Neuroanatomy Flashcards
How many pairs of cranial nerves are there?
12
How many pairs of spinal nerves are there?
31
Where does the transition from CNS to PNS occur?
As the nerve roots leave/enter the spinal cord
*What are the 3 embryological swellings of the brain and what do they go on to become?
Prosencephalon, Mesencephalon and Myelencephalon
What is the main functions of astrocytes?
Physical support, maintain extracellular environment and form BBB
What is the function of oligodendrocytes?
Produce myelin in the CNS (Schwann cells in the PNS)
What is the function of microglia?
Immune cells of the brain (antigen presenting and phagocytic)
What is the function of ependymal cells?
Line the ventricles and helps in the production of CSF
Which way round is the grey/white matter in the brain and spinal cord?
Grey is on the outside in the brain, white is on the outside in the cord
What separates the frontal and parietal lobes?
Central sulcus
What are the boundaries of the parietal lobe?
Central sulcus anteriorly, pre-occipital sulcus to preoccipital notch (bump formed by petrous bone) posteriorly and lateral sulcus below
What is the hidden 5th lobe?
Insular lobe - deep in the lateral fissure (part of the limbic system)
*What connects the lateral ventricles to the 3rd?
Interventricular foramen
*What connects the 3rd ventricle to the 4th?
Cerebral aqueduct
*What connects the 4th ventricle to the subarachnoid space?
2x lateral and 1x medial aperture
What is the mystery third nervous system (other than CNS and PNS) and where is it found?
Enteric NS (found in digestive system from oesophagus to anus in 2 plexuses: myenteric and submucosal)
Where does the venous blood of the dural sinuses drain into?
Internal jugular veins
What is a collection of cell bodies referred to in the CNS and PNS?
CNS = nucleus PNS = ganglion
What type of neuron are motor neurons, and where is their cell body?
Multipolar, and in the CNS
What type of neuron are sensory neurons generally, and where is their cell body?
Unipolar, and in the PNS e.g. dorsal root ganglion
What are nerves technically called in the CNS?
Tracts
In what direction are cranial nerves generally named?
Anterior to posterior, medial to lateral
Where are spinal nerves only found?
Intervertebral foramina
What is the pathway of sensory axons from the spinal nerve to spinal cord?
Nerve > posterior/dorsal root > dorsal rootlet > dorsal horn
What is the pathway of motor axons from spinal cord to spinal nerve?
Ventral/anterior horn > ventral rootlets > ventral roots > nerve
True or false: Roots are mixed
False, they are single modality
True or false: Rami are mixed
True
Where does the anterior rami go and serve?
Anterolateral structures of the trunk and limbs (e.g. all muscles except intrinsic back muscles)
Where does the posterior rami go and serve?
Posterior back structures (intrinsic back muscles + sensory)
Which spinal nerve dermatome supplies the male nipple?
T4
Which dermatome covers the umbilicus?
T10
Which dermatomes are the posterior scalp, neck and shoulder?
C2-4
Which dermatomes cover the upper limb?
C5-T1
Which dermatomes supply the lower limb?
L2-Co1
Which spinal levels have a lateral horn for sympathetic outflow?
T1-L2
What is the pathway of sympathetic outflow out of the lateral horn of the spinal cord?
Technically motor output so travels through the anterior rootlets and roots then via white rami communicans to sympathetic chain. Organs above the diaphragm synapse in these paravertebral ganglia, which organs below synapse in the prevertebral ganglia (except the adrenal gland which gets direct).
How do presynaptic parasympathetic axons leave the CNS?
Via cranial nerves III (via ciliary ganglion), VII, IX and X, and sacral spinal nerves
How do presynaptic parasympathetic axons leave the CNS?
Via cranial nerves III, VII, IX and X, and sacral spinal nerves
What are the symptoms of Horner’s Syndrome and what is the cause?
Impaired sympathetic innervation to the head and neck often due to compression of the cervical parts of the sympathetic trunk, causing: Miosis (constricted pupils), ptosis (drooping eyelid), anhydrosis (reduced sweating) and increased warmth/redness
What are the extrinsic back muscles?
Trapezius, Rhomboids, Levator scapulae, Lat dorsi
What are the intrinsic back muscles?
Erector spinae (made up of iliocostalis, longissimus and spinals) and transversospinalis (wedged between transverse and spinous processes of vertebrae)
*Label these muscles
*
What muscles cause flexion of the spine?
Psoas major and rectus abdominis (nothing to do with intrinsic muscles)
*Label the features on the vertebrae
*
*Label these vertebral features
*
*Label these vertebral ligaments
*
What is the function of the posterior and anterior longitudinal ligament?
Posterior prevents over-flexion of the spine, while anterior prevents over-extension
What are typical features of cervical vertebrae?
Transverse foramen, bifid spinous princess, very large and triangular vertebral canals
What makes C1, C2 and C7 each unique?
C1 - no body or spinous process (purely circular)
C2 - has an odontoid process
C7 - vertebrae prominens (first palpable)
What are the 4 stages of cervical vertebrae dislocation?
- Stage I- flexion sprain
Stage II – anterior subluxation, 25% translation
Stage III – 50% translation
Stage IV – complete dislocation
What causes the sacral hiatus to form and what is it used for clinically?
Occurs due to non-fusion of sacrum during development, and is used for administering anaesthesia
What is causal anaesthesia?
*local anaesthetic is injected into the sacral hiatus to anaesthetise the sacral spinal nerve roots of the cauda equina
At what level does the spinal cord end?
L1/2
What is the purpose of laminectomy?
Exposing spinal cord/roots or relieving pressure
What layers do you go through in a laminectomy?
Skin >superficial fascia > aponeurotic origin of trapezius/thoracolumbar fascia of latisimus dorsi > intrinsic muscles > ligaments (ligamentum flavum, supraspinous , interspinous) > lamina > spinous process > Epidural fat > dura mater and arachnoid mater
What structure suspends the spinal cord in the vertebral canal?
Denticulate ligament (made of pial and arachnoid tissue, and attaches to the dura at points along the cord)
What does the dorsal root ganglion contain and where is it located?
Contains the cell bodies of the sensory roots, and it is found in the posterior root as it passes out the intervertebral foramina
What is the white and grey matter each made up of?
The white matter consists of longitudinally oriented nerve fibres (axons), glial cells and blood vessels. The grey matter contains neuronal soma, cell processes, synapses, glia and blood vessels.
*What is the relative proportions of white and grey matter down the cord at each level?
*
What is the blood supply to the spinal cord?
A) 3 major longitudinal arteries from vertebral a. (anterior and 2 paired posterior spinal a) B) Segmental arteries from vertebral, deep cervical, intercostal and lumbar arteries C) Radicular arteries that follow the roots
What is the venous drainage of the spinal cord?
Anterior and posterior spinal veins, which empty into plexuses and then to segmental veins
Which pathway provides sensory into on fine touch and proprioception?
Dorsal Column/Medial Lemniscus
Which set of limbs corresponds to which fasiculus in the dorsal column?
Fasciculus cuneatus = upper limb and fasciculus gracilis = lower limb
Which pathway is responsible for sensory information on pain, temperature and deep pressure?
Spinothalamic tract
Which descending pathway gives the motor supply to the musculature of the body?
Corticospinal tract
What pathway gives there motor supply to the musculature of the head and neck?
Corticobulbar tract
Which are the pyramidal tracts?
Corticospinal and corticobulbar tracts (as they pass through the medullary pyramids)
What is the function of the extrapyramidal tracts, and which tracts are included?
They are responsible for the involuntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion, and they include the Rubrospinal, Tectospinal, Vestibulospinal and Reticulospinal tracts
What is the function of the Rubrospinal tract and where does it originate?
Excitatory control of tone of limb flexor muscles, and it originates in the red nucleus of the midbrain
What is the function of the Tectospinal tract and where does it originate?
Primarily used to aim the head at visual cues, and it originates in the superior colliculus of the tectum in the midbrain
What is the function of the Vestibulospinal tracts and where do they originate?
Gives excitatory input to “antigravity” extensor muscles, and they originate in the vestibular nuclei of pons and medulla which receive input from vestibular apparatus and cerebellum
What is the function of the Reticulospinal tracts and where do they originate?
They originate in the reticular formation in the pons and medulla, and they have differing functions: The medial reticulospinal tract facilitates voluntary movements, and increases muscle tone.
The lateral reticulospinal tract inhibits voluntary movements, and reduces muscle tone.
What is Brown-Sequard Syndrome?
When a patient stab wound hemisects the spinal cord, destroying one half of the cord along the midline. Results in ipsilateral paralysis as 85% of CST has crossed higher up
What are the 5 layers of the SCALP?
Skin - Connective Tissue - Aponeurosis - Loose Connective Tissue - Pericranium
Which important structure lies under the pterion and risks damage with fracture?
Middle meningeal artery
What gives the sensory supply to the dura mater?
CN V
What is the danger triangle in the venous drainage of the brain?
Trauma here risks allowing bacteria to enter into the facial vessels and spread into the cavernous sinus
What can cause an extradural haemorrhage?
Between bone and dura - can occur due to rupture of middle meningeal artery after damage to pterion
What can cause an subdural haemorrhage?
Separates the dura from the arachnoid. Occurs with torn cerebral veins, particularly with falls in elderly and those with problem drinking
What can cause an subarachnoid haemorrhage?
Ruptures aneurysms
Which structures would you pass through with a epidural anaesthesia?
Supra and interspinous ligaments, then ligamentum flavour then epidural space (full of fat and veins)
Which structures would you pass through with a lumbar puncture?
Supra and interspinous ligaments, then ligamentum flavour then epidural space, then dura and arachnoid mater to reach subarachnoid space to access CSF
What is a possible consequence of epidural catheters and lumbar punctures?
Epidural haematoma due to extradural venous plexus, which can compress SC or cauda equina
Where is the safest location for lumbar punctures and why?
L3/4 interspace - as here the subarachnoid space surrounds the cauda equina, not the SC, and the vertebrae aren’t fused
What are the two types of infratentorial herniation?
*Upwards cerebellar (transtentorial) or downwards cerebellar (tonsillar)
What are the types of supratentorial herniation?
*1) Cingulate (subfalcine - medial frontal lobe forced under fall cerebri) 2) central (medial diencephalon/temporal lobe forced through hole in tentorium) 3) uncal - the uncus (medial part) of the temporal lobe herniates inferior to the tentorium cerebelli 4) transcalvarial (through the calvaria/skullcap)
What are the 7 functional groups of cranial nerve fibres?
- General somatic afferent (GSA) – general sensory info e.g. cutaneous sensation
- Special somatic afferent (SSA) – vision, hearing and balance
- General visceral afferent (GVA) – sensation from glands and internal organs
- Special visceral afferent (SVE) – olfaction and gustation
- General somatic efferent (GSE) – voluntary muscles in eye and tongue
- General visceral efferent (GVE) – control smooth muscle and glands
- Special visceral efferent (SVE) – voluntary muscles of expression, mastication and speech
What is a common site affected by CVA?
Internal capsule
*Where is the common ‘nerve point’ of the neck?
Just above the midpoint of posterior border of SCM
Which spinal nerves contribute to the subcostal nerve?
Anterior rams of T12
What is different when testing a peripheral nerve vs a dermatome?
AP travels along a plexus to the spinal nerve, rather than a single rami
Which spinal segments contribute to the cervical plexus?
C1-C4
Which spinal segments contribute to the brachial plexus?
C5-T1
Which spinal segments contribute to the lumbosacral plexus?
L1-S4
What controls reflex muscle contractions?
Descending pathways
What symptoms are shown in upper motor neuron lesions?
Spasticity (muscle no longer being limited)
What symptoms are shown in lower motor neuron lesions?
flaccidity (skeletal muscle is no longer being innervated)
Which is the only cranial nerve to attach to the pons (not the pontomedullary junction)?
CN V (Trigeminal)
What supplies the sensory innervation for the upper and lower eyelids?
Upper = V1 and lower = V2
What supplies the sensory innervation for the tip of the nose and alae?
Tip of the nose = V1 and alae = V2
Which spinal nerve supplies the angle of the mandible and behind?
Great auricular
What supplies the sensory innervation of the beard line?
CN V3
How would you test the sensory and motor innervation of the Trigeminal nerve? Also which reflex could you test?
Sensory: ask patient to close their eyes and touch cotton wool to each of these areas, having them tell you when they feel it (compare both sides): V1 = forehead, upper eyelid and tip of nose; V2 = mid check, lower eyelid, upper lip and nostril; V3 = mid cheek, lower lip and chin
Motor = palpate strength of mastication muscles by asking to clench their teeth
First part of the afferent limb of the blink (corneal) reflex is supplied by the long ciliary nerves
How would you clinically test the motor function of the facial nerve?
Ask the patient to frown, close eyes tightly, smile and puff out cheeks
General sensory axons from which cranial nerve form the afferent limb for the gag reflex, and are commonly associated with referred pain from the pharynx to the ear and vice versa?
CN IX (Glossopharyngeal)
How would you clinically test the vagus nerve?
Ask the patient to say ‘ah’ (tests motor of uvula - pulls away from pathology); ask patient to swallow small amount of water; listen to speech; ask patient to cough
How would you differentiate CN XI Spinal accessory from named nerves of cervical plexus?
The named nerves of the cervical plexus also pass deep to the midpoint of the posterior border of SCM (at the nerve point of the neck). but they do not pass deep to trapezius as CN XI does
How would you clinically test CN XI (spinal accessory)?
Ask the patient to shrug shoulders or to turn head to look up towards the opposite side
How would you clinically test CN XII (hypoglossal)?
Ask the patient to stick their tongue straight out (points towards pathology)
What are the 3 lobes of there cerebellum?
Anterior, posterior and flocculonodular
As the main output for the cerebellum - What are the 4 pairs of deep cerebellar nuclei called and what is their location?
They are 4 pairs embedded deep in the white matter, and medial to laterally they are called the fastigial, globose, emboliform and dentate (largest) nuclei
*What are the 3 histological layers of the cerebellar cortex?
Molecular (outer), purkinje cell, and granular layer (inner)
What would be the symptoms from a unilateral cerebellar hemisphere lesion?
Disturbance of coordination in limbs. Can result in intention tremor and unsteady gait in the absence of weakness or sensory loss on the ipsilateral side
What would be the symptoms from a bilateral cerebellar hemisphere lesion?
Results in slowed, slurred speech (dysarthria), bilateral incoordination of the arms and a staggering, wide based gait (cerebellar ataxia).
What would be the symptoms from a midline cerebellar hemisphere lesion?
Disturbance of postural control. Patient will tend to fall over when standing or sitting despite preserved limb coordination.
Striatum of the basal ganglia =
Striatum = caudate nucleus + putamen
Corpus striatum =
Corpus striatum = striatum + globus pallidus
Lentiform nucleus =
Lentoform nucleus = putamen + globus pallidus (due to anatomical proximity)
What part of the brain is affected in Parkinson’s?
Substantia nigra of the basal ganglia in the midbrain is lost in Parkinson’s, as the black substance is a by-product of dopaminenand dopaminergic neurons degenerate in parkinson’s
What is the function of the direct and indirect pathways of basal ganglia?
Direct pathway facilitates purposeful movement, and indirect pathway inhibits unwanted movement
What would the effects of a basal ganglia lesion be?
Contralateral symptoms of: abnormal muscle control, changes in muscle tone and
dyskinesias (abnormal, involuntary movements) including:
tremor (sinusoidal movements); chorea (rapid, asymmetrical movements usually affecting distal limb musculature); myoclonus (muscle jerks)
