Topography of the brain Flashcards
Which structures comprise the brainstem?
Midbrain, pons and medulla.
Where is the diencephalon in relation to the brainstem?
Diencephalon lies above the midbrain and is not part of the brainstem.
Which CN’s emerge from the brainstem?
All except 1 and 2. CNIV comes from the posterior aspect, CNIII and 5-12 come from the anterior aspect. These innervate the head and neck.
What are the main functions of the brainstem?
- Pathway for fibre tracts running between higher and lower centres
- Brainstem centres produce the rigidly programmed automated behaviours that are essential for survival
Which cavity is posterior to the medulla oblongata and pons?
The cavity of the 4th ventricle. In life this is closed off as the cerebellum sits behind it.
Which structure continues from the lower part of the medulla?
Medulla continues as the spinal cord after the foramen magnum.
Name the structure that connects the medulla to the cerebellum.
Inferior cerebellar peduncle.
Which CN’s emerge from the surface of the medulla?
CNIX, CNX, CNXI and CNXII.
What are the pyramidal tracts?
These are ventral (motor) tracts that decussate (cross over) at the level of the medulla.
Which nuclei are present in the grey matter of the medulla?
- CN nuclei
- Olivary nuclei
- Nuclei of the reticular formation
- Sensory nuclei (gracile and cuneate which are for fine touch and proprioception)
Which CN’s emerge from the surface of the pons?
CNV, CNVI, CNVII and CNVIII.
Which structure connects the pons to the cerebellum?
Middle cerebellar peduncle.
What type of fibres run in the medial lemniscus?
Sensory fibres - cuneate and gracile
What are the pontine nuclei?
Nuclei in the pons involved in motor activity. Important in learning motor skills.
Which embryological structure does the midbrain develop from?
Mesencephalon
What forms the central cavity of the midbrain?
Cerebral aqueduct
Which peduncles emerge from the midbrain?
Superior cerebellar peduncle posteriorly and cerebral peduncle anteriorly.
Which CN’s emerge from the midbrain?
CNIII and CNIV (only one to emerge posteriorly).
What are the corpora quadrigemina?
The 2 superior and 2 inferior colliculi located on the dorsal aspect of the midbrain. These are reflex centres involved in vision and hearing.
Which subcortical centres for the extrapyramidal motor system are located in the midbrain?
- Red nucleus
- Substantia nigra
What does the inferior olivary nucleus control?
Motor control
What is the function of the nuclei in the reticular formation?
Maintaining behavioural arousal and consciousness.
Where does motor and sensory information cross?
- Motor: in the medulla at the pyramids
- Sensory: lower down in the spinal cord
Which structure separates the R and L hemispheres of the cerebellum?
Vermis
What are the names of the lobes in each hemisphere of the cerebellum?
Anterior, posterior and flocculonodular lobes.
What are the grooves of the cerebellum called?
Sulci are the depressions and folia are the elevations.
Describe the white matter of the cerebeuulum.
- Arbor vitae: tree-like inside of the cerebellum
- Cerebellar peduncles: connect cerebellum to the rest off the brain
What are the functions of the cerebellum?
1) Posture maintenance
2) Fine tuning motor activity
Cerebellum takes information from: pyramidal tracts (motor), ipsilateral proprioceptors and vestibular nuclei (balance and posture) –> calculates the best ways to coordinate these inputs and sends this information to the cerebrum via the superior cerebellar peduncle.
In the cerebellum, R half controls R side and L half controls L side (opposite to cerebrum).
What is ataxia?
A disorder affecting co-ordination, balance and speech - usually caused by damage to the cerebellum.
What can be done to test for ataxia?
1) Finger-nose test
2) Heel-knee test
3) Walking in a straight line
Which substance affects the cerebellum?
Alcohol
Which structures form the diencephalon?
- Thalamus (80%)
- Hypothalamus and pituitary stalk
- Epithalamus (pineal gland)
–> All are mainly grey matter
Where is the diencephalon?
Deep within the cerebral hemispheres, around the 3rd ventricle.
What is the function of the thalamus?
A sensory relay station containing anterior, medial and lateral (LGB for visual pathway is here) groups of nuclei.
Name the structure that separates the thalamus from the hypothalamus?
Hypothalamic sulcus.
What is the function of the hypothalamus?
Main visceral control centre and essential for overall homeostasis.
Which arteries supply the brain?
- 2 x ICA enter via the foramen lacerum
- 2 x vertebral arteries enter via the foramen magnum
These enter the circle of Willis which supplies the cerebrum.
Which arteries supply the brainstem and cerebellum?
Vertebral arteries join together to form the basilar artery. Vertebro-basillar system supplies the brainstem and cerebellum.
Which level does the basilar artery divide?
The basilar artery ends at the midbrain where it splits into the 2 x PCA’s.
What does the CoW protect against?
Protective feature against vaso-occlusion of large arteries, but the branches supplying the cerebral hemispheres are effectively end arteries.
Which part of the cerebrum does the ACA supply?
Medial aspect of the cerebral hemispheres, excluding the occipital lobe.
Which part of the cerebrum does the MCA supply?
Lateral aspect of the cerebral hemispheres.
Which part of the cerebrum does the PCA supply?
Inferior aspect of the cerebral hemispheres and occipital lobe.
Where do the venous sinuses of the brain lie?
Between 2 layers of dura matter.
Which veins do the dural venous sinuses ultimately drain to?
IJV’s
