A01 Topography of the Major Features of the Brain and Spinal Cord Flashcards
Define sulcus.
The furrows of the folds on the surface of the brain.
Define gyrus.
The outward projections of the folds on the surface of the brain.
Define fissure.
A long furrow that divides the brain into lobes.
What separates the temporal lobe from the frontal and parietal lobes?
The lateral / Sylvian fissure.
What separates the frontal lobe from the parietal lobe?
The central sulcus.
What does grey matter consist of?
Collections of nerve cell bodies.
What does white matter consist of?
Myelinated axons.
Which cells are responsible for the myelination of axons in the CNS?
Oligodendrocytes.
Briefly describe the organisation of grey and white matter in the spinal cord.
The grey matter lies centrally and is surrounded by white matter.
Define diencephalon.
The caudal part of the forebrain containing the:
1 - Epithalamus.
2 - Thalamus.
3 - Hypothalamus.
4 - Subthalamus.
5 - Third ventricle.
Describe the location of the corpus callosum.
- It connects the two hemispheres of the brain.
- It lies deep to the cingulate gyrus.
- It lies superficial to the fornix, to which it is connected anteriorly by the septum pellucidum.
What is the fornix?
Briefly describe it’s anatomical location.
- A C-shaped bundle of nerve fibers in the brain that acts as the major output tract of the hippocampus.
- it extends from the hippocampus to the hypothalamus.
Describe the location of the thalamus.
- It is situated at the core of the diencephalon.
- It forms the lateral walls of the third ventricle.
Describe the gross structure of the thalamus.
- The thalamus consists of two symmetrical structures divided into anterior, medial and lateral segments.
- The segments of the thalami are partitioned by a Y-shaped structure known as the internal medullary lamina.
- The thalami are elongated along the sagittal plane giving them an ovoid appearance.
- They are narrowest at the anterior end and widest at the posterior end.
Describe the location of the cerebellum.
- It is located at the base of the brain.
- It is posterior to the pons.
List the components of the brainstem.
Describe the location of each of the components.
1 - Medulla oblongata (lower half continuous with the spinal cord).
2 - Pons (between the midbrain and the medulla oblongata).
3 - Midbrain / mesencephalon (between the forebrain and the hindbrain).
List the components of the midbrain.
1 - Tectum.
2 - Tegmentum.
3 - Peduncles.
List the components of the ventricular system of the brain.
Two lateral ventricles, a third ventricle and a fourth ventricle.
Where is cerebrospinal fluid produced?
In the ventricular system of the brain.
What is the insula?
The portion of the cerebral cortex folded deep within the lateral sulcus.
What is the basal ganglia?
A group of subcortical nuclei situated at the base of the forebrain and roof of the midbrain.
What is the lentiform nucleus?
A nucleus comprised of the putamen and globus pallidus.
What is the striatum?
A nucleus of the basal ganglia comprised of the caudate nucleus (its own structure) and the lentiform nucleus.
Why does grey matter require 2.5x greater blood supply than white matter?
Because white matter is able to undergo saltatory conduction and is therefore less metabolically active.
Describe the regions of the brain supplied by the anterior, middle and posterior cerebral arteries.
- The anterior cerebral arteries supply the anteromedial portion of the cerebrum.
- The middle cerebral arteries supply the majority of the lateral part of the cerebrum.
- The posterior cerebral arteries supply both the medial and lateral parts of the posterior cerebrum.
List the components of the cerebrum.
1 - Cerebral cortex.
2 - Hippocampus.
3 - Basal ganglia.
4 - Olfactory bulb.
Where in the spinal cord is the white matter the greatest?
Why?
- In the cervical levels.
- Because ascending and descending fibres from and to all levels must pass through the cervical cord.
Where is the spinal cord largest?
Why?
- At the cervical and lumbar regions.
- Because they contain the neural components necessary to operate the limbs.
Describe the venous drainage of the spinal cord.
- Venous drainage is via three anterior and three posterior valveless spinal veins.
- The veins form an anastomosing network of plexuses along the surface of the spinal cord.
- The spinal veins drain into the radicular veins.
- The radicular veins drain into the epidural venous plexuses.
- The epidural venous plexuses drain into the external vertebral plexuses.
- The external vertebral plexuses drain into the vertebral, intercostal and lumbar veins.
Describe the arterial supply of the spinal cord.
- Arterial supply is via the longitudinally oriented spinal arteries (one anterior and two posterior) and the radicular arteries (one anterior and one posterior).
- Spinal arteries are branches of the vertebral arteries, which are branches of the subclavian arteries.
- Radicular arteries are anastomoses of the segmental spinal arteries of the abdominal aorta.
Which two pairs of vessels supply the brain with arterial blood?
1 - The vertebral arteries.
2 - The internal carotid arteries.
Describe the course of the vessels that supply the brain with arterial blood.
- The vertebral arteries pass through the foramen magnum to join as the basilar artery on the anterior aspect of the pons.
- The basilar artery divides into the posterior cerebral arteries which give many branches including the posterior communicating artery.
- The internal carotid arteries arise at the bifurcation of the common carotid artery.
- Within the subarachnoid space, the internal carotid artery bifurcates to form the anterior and middle cerebral arteries.
- The cerebral arteries, together with the communicating arteries, contribute to the circle of Willis.
List the components of the circle of Willis.
1 - Anterior cerebral arteries.
2 - Posterior cerebral artery.
3 - Anterior communicating artery.
4 - Posterior communicating artery.
5 - Internal carotid arteries.
On which surface of the brain is the circle of Willis located?
Describe the course of the circle of Willis.
- It is located on the inferior surface of the brain.
- It passes around the optic chiasm and optic tract.
- It then crosses the basis pedunculi / crus cerebri of the midbrain.
- The two halves of the circle join at the pons-midbrain junction.
