Neuroanatomy Practical 2 Flashcards by Esme Cosham

Which of the 5 major subdivisions of the brain make up the brainstem?

Mesencephalon, metencephalon and myelencephalon

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What fibres are found in the pyramids of the medulla?

Descending motor fibres
White matter

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What are descending tracts?

The descending tracts are the pathways by which motor signals are sent from the brain to lower motor neurones. The lower motor neurones then directly innervate muscles to produce movement.

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What can the descending motor tracts be divided into?

Pyramidal
Extra-pyramidal

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Where do the pyramidal tracts originate? What are they responsible for?

These tracts originate in the cerebral cortex (primary motor cortex - precentral gyrus), carrying motor fibres to the spinal cord and brain stem.
They are responsible for the voluntary control of the musculature of the body and face.

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Are there any synapses in the descending motor pathways?

No:

At the termination of the descending tracts, the neurones synapse with a lower motor neurone.
- Thus, all the neurones within the descending motor system are classed as upper motor neurones.
- Their cell bodies are found in the cerebral cortex or the brain stem, with their axons remaining within the CNS.

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Where do the pyramidal tracts derive their name from?

The pyramidal tracts derive their name from the medullary pyramids of the medulla oblongata, which they pass through.

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Functionally, what can the pyramidal tracts be divided into

Corticospinal
Corticobulbar

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Course of corticospinal tract explained

Neurones originate in cerebral cortex
Converge and descend through the posterior limb of the internal capsule
Then pass through the crus cerebri of the midbrain, the pons and into the medulla.
In the most inferior (caudal) part of the medulla, the fibres decussate (cross over to the other side of the CNS) –> decussation of pyramids
Then descend into the spinal cord

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What is the internal capsule?

a white matter pathway, located between the thalamus and the basal ganglia

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Why is the internal capsule clinically important?

As the internal capsule is particularly susceptible to compression from haemorrhagic bleeds, known as a ‘capsular stroke‘. Such an event could cause a lesion of the descending tracts.

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What structure is this?

Olfactory bulb and tract

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What structure is this?

Optic nerve (attached to eye balls)

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Where do the optic nerves converge?

At the optic chiasma (crossing over of fibres from either eye)

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What is this?

Infundibulum (pituitary stalk) - connects the hypothalamus and the posterior pituitary gland.

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The infundibulum, optic nerves and chiasma and mamillary bodies are all extensions of what?

Diencephalon

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What structure is being pointed to?

Cerebral peduncle of midbrain (one on each side)

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Diagram of pons and transverse pontine fibres. What does the pons connect?

The pons is a bridge that connects the cerebellar hemispheres

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What sulcus is found here? What is found either side?

Anterior median sulcus
Pyramids either side

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What is found lateral to the pyramids?

Olives (small bumps)

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What is the medulla continuous with inferiorly?

Spinal cord

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How does the spinal cord exist the cranium?

Foramen magnum

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What is found just inferior to middle cerebellar peduncles?

Flocculus (one on either side)
These are pieces of cerebellar tissue

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What is this?

Cerebellar tonsil (one on each side)
Project inferiorly and are closely related to medulla

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View of optic nerves and chiasma

What is the function of the optic chiasm?

* Allows the visual cortex to receive the same hemispheric visual field from both eyes. * 2 optic tracts then leave the optic chiasma and travels to its corresponding cerebral hemisphere

Where do the optic tracts travel to?

* Winds around thalamus * Reach the **lateral geniculate nucleus (LGN**), a relay system located in the **thalamus**; the fibres synapse here. * Axons from the LGN then carry visual information via a pathway known as the optic radiation.

Clearer view of cerebral peduncles

What is the space between the 2 cerebral peduncles called?

Interpeduncular fossa

Which nerve emerges between the pyramids and olives?

Root fibres of CN XII (hypoglossal)

Telencephalon has been removed and left with diencephalon. What are these 2 egg shaped structures?

One thalamus either side (bilateral egg shaped matters that sit on top of brainstem)

Which ventricle sits between the two thalami?

3rd ventricle

What are the mamillary bodies?

* Part of diencephalon * Found on underside/ventral side of brain * Paired - one on either side of brain

View of interpeduncular fossa and 2 cerebral peduncles (without telencephalon)

Which CN emerges from the interpeduncular fossa?

CN III oculomotor

What nerve stump is this?

Trigeminal

Which nerves emerge from the cerebellopontine angle?

CN VII and CN VIII

Cross section of midbrain

* Mickey mouse shape --\> ears are the cerebral peduncles * Space between ears --\> interpeduncular fossa * Can see oculomotor nerves emerging

Direction of fibres in cerebral peduncle vs pons?

Cerebral peduncle: horizontal Pons: transverse pontine fibres

What structure is this? (cross section of midbrain)

Cerebral aquaduct

What is this darker area of the midbrain called? What can be found here?

* Substantia nigra / 'black substance' * Considered part of the basal ganglia * Most of **dopamine neurons** of the brain can be found here

Where does the anterior median fissure disappear?

At decussation of pyramids

View of cerebellopontine angle (CN VIII being pointed to)

Cranial nerves emerging diagram

What nerve is being pointed to?

spinal accessory - travels upwards to join with cranial accessory (receives spinal nerve roots from spinal cord)

How does CN XI leave the cranium?

jugular foramen

Which nerve is this emerging from the dorsal aspect of the brainstem?

CN IV - trochlear

Which vessel is located besides the optic chiasm?

Internal carotid

Cranial nerves diagram 2

Clear view of cerebral aquaduct

Where does CN VI emerge?

At junction between pons and medulla - **pontomedullary junction**

What 2 main parts can the midbrain be divided into?

1. Tectum --\> located posterior to the cerebral aqueduct 2. Paired cerebral peduncles --\> located anteriorly and laterally

What four rounded prominences does the tectum house?

The superior and inferior colliculi

Which nerve emerges inferior to colliculi?

Trochlear nerve - wraps itself round brainstem to move anteriorly

View of floor of 4th ventricle --\> if you follow probe it will connect to cerebral aquaduct N.B. this is dorsal aspect of brainstem

What is the 4th ventricle continuous with inferiorly?

Central canal of medulla and spinal cord

What is point called where 4th ventricle ends and continous with central canal?

Obex

What is the midline structure of the posterior surface of the medulla?

Posterior median sulcus (continuous below as the posterior median sulcus of the spinal cord)

Where does the posterior median sulcus end superiorly?

at the point in which the fourth ventricle develops.

Open vs closed medulla

As we move lateral from the posterior median sulcus, what bumps are seen?

* Gracile fasciculus * Brings **ascending sensory fibres** from body * Dilates rostrally to form gracile tubercle * Underlying this area is a **nucelus** (where ascending fibres connect and synapse) * Cuneate fasciculus * Contains **ascending sensory fibres** * Dilates rostrally to form cuneate tubercle

What is a fasciculus?

bundle of white matter fibres

view of cuneate and gracile fasciculi

Are the cerebellar peduncles seen in doral or ventral view?

Ventral

When there is increased intracranial pressure, structures of the brain may be distorted and displaced. * Herniation of the cerebellar tonsils would occur through which foramen? * What brainstem structures would be compressed?

* Foramen magnum * Medulla

How is the brainstem connected to the cerebellum?

Via 3 paired cerebellar peduncles

What structure is this? What does it connect?

Superior cerebellar peduncle --\> connects cerebellum to midbrain

What structure is this? What does it connect?

Middle cerebellar peduncle - connects cerebellum to pons

What structure is this? What does it connect?

Inferior cerebellar peduncle - connects cerebellum to medulla

What structure is seen in midline of ventral cerebellum?

Vermis

More ventrally, what is this aspect of the vermis called?

Nodule

* The cerebellum is located at the back of the brain, immediately inferior to which lobes? * How is it separated from these lobes? * Which cranial fossa is it in? * How is it separated from the pons?

* occipital and temporal lobes * separated from these lobes by the tentorium cerebelli, a tough layer of dura mater. * within the posterior cranial fossa * ies at the same level of and posterior to the pons, from which it is separated by the **fourth ventricle.**

The cerebellum consists of two hemispheres which are connected by which structure?

Vermis (a narrow midline area)

The cerebellum can be divided into 3 anatomical lobes. What lobes are these? How are these lobes divided?

1. Anterior 2. posterior 3. flocculonodular These lobes are divided by two fissures – the **primary fissure and posterolateral fissure.**

What fissure is this? What does it separate? NB. this is superior surface of cerebellum

Primary fissure - separates anterior and posterior lobe of cerebellum

Tonsils compressing medulla if herniation occurred

View of 2 vertebral arteries joining on **ventral surface of pons** to form basilar artery

Which arterial branches supply the cerebellum?

* PICA * AICA * SCA

Which branch is this? Where does it arise from?

PICA - arises from vertebral artery (paired) to supply posterior and inferior cerebellum

Which branch is this? Where does it arise from?

AICA - arises from basilar artery

Which branch is this? Where does it arise from?

SCA - arises from basilar artery

What does PICA supply?

* posteroinferior cerebellar hemispheres * lower part of the medulla

Cross-section of upper **midbrain** (at level of superior colliculus)

Cross-section of lower midbrain (at level of inferior colliculus)

Cross section of upper pons

Cross section of mid pons

Cross section of lower pons

Cross section of upper medulla

Cross section of mid medulla

Cross section of lower medulla

What is this a cross section of?

* Midbrain * Ventral region is interpeduncular fossa * CN III emerges ventrally * CN IV emerges dorsally * Dorsal region is cerebral aquaduct * Colliculi found dorsally * Mickey mouse ears are cerebral peduncles

What is this a cross section of?

* Pons * Basilar groove found ventrally (where basilar artery sits) * 4th ventricle found dorsally * Cerebellar peduncles found * More caudal aspect of pons

What is this a cross section of?

* Open/rostral medulla * 4th ventricle dorsally * Pyramids and olives found ventrally * Olives have characteristic squiggly squished feature * Inferior cerebellar peduncle --\> white matter found laterally dorsally

What is this a cross section of?

* Caudal/closed medulla * Central canal * Pyramids ventrally * Cuneate tubercle dorsally and laterally to gracile tubercle

* Cranial CT shows a basal skull fracture extending through the **jugular foramen** * Assuming that the nerve(s) that transverse this opening are damaged, what deficits are likely to be seen?

* CN IX, CN X and CN XI pass through jugular foramen * Drooping and difficulty elevating shoulder (CN XI)

In a presentation of: * Dilated right pupil * Loss of most eye movement on right * No other motor or sensory difficulties What nerve is likely to be damaged?

Oculomotor CN III

The patient is attempting to retract both angles of the mouth and raise both eyebrows. Which cranial nerve has been damaged?

Right facial nerve

Which cranial nerve is damaged?

Left hypoglossal nerve

In the tearing/lacrimal reflex, where is the location of the postganglionic cell bodies that innervate the lacrimal gland?

Pterygopalatine ganglion

Which cranial nerves pass through the cribriform plate of the ethmoid mode?

CN I olfactory

Where are the true olfactory nerves (olfactory receptors) located?

Nasal epithelium

Which cranial nerves pass through the optic canal?

CN II optic nerve - passes through orbit

Which cranial nerves pass through the superior orbital fissure?

* CN III oculomotor * CN IV trochlear * CN V₁opthalmic branch * CN VI abducens Enter/leave the orbit

Which cranial nerves pass through the foramen rotundum?

CN V₂

Which cranial nerves pass through the foramen ovale?

CN V₃

Which cranial nerves pass through the internal acoustic meatus?

CN VII and CN VIII * CN VIII then stays in petrous bone (here is where tiny structure of inner aer are located) * CN VII then takes path within petrous temporal bone (giving off branches) and then leaves skull via **stylomastoid foramen**

Stylomastoid foramen

Which cranial nerves pass through jugular foramen?

CN IX, CN X, CN XI

Which cranial nerves pass through the hypoglossal canals?

CN XII

View of ventral surface of brain

What limb of the internal capsule do corticospinal fibres pass through?

Posterior limb

What is the crus cerebri?

the **anterior portion** of the **cerebral peduncles** which contains the **motor** tracts, travelling from the cerebral cortex to the pons and spine

Neuroanatomy Practical 2 Flashcards

(112 cards)