A1- Protection of CNS Flashcards
What regions form the hindbrain?
Pons, cerebellum and medulla
What are the 3 types of fibres within the brain and what areas do they connect?
Commisural fibres: connect L and R side of the brain
Projection fibres: connect cortex with subcortical regions and the spinal cord
Association fibres: connect areas within the same hemisphere
What is the function of arachnoid granulations (villi)?
Reabsorb CSF and transfer it into dural venous sinuses
What are the layers of the brain in order from skull to the cerebrum?
Cranial bones
Periosteal layer of dura mater
Meningeal layer of dural mater
Arachnoid mater
Subarachnoid space
Pia mater
Brain/ cerebrum
What are the 4 dura mater reflections and where are they found?
Falx cerebri - seperates L and R cerebral hemispheres
Falx cerebelli - seperates L and R cerebellar hemispheres
Tentorium cerebelli - seperates cerebrum (occipital lobe) from the cerebellum
Diaphragm sellae - covers hypophysial fossa of sphenoid bone, contains opening for pituitary stalk (find it by lifting optic chiasm)
What is the function of dural reflections?
Compartmentalise the cranial cavity, keeps the brain in place and stops it rotating
What type of haematoma occurs when a blood-filled space occurs between the dura mater and the skull?
Extradural haematoma
Name the venous sinuses
Superior sagittal
Inferior sagittal
Straight sinus
Transverse sinus (paired)
Sigmoid sinus
Superior petrosal sinus
Inferior petrosal sinus
Cavernosus sinus (paired)
Where does the transverse sinus drain into?
Sigmoid sinus then into internal jugular vein
Where is the cavernosus sinus located?
Middle cranial fossa
What are the implications of a lesion in the anterior, middle or posterior cerebral arteries?
Anterior cerebral: motor and sensory loss of lower limb
Middle cerebral: extensive effects - motor and sensory loss in upper limb and face, speech and hearing problems
Posterior cerebral: may affect vision
What is the neurovascular supply to the dura mater?
Blood supply: mainly from middle meningeal artery (branch of maxillary), some from anterior and posterior meningeal arteries
Innervation: trigeminal nerve (V1, V2, V3)
Describe the characteristics of the 3 layers of meninges
Dura mater (outer): thick, tough, inextensible
Arachnoid mater (middle): thin, avascular, no innervation
Pia mater (inner): tightly adhering (to brain and spinal cord), highly vascularised
Why are cisterns formed?
The pia mater is closely fitted but the arachnoid matter is loose, means the subarachnoid space is of varying depths. Where there is significant depression = subarachnoid cisterns.
Name the 2 large cisterns and where they are found
Cisterna magna - between cerebellum and medulla
Interpeduncular cistern - base of brain, where the arachnoid mater spans the space between the 2 temporal lobes (conains the otic chiasm)
What are the functions of CSF?
1- Protection, limit neural damage in cranial injuries
2- Buoyancy, decrease weight of brain as it immerses it in fluid (lowers pressure)
3- Chemical stability, allows for functioning (i.e. low extracellular K+)
How is CSF produced?
By choroid plexus, located in linings of ventricles (specialised cells = ependymal cells)
Describe the circulation of CSF
1- Lateral ventricle
2- Interventricular foramen
3- Third ventricle
4- Cerebral aqueduct
5- Fourth ventricle
6- Foramen of Magendie (links 4th ventricle with superior cistern and cisterna magna) and Foramen of Lushka (links 4th ventricle with cisterna magna)
7- Subarachnoid space
8- Arachnoid granulations
9- Superior sagittal sinus
10- Transverse sinus
11- Confluence of sinuses
12- Sigmoid sinus
13- Internal jugular vein
What are the 2 protrusions of the third ventricle?
Supra-optic recess: above optic chiasm
Infundibular recess: above optic stalk
What 3 sinuses converge to the confluence of sinuses?
Straight, superior sagittal and inferior sagittal
Between which dural mater reflections is the straight sinus found?
Falx cerebri and tentorium cerebelli
What is the straight sinus a continuation of?
Great cerebral vein and inferior sagittal sinus
Where are the superior and inferior petrosal sinuses found and what do they drain?
Found above the petrosal bone
Drains the cavernous sinus into the transverse sinus
Where does the cavernous sinus receive blood from and what does it drain into?
Receives blood from the middle cerebral vein
Drains into the internal jugular and transverse sinus
What travels through the cavernous sinus?
Nerves - abducens, occulomotor, trochlear, ophthalmic (V1) and maxillary (V2)
Internal carotid artery
Where do the vertebral arteries arise from?
Subclavian arteries
What are the 3 main branches of the vertebral artery and what do they supply?
Anterior spinal - spinal cord
Posterior spinal - spinal cord
Posterior inferior cerebellar - posterior and inferior part of the cerebellum
What are the branches of the basilar artery and what do they supply?
Anterior inferior cerebellar artery - anterior and inferior part of the cerebellum
Labyrinthine artery - inner ear (via internal auditory canal)
Superior cerebellar - superior part of cerebellm
Posterior cerebral - occipital and temporal lobes
Pontine branches - smaller branches, supply the pons
What does the internal carotid artery give rise to and where do these branches supply?
Ophthalmic artery - orbit
Hypophyseal artery - pituitary portal vessels
Posterior communicating artery - connecting vessel between ICA and posterior cerebral
Middle cerebral artery - middle of cerebrum
Anterior choroidal - motor regions of the brain
Anterior cerebral artery - anterior of cerebrum
What do the internal and external carotids supply?
Internal carotid = brain, including eyes
External carotid = outside the brain, i.e. scalp, face, skull
What is the denticulate ligament?
Fibrous sheet of pia mater which suspends the spinal cord in the dural sac. It extends laterally from the spinal cord and attaches to the inner surface of the dural sac
What is the name of the plane that extends between the highest points of the iliac crests?
Supracristal plane
Where is the pontocerebellar cistern?
Lies anterior to the pons
Where is the chiasmatic cistern? What does it contain?
Lies inferior and anterior to the optic chiasma
Contains the decussation of the optic nerve fibres
Where is the interpeduncular (basal) cistern?
Between the cerebral peduncles of the midbrain
What are some examples of association fibres?
Superior longitudinal fasciculus
Inferior longitudinal fasciculus
What are some examples of commissural fibres?
Corpus callosum - runs down middle of longitudinal fissure
Anterior commissure
What are some examples of projection fibres?
Corona radiata
Internal capsule
What are the roles of the 4 lobes of the brain?
Occipital - vision
Temporal - auditory
Parietal - sensory
Frontal - motor
Where is Broca’s area and what does it control?
Within the frontal lobe, just above the lateral fissure. It controls movement when articulating speech, so if damaged the individual will not be able to pronounce the sentence even though they can think of it
What does Wernicke’s area control?
How you put words together - if damaged they can say the words but it wont make any sense
What does the diencephalon include?
Thalamus - relays sensory and motor signals, regulates consciousness and alertness
Epithalamus - circadian rhythms, contains the pineal gland
Hypothalamus - temperature control, endocrine, water control
What does the midbrain include?
Crus cerebri
Superior colliculus - involved in visual pathway
Inferior colliculus - involved in hearing pathway
Trochlear nerve
