Neuro: Neuroanatomy 2 Flashcards
What are the three types of long projector systems of axons in the brain?
Association fibres (axons stay in one hemisphere).
Commissural fibres (axons connect both hemispheres).
Projection fibres (axons project down into spinal cord).
What is the largest set of commissural fibres in the brain?
Corpus callosum.
What happens in tonsillar herniation (coning)?
Cerebellum herniates out of the foramen magnum and the medulla is compressed.
Why is rupture of an atheroma at the bifurcation of the common carotid likely to block the middle cerebral artery?
The middle cerebral artery is continuous with the internal carotid artery, which originates at the bifurcation of the common carotid.
CSF is mostly drained back into the blood via arachnoid granulations. What other route can some CSF take?
Some CSF drains through the cribriform plate into lymphatic system, enters cervical lymph nodes.
What area of the brain do all cranial nerves originate from?
The brainstem.
Which cranial nerve leaves the brainstem posteriorly?
Trochlear (CN IV)
What is the largest cranial nerve?
Trigeminal (CN V)
How does the pons communicate with the cerebellum?
Via peduncles (superior, middle, inferior cerebellar peduncles).
The dorsal column carries information about touch, vibration, and body position. What are the two tracts that form the dorsal column in the medulla?
Fasciculus cuneatus.
Fasciculus gracilis.
The cerebral aqueduct can be used as a landmark to divide transverse section of the midbrain into what two areas?
Tectum (dorsal) and tegmentum (ventral).
Parkinson’s disease is caused by a loss of nerve cells in the part of the brain called the substantia nigra. Why do people with Parkinson’s struggle with movement?
Substantia nigra produces dopamine which is needed to begin and control movement.
In an evolutionary sense, what is the oldest part of the cerebellum, involved in controlling basic posture and sitting upright?
Flocculonodular lobe.
What worm-like part of the cerebellum is involved in more sophisticated balance and separates the two cerebellar hemispheres?
Vermis.
What separates the superior and inferior cerebellum?
Horizontal fissure.
What are the small leaflike laminae (folds) of the cerebellum called?
Folia
What bulbous area, most posterior of the corpus callosum, carries lots of visual fibres between both hemispheres to knit images from both sides together?
Splenium
Which ventricle lies between left and right thalamus?
Third ventricle
The Papez circuit is a fundamental component of the limbic system with a significant role in memory functions. Where does the Papez circuit start and finish?
Hippocampus.
What would happen to memory function if both hippocampus removed?
Won’t be able to form new memories (but old memories will remain intact).
Which lobe is the hippocampus in?
Temporal lobe.
What a group of nerve cell clusters, linked to the thalamus, control voluntary movement, learning, and emotions?
Basal ganglia.
What important a white matter structure in the brain connects the cerebral cortex to the spinal cord and brainstem?
Internal capsule.
What are the three contiguous subcortical structures in the striatum?
The caudate, putamen, and nucleus accumbens.
The nigrostriatal pathway is a dopamine-dependent system that controls voluntary movement and balance.
What areas does the nigrostriatal pathway connect?
The substantia nigra in the midbrain to the caudate nucleus and putamen in the striatum.
The hypothalamus receives a lot of information from various areas of the brain and the blood. What structure below the hypothalamus does it send most of its efferent fibres to?
Pituitary gland.
The neocortex is the largest part of the cerebral cortex. How many layers does the neocortex have?
Six
Which is longer, the spinal cord or the vertebral column?
The vertebral column.
What sensory pathway carries information about pain, temperature, touch, and pressure from the skin to the thalamus?
Spinothalamic tract.
What happens to the corticospinal tract in the medulla that means movement occurs on the side of the body contralateral to the hemisphere of the brain in which they originated?
Fibres from left & right corticospinal tracts decussate (cross over) before entering the spinal cord as the lateral corticospinal tracts.
Where do the left and right spinothalamic tracts decussate (cross over)?
In the spinal cord (before ascending upwards to the brain).
Do upper or lower motor neurons control muscle movements?
Both; upper motor neurons act on lower motor neurons which then innervate muscle.
The pons contains nuclei of what four cranial nerves?
Trigeminal (CN V), Abducens (CN VI), Facial (CN VII), and Vestibulocochlear (CN VIII).
(5 to 8!)
On the ventral surface of the medulla, what does the anterior median fissure separate?
The medullary pyramids.
The medulla contains nuclei of what four cranial nerves?
Glossopharyngeal (CN IX), Vagus (CN X), Accessory (CN XI) and hypoglossal (CN XII).
(9 to 12!)
The midbrain contains nuclei of what two cranial nerves?
Oculomotor (CN III) and Trochlear (CN IV).
Using your excellent nmemonic, list the 12 cranial nerves in order.
I Olfactory
II Optic
III Oculomotor
IV Trochlear
V Trigeminal
VI Abducens
VII Facial
VIII Vestibulocochlear
IX Glossopharyngeal
X Vagus
XI Accessory
XII Hypoglossal
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Which cranial nerves carry sensory, motor, or both fibres?
I Olfactory = Sensory
II Optic = Sensory
III Oculomotor = Motor
IV Trochlear = Motor
V Trigeminal = Both
VI Abducens = Motor
VII Facial = Both
VIII Vestibulocochlear = Sensory
IX Glossopharyngeal = Both
X Vagus = Both
XI Accessory = Motor
XII Hypoglossal = Motor
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Why might it be argued the accessory nerve (CN XI) is not a “real” cranial nerve?
Part of it originates in the spinal cord.
Why might it be argued that the olfactory (CN I) and optic (CN II) nerves are not “real” cranial nerves?
The have different embryological origins which means they originate in the cerebrum and diencephalon respectively, not the brainstem.
What four cranial nerves contain parasympathetic fibres?
Oculomotor (CN III), Facial (CN VII), Glossopharyngeal (CN IX), and Vagus (CN X).
What parasympathetic functions does the oculomotor nerve (CN III) have?
Pupillary constriction; innervates sphincter pupillae.
What parasympathetic functions does the facial nerve (CN VII) have?
Innervates submandibular and sublingual salivary glands, and the lacrimal gland.
What parasympathetic functions does the glossopharyngeal nerve (CN IX) have?
Innervates parotid salivary gland.
What organs have parasympathetic innervation from the vagus nerve (CN X)?
Thoracic and abdominal organs.
In the parotid gland the facial nerve (CN VII) divides into five branches which spread out across the face.
What are the five branches of the facial nerve?
Temporal, zygomatic, buccal, marginal mandibular, and cervical.
The facial nerve (CN VII) first exits through the internal auditory meatus. The facial nerve progresses through the middle ear cavity and then exits the temporal bone through what foramen?
Stylomastoid foramen.
How does the accessory nerve (CN XI) enter and leave the skull?
Enters via the foramen magnum.
Leaves via the jugular foramen.
What two muscles does the accessory nerve (CN XI) innervate?
Sternocleidomastoid and trapezius.
Information from which visual field crosses over at the coptic chiasm to enter the opposite side of the brain?
Temporal visual field (received by nasal retina).
Where do the majority of optic tract fibres synapse and divide into the superior (parietal) and inferior (temporal) optic radiations?
Lateral geniculate nucleus in the thalamus.
All three branches of the trigeminal nerve (CN V) contain sensory fibres, providing sensory innervation of the face.
Which branch of the trigeminal nerve innervates muscles involved in mastication?
Mandibular (V3)
The glossopharyngeal nerve (CN IX) has sensory and parasympathetic fibres, and a very small number of motor fibres.
What motor function does the glossopharyngeal nerve provide?
Innervates one muscle (stylopharyngeus) involved in swallowing.
What is the definition of pain, as per the International Association for the Study of Pain?
“An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.”
What is chronic pain?
Pain lasting longer than 12 weeks, or persisting beyond the tissue healing time.
What is nociplastic pain?
Pain arising from altered nociception despite no clear evidence of tissue damage (nociceptive pain) or disease/lesion of somatosensory system (neuropathic pain).
The nociceptive pathway to the brain involves three neurons: 1st order (AKA ‘primary afferent’), 2nd order, and 3rd order neurons. Where do these synapse with each other?
1st & 2nd = ipsilateral spinal cord (2nd then decussates)
2nd & 3rd = contralateral thalamus
3rd then reaches the primary somatosensory cortex
Nociceptors are the free nerve endings of primary afferent neurons. There are two types: AΔ fibres and C fibres. Which have a faster conduction speed and why?
AΔ fibres; because they are myelinated and C fibres are not myelinated.
Where are the cell bodies of nociceptors for the body?
Dorsal root ganglia.
Explain, with reference to nociceptors, why visceral pain is harder to locate than somatic pain?
Visceral nociceptors have more secondary afferent fibres (2nd order) than primary.
What nucleus in the tegmentum of the midbrain supplies parasympathetic fibres of the occulomotor nerve (CN III) which are involved in pupillary constriction (sphincter pupillary muscles) and focusing (ciliary muscles)?
Edinger-Westphal nucelus.
Which four nerves run along the lateral wall of the cavernous sinus?
III Occulomotor
IV Trochlear
V1&2 Opthalmic and maxillary branches of trigeminal nerve.
Which cranial nerve runs along the floor of the cavernous sinus laterally to the internal carotid artery?
Abducencs (CN VI)
The medial geniculate body and the lateral geniculate body are each associated with either the optic or auditory pathways. Which (medial or lateral) is associated with which (optic or auditory)?
Medial geniculate body = auditory.
Lateral geniculate body = optic.
What cranial nerve might be damaged in someone complaining of double vision when looking down e.g. when walking downstairs?
Trochlear (CN IV).
Damage to the hypoglossal nerve (XII) will cause paralysis on the ipsilateral or contralateral half of the tongue?
Ipsilateral (“lick the lesion”).
Babinski’s reflex results in fanning the toes out when sole of foot is stroked. When is this reflex abnormal and suggestive of pathology e.g. MS or stroke?
> 2 years old (normal in babies).
How many vertebrae form the vertebral column?
33
How many cervical vertebrae are there?
7
How many thoracic vertebrae are there?
12
How many lumbar and sacral vertebrae are there?
5 each (though sacral vertebrae are fused together to form the sacrum).
How many coccygeal vertebrae fuse together to form the coccyx?
4
The vertebral column has several distinct curvatures, ‘inwards’ and ‘outwards’.
Using the correct terminology for these curvatures, describe how the vertebral column curves in the cervical, thoracic, and lumbar spine.
Cervical = lordosis (inwards)
Thoracic = kyphosis (outwards)
Lumbar = lordosis (inwards)
What two parts of a vertebra joins the body and the lamina together, forming the spinal canal?
The pedicles.
In cervical vertebrae, foramina in what structure forms canals for the vertebral arteries?
Transverse processes
What vertical protrusions from vertebrae provide a site of attachment to vertebrae above and below via synovial facet joints?
Articular processes
Via what foramina, formed by the spaces between the bodies and pedicles of neighbouring vertebrae, do spinal nerves leave the spinal cord?
Intervertebral foramina
What are the atlas and axis?
C1 (atlas) and C2 (axis) vertebrae.
The atlas (C1 vertebra) articulates directly with the occipital bone of the skull and allows nodding of the head.
Give 3 identifying features of the atlas.
- Ring shaped.
- Lacks a vertebral body.
- No spinous process.
The axis (C2 vertebra) allows turning of the head via a pivot joint called the atlanto-axial joint.
Describe the key identifying feature of the axis that allows this movement.
The odontoid process (AKA peg) is the body of the axis and protrudes vertically upwards to articulate with the atlas (C1) so that the atlas can spin around the axis.
Give 3 identifying features of C3-C6 vertebrae.
- Smaller than thoracic/lumbar vertebrae.
- Transverse foramina in transverse processes.
- Bifid (‘two-pronged’) spinous process.
Why is C7 sometimes referred to as ‘vertebra prominens’?
The spinous process is more prominent and is usually the most superior spinous process that can be palpated.
The thoracic vertebrae become increasingly larger from superior to inferior because the most inferior vertebrae have to support more weight.
Give three identifying features that all the thoracic vertebrae have in common.
- Additional articular surfaces for the ribs (body and transverse processes).
- Long, sharp, down-sloping spinous process.
- Heart-shaped vertebral body.
The lumbar vertebrae are the largest individual vertebrae in the spine.
Give three identifying features of lumbar vertebrae.
- Very large vertebral bodies.
- Long, flat transverse processes that project more laterally.
- Large but shorter and rectangular spinous process.
What is the sacral promontory?
Anterior prominence at the top of the sacrum.
What is the name of the joints that articulate the pelvis and the sacrum?
Sacroiliac joints.
Intervertebral discs are fibrocartilaginous structures that allow flexibility and movement between vertebrae, and can withstand compression forces.
What are the two different sections of an intervertebral disc?
Nucleus pulposus (central gelatinous core).
Annulus fibrosus (concentric rings of collagen).
What separates an intervertebral disc from a vertebra?
Hyaline cartilage.
What two spinal ligaments run on either side of the vertebral bodies?
Anterior longitudinal ligament.
Posterior longitudinal ligament (anterior to spinal canal).
What spinal ligament runs along the inside of the laminae?
Ligamentum flavum.
What spinal ligament runs between the spinous processes?
Interspinous ligament.
What spinal ligament runs along the tips of the spinous processes (the most posterior spinal ligament)?
Supraspinous ligament.
What group of paraspinal muscles contribute to maintaining an upright posture and can often be palpated either side of the lumbar spine when standing?
Erector spinae muscles.
Explain why there are 33 vertebrae but only 31 pairs of spinal nerves.
Cervical spinal nerves leave above their corresponding vertebrae.
There is an additional cervical spinal nerve pair (C8) which leaves below C7.
All other spinal nerves leave below their corresponding vertebrae.
There is only one pair of coccygeal spinal nerves (Co1) but 4 coccygeal vertebrae.
33 -3 (missing coccygeal) +1 (C8) = 31
At what vertebral level does the spinal cord taper into a cone shape called the conus medullaris?
L1-L2 junction.
What thin strand of thickened pia mater continues from the conus medullaris to the coccyx, to help tether the spinal cord in position?
The filum terminale.
Shortly before terminating at the conus medullaris, the spinal cord gives off all its remaining spinal nerves yet to leave the spinal canal, forming the cauda equina.
Which spinal nerves form the cauda equina?
L3-L5, S1-S5, Co1.
What two roots form each spinal nerve and how do these correspond to function (sensory or motor)?
Dorsal (sensory) and ventral (motor) roots.
What shape is the grey matter in the centre of the spinal cord?
H-shaped.
Describe the typical ascending sensory pathway of spinal nerves in three steps.
- First order neuron from receptor to CNS (spinal cord/brainstem, with cell body in dorsal root ganglion.
- Second order neuron from CNS to thalamus.
- Third order neuron from thalamus to somatosensory cortex.
Describe the typical descending motor pathway of spinal nerves in two steps.
- First order neuron (upper motor neuron) from the motor cortex to ventral horn of spinal cord.
- Second order neuron (lower motor neuron) from ventral horn of spinal cord to muscle.
What four key types of sensory information do the DCML (dorsal columns medial lemniscus) spinal tracts transmit to the primary somatosensory cortex?
Fine touch, two-point discrimination, vibration, and proprioception.
Which dorsal column tract carries some sensory information from the lower limbs?
Fasciculus gracilis (medial)
Which dorsal column tract carries some sensory information from the upper limbs?
Fasciculus cuneatus (lateral)
Where do the first order neurons of the DCML (dorsal column medial lemniscus) tract synapse and then decussate as second order neurons?
Medulla.
The DCML (dorsal column medial lemniscus) tract second order neurons decussate then travel from the medulla via the medial lemniscus tract. The third order neurons travel to the somatosensory cortex via the internal capsule.
Where do the second order neurons synapse with third order neurons?
In the thalamus.
What three key types of sensory information does the spinothalamic tracts transmit to the primary somatosensory cortex?
Crude touch, pain, temperature.
The first order neurons of the spinothalamic tract enter the spinal cord via the dorsal root. Where do the first oder neurons synapse with the second order neurons?
Within the dorsal horn
Where do the second order neurons of the spinothalamic tract decussate?
Within the spinal cord, usually after travelling upwards one or two spinal levels.
Where do the second order neurons of the spinothalamic tract synapse with the third order neurons, which then travel to the primary somatosensory cortex via the internal capsule?
In the thalamus.
What function do the lateral corticospinal tracts provide?
Carry motor impulses to the limbs.
The first order neurons of the lateral corticospinal tract leaves the motor cortex and passes through the internal capsule. Where do the first order neurons decussate?
In the medullary pyramids (in the medulla).
Where do the first order neurons of the lateral corticospinal tract synapse with the second order neurons?
In the ventral horn of the spinal cord, at the vertebral level of the target muscle.
The anterior corticospinal tract is smaller than the lateral corticospinal tract and is only present above mid-thoracic level.
What function does the anterior corticospinal tract provide?
Carries voluntary motor impulses to large proximal and postural muscles of the thorax.
The corticobulbar tract (AKA corticonuclear tract) upper motor neurons only travel as far as the nuclei of the cranial nerves. What function does the corticobulbar tract provide?
Carries motor fibres related to movement of the head, face, and neck (CN V, VII, IX, X, XI, XII OR 5,7,9-12).
The anterior and posterior spinocerebellar tracts are located the most laterally in the spinal cord. What is their main function?
Carrying unconscious proprioceptive information to the cerebellum.
Explain how the anterior and posterior spinocerebellar tracts decussate.
The anterior spinocerebellar tract decussates twice; once at level of entry into cord, and again at entry to the cerebellum.
The posterior spinocerebellar tract does not decussate.
Do white rami communicantes carry preganglionic sympathetic fibres or postganglionic sympathetic fibres between the spinal nerve and the sympathetic chain ganglion?
Preganglionic fibres.
Grey rami communicantes carry postganglionic fibres from ganglion back to spinal nerve and then to effector e.g. smooth muscle.
What do the three pairs of cerebellar peduncles (superior, inferior, and middle) connect?
Cerebellum to the brainstem.
What are the three lobes of the cerebellum?
Anterior, posterior, and flocculonodular.
In the cerebellum, what fissure separates the anterior lobe from the larger posterior lobe?
The primary fissure.
In the cerebellum, where is the horizontal fissure?
In the posterior lobe.
In the cerebellum, what two structures form the flocculonodular lobe?
Flocculus and nodule.
The cerebellum has folds similar to the cerebral gyri, but much smaller. What are these cerebellar folds called?
Folia.
What functional area of the cerebellum is located in the vermis, and receives input from the spinocerebellar tracts via the superior and inferior cerebellar peduncles?
Spino-cerebellum.
What functional area of the cerebellum is located in the lateral hemispheres, and receives input from the cerebral cortex via the middle cerebellar peduncle?
Cerebro-cerebellum.
What functional area of the cerebellum is located in the flocculonodular lobe, and receives input from the vestibular system via the inferior cerebral peduncle?
Vestibulo-cerebellum.
What three paired arteries supply the cerebellum?
Superior cerebellar arteries.
Anterior inferior cerebellar arteries.
Posterior inferior cerebellar arteries.
What is connected to the hypothalamus by the stalk-like infundibulum?
Pituitary gland.
What gland in the diencephalon, situated immediately posterior to the colliculi of the midbrain, secretes melatonin?
Pineal gland.
What small round nuclei, located at the anterior tip of the fornix, are part of the limbic system and an important landmark when looking at imaging?
Mammillary bodies.
What group of association fibres travel from the cingulate gyrus to other parts of the limbic system such as the parahippocampal gyrus?
The cingulum.
The basal ganglia are a group of deep nuclei located close to the thalamus, but spread throughout the cerebrum, diencephalon, and midbrain.
What are the five main named parts of the basal ganglia?
Substantia nigra.
Subthalamic Nucleus.
Putamen.
Caudate Nucleus.
Globus Pallidus.
Substantially Scarily Nuts Putin Caused Nuclear Global Panic.
What two parts of the basal ganglia make up the lentiform nucleus?
Putamen and globus pallidus.
What two parts of the basal ganglia make up the striatum?
Putamen and caudate nucleus.
What two parts of the basal ganglia make up the corpus striatum?
Caudate nucleus and lentiform nucleus.
The axons that pass from the internal capsule to the cortex ‘radiate’ outwards, forming what structure?
The corona radiata.
