Brain and Spinal Cord Flashcards
What is the difference between a CNS neuron and a PNS neuron?
CNS neuron is entirely contained within the brain/spinal cord.
PNS neuron - part of it projects out of the brain/spinal cord.
What causes grey matter to be grey?
Presence of cell bodies.
What causes white matter to be white?
Presence of myelin sheath and glial cells.
What is the purpose of grey matter?
Processing and cognition.
Where is the grey and white matter found in the brain and spinal cord?
Brain:
- inside = white matter.
- outside = grey matter.
Spinal Cord:
- inside = grey matter.
- outside = white matter.
What is the forebrain made up of?
Cortex and deep nuclei.
What is the roof of the midbrain called and what is it responsible for?
Tectum.
Responsible for auditory and visual reflexes
What is the hindbrain made up of?
Pons, cerebellum, medulla oblongata.
What is the oldest part of the brain?
Medulla oblongata.
What does ventral/dorsal mean?
Ventral = bottom Dorsal = top
How many spinal nerves are there? What are they divided into?
31 pairs.
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
Where does the spinal cord end at?
L1/L2.
Where do the rest of the nerves travel through after the spinal cord ends?
Through the lumbar cistern
What is the lumbar cistern?
Subarachnoid space in the lower lumbar spinal cord.
What is the part of the spinal cord after L1/L2 called?
Cauda equina.
Where is the best place for CSF to be obtained during a lumbar puncture? Why?
Subarachnoid space between L2/L3.
- Less likely to cause paralysis as spinal cord ends before this.
What is the grey matter of the spinal cord divided into?
Dorsal horn, Intermediate column, Lateral horn and Ventral horn.
Where are cell bodies of the sensory neutrons located?
In the dorsal root ganglion.
What does the dorsal horn contain?
Neurons that receive somatosensory information from the body that is transmitted to the brain via ascending pathways.
What does the ventral horn contain?
Effector motor neurons that innervate skeletal muscle.
What do the Intermediate column and Lateral horn contain?
Neurons that innervate visceral and pelvic organs.
What is the outer part of the cerebrum known as?
Cerebral cortex.
What are gyri?
Ridges
What are sulci?
Grooves
What are the purpose of the gyri and sulci?
Increase surface area of the brain to approximately 2500cm (squared) to allow more neural material to be contained within the skull.
What are the main sulci?
Central, lateral and lunate sulcus.
What are the main gyri?
Precentral, postcentral and superior temporal gyrus
What are the names of the 4 cerebral lobes?
Frontal, parietal, Temporal, Occipital
What fissure separates the frontal lobe and the temporal lobe?
Lateral fissure (sulcus)
What fissure separates the frontal lobe and parietal lobe?
Central fissure (sulcus).
What fissure divides the cerebral hemispheres?
Longitudinal fissure
What fissure divides the cerebral and cerebellar hemispheres?
Transverse/horizontal fissure.
What lobe is responsible for motor functions?
Frontal lobe
What lobe is responsible for somatosensory functions?
Parietal lobe
What lobe is responsible for vision?
Occipital lobe
What lobe is responsible for memory?
Temporal lobe (hippocampus) - limbic system.
What lobe is responsible for language?
Temporal lobe
What is the purpose of the ventricular system?
Production, transport and removal of CSF which bathes the CNS.
Where does the central canal run?
Runs the length of the spinal cord and is continuous with the ventricular system of the brain.
What does the 4th ventricle continue with?
Continues inferiorly with the central canal of the spinal cord.
What lines the ventricles?
Ependymal cells.
What do the ependymal cells form?
Choroid plexus.
What is the choroid plexus made of?
Ependymal cells.
Where is CSF produced?
Choroid plexus.
Embryologically, where is the ventricular system derived from?
Lumen of the neural tube.
How many ventricles are there?
4
Name the ventricles of the brain
Left lateral ventricle
Right lateral ventricle
3rd ventricle
4th ventricle
What is CSF (Cerebrospinal fluid)?
Ultrafiltrate of plasma that surrounds the brain and spinal cord.
How much CSF is made per day?
500ml per day
Where is the choroid plexus located?
In the lining of the ventricles.
How is CSF produced?
Choroid plexus consists of capillaries and loose connective tissue surrounded by cuboidal epithelial cells.
Plasma is filtered by these epithelial cells to produce CSF.
Where is CSF drained?
Subarachnoid cisterns.
CSF –> subarachnoid space –> superior sagittal sinus –> venous circulation via arachnoid granulations
Why are arachnoid granulations one way?
CSF pressure is greater than venous pressure, allowing reabsorption.
What are arachnoid granulations?
Small projections into the dura mater/dural venous sinuses to allow fluid drainage.
What can happen if CSF isn’t reabsorbed into the venous bloodstream?
Hydrocephalus.
What is Hydrocephalus?
Accumulation of CSF, causing an increase in intracranial pressure.
Why is hydrocephalus more dangerous in adults than children?
Children’s sutures are not fully formed so the skull can expand.
What are the functions of CSF?
- Protects the brain.
- Buoyancy to the brain so prevents excess pressure to the base of the brain.
- Provides chemical stability to the brain to allow proper functioning.
- Removal of waste products.
What are the meninges?
Membranous outer covering of the brain/spinal cord.
What are the 3 layers of the meninges?
Pia mater
Arachnoid mater
Dura mater
What are the functions of the meninges?
- Protects CNS.
- Provides supportive framework for cerebral and cranial vasculature.
Which layer of the meninges is avascular?
Arachnoid mater
What is the purpose of the vasculature of the pia mater?
- Vascular so allows entry of blood vessels into the CNS.
- Provides an impermeable layer for containing CSF.
What are the 2 layers of the dura mater?
Endosteal layer - lines inner surface of bone.
Meningeal layer - lines endosteal layer inside cranial cavity.
Why do the 2 dura mater layers separate in places?
To form dural venous sinuses that carry venous blood and drain into internal jugular veins.
Where is the dura mater attached to surrounding the brain and spinal cord?
Brain - Periosteum of the cranium.
Spinal cord - hangs loosely except is attached at foramen magnum.
What blood vessels supply the dura mater?
Middle meningeal artery and vein.
What nerve innervates the dura mater?
CN V - trigeminal.
What is the space called between the pia mater and arachnoid mater?
Subarachnoid space.
Why can you not see the dura mater on brains outside of the body?
It is adhered to the cranium.
Why is the spinal cord enlarged in cervical and lumbar regions?
They supply the upper and lower limbs.
What is a nucleus?
Group of cell bodies of the same or similar function in the CNS.
What is a ganglia?
Group of cell bodies outside the CNS (except basal ganglia - group of cells responsible for motor control).
What are tracts?
Axonal pathways within the CNS.
What are ascending tracts?
Sensory (information in)
What are descending tracts?
Motor (information out)
What is a pathway?
More than one tract put together.
What is the brainstem?
Midbrain + Hindbrain.
Posterior region of the brain that is continuous with the spinal cord.
What does the brainstem contain?
- Medulla oblongata
- Pons
- Cerebellum
- Midbrain
(- Sometimes parts of diencephalon included)
What are cerebellar peduncles?
Attachment sites of the cerebellum to the brainstem containing axon bundles.
What is the tegmentum?
Forms the floor of the midbrain.
What is the tectum?
Forms roof of the midbrain.
What reflexes are associated with the brainstem?
Swallowing Salivation Mastication Coughing Vomiting Suckling
What is the purpose of the reticular formation?
Regulates sleep/wake cycle
What is the purpose of the raphe nucleus?
Releases serotonin to the rest of the brain (good for sleep)
What is the purpose of the Locus Coeruleus nuclei?
Origin of the adrenergic pathways (pain/stress response)
What is the purpose of the Substantia Nigra (in midbrain)?
Movement control
Which areas of the cranial nerve nuclei are motor and sensory?
Left = sensory Right = motor
True or false: - Right hand side of the brain controls the left side of the body
True
Why is there crossover of pathways and where does it crossover?
RHS of brain controls LHS of body.
LHS of brain controls RHS of body.
Medulla.
Where do most motor neurone decussate (cross midline)?
In inferior aspect of medulla.
True or false: Sensory decussation occurs more superior to motor decussation.
True
Where does the basilar artery run in the pons?
Along ventral surface of the pons.
What causes cot death?
Defective raphe nuclei in the brainstem and don’t produce enough serotonin.
We usually wake up if there is a fall in heart rate/BP/ breathing (serotonin regulates this) but this doesn’t happen in cot death babies.
Why does the substantia nigra appear pigmented?
It contains high levels of neuromelanin.
What can occur if the substantia nigra is not pigmented/not present?
Loss of dopaminergic neurons
Parkinson’s disease.
Are the corticospinal tract fibres ascending or descending?
Both
What would the consequences of a blockage in the cerebral aqueduct be?
Hydrocephalus.
Which meningeal layer cannot be seen without a microscope?
Pia mater
What happens to the skull in the event of hydrocephalus?
Bulging fontanelles
