Anatomy
Central Nervous System
Which of the following brainstem nuclei is NOT located in the pons:
Answer:
The pons houses nuclei of the trigeminal nerve, the abducens nerve, the facial nerve and the vestibulocochlear nerve. The trochlear nucleus (together with the oculomotor nucleus) lies in the midbrain.Brainstem
Anatomy / Central Nervous System
Last Updated: 11th April 2019
The brainstem comprises the midbrain, the pons and the medulla. It extends from the tentorial aperture to the level of C1. The medulla passes out of the cranial cavity via the foramen magnum and becomes the spinal cord as C1 roots emerge. The cells of the brainstem are predominantly clumped into nuclei.
Brainstem. (Image by OpenStax [CC BY 4.0 , via Wikimedia Commons)
Midbrain
The midbrain lies predominantly within the posterior cranial fossa. The aperture in the tentorium cerebelli lies on its dorsal surface.
The midbrain receives its blood supply from the posterior cerebral and superior cerebellar arteries (ex-basilar).
Dopaminergic cells sit within the midbrain within the substantia nigra; loss of dopaminergic neurons is the basis of Parkinson’s disease.
Pons
The pons receives its blood supply from pontine branches of the basilar artery. The pons houses nuclei of the trigeminal nerve, the abducens nerve, the facial nerve and the vestibulocochlear nerve. This knowledge allows prediction of the clinical effects of a pontine haemorrhage:
- Abducens nucleus (lateral rectus paralysis)
- Vestibular nuclei (nystagmus, nausea, vomiting, vertigo)
- Cochlear nuclei (central nerve deafness)
- Trigeminal nuclei (paralysis of muscles of mastication, jaw deviation, loss of facial sensation)
- Facial nucleus (facial nerve paralysis and loss of taste sensation from anterior tongue)
Brainstem Nuclei. (Image by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
Medulla
The medulla oblongata is the upward continuation of the spinal cord. It receives its blood supply from the posterior inferior cerebellar arteries and branches of the vertebral and basilar arteries.
Formatio Reticularis of the Medulla Oblongata: 1. Anterior median fissure. 2. Fourth ventricle. 3. Formatio reticularis, with 3’, its internal part (reticularis alba), and 3’’, its external part (reticularis grisea). 4. Raphé. 5. Pyramid. 6. Lemniscus. 7. Inferior olivary nucleus with the two accessory olivary nuclei. 8. Hypoglossal nerve, with 8’, its nucleus of origin. 9. Vagus nerve, with 9’, its nucleus of termination. 10. Lateral dorsal acoustic nucleus. 11. Nucleus ambiguus (nucleus of origin of motor fibers of glossopharyngeal, vagus, and cerebral portion of spinal accessory). 12. Gracile nucleus. 13. Cuneate nucleus. 14. Head of posterior column, with 14’, the lower sensory root of trigeminal nerve. 15. Fasciculus solitarius. 16. Anterior external arcuate fibers, with 16’, the nucleus arcuatus. 17. Nucleus lateralis 18. Nucleus of fasciculus teres. 19. Ligula.
Lateral medullary syndrome results from occlusion of the intracranial portion of the vertebral artery (most commonly) or of the posterior inferior cerebellar artery (PICA). The resultant structures affected are the:
- Vestibular nuclei (nystagmus, nausea, vomiting, vertigo)
- Inferior cerebellar peduncle (cerebellar signs)
- Nucleus ambiguus of glossopharyngeal and vagus nerve (ipsilateral laryngeal, pharyngeal and palatal paralysis with dysarthria, dysphagia, dysphonia)
- Spinothalamic tracts (contralateral loss of pain and temperature from trunk and limbs)
- Spinal trigeminal nucleus and tract (ipsilateral loss of pain and temperature from face)
- Descending sympathetic tract (ipsilateral Horner's syndrome)
Medial medullary syndrome results from occlusion of small perforating branches from the vertebral or proximal basilar artery such as the anterior spinal artery. The resultant structures affected are the:
- Corticospinal tract (contralateral hemiparesis of trunk and extremities)
- Medial lemniscus (contralateral loss of proprioception, two-point discrimination and vibration of trunk and limbs)
- Hypoglossal nerve roots (ipsilateral flaccid paralysis of tongue)
Report A Problem
Is there something wrong with this question? Let us know and we’ll fix it as soon as possible.
Loading Form...
- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
