Forebrain & Ventricles Flashcards
Label the coronal sections of the brain
Label the sagittal sections through the brain
Label the horizontal sections through the brain
What is the forebrain (cerebrum) derived from?
What are the 2 parts of the forebrain and what are their functions?
Derived from the prosencephalon
Consists of:
- telencephalon (outer brain / cerebral hemisphere)
- diencephalon (inner brain)
Together they are responsible for “higher level processing” - this involves linking and memorising information
Label the components of the brain
What is significant about the embryological growth of the telencephalon?
What does it go on to form?
Growth of the telencephalon is rapid and overshadows other parts of the nervous system
Two swellings either side of the midline are connected via the lamina terminalis
the telencephalon goes on to become the cerebral hemispheres on each side
the lamina terminal is goes on to become the corpus callosum and anterior commissure
As a result of development, what shape does the brain develop?
How does this affect internal structures?
The telencephalon folds over the developing diencephalon, causing the brain to develop a C - shape
Many of the internal structures within each hemisphere are also C-shaped
What are the following components of the ventricular system and where do they develop from?
- Lateral ventricle - between hemispheres
- third ventricle - diencephalon
- cerebral aqueduct - midbrain
- fourth ventricle - pons, medulla and cerebellum
- central canal - medulla and spinal cord
Label the components of the ventricular system
Which lobes are the horns located in?
The anterior horn of the LV is located in the frontal lobe
The inferior horn of the LV is located in the temporal lobe
The posterior horn of the LV is located in the occipital lobe
What is the role of the interventricular foramina (of Monroe) and the cerebral aqueduct (Caq)?
The interventricular foramina of Monroe connects the lateral ventricles with the 3rd ventricle
The cerebral aqueduct connects the 3rd ventricle to the 4th ventricle
What lobes are occupied by the body of the lateral ventricle?
It runs from the frontal to the parietal lobes
What happens to CSF when it reaches the 4th ventricle?
CSF leaves the 4th ventricle and floats in the subarachnoid space
It can leave via:
- Lateral apertures (foramina of Luschka)
- Median aperture (foramen of Magendie)
- Central canal of spinal cord
What is the course of the lateral ventricle like?
It follows a C-shaped course through all the lobes of a cerebral hemisphere
Label the components of the ventricular system
Where are the 3rd and 4th ventricles located?
The third ventricle is located between the two thalami of the diencephalon
The fourth ventricle is located between the pons and cerebellum
Label the components of the ventricular system
Which parts of the ventricles are the arrows pointing up?
Where is the ventricular system locate?
What is its role?
Throughout the CNS there are a 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, this is due to the enormous growth and distortion forming an elaborate system of ventricles
What do ventricles develop as?
What do they contain and produce?
They develop as dilations from the central canal of the embryological neural tube
They contain choroid plexus which produces CSF
What are the 4 ventricles and where are they located?
- 2 lateral ventricles - one within each cerebral hemisphere
- 3rd ventricle between the thalami
- 4th ventricle between the pons (anteriorly) and cerebellum (posteriorly)
they are all interconnected
How does CSF leave the ventricular system?
A series of apertures allow CSF to escape ventricular system into subarachnoid space
there is the median aperture (foramen of Magendie)
and
the lateral apertures (foramina of Luschka)
Complete the schematic summary of the ventricular system
What is CSF and what does it contain?
It is blood derived clear, colourless fluid
it contains glucose and inorganic salts, little protein and few cells
What are the functions of CSF?
Where is it produced?
It is produced in the ventricles by specialised areas of the ventricular lining - choroid plexus
it fills the subarachnoid space and ventricular system of the brain
it is involved in buoyancy, support, shock absorption and the transport of waste and nutrients
Label the pathway of CSF production and circulation
What is the passage of CSF like through the ventricular system?
Produced in lateral ventricles and passes through the foramina of Monroe into the third ventricle
the CSF then passes through the cerebral aqueduct into the fourth ventricle
it then passes through the foramen of Magendie, foramina of Luschka or central canal into the subarachnoid space
How is CSF drained from the ventricular system into the venous system?
Through arachnoid granulations (villi)
it is drained into the venous dural sinuses (mainly the superior sagittal sinus)
What are cisterns?
Label the cisterns present in the brain?
Cisterns are expansions of the subarachnoid space
- prepontine cistern
- cisterna magna
- quadrageminal cistern
- interpeduncular cistern
What is the favoured site for sampling of CSF?
Why?
Lumbar cistern
a needle can be inserted here with very little risk of damaging the CNS
the spinal cord ends above the lumbar cistern, so there is no risk of piercing the spinal cord
there will be lots of CSF present in the lumbar cistern as it is an expansion of the subarachnoid space
Label the diagram showing CSF being recycled into the venous system via the dural sinuses
What is hydrocephalus?
Why can it not occur in adults?
If CSF circulation is blocked, CSF accumulates upstream of the blockage
this leads to swelling of the head, visible in babies as the bones of the skulll haven’t fused together yet
in an adult, the brain would be compressed
this occurs due to problems with production, circulation or reabsorption of CSF
What are the 4 main functions of the CSF?
Buoyancy:
- brain and spinal cord float to reduce traction
Cushioning:
- this dampens trauma
Transport of substances:
- nutrients, dissolved gasses and removal of metabolites
Providing a stable environment
What are the 4 components of the diencephalon (inner brain)?
It sits on top of the brainstem and connects it to the cerebral hemispheres
- Thalamus
- Hypothalamus
- Subthalamus
- Epithalamus
What are the functions of the thalamus and hypothalamus?
Thalamus:
- made up of several nuclei
- it is a relay station between parts of the CNS
hypothalamus:
- made up of several nuclei
- it has autonomic and neuroendocrine functions
What are the functions of the subthalamus and epithalamus?
Subthalamus:
- involved in motor control
- has a basal ganglia component that produces active movements
Epithalamus:
- includes the pineal gland that secretes melatonin
- this regulates the sleep wake cycle
What are the components of the diencephalon?
How does the diencephalon develop embryologically?
It appears as a swelling of the lateral aspect of the central canal
the lumen of the central canal is diminished as two pairs of swellings appear - the thalamus dorsally and the hypothalamus ventrally
What is the location of the thalamus like?
The thalami are large bilateral egg-shaped masses of grey matter (collection of nuclei)
they sit on top of the brainstem
the IIIrd ventricle is wedged between the two thalami
What are the functions of the thalami?
- Act as the “receptionist” of the brain as they receive information, process it and pass it on
- relay nuclei send fibres to the cerebral cortex, either to a sharply defined area or more diffusely
- sensory processing (except olfaction)
- motor processing through connections with the basal ganglia and cerebellum
Label the diagram showing the nuclei of the thalamus
What are their functions?
Ventral posterior lateral (VPL) and ventral posterior medial (VPM):
- these travel to the somatosensory cortex
lateral geniculate:
- this relays to the visual cortex
medial geniculate:
- this relays to the auditory cortex
Label the features surrounding the hypothalamus
What is meant by corpus striatum (“striped body”)?
Internal structures of grey matter (nuclei) of each cerebral hemisphere
they are part of the basal ganglia
they are involved in motor control
Label the components of the corpus striatum
What is the relationship between the caudate nucleus and the lateral ventricle?
The caudate nucleus is C-shaped and follows the path of the lateral ventricle
head and body of the caudate nucleus form the lateral wall of the lateral ventricle
tail of the caudate nucleus forms the roof of the inferior horn of the LV
Which nuclei of the corpus striatum are represented by each colour?
The caudate nucleus is lateral to the LV
the putamen is the most lateral
globus pallidus is medial to the putamen
Label the components of the corpus striatum
What are the 3 classes of nerve fibres in the white matter of the hemispheres?
- Association fibres
- Commissural fibres
- Projection fibres
What is the role of association fibres?
They interconnect areas within a hemisphere and adjacent gyri within a hemisphere
short association fibres will connect adjacent gyri
long adjacent fibres connect between the lobes of a hemisphere
What are commissural fibres?
What are the 2 types of commissural fibres?
They interconnect areas between hemispheres
the two main commissural fibres are the corpus callosum (great cerebral commissure)
and
anterior commissure (rostral commissure) between the temporal lobes
Label the commissural fibres
Where do they originate from?
They originate from the lamina terminalis
Label the features of the corpus callosum
What are the roles of the projection fibres?
What are the 2 types?
They interconnect the cerebrum with the rest of the CNS
consists of the corona radiata
and
internal capsule
What is the course of the internal capsule like?
- It passes between the head of the caudate and lentiform nuclei
- it connects to crus cerebri (cerebral peduncles), anterior part of the pons and the pyramids of the medulla
- it contains descending motor fibres
Where is the internal capsule located?
It is between the caudate nucleus and the lentiform nucleus
Label the parts of the internal capsule
The internal capsule consists of white matter that travels between brain structures
there are different fibre types in specific regions of the IC
