension, by leukocytic trafficking, or by retrograde axonal transport
What is the term for the lesions that occur in the meninges, likely related to aging or degeneration?
Meningeal cells on the outer surface of the arachnoid membrane
What is the result of persistent activation of glutamate receptors of target cells?
Excitotoxicity
What is the result of the early increase in ATP-dependent release of normally sequestered intracellular calcium ions?
Neuronal depolarization
What is the cause of the laminar pattern of neuronal necrosis observed in thiamine deficiency–induced polioencephalomalacia?
Microanatomic arrangement of the cerebral cortex
What is the process by which macrophages surround and infiltrate the necrotic neuron cell body?
Neuronophagia
What is the result of the influx of extracellular calcium into cells?
Further impairment of mitochondrial function
What is the significance of IHC stains for neuronal specific markers?
They delineate a linear pattern of neuronal necrosis
What is the consequence of the altered activity of glutamate receptors of target cells?
Disturbance of mitochondrial function
What is the term for the lesions observed in thiamine deficiency–induced polioencephalomalacia?
Laminar lesions
What is the role of spinal cord ependymal cells in CNS injury?
Serving as stem cells capable of forming other glial cell types
What is the result of suppurative exudate forming in the CSF in the case of bacterial infection?
Obstructive hydrocephalus
What is the role of microglia in the CNS?
Antigen presentation
What type of cells are called gitter cells?
Macrophages derived from blood monocytes
What is the response of microglia to injury in the CNS?
Hypertrophy, hyperplasia, phagocytosis, and neuronophagia
What is the result of ependymal cell loss in the CNS?
Hydrocephalus
What is the role of astrocytes in the CNS?
Coordination of inflammatory events
What is the result of inflammation of the ependyma in the CNS?
Ependymitis
What is the characteristic of the exudate produced by Streptococcus spp., Staphylococcus spp., and Corynebacterium spp.?
Pale-yellow to yellow
What is the effect of bovine viral diarrhea virus on the granule layer of the cerebellum?
It kills mitotic cells
What is the result of necrosis of mitotic cells in the granule layer of the cerebellum?
The granule layer is not formed
What is the characteristic of the exudate produced by Coliforms, such as E. coli and Klebsiella spp.?
White to gray
What is the characteristic of the exudate produced by Pseudomonas spp.?
Green to bluish-green
What is the effect of viral infection on the granule layer of the cerebellum?
It kills mitotic cells
What is the result of the absence of mitotic cells in the granule layer of the cerebellum?
The cerebellum does not obtain full size
What is the characteristic of the cerebellar hypoplasia in calves?
Discontinuous granule cell layer and sparse Purkinje cell layer
What is the primary consequence of necrosis of undifferentiated cells in the external granule layer in the cerebellum of calves?
Hypoplasia or atrophy of the cerebellum
What is the underlying mechanism of the second process involved in cerebellar hypoplasia/atrophy in calves?
Viral-induced vasculitis and ischemia
What is the characteristic histopathological change observed in the cerebellum of calves infected with the virus?
All of the above
What is the probable reason for the degeneration of Purkinje cells in the cerebellum of calves infected with the virus?
Both A and B
What is the consequence of viral-induced vasculitis and ischemia in the cerebellum of calves?
All of the above
What is the characteristic feature of the Purkinje cells in the cerebellum of calves infected with the virus?
Malpositioned and located in the molecular layer
What is the underlying mechanism of leptomeningitis in the cerebellum of calves?
Both A and B
What is the consequence of septicemia in the cerebellum of calves?
Bacteria being trapped in vascular beds within the neuroparenchyma and meninges
What is the primary effect of bovine viral diarrhea virus on the granule cells of the cerebellum during organogenesis?
Cytolysis of dividing germinal cells
What is the characteristic feature of the cerebellum in bovine viral diarrhea virus infection?
Hypoplastic and dysplastic folia with reduced thickness of the molecular layer
What is the result of the loss of neuron cell bodies or failure of neurons to migrate properly in the cerebellum?
Large gaps between adjacent cells in the Purkinje cell layer
What is the characteristic feature of the granule cell layer in bovine viral diarrhea virus infection?
Reduced number of neuronal nuclei
What is the outcome of the infection of dividing germinal cells during the earliest stages of cellular differentiation?
Severe lesions involving the granule cells
What is the characteristic feature of the cerebral abscess in the goat?
A large, encapsulated abscess replacing most of the right cerebral hemisphere
What is the result of the extension of the exudate into the ventricular system?
Hydrocephalus
What is the outcome of the injury to the cerebellum during organogenesis?
Cerebellar hypoplasia and dysplasia
What regulates the free movement of certain substances from the blood to the endoneurium of peripheral nerves?
Blood-nerve barrier
What is the term for the disease that affects the PNS, characterized by substrate accumulation in cell bodies of lower motor neurons?
Lysosomal storage disorders
What is the term for the disease that affects the PNS, characterized by damage to neuron cell bodies of lower motor neurons residing in the CNS?
Neuronopathy
What is the term for the disease that affects the PNS, characterized by substrate accumulation in cell bodies of sensory neurons located in dorsal root ganglia?
Lysosomal storage disorders
What is the term for the disease that affects the PNS, characterized by cell death and axonal degeneration?
Neuropathy
What is the term for the structure that regulates the free movement of certain substances from the blood to the endoneurium of peripheral nerves?
Blood-nerve barrier
What is the term for the process of substrate accumulation in cell bodies of lower motor neurons, leading to cell death and axonal degeneration?
Lysosomal storage disorders
What is the term for the disease that affects the PNS, characterized by damage to axons of lower motor neurons?
Axonopathy
Which part of the nervous system regulates visceral sensation and vasomotor and respiratory reflexes through baroreceptors and chemoreceptors?
Afferent nerves
What is the function of the parasympathetic system in relation to the sympathetic system?
It acts to lessen the effects of increased vasoconstriction and heart rate
Which division of the peripheral nervous system exerts effects on blood flow and digestive processes?
Enteric nervous system
What are the main components of the enteric nervous system?
Myenteric and submucosal plexuses
What can occur due to injury to the myenteric and submucosal plexuses?
Dysautonomias
What is the function of the autonomic nervous system in the medulla oblongata, pons, and hypothalamus?
Regulation of autonomic and enteric functions
Which system has two structural and functional components: the sympathetic and parasympathetic systems?
Autonomic nervous system
What is the opposing effect of the parasympathetic system on the sympathetic system?
Decreased vasoconstriction and heart rate
What is a clinical feature of diabetic neuropathy in cats?
Rear limb weakness and a characteristic plantigrade stance
Which vitamin deficiency is associated with a sensory neuropathy in pigs?
Pantothenic acid
What is the primary effect of methylmercury on the nervous system?
Directly altering biochemical reactions
What is the characteristic of curled-toe paralysis in poultry?
Demyelinating neuropathy with swollen peripheral nerves
Which type of neuropathy is caused by vitamin A deficiency in calves and pigs?
Peripheral neuropathy caused by narrowing of the optic foramina
What is the primary site of toxic effect of organomercurial compounds such as methylmercury?
Neuron cell body
What is the result of pantothenic acid deficiency in pigs?
Proprioceptive deficits, goose-stepping, and dysmetria
Which type of neuropathy is caused by riboflavin deficiency in poultry?
Demyelinating neuropathy with swollen peripheral nerves
Study Notes
Structure of Neurons
- Neurons vary in size, shape, and function
- Cell bodies are organized into functional groups (nuclei, horns of gray matter, cerebral lamina)
- Neuronal processes (axons and dendrites) traverse through the brain and spinal cord
- Each neuron makes approximately 10,000 synapses with other neurons
Glial Cells
- Glial cells (microglia, astrocytes, oligodendrocytes) maintain a close association with neurons
- Glial cells outnumber neurons 10 to 1 in the mammalian CNS
- Glial cells play a crucial role in maintaining CNS homeostasis and immune response
Meninges
- The exterior of the CNS is covered by the meninges (dura mater, arachnoid, pia mater)
- Meninges consist of three layers: dura mater, arachnoid, and pia mater
Nerve Impulse Conduction
- Neurons modulate and transmit chemical and electric signals from one neuron to another via synapses
- The process of nerve impulse conduction is made possible by the establishment and maintenance of an electric potential across the cell membrane
Microglia
- Microglia are the first cells to react to injury in the CNS
- Microglia respond to injury by hypertrophy, hyperplasia, phagocytosis of cellular and myelin debris, and neuronophagia
Meningitis
- Meningitis refers to inflammation of the meninges
- Inflammation of the meninges can be suppurative, nonsuppurative, or granulomatous
- Infectious agents spread to the meninges hematogenously, by direct extension, or by retrograde axonal transport
Cerebellar Hypoplasia
- Cerebellar hypoplasia results from the necrosis of developing cells in the external granule layer
- The cerebellum does not obtain full size due to the lack of migration of cells to form the granule layer
Neuronal Necrosis
- Neuronal necrosis can occur due to ischemia, injury, or infection
- Ischemic neurons often occur in a laminar pattern due to the microanatomic arrangement of the cerebral cortex### Blood-Nerve Barrier
- Regulates the movement of substances from blood to the endoneurium of peripheral nerves
- Barrier properties are due to tight junctions between endothelial cells and selective transport systems in endothelial cells
Diseases Affecting the PNS
- Lysosomal storage disorders can affect the PNS, causing substrate accumulation in neuron cell bodies, leading to cell death and axonal degeneration
- Disorders primarily affecting the PNS can manifest as motor disturbances, sensory deprivation, or a combination of both
Classification of PNS Disorders
- Neuronopathy: primary problem involves neurons
- Axonopathy: primary problem involves axons
- Myelinopathy: primary problem involves myelin
- Neuropathy: primary problem involves nerves in general
Clinical Signs of PNS Disorders
- Can be difficult to distinguish from hormonal-influenced injury of myofibers
- Clinical signs can be caused by sensory and motor deficits
- Examples of clinical signs: rear limb weakness, muscle wasting, depressed patellar reflexes, and plantigrade stance (diabetic neuropathy in cats)
Nutritional Disorders
- Nutritional axonopathies are relatively uncommon
- Caused primarily by deficiencies of vitamin A and some B vitamins
- Vitamin A deficiency can cause peripheral neuropathy by affecting bone growth and remodeling
- B vitamin deficiencies can cause sensory neuropathy with axonal degeneration, demyelination, and neuron loss (pantothenic acid deficiency in pigs)
Toxic Disorders
- Toxins can affect the PNS with or without damage to the CNS
- Initial toxic effect can be at the level of the neuron cell body, the axon, or the myelin sheath
- Examples of toxins targeting neuronal cell bodies: organomercurial compounds (methylmercury) and cancer chemotherapeutic agents (doxorubicin)
Learn about kinesin and cytoplasmic dynein, microtubule motor proteins that facilitate cell transport and movement. Understand their role in recycling and pathogen spread.
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