Nervous system pathology 1 Flashcards
In vertebrates what is the preliminary requirement for further CNS organ development?
Formation and closure (neurulation) of the neural tube
Neurulation is the driver of which process?
Sagittal closure of overlying structures (skin, ectoderm, and muscle and subcutis, mesoderm)
What structure separates the left and right hemispheres of the brain?
Falx cerebri
- line of collagen
What are the names of the dome shaped projections and crevices on the brain surface?
Gyri (dome shaped projections)
Sulci (cervices)
What separates the brainstem from the 4th brain?
Collagenous tissue
Name some structures that can be viewed on the ventral view of the brain?
- olfactory bulb
- optic chiasm
- pituitary gland
Name the structure that separates the cerebrum from the cerebellum and brainstem
Tentorium cerebelli
What colour are the grey and white matter when stained?
White matter = dark blue
Grey matter = light purple/pink
On an evolutionary scale, number and depth of sulci increases proportionally to
Cortical development
A bisected (medial) slice of the brain through the telencephalon would show which structures?
Cerebral cortex
Basal nuclei
- cranial potion of the brain
A bisected (medial) slice of the brain through the diencephalon would show which structures?
Some of the cerebral cortex with the hippocampus and thalamus lying centrally beneath it
A bisected (medial) slice of the brain through the metencephalon would show which structures?
Cerebellum and pons
A bisected (medial) slice of the brain through the myelencephalon would show which structures?
Medulla oblongata
A slice through the spinal cord would show which structures?
- Grey matter centrally: dorsal and ventral horn
- White matter peripherally
- Ventral and dorsal nerve roots
How can spinal grey and white matter be differentiated histologically?
Grey matter is a slightly paler pink colour
What is the function of the choroid plexus?
Production of CSF
Where is the choroid plexus located?
Found in the lateral, third and fourth ventricles of the brain
What is ependyma?
Thin neuroepithelial (simple columnar ciliated epithelium) lining of the ventricular system of the brain and the central canal of the spinal cord
What is the function of CSF?
Acts as a cushion (mechanically) and provides nutrients to the neuroparenchyma
Which structure drains CSF from the ventricles?
Dorsal sagittal sinus
Name the 4 cells of neuroectodermal origin in the CNS
- Neurons
- Astrocytes
- Oligodendrocytes
- Ependymocytes
Name the 3 cells of mesenchymal origin in the CNS
- Microglia
- Blood vessels
- Cells of meninges
What is the role of Schwann cells in the CNS?
Not directly involved in the CNS but they produce myelin
- A Schwann cell forms a myelin sheath by wrapping its plasma membrane concentrically around the inner axon
What is the principle cell type in nervous tissue?
Neuron
What is the function of neurons?
Receipt, generation, conduction and transmission of stimuli as electric signals (waves of depolarization)
Neurones are structurally composed of which components?
- Large nucleus with prominent nucleolus
- Soma or perikarion, with prominent RER (Nissl substance)
- Dendrites: multiple, receiving information from myriad adjacent or distant neurons
- Axon: single, projecting signal from the soma to the effector cell (other neurons, skeletal muscle, glandular epithelium, etc..)
What are the functions of astrocytes?
- Creation and maintenance of the integrity of the Blood Brain Barrier (BBB)
- Uptake and recycling of neurotransmitters
- Maintenance of extracellular pH and osmotic pressure (via uptake of K+)
- Supporting metabolic demands of neurons
- Supporting migration of neurons during neurogenesis
What is the function of oligodendrocytes?
Responsible for the production of myelin within the CNS
How do oligodendrocytes appear in H&E?
Appear surrounded by clear (empty) halo (lipids)
Describe how the boundary of the CNS and PNS looks
- Happens at the level of the eye
- Schwann cells are elongated
- Oligodendrocytes are rounded and arrange themselves as rows of cells
What is the function of microglia?
- Resident macrophage-like cells in the CNS
- Immune surveillance
Name and describe the 3 layers of the meninges
- Dura mater: thicker and rich in collagen
- Arachnoid: fine trabecules gently surrounded by supporting vasculature
- Pia mater: thin layer in contact with the neuroparenchyma
What is Malacia?
Abnormal softening of a biological tissue, most often cartilage
Define Satellitosis
Abnormal clustering of one type of cell around another especially: the clustering of glial cells around neurons in the brain that is associated with certain pathological states (as oligodendroglioma)
Define spongiosis
Mainly intercellular oedema (abnormal accumulation of fluid) in the epidermis
Define infarct
Local tissue damage due to reduced blood flow (ischemia) or prolonged reduced oxygenation (hypoxia)
What are spheroids?
Cross section of enlarged axons (acute to subacute degeneration)
What is a neuropil?
A dense network of interwoven nerve fibres and their branches and synapses, together with glial filaments
Which features of neurones make them susceptible to damage/lesions, etc
- Stable, fully developed and extremely specialized cells
- Lack of proliferating activity
- High metabolic demands
- Low capacity of “metabolic adaptation”
- The majority of neurons extend their processes far from the perikarion (cell body)
What happens to neurones if there is over stimulation?
The neurones will die = excitotoxicity
What are some reactions neurones have when they are damaged?
- Chromatolysis
- Hypoxic necrosis
- Apoptosis
- Intracytoplasmic accumulation
- Vacuolation
- Intranuclear and intracytoplasmic inclusions (viruses and regressive phenomena)
How do neurones that have undergone hypoxic necrosis appear?
‘Red dead cells’
Cell has shrunk and the cytoplasm is spikey and red
What is chromatolysis and what is the cause?
- The dissolution of the Nissl bodies in the cell body of a neuron
- Caused by a change in the availability of oxygen
What is astrogliosis?
Increase in number/hyperplasia of astrocytes
What is astrocytosis?
Increase in cell volume/hypertrophy of astrocytes
Damage to the oligodendrocytes alters cell membrane and causes?
- Impaired or defective myelin formation (primary demyelination)
- Myelin destruction and phagocytosis (secondary demyelination)
Define leukodistrophy
Congenital or primary oligodendrocyte dysfunction causing the formation of abnormal myelin
What are 3 reactions of microglia to damage?
- Neuronophagic nodule
- Gitter cell formation
- Rod cell proliferation (activation)
What are the 4 types of oedema in the CNS
- cytotoxic
- vasogenic
- hydrostatic
- hypo-osmotic
A vascular injury with breakdown of the BBB causes which type of oedema?
Vasogenic
