NEUROSCIENCE Flashcards
Give 3 functions of the cranial meninges.
- Protects the brain and spinal cord form injury.
- Provides a framework for cerebral and cranial vasculature.
- Provides a space for the flow of CSF.
What are the 3 meningeal layers?
- Dura mater (outermost).
- Arachnoid mater.
- Pia mater (inner most).
What are the 2 connective tissue sheets of dura mater?
- Endosteal layer - lines the cranium.
- Meningeal layer.
- Endosteal layer - lines the cranium.
- Meningeal layer.
Between the endosteal layer of dura and the meningeal layer.
What vein do the dural venous sinuses drain into?
The internal jugular veins.
Name 3 locations where the dura mater folds inwards as dural reflections?
- Falx cerebri.
- Tentorium cerebelli.
- Falx cerebelli.
Where is the falx cerebri located?
It lies in the longitudinal fissure between the cerebral hemispheres.
Where is the tentorium cerebelli located?
The tentorium cerebelli is a thick fibrous roof lying over the posterior cranial fossa and the cerebellum.
Where is the falx cerebelli located?
Between the 2 lobes of the cerebellum.
What lies beneath the arachnoid mater?
The subarachnoid space containing CSF and arteries.
What is the function of the blood-brain barrier?
It protects the brain by preventing the passage of some substances from the circulation into the nervous tissue.
Which meningeal layers are highly vascularised?
The dura and pia mater. The arachnoid mater is avascular.
Name the 3 elements that make up the blood-brain barrier.
- Capillary endothelial cells.
- Basement membrane.
- Astrocytic end-feet.
What are the 2 main arteries that supply blood to the brain?
- Vertebral arteries.
- Internal carotid arteries.
Which arteries supply about 80% of blood to the brain?
The internal carotid arteries.
What are the vertebral arteries a branch of?
The subclavian arteries.
Where do the vertebral arteries enter the skull?
Through the foramen magnum.
What are the internal carotid arteries branches of?
The common carotids. Arise from bifurcation at the same level as the upper border of the thyroid cartilage.
What do the vertebral arteries supply?
The posterior cerebrum and the
contents of the posterior cranial fossa.
What do the internal carotid arteries supply?
The anterior and middle parts of the cerebrum and the diencephalon.
Where do the internal carotid arteries enter the skull?
Through the carotid foramina.
What are the terminal branches of the internal carotid arteries?
The middle and anterior cerebral arteries.
What does the middle cerebral artery supply?
The lateral surface of the hemispheres.
What does the anterior cerebral artery supply?
The medial aspect of the hemispheres and the corpus callosum.
What does the posterior cerebral artery supply?
The occipital lobe.
What artery passes through foramen spinosum?
The middle meningeal artery.
What do the two vertebral arteries form?
The basilar artery.
Where is a berry aneurysm likely to occur?
At branching points in the circle of willis, especially at the anterior communicating artery.
What is a berry aneurysm?
A sac-like out pouching that will progressively enlarge until it ruptures resulting in haemorrhage.
What are the two types of stroke?
- Ischaemic.
- Haemorrhagic (intracerebral or subarachnoid).
Where are dural venous sinuses located?
In between the endosteal and meningeal layers of dura.
Where do cerebral veins drain into?
Into dural venous sinuses.
What does the great cerebral vein drain?
Deep brain structures.
What sinus does the great cerebral vein drain into?
The straight sinus.
Where is the straight sinus located?
In the midline of the tentorium cerebelli.
What vessels lie in the cavernous sinus?
- Cn 3, 4, 5(1), 5(2) and 6.
- Internal carotid artery.
Why is the cavernous sinus of clinical importance?
If this sinus is infected Cn 3, 4, 5(1), 5(2) and 6 and the internal carotid artery could be affected.
How do dural venous sinuses and veins outside the skull communicate?
Via emissary veins.
What is the clinical significance of emissary veins?
They represent a possible route for infection to spread into the cranial cavity.
Briefly describe the pathway of venous drainage starting at the great cerebral vein.
Great cerebral vein -> straight sinus -> transverse sinus -> sigmoid sinus -> internal jugular vein -> jugular vein -> brachiocephalic vein -> SVC.
What sinuses form the confluence of sinuses?
The straight sinus and the superior sagittal sinus.
Where is the largest aggregation of choroid plexus?
In the lateral ventricles.
Where is the majority of CSF produced?
In the lateral ventricles (greatest amount of choroid plexus here`).
What is ependyma?
A thin-epithelial like structure lining the ventricles.
Tight junctions prevent the passage of fluid into the ventricles. Why is this important?
It means that the volume and composition of CSF can be closely controlled.
What embryonic part of the brain is the midbrain formed from?
Mesencephalon.
What embryonic part of the brain is the pons formed from?
Metencephalon of Rhombencephalon.
What embryonic part of the brain is the medulla oblangata formed from?
Myelencephalon of Rhombencephalon.
- What is the name of Cn1?
- Where does it exit the skull?
- Sensory, motor or both?
- Olfactory.
- Cribriform plate of ethmoid bone.
- Sensory.
- What is the name of Cn2?
- Where does it exit the skull?
- Sensory, motor or both?
- Optic.
- Optic canal.
- Sensory.
- What is the name of Cn3?
- Where does it exit the skull?
- Sensory, motor or both?
- Occulomotor.
- Superior orbital fissure.
- Motor and parasympathetic.
- What is the name of Cn4?
- Where does it exit the skull?
- Sensory, motor or both?
- Trochlear.
- Superior orbital fissure.
- Motor.
- What is the name of Cn5?
- Where does it exit the skull?
- Sensory, motor or both?
- Trigeminal.
- V(1)-superior orbital fissure. V(2)-foramen rotundum. V(3)-foramen ovale.
- Both: sensory and motor.
- What is the name of Cn6?
- Where does it exit the skull?
- Sensory, motor or both?
- Abducens.
- Superior orbital fissure.
- Motor.
- What is the name of Cn7?
- Where does it exit the skull?
- Sensory, motor or both?
- Facial.
- Internal acoustic meatus.
- Both: sensory and motor and parasympathetic.
- What is the name of Cn8?
- Where does it exit the skull?
- Sensory, motor or both?
- Vestibulocochlear.
- Internal acoustic meatus.
- Sensory.
- What is the name of Cn9?
- Where does it exit the skull?
- Sensory, motor or both?
- Glossopharyngeal.
- Jugular foramen.
- Both: sensory and motor and parasympathetic.
- What is the name of Cn10?
- Where does it exit the skull?
- Sensory, motor or both?
- Vagus.
- Jugular foramen.
- Both: sensory and motor and parasympathetic.
- What is the name of Cn11?
- Where does it exit the skull?
- Sensory, motor or both?
- Accessory.
- Jugular foramen.
- Motor.
- What is the name of Cn12?
- Where does it exit the skull?
- Sensory, motor or both?
- Hypoglossal.
- Hypoglossal canal.
- Motor.
- What does Cn1 innervate?
- What are its functions?
- Innervates: olfactory epithelium.
- Function: olfaction.
- What does Cn2 innervate?
- What are it’s functions?
- Innervates: retina.
- Function: vision.
- What does Cn3 innervate?
- What are it’s functions?
- Innervates: medial, superior and inferior rectus muscles and inferior oblique and levator palpebrae superioris.
- Motor function: movement of eyeball.
- Parasympathetic function: constriction and accommodation.
- What does Cn4 innervate?
- What are it’s functions?
- Innervates: superior oblique.
- Functions: movement of eyeball.
- What does Cn5 innervate?
- What are it’s functions?
- Sensory innervation: face, scalp, cornea, nasal and oral cavities, anterior 2/3 of tongue, dura mater.
- Motor innervation: muscles of mastication and tensor tympani.
- Sensory function: general sensation.
- Motor functions: open and close the mouth. Tenses tympanic membrane.
- What does Cn6 innervate?
- What are it’s functions?
- Innervates: lateral rectus.
- Function: eye movement, abduction.
- What does Cn7 innervate?
- Special sensory innervation: anterior 2/3 of tongue - taste.
- Motor innervation: muscles of facial expression and stapedius.
- Parasympathetic innervation: submandibular and sublingual and lacrimal glands.
- What does Cn8 innervate?
- What are it’s functions?
- Innervation: cochlea and vestibular apparatus.
- Functions: hearing and proprioception of head and balance.
- What does Cn9 innervate?
- Sensory innervation: posterior 1/3 of tongue, middle ear, pharynx, carotid bodies.
- Motor innervation: stylopharyngeus.
- Parasympathetic innervation: parotid gland.
- What does Cn10 innervate?
- Sensory innervation: pharynx, larynx, oesophagus, external ear, aortic bodies, thoracic and abdominal viscera.
- Motor innervation: soft palate, larynx, pharynx.
- Parasympathetic innervation: CV, respiratory and GI systems.
- What are the functions of Cn10?
- Sensory functions: general sensation.
- Motor functions: speech and swallowing.
- Parasympathetic functions: control over CV, respiratory and GI systems.
- What are the functions of Cn9?
- Sensory functions: general sensation, taste, chemo/baroreception.
- Motor functions: Swallowing (larynx and pharynx are elevated).
- Parasympathetic function: salivation.
- What are the functions of Cn7?
- Sensory function: taste.
- Motor function: facial movement and tension of ossicles.
- Parasympathetic function: salivation and lacrimation.
- What does Cn11 innervate?
- What are it’s functions?
- Innervation: trapezius and sternocleidomastoid.
- Functions: movement of head and shoulders.
- What does Cn12 innervate?
- What are it’s functions?
- Innervation: intrinsic and extrinsic muscles of the tongue.
- Function: movement of the tongue.
What are the characteristic features of a cervical vertebra?
- Small vertebral body.
- Transverse foramen for vertebral arteries.
- Bifurcation of spinous processes (except C7).
- Triangular intervertebral foramen.
What region of the vertebral column has the greatest capacity for rotation?
The thoracic region.
What region of the vertebral column has the least capacity for flexion?
The thoracic region; this is due to the presence of the ribcage.
What are the 2 components of an intervertebral disc?
- Nucleus pulposus.
- Annulus fibrosus: concentric layers of collagen surrounding the nucleus pulposus.
What does the ligamentum flavum connect?
Connects the laminae of adjacent vertebrae.
Where does the spinal cord end?
a) in an adult.
b) at birth.
c) in the embryo.
a) L2.
b) L3.
c) runs the entire length of the vertebral column.
Where would you insert a lumbar puncture needle?
At the L3/L4 level in the sub-arachnoid space in order to take CSF.
Where would you insert an epidural needle?
Between the dura mater and vertebrae in order to inject anaesthesia.
What is the conus medullaris?
The tapered, lower end of the spinal cord.
What is the filum terminale?
A fibrous strand that proceeds downwards from the apex of the conus medullaris.
What is the cauda equina?
Spinal nerves from the lower spinal cord that hang obliquely downwards.
Define dermatome.
An area of skin with a sensory nerve supply from a single root of the spinal cord.
What is the dermatome for the thumb?
C6.
What is the dermatome for the knee?
L3.
What is the dermatome for the big toe?
L5.
Name 4 ascending spinal pathways.
- DCML.
- Spinothalamic.
- Spinocerebellar.
- Spinoreticular.
What sensations does the DCML pathway convey?
Fine touch, 2-point discrimination and proprioception.
What sensations does the spinothalamic pathway convey?
- Lateral spinothalamic - pain and temperature.
- Anterior spinothalamic - crude touch.
Describe the DCML pathway.
Fine sensation is detected by touch or proprioception receptors. Afferent signals are carried along 1st order neurones to the dorsal columns and up to the medulla where they synapse. 2nd order neurones decussate in the medulla and travel up to the thalamus where they synapse. 3rd order neurones then travel through the internal capsule to the somatosensory cortex.
Which dorsal column would an afferent signal from the lower limb use?
The gracile fasciculus (medial part of dorsal column). They then synapse at the gracile nucleus of the medulla.
Which dorsal column would an afferent signal from the upper limb use?
The cuneate fasciculus (lateral part of dorsal column). They then synapse at the cuneate nucleus of the medulla.
Describe the spinothalamic pathway.
Nociceptors or thermoreceptors detect pain, temperature or crude touch. 1st order neurones carrying these signals enter the spinal cord and ascend 2-3 spinal levels before synapsing in the dorsal horn of grey matter. 2nd order neurones decussate either through the anterior or lateral tracts and then travel up to the thalamus where they synapse. 3rd order neurones travel through the internal capsule to the primary somatosensory cortex.
Where is the somatosensory cortex located?
Post-central gyrus in parietal lobe.
What sensations is the lateral spinothalamic tract responsible for?
Pain and temperature.
What sensation is the anterior spinothalamic tract responsible for?
Crude touch.
What is the function of the spinocerebellar tracts?
They carry unconscious proprioceptive information to the ipsilateral cerebellum.
Do the fibres decussate in the spinocerebellar tracts?
No! They go to the ipsilateral cerebellum.
What sensation does the spinoreticular tract convey?
Deep/chronic pain.
Name 5 descending pathways.
- Corticospinal.
- Vestibulospinal.
- Rubrospinal.
- Tectospinal.
- Reticulospinal.
Where in the thalamus do the DCML and spinothalamic tracts synapse?
In the ventral posterio-lateral division (VPL) of the nucleus of thalamus.
What descending pathways are described as pyramidal?
Corticospinal and corticobulbar tracts - responsible for voluntary control.
What descending pathways are described as extrapyramidal?
Vestibulospinal, rubrospinal, tectospinal, reticulospinal - responsible for involuntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion.
Are there any synapses within the descending pathways?
No. At the termination of the descending tracts, the neurones synapse with a lower motor neurone. (All the neurones within the descending motor system are UMNs).
What are the corticospinal tracts responsible for?
The control of voluntary muscles. Anterior - axial muscles. Lateral - limb muscles.
Describe the corticospinal tracts.
Originate in the primary motor cortex, descends through corona radiata and internal capsule to the medullary pyramids. 90% decussates here and becomes the lateral corticospinal tract; the remaining 10% forms the anterior corticospinal tract. The anterior tract then decussates through the anterior white commissure. Both tracts terminate in the ventral horn.
Describe the corticobulbar tracts.
Originate in the primary motor cortex, descends through corona radiata and internal capsule to the brainstem. The fibres terminate on motor nuclei of cranial nerves. They synapse with LMN’s which carry motor signals to the face and neck.
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Where do the extrapyramidal tracts originate?
The brainstem.
Where do the vestibulospinal tracts originate and what are they responsible for?
- Originate from vestibular nucleus.
- Responsible for muscle tone and postural control.
- Remains ipsilateral.
Where do the reticulospinal tracts originate and what are they responsible for?
- Originate from reticular formation.
- Responsible for spinal reflexes.
Where do the tectospinal tracts originate and what are they responsible for?
- Originate from tectum nuclei (superior and inferior colliculi).
- Responsible for head turning in response to visual and auditory stimuli.
Where do the rubrospinal tracts originate and what are they responsible for?
- Originate from red nucleus.
- Responsible for assisting motor functions.
- Contralateral.
What tracts are known as the ventrolateral/anterolateral system?
Spinothalamic tracts.
Damage to the anterolateral system will present with what symptoms?
Contralateral loss of pain and temperature sensation.
What tracts are known as the dorsomedial system?
DCML.
What would be the signs of a complete spinal cord lesion?
- Weakness in all muscle groups below the lesion.
- Complete sensory loss below lesion.
- Spasticity and hyperreflexia.
What is Brown-Sequard syndrome?
Hemi-section of the spinal cord.
What would be the signs of Brown-Sequard syndrome?
- Ipsilateral weakness and loss of motor function below the lesion.
- Ipsilateral loss of proprioception, 2-point discrimination and fine touch.
- Contralateral loss of pain and temperature sensation 2-3 spinal segments below the lesion.
What are the 3 primary vesicles?
- Prosencephalon (forebrain).
- Mesencephalon (midbrain).
- Rhombencephalon (hindbrain).
What are the sub-divisions of the prosencephalon?
- Telencephalon.
- Diencephalon.
What does the telencephalon form?
- The cerebral hemispheres.
What does the diencephalon form?
- Thalamus.
- Hypothalamus.
What does the mesencehpalon form?
- Midbrain.
- Colliculi.
What are the sub-divisions of the rhombencephalon?
- Metencephalon.
- Myelencephalon.
What does the metencephalon form?
- Cerebellum.
- Pons.
What does the myelencephalon form?
- Medulla oblangata.
Where are the lateral ventricles formed in the embryo?
Telencephalon.
Where is the 3rd ventricle formed in the embryo?
Diencephalon.
Where is the 4th ventricle formed in the embryo?
Rhombencephalon
What are the pluripotent stem cells that lie within the neural folds?
Neural crest cells.
What do neural crest cells develop into?
Schwann cells, pigment cells, adrenal medulla, dorsal root ganglia, Cn 5, 7, 9 and 10.
How is the neural tube formed?
Notochord in mesoderm signals the ectoderm to form a thickened neural plate. Mitosis forms a neural groove. There are neural folds either side of the groove. These fuse at the midline forming the neural tube.
When should the neural tube fuse?
By the end of the 4th week.
What vitamins are needed to ensure the neural tube fuses.
B9 (folic acid) and B12.
Approximately how much CSF do we have?
120ml.
What is hydrocephalus?
An accumulation of CSF in the ventricular system. Often due to a blockage in the cerebral aqueduct.
Name 4 substances contained within the CSF.
- Protein.
- Urea.
- Glucose.
- Salts.