Neuroanatomy | Master Of Medicine

Category Archives: Neuroanatomy

Ventricles in the brain

What is a ventricle in the brain?

The ventricles of the brain are a communicating network of cavities filled with cerebrospinal fluid (CSF) and located within the brain parenchyma.

Which are the ventricles?

The ventricular system is composed of 2 lateral ventricles, the third ventricle, the cerebral aqueduct, and the fourth ventricle . The choroid plexuses located in the ventricles produce CSF, which fills the ventricles and subarachnoid space, following a cycle of constant production and reabsorption

 Where is the location of the ventricles?

  • 2 Lateral Ventricle- Lies in the cerebral cortex
  • 3rd ventricle-Lies between the two thalami
  • 4th Ventricle-Lies on the brain stem between medulla and cerebellum

Vertebral artery segments and branches

  1. Vertebral artery arises from the first part of Subclavian artery.
  2. Vertebral artery is the first and the largest part of Subclavian artery.

Divisions of vertebral artery

V1 segment - From origin to transverse process of C6 vertebra

V2 segment- Runs through foramen transversaria of upper six cervical vertebrae.

V3 Segment – Lies in the suboccipital triangle

V4 segment

  1. Extends from posterior atlanto occipital membrane to lower border of Pons.
  2. Traverses foramen magnum
  3. Pierces duramater, arachnoid mater and enters subarachnoid space.

Branches

Cervical branches- Spinal and muscular branches.

Intracranial branches

  1. PICA
  2. Medullary artery
  3. Anterior spinal artery
  4. Rarely Posterior spinal artery(Usually branch of PICA)

 

Basal ganglia and their classification

This diagram shows the pathways between the nu...

Image via Wikipedia

The basal ganglia is an important part of the brain which program impulses from cerebral cortex and initiates motor activities through cerebellum and corticospinal tracts. Parkinsonism is a disorder in which there is decrease in the dopaminergic neurons in the striatum which results in motor impairment.

The components of the basal ganglia are:

Corpus Striatum- Caudate+Lentiform nucleus.

Lentiform nucleus- Putamen+Globus pallidus.

Striatum - Caudate nucleus+Putamen.

 

 

Cranial Nerves and associated ganglia

Four cranial nerves ,CN III, VII, IX, Xcarry parasympathetic fibres as they emerge from brain stem.

The Cranial nerves and their associated ganglia are mentioned below.

  1. Oculomotor – Ciliary ganglion.
  2. Facial – Pterygopalatine and submandibular ganglion.
  3. Glossopharyngeal – Otic ganglion
  4. Vagus – Visceral ganglions

Mnemonic for 12 cranial nerves and their types.

We know that there are 12 pairs of cranial nerves which originate from the brain and brainstem. Remembering the names of these cranial nerves is easily mastered but it is difficult to remember their type ie whether they are Sensory nerves, motor nerves or mixed nerves.

  1. Olfactory
  2. Optic
  3. Oculomotor
  4. Trochlear
  5. Trigeminal
  6. Abducens
  7. Facial
  8. Auditory/Vestibulocochlear
  9. Glossopharyngeal
  10. Vagus
  11. Spinal Accessory
  12. Hypoglossal

A simple mnemonic will help you to remember the types of cranial nerves.

Mnemonic: Some Say More Money But My Brother Says Big Books Matter More

S Represents sensory nerves, M represents Motor and B -represents Both/Mixed nerves.

So the Cranial nerves and their types become.

  1. Olfactory – Some -Sensory
  2. Optic- Say- Sensory
  3. Oculomotor- More- Motor
  4. Trochlear- Money- Motor
  5. Trigeminal- But – Mixed
  6. Abducens- My- Motor
  7. Facial- Brother- Mixed
  8. Auditory/Vestibulocochlear- Says- Sensory
  9. Glossopharyngeal- Big- Mixed
  10. Vagus- Books- Mixed
  11. Spinal Accessory- Matter- Motor
  12. Hypoglossal- More- Motor

Learn the exit routes of cranial nerves with the picture given below.

If this post has helped you memorize this topic, and if you have a tip to share, do post a comment below.

Brodman areas of brain and their lesions

Frontal Lobe

Primary motor cortex(Ms1)- Area 4, located in precentral gyrus( front of central sulcus)

Premotor area- Area 6 and 8

Prefrontal cortex-9,10,11

Frontal eye field- Common area supplied by premotor area and prefrontal cortex.

Supplementary motor area(MsII)- On medial surface.

Lesions of frontal lobe

MsI- Contralateral hemiplegia

Premotor area-Difficulty to perform skilled movements

MsII-B/L flexor hypotonia

Prefrontal cortex-Also called silent area of brain.Concerned with Intelligence,memory,absract thinking,behaviour,pleasure and displeasure.Involved in depressed fracture of frontal bone.

Frontal eye field-Deviation of eyes to the side of lesion and inability to move eyes to the opposite side(Loss of conjugate eye movements)

Parietal lobe

Primary sensory area(SmI)- Areas 3,1,2

Sensory association area-5,7

Sensory speech area-39,40

Secondary sensorya Area(SmII)-Upperlip of posterior ramus of parietal lobe.

Lesions of parietal lobe

SmI-Loss of appreciation of all sensations from opposite half of body.

SmII-Ablation may relieve intractable pain.

Sensory association area-Tactile agnosia/astereognosis

Wernicke’s area-22,39,40-Sensory aphasia/receptive aphasia.Inability to understand written word(Word blind)

Temporal lobe

Primary auditory area-41,42

Secondary auditory area(Auditary association area)-22

Lesions

Dejavu-due to temporal lobe lesion

b/l lesion-total deafness.

secondary association area-Inability to intepret meanings of words heard(Word deafness)

Psychic Cortex-Anterior part of temporal lobe.In lesions visual and auditory hallucinations develop.Dejavu.Removal of this part leads to deletion of past experiences from memory.

Occipital lobe

Primary visual area-Striate area-area 17

Secondary visual areas/psychovisual areas

  • Peristriate area-area 18
  • Parastriate area-area 19

Lesions

Primary visual area-Loss of vision in opposite visual field(Crossed homonemous hemianopia)

Secondary visual area-Inabiliy to recognize objects in opposite visual field.

Other areas

Area -44 -Area for taste

Area 28-Olfactory area

Lemniscus

lemniscus : is a bundle of secondary sensory fibers within the brain stem which terminates in specific relay nuclei of the diencephalon

There are four Lemnisci

Medial lemniscus- Fine touch and pressure. Tactile localization and 2 point discrimination.

Lateral lemnicus-Fibres from trapezoid body. Auditory pathway.

Spinal lemniscus-Fibres from lateral spinothalamic tract. Pain and temperature.

Trigeminal lemniscus- General sensations from trigeminal area of face.

Anterior spinothalamic tract carrying crude touch and pressure joins medial lemniscus.

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