- Composed of cell bodies and dendrites primarily - Highly vascular - Most computation occurs here - Contains some axons, in order to communicate with white matter

Nervous System Topography Flashcards by Ronit Hardasani

Describe Grey Matter

Composed of cell bodies and dendrites primarily
Highly vascular
Most computation occurs here
Contains some axons, in order to communicate with white matter

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Describe White Matter

Composed of axons

- White due to presence of fatty Myelin

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What are the PNS equivalents of Grey and White matter?

Grey- Ganglia (Not basal ganglia, these are part of CNS)

White- Peripheral nerves

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What is a Nucleus?

What is a Cortex?

Nucleus: A collection of functionally related cell bodies

Cortex: A folded sheet of cell bodies found on the surface of a brain structure

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What is a fibre?

What are the 3 types of fibre?

An axon in association with its supporting cells

Association fibres
Commissural fibres
Projection fibres

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What do Association fibres connect?

Connect cortical region within a single hemisphere

E.g Parietal and temporal lobes of same hemisphere

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What do Commissural fibres connect?

Connect the Left and Right hemispheres

E.g Corpus Callosum

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What do Projection fibres connect?

Connect the cerebral hemispheres with the cord/brainstem and vice versa

(E.g Corticospinal fibres or Spinothalamic fibres)

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Describe the spinal cord

31 segments
Central grey matter core, outer white matter shell
Each segment connects with a Spinal (mixed) nerve via Ventral (motor) and Dorsal (sensory) nerve roots

(Roots are actually formed from convergence of multiple rootlets)

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What is a Funiculus?

A segment of white matter containing multiple distinct pathways which both ascend (sensory) and descend (motor)

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What is a Tract?

These are found in Funiculi

A white matter pathway connecting 2 regions of grey matter, in which impulses travel in a single direction only

E.g;

Dorsal funiculus contains dorsal column tract (ascends)
Lateral funiculus contains lateral corticospinal tract (descends) and spinothalamic tract (ascends)
Ventral funiculus contains ventral corticospinal tract (descends)

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What is a Fasciculus?

(Found in Tracts)

Compare the 2 Fasciculi of the Dorsal Column Tract which is prt of the Dorsal Funiculus

A subdivision of a tract that supplies a distinct body region

Fasciculus gracilis/ Gracile Fasciculus supplies lower body half
Fasciculus cuneatus/ Cuneate Fasciculus supplies upper body half

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Describe the organisation of the grey matter of the spinal cord

Cell bodies are organised into cell columns

- These columns are organised into Laminae

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List the Key function of the parts of the Brainstem

Midbrain;

Eye movement
Reflex responses to sound and vision

Pons;

Feeding
Sleep

Medulla;

Cardiovascular and respiratory homeostasis
Contains a major motor pathway (medullary pyramids)

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What are the Cerebral peduncles of the Midbrain?

Areas of white matter that contain descending corticospinal fibres from the Ipsilateral hemisphere

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What is the Substantia Nigra of the midbrain?

Area of grey matter containing dopaminergic neurons that project to the Striatum (Nigrostriatal fibres)

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What is the Red Nucleus of the midbrain?

An area of grey matter that gives rise to axons that travel to the spinal cord in the Vestigial Rubrospinal tract

(Has some motor functions)

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What is the Oculomotor nucleus of the midbrain?

An area of grey matter containing
lower motor neurone cell bodies that
project though the oculomotor nerve
to all except 2 of the extra ocular muscles

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What is Periaqueductal grey matter of the midbrain?

An area surrounding the cerebral aqueduct that has roles in;

Pain transmission
Micturition

What 2 ventricles are connected by the Cerebral Aqueduct?

3rd ventricle and 4th ventricle

List 2 structures that pass through the midbrain to get to the thalamus

Medial lemniscus (Connects Gracile/ Cuneate nuclei to thalamus)
Spinothalamic tract (Connects spinal dorsal horn to thalamus)

What do the Superior and Inferior Colliculi of the midbrain do?

These are regions of grey matter

Superior: Regulates reflex responses to visual stimuli

Inferior: Regulates reflex responses to auditory stimuli

List 4 key features of the midbrain

CN V exits from lateral aspect
Corticospinal fibres travel ventral
Beneath 4th ventricle so can get compressed if this expands
Contains reticular formation regions important for sleep

Describe the Medullary Pyramids (white matter)

Ventral swellings containing corticospinal fibres from the Ipsilateral hemisphere.

(These fibres decussate in the caudal medulla at the decussation of the pyramids)

A Gyrus is a raised fold of cerebral cortex. What sits anterior and posterior to the central gyrus?

Anterior: Precentral gyrus (Contains primary motor cortex) Posterior: Postcentral gyrus (Contains primary sensory cortex)

Which lobes are separated by the Sylvian/ Lateral fissure?

Temporal lobe separated from frontal and parietal lobes

Is the Parieto-Occipital sulcus visible on a Superfical view?

The Primary Visual Cortex surrounds the Calcarine Sulcus of the Occipital lobe. Compare the functions of the visual cortex above and below the Calcarine Sulcus

Above: Supplies the contralateral inferior visual field Below: Supplies the contralateral superior visual field

Describe the Uncus

- Most medial part of temporal lobe - Contains the olfactory cortex - Can herniate below Tentorium Cerebelli

What is the Parahippocampal Gyrus?

Part of the medial temporal lobe that provides input to the underlying hippocampus (Key region for memory encoding)

Describe the Thalamus

- Important for conscious sensation | - Acts as a sensory relay station projecting to the Primary sensory cortex

Describe the role of the Cingulate Gyrus

- Important role in emotion and memory | - Participates in the Papez Circuit

Describe the Fornix

- A major output pathway from the Hippocampus | - Part of the Papez Ciruit

Describe the Tectum

- Posterior part of midbrain - Contains the Superior and Inferior Coliculi (so involved in regulation of the reflex responses to auditory and visual stimuli)

Describe the Cerebeller Tonsils

Part of the cerebellum that can herniate through the Foramen Magnum and compress medulla (Therefore raised ICP can lead to death through cardiorespiratory compromise)

Brain ventricles are hollow cavities containing CSF What do each of them contain?

Choroid plexus, which is highly vascular and makes 600-700ml of CSF a day

What are 2 functions of CSF?

Mechanical: Shock absorbs the brain and renders it weightless Metabolic: Contains glucose and maybe hormones

Describe briefly the circulation of CSF

- Circulates through ventricular system and subarachnoid space - Reabsorbed at Arachnoid granulations (Cauliflower-resembling projections into Superior Sagittal sinus) by entering Venous Blood

Which ventricles are the largest and make the most CSF? What are the 3 parts of these ventricles

Lateral ventricles (Large C shapes) - Frontal horn (in frontal lobe) - Temporal horn (in temporal lobe) - Occipital horn (in occipital lobe)

Which brain ventricle sits below the Cerebellum

The 4th Ventricle

Describe the flow of CSF from the Lateral ventricles

Flows through Interventricular foramen into the 3rd Ventricle (3rd ventricle is flattened in midline by the thalami on each side)

Describe the flow of CSF from the 3rd ventricle

Drains from 3rd to 4th Ventricle by the Cerebral Aqueduct of the Midbrain

Describe CSF flow once it enters the subarachnoid space

Bathes the superficial surfaces of the brain and spinal cord, before being reabsorbed in the arachnoid granulations (Goes to RA then kidney to be excreted)

How would the Lateral, 3rd and 4th ventricles be affected in blockage of the cerebral aqueduct

Lateral- Dilated 3rd- Dilated 4th- Normal

Describe CSF flow as it exits the 4th Ventricle

Drains into Subarachnoid space via 2 Lateral and 1 Median Apertures Negligible drainage via central canal of the spinal cord (Lateral- Foramen of Luschka, Median- Foramen of Magendie)