Term
| what is the brain derived from? |
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Definition
| is derived from the neural tube rostral (cranial) to the 4th pair of somites |
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Term
| what are the 3 primary vesicles of the brain? |
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Definition
Forebrain – prosencephalon
Midbrain – mesencephalon
Hindbrain - rhombencephalon |
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Term
| the prosencephalon gives rise to what 2 secondary vesicles? |
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Definition
Telencephalon
Diencephalon |
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Term
| the rhombencephalon gives rise to what 2 secondary vesicles? |
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Definition
Metencephalon
myelencephalon |
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Term
| the telencephalon gives rise to what structures? |
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Definition
cerebral hemispheres
Cerebral cortex
Basal ganglia
Lateral ventricles are remnant of vesicle |
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Term
| the diencephalon gives rise to what structures? |
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Definition
thalami
Hypothalamus
Pineal
Third ventricle remnant of vesicle |
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Term
| the mesencephalon gives rise to what structures? |
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Definition
the midbrain
Cerebral aqueduct (aqueduct of Sylvius) is remnant of vesicle |
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Term
| the metencephalon gives rise to what structures? |
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Definition
the pons and cerebellum
4th ventricle |
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Term
| the myelencephalon gives rise to what structure? |
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Definition
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Term
| what is the temporal lobe responsible for? |
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Definition
| memory, olfaction, emotions |
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Term
| primary motor function localization is located in what part of the cortex? |
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Definition
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Term
| sensory function localization is located in what part of the cortex? |
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Definition
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Term
| which lobe of the brain is responsible for vision? |
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Definition
| Occipital lobe, on banks of calcarine fissure |
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Term
| which region of the brain is responsible for audition? |
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Definition
| Superior gyrus of temporal lobe |
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Term
| where is the primary motor cortex of the brain? |
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Definition
Primary motor cortex is in the prefrontal gyrus, Brodmann’s area 4.
The gyrus is somatotopically organized as shown by the motor humunculus
Axons from “upper motor neurons” leave the cortex, descend in the internal capsule, through the cerebral peduncle, into the pons and medulla where they are in the pyramids. The fibers cross (90%) in the pyramidal decussation.
Descend in the lateral corticospinal tract and synapse on motor neurons in the ventral horn |
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Term
| the lateral corticospinal tract innervates which neurons? |
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Definition
Lateral tract – crossed
Innervates motor neurons of limbs (lower motor neurons) |
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Term
| the anterior (medial) corticospinal tract innervates which muscles? |
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Definition
anterior (medial) tract – uncrossed
Innervates trunk muscles |
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Term
| how is the primary sensory cortex organized and what are its' 2 sensory pathways? |
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Definition
Postcentral gyrus, Brodmann’s areas 3,1,2 is primary sensory cortex
Organized somatotopically (sensory humunculus)
Two major sensory pathways
Dorsal columns – discriminative touch, proprioception, and vibratory sense
Anteriolateral (spinothalamic) system – crude touch, pain and temperature
Systems cross either in the brainstem (dorsal columns) or in the spinal cord (anterolateral system)
Relay through the thalamus |
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Term
| where is 2 point discrimination best? |
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Definition
| two point discrimination is best on lips, second best on fingers, not very good on trunk |
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Term
| which sensory pathway crosses in the brainstem? |
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Definition
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Term
| which sensory pathway crosses in the spinal cord? |
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Definition
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Term
| injury of the corticospinal system (pyramidal tract) anywhere above the pyramidal decussation causes what? |
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Definition
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Term
| injury below the pyramidal decussation will cause what? |
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Definition
| ipsilateral paralysis below the lesion |
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Term
| injury to the spinal cord will cause what damage? |
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Definition
Injury to the spinal cord will cause loss of pain and temperature sense (spinothalamic tract) on the contralateral side below the lesion.
Such an injury will cause ipsilateral loss of fine (discriminative) touch, proprioception and vibration below the lesion (dorsal tract). |
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Term
| what is found in the midbrain? |
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Definition
Cerebral peduncles
Interpeduncular fossa
Corpora quadrigemini
Superior colliculi (visual input)
Inferior colliculi (auditory input) |
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Term
| which 2 arterial systems contribute to the blood supply of the brain? |
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Definition
Internal carotid artery
Comes off common carotid artery
Enters cranial cavity via the carotid canal
Supplies primarily the orbit, eye and brain
Mostly forebrain
Vertebral artery
1st branch of subclavian artery
Travels through the transverse foramina of C6-C1
Enters foramen magnum
Joins artery of opposite side to form basilar artery
Posterior blood supply/brainstem |
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Term
| describe the vertebral artery, where is arises and where it enters the cranial cavity. what 3 branches does it give off? |
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Definition
Arises from the subclavian artery.
Traverses the transverse foramina of the upper 6 cervical vertebrae.
Enters the cranial cavity via the foramen magnum.
Gives rise to 3 branches:
Anterior spinal artery
Posterior spinal artery
Posterior inferior cerebellar artery
Then fuses to form the basilar artery on the inferior surface of the pons.
Supplies the medulla oblongata |
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Term
| where does the basilar artery travel and what branches does it give off? |
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Definition
Travels rostrally on the anterior aspect of the pons
Gives rise to paired branches from caudal to rostral:
Anterior inferior cerebellar arteries
Pontine arteries (about 3)
Superior cerebellar arteries
Bifurcates into 2 posterior cerebral arteries |
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Term
| where does the internal carotid artery enter the cranial cavity and what are its branches? |
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Definition
Enters the cranial cavity via the carotid canal
Passes through the cavernous sinus
First branch is the ophthalmic artery
Terminal branches are:
Posterior communicating artery
Middle cerebral artery- lateral part of the cerebrum
Anterior cerebral artery- medial part of the cerebral cortex |
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Term
| where does the circle of willis form and what is it formed by? |
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Definition
Forms at the base of the brain.
Anastomosis between the vertebrobasilar and internal carotid systems
Formed by:
Anterior communicating connects left and right anterior cerebral arteries
Posterior communicating arteries, one on each side, connects the internal carotid to the posterior cerebral artery |
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Term
| describe the layers of the cranial dura mater |
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Definition
Two layers
Outer layer - periosteal layer
firmly attached to the skull
Continuous with periosteum of outer skull at the foramen magnum
Inner - meningeal layer
Close contact with arachnoid mater
Continuous with the spinal dura mater through the foramen magnum |
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Term
| the intracranial dura forms which specialized structures? |
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Definition
Dural partitions
Inward projections of dura that separate parts of the brain
Dura venous sinuses
Endothelial-lined venous spaces formed between the layers of dura |
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Term
| what is the falx cerebri? |
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Definition
Cresent-shaped
Projects downward between the cerebral hemispheres
Attached anteriorly to the Crista galli of the ethmoid bone and the frontal crest of the frontal bone
Posteriorly, attaches and blends with the tentorium cerebelli
separates right and left cerebral hemispheres |
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Term
| what is the tentorium cerebelli? |
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Definition
Horizontal shelf of meningeal dura
Separate the cerebellum, which rests in the posterior cranial fossa, from the overlying posterior lobes of the cerebral hemispheres.
Attached posteriorly to the occipital bone.
Laterally attaches to the superior border of the petrous part of the temporal bone.
Anterior and medial borders are free, forming the tentorial notch through which the midbrain passes |
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Term
| where is the tentorial notch and what are the cavities above and below it? |
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Definition
Intracranial cavity above the notch is called supratentorial
That below the notch is infratentorial
Important structures pass through the tentorial notch
Midbrain
Basilar artery
Transtentorial herniation – herniation of medial temporal lobe and uncus through the notch |
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Term
| what is the clinical triad of an uncal herniation? |
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Definition
Uncal herniation is heralded by the clinical triad of:
Blown pupil –ipsilateral, dilated unresponsive pupil
Hemiplegia – compression of the cerebral peduncles
Coma – due to distortion of the midbrain reticular system |
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Term
| what is the falx cerebelli? |
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Definition
Small midline projection of meningeal dura in the posterior cranial fossa.
Attached posteriorly to the internal occipital crest of the occipital bone.
Superiorly attached to the tentorium cerebelli.
“Separates” two hemispheres of the cerebellum. |
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Term
| what is the diaphragma sellae? |
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Definition
Small horizontal shelf of meningeal dura mater that covers the hypophyseal fossa of the sella turcica.
Infundibulum passes through a small opening in the sella turcica. |
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Term
| which arteries supply the dura mater of the anterior cranial fossa? |
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Definition
anterior meningeal arteries
Branches of ethmoidal arteries |
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Term
| which arteries supply the dura mater of the middle cranial fossa? |
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Definition
Middle and accessory meningeal
Branches of maxillary artery
Middle enters skull through the foramen spinosum
Accessory enters through the foramen ovale |
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Term
| the posterior meningeal artery is a branch of which artery? |
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Definition
| the ascending pharyngeal artery |
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Term
| true or false: the middle meningeal artery is running outside of dura in the epidural space |
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Definition
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Term
| what causes an epidural bleed? |
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Definition
Epidural, AKA extradural hemorrhage
Usually caused by tearing of the middle meningeal artery, particularly anterior branch from trauma to the pterion
Blood collects between the bone of the calvarium and the periosteal layer of dura
Slowly separates the periosteal dura from the bone
Rapid bleed because it is arterial
Patient can die from it; brief concussion occurs
Lens shaped accumulation of blood |
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Term
| which nerve innervates the dura mater? |
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Definition
Brain has no touch or pain receptors and therefore is insensate.
One cause of headache is from stretching of the dura mater.
Mostly innervated by the trigeminal nerve except for the posterior fossa
Cervical nerves 2 and 3 innervate the posterior fossa below the tentorium
Fibers enter via foramen magnum, hypoglossal canal and jugular foramen. |
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Term
| what is the arachnoid mater? |
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Definition
Thin, avascular membrane
Against, but NOT adherent to the dura
Therefore there is a potential space, the subdural space
Subarachnoid space between the arachnoid and pia mater
Fine trabeculae attach arachnoid to pia
Blood vessels travel in the subarachnoid space |
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Term
| what occurs in a subdural bleed? |
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Definition
Blood from torn veins fills the potential space between the dura and the arachnoid mater
Typically occurs in older individuals
Brain is atrophied and therefore more space between the brain and arachnoid
Puts strain on veins from brain to dural venous sinuses
Slow, insidious
History may be a trivial injury with or without loss of consciousness.
Crescent shaped hemorrhage; pushes brain medially |
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Term
| what causes a subarachnoid bleed? |
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Definition
May be the result of SIGNIFICANT head trauma or burst aneurism.
More frequently caused by the bursting of a cerebral aneurysm.
Arterial blood flows between the gyri of the brain, into the sulci. |
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Term
| what are the 4 typical sites of brain herniation? |
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Definition
Four typical sites of herniation.
Subfalcine – under the falx cerebri
Central – downward herniation of the brainstem
Uncal – herniation of the medial temporal lobe and the uncus through the tentorial notch
Tonsilar herniation – herniation of the cerebellar tonsil through the foramen magnum |
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Term
| what are dural venous sinuses? |
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Definition
Endothelial lined spaces between layers of dura.
Empty into the internal jugular veins via the jugular foramen.
Dural sinuses include:
Superior sagittal, inferior sagittal, straight, transverse, sigmoid, confluence of sinuses, cavernous sinus, sphenoparietal sinus, superior petrosal, inferior petrosal and basilar sinuses |
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Term
| the inferior sagittal sinus drains where? |
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Definition
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Term
| where is the cavernous sinus located and what structures pass through it and in the wall of it? |
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Definition
The two cavernous sinuses lie lateral to the body of the sphenoid bone on either side of the sella turcica
Very important clinically
Passing through the sinus:
Internal carotid artery
Abducens nerve
In the wall:
Oculomotor nerve
Trochlear nerve
Trigeminal, ophthalmic division (V1)
Trigeminal, maxillary division (V2) |
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Term
| what is cavernous sinus syndrome and what can it cause? |
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Definition
Cavernous sinus can be the site of metastatic breast, prostate and lung cancer
Can be the site of a carotid artery aneurysm
Cavernous sinus syndrome can cause diplopia, painful ophthalmoplegia
May be trigeminal sensory loss |
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Term
| where are the ventricles of the brain located? |
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Definition
The brain has CSF-filled spaces called ventricles
Two lateral, one in each cerebral hemisphere
One third ventricle between the right and left halves of diencephalon
One 4th ventricle in the region of the pons, beneath the cerebellum |
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Term
| what joins the 3rd and 4th brain ventricles? |
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Definition
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Term
| what joins the 2 lateral ventricles of the brain? |
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Definition
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Term
| describe the flow of CSF throughout the brain starting with where it is made |
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Definition
CSF made in the lateral ventricles
Approximately 500cc per day
Flows via the foramina of Monro to the third ventricle
From third ventricle, flows via the aqueduct of Sylvius to the 4th ventricle
Leaves the 4th ventricle via the median foramen of Magendie and the two lateral foramina of Lushka
Reabsorbed in the arachnoid villi in the superior sagittal sinus |
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Term
| what are arachnoid villi? |
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Definition
| arachnoid villi (arachnoid granulations) are prolongations of arachnoid that protrude through meningeal layer of dura mater into dural venous sinuses and lateral venous lacunae; they transfer CSF to venous system |
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Term
| what causes hydrocephalus? |
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Definition
Can be due to congenital obstruction of aqueduct of Sylvius
Tumors can block the aqueduct
In young children, before the skull sutures are fused, the head swells
Hydrocephalus can severely damage brain tissue |
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Term
| how would you treat hydrocephalus? |
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Definition
put a tube in lateral ventricle, run it out subcutaneously that drains into abdominal cavity, draining CSF, as child grows shunt extends with growth
passes within cervical region subcutaneously, right under neck |
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