Lecture 5: Forebrain and Ventricles Flashcards
What is the forebrain made up of, what is its embryological origin?
Made up of the diencephalon and the cerebral hemispheres
All structures rostral to the midbrain and derived from the prosencephalon
What is the forebrain responsible for?
Higher level processing of information
Perception, analysis, interpretation, integration, storage, planning
What separates the thalamus from the hypothalamus?
The hypothalamic sulcus
Where does the 3rd ventricle lie?
Between the 2 thalami
Embrologically, the thalamus and hypothalamus appears as 2 swellings of the lateral aspect of the central canal, which lies dorsally and which ventrally?
Thalamus - dorsally
Hypothalamus - ventrally
What is the thalamus?
Large, egg shaped collection of nuclei
What do the nuclei of the thalamus do?
Send fibres to the cerebral cortex - either to a sharply defined area or more diffusely
Those connecting to defined cortical area (eg. to visual cortex) are called relay nuclei, may be sensory or motor
What is the hypothalamus made up of?
Several nuclei
What is the role of the hypothalamus?
In control of the ANS and has neuroendocrine function
Other than the thalamus and the hypothalamus, what other structures make up the diencephalon?
The subthalamus and the epithalamus
Where is the subthalamus found and what is its function?
Found underneath the thalamus
Involved in motor control
What can damage to the subthalamus result in?
Lots of random motor contractions - involuntary movements
What is the epithalamus and what is its role?
Includes the pineal gland, can be seen posterior to the hypothalamic sulcus
This is in control of circadian rhythm and secretes melatonin
What are the 3 parts of the corpus callosum and where do they lie?
1) Splenium - most posterior part of the corpus callosum
2) Body - middle part of the corpus callosum
3) Genu - most anterior part of the corpus callosum
What is the septum pellucidum?
Lies inferior to the corpus callosum, its a thin membrane which covers the medial wall of the third ventricle
What is the fornix?
Bundle of white matter which lies inferior to the inferior border of the septum pellucidum
What is the function of the fornix?
Relay information between the temporal lobe and the hypothalamus, temporal lobe is involved in the storage of memories, the fornix conveys the information which leads to autonomic controlled processes related to previous experiences - eg. sweating at an interview
What is the anterior commissure?
Lies anterior to the fornix, its another bundle of white matter
What is the function of the anterior commissure?
Helps to connect the 2 cerebral hemispheres
The fornix, corpus callosum and septum pellucidum are all part of what?
The cerebral hemispheres
Where does the optic nerve lie in relation to the hypothalamus?
Projects from the hypothalamus at the most inferior anterior aspect
Where do the mamillary bodies lies in relation to the hypothalamus?
At the most inferior posterior aspect
Where does the pituitary stalk (infundibulum) lie in relation to the hypothalamus?
Projects from the inferior border, in between the optic nerve and the mamillary bodies
What is the interthalamic adhesion?
The point of contact of the 2 thalami, bisecting through the 3rd ventricle
What are the 2 swellings of the telencephalon either side of the midline connected by?
The lamina terminalis
What does the embryological lamina terminalis go on to form?
The anterior commissure and the corpus callosum
What are the 3 horns of the lateral ventricles and which lobe does each occupy?
Anterior horn - occupies the frontal lobe
Posterior horn - occupies occipital lobe
Inferior horn - occupies the temporal lobe
How thick is the cerebral cortex?
Varies in thickness, between 2-4mm thick
How much of the total surface area of the cerebral cortex is hidden by the sulci?
Over half
What is the difference between a short association fibre, a long association fibre and commisural fibre?
Short association fibres - connect 2 adjacent gyri in the same hemisphere
Long association fibres - connect 2 non-adjacent gyri in the same hemisphere
Commissural fibres - connect 2 gyri in different hemispheres
Corpus callosum and anterior commissure contain what kind of fibres?
Commissural fibres
What are the 3 types of fibres found within the brain?
1) Association fibres
2) Commissural fibres
3) Projection fibres
What is the function of projection fibres?
To carry information to or from the hemispheres
The internal capsule contains what kind of fibres?
Projection fibres
What does the deep grey matter of the cerebral hemispheres form?
Forms a group of nuclei called the basal ganglia
Name 2 nuclei found within the basal ganglia?
1) Caudate nucleus
2) Lentiform nucleus
What 2 parts make up the lentiform nucleus, which lies deeper?
Globus pallidus
Putamen
globus pallidus is deeper
In a horizontal section of the brain which 2 parts of the caudate nucleus can be seen, what shape is it?
Its C shaped so in horizontal section the head and tail of the caudate nucleus can be seen seperately
What is the basal ganglia surrounded by?
White matter
What is the function of the basal ganglia?
Involved in movement
What is the ventricular system?
Series of interconnecting chambers all derived from the lumen of the neural tube
In the spinal cord this is the central canal
In the brain an elaborate system of ventricles is formed
Where are the lateral ventricles found?
Within the cerebral hemispheres
Where is the 4th ventricle found?
Between the cerebellum, pons and medulla
How are the 2 lateral ventricles and the 3rd ventricle connected?
By the interventricular foramen
How are the 3rd ventricle and 4th ventricle connected?
By the cerebral aquaduct
How does the CSF produced in the ventricular system pass into the subarachnoid space?
Via the 2 lateral apertures and the 1 median aperture of the 4th ventricle
What can be found passing through the middle of the 3rd ventricle, does this have a function?
The interthalamic adhesion
Has no function - no fibres pass through it
As well as physical protection what else does CSF provide for the brain?
Chemical stability
What is CSF produced by?
Specialised areas lining the ventricles called the choroid plexus
What is the total volume of CSF in an adult, how much is produced per day?
Total volume in adult ~150ml
500ml is produced per day
Give the 4 functions of CSF?
1) Brain and spinal cord float to reduce traction
2) Cushioning effect to dampen trauma
3) Removes metabolites from the CSF
4) Provides stable environment
How basically does the choroid plexus produce CSF?
Made of epitheloid cells
Receives blood supply from the choroid plexus
Passes through the epithelium into the ventricles
What happens if CSF circulation is blocked?
CSF accumulates upstream of the blockage, CSF then accumulates in the brain and hydrocephalus results
In which ventricles is the majority of CSF produced?
In the lateral ventricles
How is CSF recycled into the venous system?
Arachnoid granulations pass from the subarachnoid space into dural sinuses
CSF recycled into the dural sinuses, predominantly the superior sagittal sinus
