General Features of the Brain Flashcards
What are the frontal lobes made up of?
Primary motor cortex and prefrontal cortex
What are the temporal lobes made up of?
Primary auditory cortex and auditory association cortex
What are the occipital lobes made up of?
Primary visual and visual association cortex
What are the parietal lobes made up of?
Primary somatosensory cortex and association cortex
What does the cerebellum control?
Balance
Posture
Muscle tone
Fine movement
Coordination
What does the brainstem contain?
Made up of midbrain, pons, medulla
Contains:
Ascending and descending tracts
Cranial nerve nuclei
What are gyri?
The rolls/ridges of the cerebral cortex
What are sulci?
The grooves between the gyri
What is the central sulcus?
Separates the frontal lobes from the parietal lobes, it is the deepest and longest sulcus
What is the lateral sulcus?
Separates the temporal lobe from the parietal and frontal lobes, also called the sylvian sulcus
What does the insula form the floor of?
The lateral sulcus
What is the oppercula (lips)?
The parts of the temporal, fronal and parietal lobes that overlie the insula
What is the longitudinal fissure?
Large fissure separating the two hemispheres
What is the corpus callosum?
A large bundle of white matter connecting the two hemispheres
What are the olfactory tracts?
Bilateral bundle of afferent nerve fibres that connects the olfactory bulb to the cerebral cortex
Where do the optic nerves converge?
The optic chiasm
What are mammillary bodies?
Two rounded eminences behind the optic chiasm
Where is the hypothalamus located when looking at the inferior side of the brain
Behind the optic chiasm and up to the mammillary bodies- only part of diencephalon visible on the outside of the brain
What are the cerebral peduncles/crus cerebri and where are they?
Two large masses of white matter- they are stalks that attach the cerebrum to the brainstem
They are behind the mammillary bodies on each side, from the cerebral hemisphere, they pass backwards and converge in the midline at the border of the pons
What is the interpeduncular fossa?
The space between the peduncles/crura roofed over by the arachnoid
Where is the pons?
Behind the point where the peduncles/crura meet.
Part of the brainstem –> Forms a bridge of neural tissue between the midbrain and medulla
What is the cerebellum?
Two lobes, one on either side of the medulla and a central vermis joining the two hemispheres
Where is the medulla?
Runs from the border of the pons to where the spinal cord was cut when the brain was removed
What is the parietal lobe involved in?
Perception
Interpretation of sensory information
Idea of complex meaningful motor responses
Dominant lobe (left) control language and mathematical operations
Non-dominant lobe (right) controls visuospatial functions
What is the frontal lobe involved in?
Motor function
Problem solving
Memory
Language
Judgement
Personality
Impusle control
social and sexual behaviour
Idea is that the frontal cortex is what makes you you
What is the temporal lobe involved in?
Language- Wernicke’s area (superior temporal gyrus)-> understanding spoken language
Memory
Emotion
Perceiving sounds
Assigning meaning to those sound
Contains amygdala, hippocampus, primary auditory cortex
What is the occipital lobe involved in?
Visual information
What does the limbic system include?
Thalamus
Hypothalamus
Hippocampus
Amygdala
Fornix
Cingulate
What does the limbic system regulate?
Emotion
Memory
Behaviour
Olfaction
What is the hippocampus invovled in?
Long term memory formation
What is the amygdala invovled in?
Fear and Reward
What systems does the limbic system regulate?
The endocrine system
The autonomic nervous system
What are the two layers of the dura mata?
- Outer endosteal layer- lines the interior of the skull, adhering to and sending blood vessels and fibrous processes into the cranial bones
- Inner meningeal layer- envelops the brain and spinal cord and provides tubular sheaths for the cranial nerves
What is the falx cerebri?
An arched crescent of dura lying in the longitudinal fissure between the two hemispheres
Where is the superior saggital sinus?
Where the falx cerebri attaches to the cranium
What is the superior saggital sinus?
It is a midline venous structure that receives blood from multiple draining vessels and drains the bilateral cerebral hemispheres
Where is the inferior saggital sinus?
At the inferior margin of the falx cerebri
What is the inferior saggital sinus?
A dural venous sinus that drains into the straight sinus
What is the tentorium cerebelli?
Dura that forms a thick fibrous roof over the posterior cranial fossa and the cerebellum
Where is the straight sinus?
Within the tentorium cerebelli at its attachment to the falx cerebri
Where is the sigmoid sinus?
It begins as a continuation of the transverse sinus around the opening on the tentorium cerebelli. From here, it descends downward, forming an S-shaped curve in a groove on the mastoid process of temporal bone.
What is the straight sinus?
It is where the great cerebral vein (great vein of Galen) and inferior saggital sinus join together to form one of the main dural venous sinuses
What is the tentorial inscisure/tentorial notch?
An oval opening in the tentorium cerebelli, that surrounds the midbrain, and gives passage to the posterior cerebral arteries
Pressure on this can lead to inactivation of the oculomotor nerves
Where is the transverse sinus?
Runs along the line of attachment of the tentorium cerebelli to the occipital bone
What is the transverse sinus
A paired venous vessel that runs beneath the brain and allows blood to drain from the back of the head
Where is the cavernous sinus?
Lateral to the body of the sphenoid, located behind the eye sockets
It contains 5 cranial nerves and the internal carotid artery
Where is the inferior petrosal sinus?
In the groove between the petrous temporal bone and the basal part of the occipital bone
Where is the superior petrosal sinus?
In the lateral margin of the tentorium cerebelli
What is the cavernous sinus?
A sinus that carries blood away from the anterior part of the brain and middle cerebral veins, it empties into the jugular vein
Where is Meckel’s (trigeminal) cave?
Next to the apex of the petrous part of the temporal bone and envelops roots of the trigeminal nerve
The trigeminal cave is a dura mater pouch containing cerebrospinal fluid.
What is Meckel’s cave?
A cerebrospinal fluid-containing dural pouch in the middle cranial fossa
What is the diaphragma sellae?
A small circular horizontal fold of dura mater which forms the roof of the pituitary fossa
What is the falx cerebri?
A small vertical sickle-shaped reflection of dura separating the two lobes of the cerebellum
What is the arachnoid mater?
The thin transparent middle layer of the meninges that lies directly below the dura mater
What is the foramen of magendie
A midline communication between the 4th ventricle and the subarachnoid space
What is the foramen of luschka?
A lateral communication between the 4th ventricle and the subarachnoid space
What are subarachnoid cisterns?
Spaces between the arachnoid and the pia that are full of CSF
What does the interpeduncular cistern contain?
The circle of Willis
What does the superior cistern contain?
The great cerebral vein (of Galen) and the pineal gland
What is the cisterna ambiens
A group of subarachnoid cisterns which completely encircle the midbrain
What is the pia mater?
The third layer of the meninges which closely adheres to the underlying nervous tissue
It forms part of the BBB
What is the BBB and what is it made up of?
The BBB protects the tissue from toxic substances as well as regulating the movement of ions, molecules and cells between the blood and the brain
It is made up of:
- Endothelial cells of the capillaries which have ‘tight junctions’ to prevent molecules passing between them
- The basement membrane of CNS blood vessels which lack ‘fenestrations’ (small holes)
- Pericytes which are cells that wrap around endothelial cells and regulate capillary blood flow, immunity and vascular permeability
4.Astrocytes which envelop CNS capillaries and restrict the flow of molecules into the CNS parenchyma
What is meningitis?
Inflammation of the meningees caused by infection.
Symptoms
Headaches, neck stiffness and photophobia
Nausea, vomiting and fever
Viral meningitis- mild & self-limiting
Bacterial meningitis-requires urgent treatment or else it leads to brain damage and death
-the rash from BM is a sign of meningoccal septicaemia
What is an extradural haemorrhage?
Blood between the skull and dura mater typically after a head injury
It strips the dura from the bone and compresses the brain
The haemorrhage is from the meningeal arteries
What is a subdural haemorrhage?
Blood between the dura and the arachnoid typically after a high impact injury e.g. car accident
It appears as a crescent on CT head
The haemorrhage is from tears in the bridging veins
(Chronic subdural haematoma occurs 4-8 weeks following mild-moderate head injury in the elderly)
What is a subarachnoid haemorrhage?
Blood between the arachnoid and pia mater typically after a head injury
Traumatic subarachnoid haemorrhage or after rupture of a berry aneurysm- blood surround the brain and fills the sulci near the site of injury/aneurysm
Pathognomic symptom= sudden severe headache
What is an intracerebral haemorrhage?
Rupture of small vessels and microaneurysms in perforating vessels leading to bleeding within the brain tissue
Classical location- internal capsule following rupture of the lenticulostriate artery due to high blood pressure
What is amaurosis?
Temporary loss of vision to one eye due to part of a carotid plaque breaking off and occluding the central retinal artery
Its a warning of thrombus of the interal carotid artery which is the potential for impending stroke
Arterial blood arrives to the brain via which two pairs of vessels?
Internal Carotid and Vertebral Arteries
What do the Vertebral arteries supply?
20% of blood supply
Goes to:
Posterior Cerebrum
Posterior Cranial Fossa
What do the Internal Carotids supply?
80% of blood supply
Goes to:
Anterior parts of cerebrum
Middle parts of cerebrum
Diencephalon
What does the interal carotid terminate into?
Anterior AND middle cerebral arteries
Commonly called anterior circulation
What does the anterior cerebral artery supply?
Corpus callosum
AND
Medial aspects of the hemisphere
What does the middle cerebral artery supply?
Majority of the lateral surface of the hemisphere
AND
Deep structures of the anterior part of the cerebral hemisphere via its anterior perforating branches
What does the anterior communicating artery do?
Connects together the two anterior cerebral arteries and provides anterior perforating branches
What does the posterior communicating artery do?
Connects the interal carotid and vertebro-basilar systems via the posterior cerebral artery
Where do the vertebral arteries arise from?
The first part of the subclavian artery
Where do the vertebral arteries enter the skull?
Through the foramen magnum
The two vertebral arteries meet in the midline to form what?
The basilar artery lying in the anterior median fissure on the pons
The posterior circulation consists of what?
The vertebral and basilar arteries and the posterior cerebral artery
The anterior and posterior circulations are linked via what?
The circle of Willis
What is a berry aneurysm?
A weakness in the wall of a cerebral artery or vein causes a localized dilation or ballooning of the blood vessel which enlarge until they rupture causing a subarachnoid or intracerebral haemorrhage
Most commonly occur on the anterior communicating artery which lies in the subarachnoid space
What haemorrhages can cause stroke?
Intracerebral or subarachnoid haemorrhages
What are internal cerebral veins?
Veins that run within the substance of the brain tissue
What are external cerebral veins?
Veins that run on the surface of the brain crossing the subarachnoid space to drain into dural venous sinuses
What are external cerebral veins?
Veins that run on the surface of the brain crossing the subarachnoid space to drain into dural venous sinuses
What is venous sinus thrombosis?
Occurs when a blood clot forms in the brains sinuses
–> Obstruction of venous drainage causes cerebral oedema and raised intercranial pressure which results in brain damage
Symtoms:
Headahce
Epileptic seizures
Focal motor deficits
Deterioration in consciousness
Where is the largest aggregation of choroid plexus?
Lateral ventricles where the majority of CSF is produced
The brain develops from a hollow neural tube- what are the remaining hollow spaces in the brain referred to?
Ventricles
What is the intraventricular foramen?
A narrow opening which is the only communication between the lateral ventricles and the rest of the ventricular system and is almost entirely filled with choroid plexus
It is behind the upper end of the column of the fornix and permits CSF flow from the lateral ventricles to the 3rd ventricle
What is the third ventricle?
A narrow slit like cavity lying in the midline between the two halves of the diencephalon, it is below the optic chiasm, pituitary stalk, mammillary bodies and tegmentum
What is the pathway of CSF originating in the lateral ventricles?
CSF passes from the lateral ventricles via the interventricular foramen into the 3rd ventricle, then backwards through the cerebral aqueduct into the 4th ventricle.
The 4th ventricle communicates with the subarachnoid space via the median foramen of magendie and the lateral foramen of luschka- through these openings CSF passes out to occupy the subarachnoid space around the brain and the spinal cord
What do arachnoid granulations (arachnoid VILLI) do?
They allow CSF to pass from the subarachnoid space into the venous system.
What is the CSF brain barrier?
It is formed by tight junctions between neighboring choroid plexus epithelial cells and stops the paracellular movement of molecules in and out of the brain.
