The Human CNS: Development & Spinal Cord Flashcards
What is the CNS formed from?
Neural tube
Essentially, what is the human CNS?
An over-blown tube which expands during development
How does the nervous system develop?
1) Starts as flat sheet of cells called the neural plate on the surface of the developing embryo
2) The neural plate starts to sink to form a neural groove
3) The edges start to rise up and fuse together. Ends called neuropores
What is the name given to the flat sheet of cells on the surface of the developing embryo from which the nervous system develops?
Neural plate
What is formed when the neural plate sinks?
Neural groove
What are the ends of the neural tube called?
Neuropores
Give some examples of diseases caused by neural tube defects
- Spina bifida
- Anencephaly
How is spina bifida caused?
Failure of neural tube closure
What is anencephaly and how is it caused?
Absence of a portion of the brian and it’s caused when the cranial/rostral end of the neural tube fails to close
What end of the neural tube fails to close properly to lead to anencephaly?
The cranial end
What can prevent most defects associated with the neural tube?
Folic acid
What are the 3 primary brain vesicles?
- Prosencephalon (forebain)
- Mesencephalon (midbrain)
- Rhombencephalon (hindbrain)
What are primary brain vesicles?
Fluid-filled swellings at the rostral end of the neural tube from which the brain develops
In which primary brain vesicle is the tectum found?
Mesencephalon
What are the 4 secondary brain vesicles?
- Telencephalon
- Diencephalon
- Metencephalon
- Myelencephalon
In which secondary brain vesicle in the optic vesicle found?
The diencephalon
What is found at the caudial end of the neural tube below the brain vesicles?
The spinal cord
What is the spinal cord encased in?
Bony vertebrae
What does a transverse section of the spinal cord show?
White and grey matter around central canal
Dorsal root, dorsal root ganglion, ventral root
What does grey matter of the brain contain?
Most of the brain’s neuronal cell bodies
What does white matter of the brain contain?
Lots of myelinated axons
What gives white matter its white colour?
Myelin
Which root has sensory input: dorsal or ventral?
Dorsal
What does the dorsal root have which the ventral root doesn’t?
The dorsal root ganglion
What does the ventral root carry?
Motor output
Why do sensory neurone in the spinal cord activate multiple, contralateral interneurons?
So that the whole body can react
What are spinal cord columns?
Set of axons that run up/down spinal cord
Where does decussation of the spinal cord columns occur?
In the medulla
What is decussation?
When pathways cross over onto opposite sides
What are the meninges?
Membranes that line the spinal cord and brain
Name the meninges (in order from most lateral to medial)
- Dura mater
- Arachnoid
- Pia mater
The meninges are ________ with those of the brain
Continuous
Which meninges has two layers?
Dura mater
What are the two layers of the dura mater?
Endosteal and meningeal
Which layer has the richest supply of blood vessels?
Dura mater: endosteal layer
Are the endosteal and meningeal united?
Yes except at certain lines where they form large venous vessels called dura sinus
What colour is cerebrospinal fluid (CSF)?
Straw-coloured
Where does CSF flow?
- Central canal
- Brain ventricles
- Subarachnoid space
What flows in the central canal, brain ventricles and subarachnoid space?
Cerebrospinal fluid
What is CSF formed by and how does it reach the subarachnoid space?
Formed by the choroid plexus and gets through the medial and lateral aperture to reach the the subarachnoid space
What does the CSF do?
Float and cushions the CSF
What is the blood brain barrier and what is it formed by?
The blood–brain barrier (BBB) is a highly selective semipermeable membrane barrier that separates the circulating blood from the brain extracellular fluid in the central nervous system (CNS). The blood–brain barrier is formed by brain endothelial cells, which are connected by tight junctions.
How would you retrieve important information on the state of the CNS?
Sample the CSF
How would you sample CSF?
Lumbar puncture between 3rd and 4th lumbar vertebrae
Why won’t the spinal cord be damaged when sampling CSF correctly?
Spinal cord won’t be damaged as it finishes before the end of the vertebral column
Give an example of a disorder associated with abnormal CSF flow and what are potential consequences
Hydrocephaly - too much CSF
- pressure on skin, incomplete cranium, pressure built up, reduced blood flow
