Nervous System Flashcards
What vertebral level is the most typical position of the conus medullaris of the spinal cord in an adult? Is it different in a neonate? Explain
In adult at L1/L2 intervertebral disc. In neonate it is at L2/L3. This is because different timings of growth in vertebral column compared to spinal cord
The cranial and spinal nerves and ganglia of the peripheral nervous system develop mainly from which embryological structure? Describe this structure
Neural crest
The neural crest is a transient population of cells that arises at the border of the neural tube (which forms the central nervous system) and the non-neural ectoderm during early development. These neural crest cells migrate extensively throughout the developing embryo and give rise to a variety of structures, including sensory and autonomic ganglia, as well as the neurons that form the peripheral nerves.
Which embryological zone of the neural tube wall becomes the white matter? What are the other 2 zones of the neural tube
Marginal zone: The marginal zone is the outermost layer of the neural tube wall. It consists of axons that extend from the neurons in the grey matter. These axons form the white matter, which contains myelinated nerve fibres that transmit signals within the nervous system.
Others:
Intermediate zone: The intermediate zone contains neural progenitor cells that give rise to neurons. As neurons differentiate and mature, they form the grey matter, which is the region of the central nervous system where the cell bodies of neurons are located.
Ventricular zone: The ventricular zone lines the central canal of the neural tube and plays a role in cerebrospinal fluid production and circulation.
How is spina bifida related to neurulation? What are the 3 types of spina bifida
Spina bifida is a neural tube defect that occurs when there is a failure in the proper closure of the caudal portion of the neural tube, leading to incomplete development of the spinal cord and surrounding structures. In spina bifida, there is a gap or opening in the spinal column, and the spinal cord may be exposed or protrude through this gap. This can result in a range of neurological and physical problems, depending on the severity and location of the defect.
Spina bifida is often attributed to a combination of genetic and environmental factors. It is one of the most well-known consequences of a disruption in the process of neurulation.
The severity of spina bifida can vary, and there are different types, including spina bifida occulta (mildest form), meningocele (meninges protrude through the opening), and myelomeningocele (most severe form, with spinal cord tissue exposed). Myelomeningocele is the type most commonly associated with significant disabilities.
Describe the different embryological origins of the adenohypophysis and neurohypophysis. What functional difference results from these different origins?
Adenohypophysis develops as upgrowth of mouth ectoderm. Anterior pituitary lobe
Neurohypophysis develops as downgrowth of diencephalon. Posterior pituitary lobe
What does the term actin treadmilling refer to?
Actin treadmilling involves two simultaneous processes within an actin filament (reorganisation):
Polymerization (Assembly): Actin monomers can add to the “plus end” of the filament, leading to the elongation of the filament. This is known as polymerization, and it is the process of actin monomers forming new filament structures. The plus end is also called the “barbed end.”
Depolymerization (Disassembly): Simultaneously, actin monomers can be removed from the “minus end” of the filament, causing the filament to shorten. This is known as depolymerization. The minus end is also referred to as the “pointed end.”
Occurs in filopodia which branch off lamellipodia (growth cones)
What happens to the filopodia when it comes into contact with a chemorepulsive cue? How is this different to how it behaves when it comes into contact with a chemoattractive cue?
Chemorepulsive- inhibition of extension of filopodia
Chemoattractive- Filopodia extend to direction of cue
What does microtubule capture refer to?
In response from attractive signal from actin treadmilling, some of microtubules form an interaction with the actin filaments in the filopodium that is being stimulated
Create a mnemonic or memory tool to help you to remember the relationship between primary and secondary brain vesicles
PROCHAZKA vs TEIXEIRA DUMB
P- prosencephalon (primary)
T- telencephalon (secondary)
D-diencephalon (secondary)
MAGOMED MAGOMEDOV
M- mesencephalon (primary)
M- mesencephalon (secondary)
RORY MACDONALD MMA
R- Rhombencephalon (primary)
M- Metencephalon (secondary)
M- Myelencephalon (secondary)
Is the term ‘neural tube defect’ synonymous with ‘spina bifida’? Explain
Yes as neural tube defect is failed closure of neuropores. Spina bifida myeloschisis is most severe form of spina bifida which is failed neuropore closure because neural folds failed to fuse at particular site
Daily folic acid intake has been associated with the incidence of neural tube defects (NTDs). What stage of pregnancy is the most critical time to ensure high levels of folic acid are taken to avoid the embryo developing NTDs?
Taking folic acid before and during first weeks of pregnancy lowers the chance of NTD’s. Within first 4 weeks until neural tube has closed
Why do symptoms progress more rapidly in hydrocephalus in an adult compared to a foetus?
Hydrocephalus is a condition characterized by an abnormal accumulation of cerebrospinal fluid (CSF) within the brain’s ventricles, leading to increased intracranial pressure.
Cranial sutures and fontanelles: In a developing foetus, the cranial bones are not yet fused, and there are open spaces called fontanelles between the skull bones. These fontanelles allow for some flexibility and expansion of the skull, accommodating the accumulation of excess CSF to some extent. In adults, the cranial bones are fully fused, and there is less room for expansion, making it more challenging for the brain to adapt to increased CSF volume.
What is a lumbar puncture? How is it different to an epidural block? Why are lumbar punctures relatively safe in adults (ie. consider why we don’t collect CSF from the thoracic or cervical levels typically) but not safe in neonates?
A lumbar puncture is a diagnostic procedure that involves the removal of cerebrospinal fluid (CSF) from the spinal canal for various medical purposes, such as diagnosing infections (meningitis, encephalitis), evaluating certain neurological conditions, or measuring CSF pressure.
An epidural block is a medical procedure used for pain relief, typically during labour and delivery or for postoperative pain management.
Lumbar punctures are relatively safe in adults because the spinal cord typically ends around the first or second lumbar vertebra (L1-L2), meaning that the needle is inserted below the spinal cord. This reduces the risk of damaging the spinal cord while performing the procedure. In neonates, the spinal cord extends lower down the vertebral column compared to adults. As a result, the lumbar puncture site for CSF collection is much closer to the end of the spinal cord.
What is the embryological significance of the filum terminale?
During early embryonic development, the spinal cord and spinal nerves extend throughout the vertebral column, but as the foetus grows, the spinal cord itself stops elongating at around the L1 to L2 vertebral level. However, the vertebral column continues to grow, and this lengthening discrepancy results in the spinal cord ending higher in the vertebral column than its eventual location in the adult.
The filum terminale acts as a “tether” for the spinal cord, helping to anchor it in place as the vertebral column continues to grow. This anchoring prevents excessive stretching or tension on the spinal cord and its associated nerves. It is especially important during the later stages of foetal development and into early childhood as the body grows.
What areas of the brain would be most affected by a blockage to the cerebral aqueduct in the case of an obstructive hydrocephalus? In a foetus, why is obstructive hydrocephalus more serious than non-obstructive hydrocephalus? How is obstructive hydrocephalus treated surgically?
-The third ventricle, where the blockage usually occurs.
-The lateral and fourth ventricles, which can become enlarged due to the backup of CSF.
-The periventricular regions surrounding these ventricles.
Obstructive hydrocephalus is often caused by a structural blockage in the flow of CSF, which can lead to a more rapid accumulation of CSF and increased intracranial pressure. This can result in more severe and acute symptoms.
Foetal Shunt Placement: In some cases, a shunt (a thin tube) may be placed in the foetus’s brain ventricles to redirect the excess CSF to another part of the body, such as the amniotic cavity or the foetal heart. This is known as foetal shunt placement.
