Neuroanatomy (Lec. 3)

chronic traumatic encephalopathy (CTE)

degenerative brain disease associated with repeated hits to the brain

• commonly found in athletes of contact sports (e.g. football and boxing)

• diagnoised after death

chronic traumatic encephalopathy (CTE) symptoms

• memory loss

• depression

• aggressive behaviour

• (sometimes) suicidal thoughts

how CTE occurs

• tau (protein) builds up over time in certain patterns

• the tau clumps strangle brain cells, diminishing their ability to function

• affecting the dorsolateral frontal cortex (responsible for cognition and executive function - working memory, planning & abstract reasoning

dura mater

• outermost layer

• connected to the skull (outter layer)

• covers the gyri in foldings of the brain (inner layer)

• white covering aroudn the brain

arachnoid mater

• middle spider-like layer

• attaches tightly to the inner dural layer

• ensuring room for cerebrospinal fluid to flow

what suports the brain & spinal cord

• bone (skull verta)

• meninges 

• cerebrospinal fluid (found in the gap between the brain and the skull)

pia mater

• innermost layer

• adheres tightly to the brain followign gyri and sulci

falx cerebri

• cresecent shape (following the lognitudinal fissure)

• descends vertically in the longitudinal fissure, separating the 2 CEREBRUM hemispheres

tentorium cerebelli

• “tent of the cerebellum”

• U-shaped

• parallel to the floor

• runs between the occipital lobe and the cerebellum

falx cerebelli

a small midline fold that runs in the space between the 2 CEREBELLUM hemispheres

subarachnoid space

• located between the arachnoid and pia mater

• filled with cerebral spinal fluid (CSF) and major cerebral arteries

anterior fossa

ventral apsect of the frontal lobe

middle fossa

much of the temporal lobe

posterior fossa

brainstem and cerebellum

foramen magnum (aka “great hole”)

• oval-shaped opening in the occipital bone of the skull

• the spinal cord passes through when exiting the cranial cavity

cerebral spinal fluid (CSF)

the fluid that fills the brain’s ventriclar spaces 

• freuqent bleeding after trauma/cerbral artery rupture

meningiomas

benign tumours arising from the dura mater

meningiomas symptoms

• vision changes

• headaches

• hearing loss

• memory loss

• loss of smell

• laguage difficulty

• arms & legs weakness

meningitis

an infection and inflammation of the 2 inner menial layers

major functions of the ventricular system

1. protects the brain - shock absorber

2. provides buoyancy - reducing brain weight

3. provides a medium for the exchange of materials between blood vessels and brian tissue

lateral ventricles

• aka 1st and 2nd ventricles

• 1 is located in each hemisphere

• spans all 4 lobes

third ventricle

a narrow midline space between the right and left ventricle diencephalon (thalamus

• hypothalamus)

fourth ventricle

betwene the dorsal brainstem adn cerebellum

cerebral aqueduct

connects the third and fourth ventricle

septum pellucidum

a thin membrane separting the fontal horns and body of the L and R ventricles

choroid plexus

modified vascular structure lining the ventricles producing CSF by filtering blood

circulation of CSF

1. lateral ventricles

2. 3rd ventricle

3. cerebral aqueduct

4. 4th ventricle

5. subarachnoid space

6. arachnoid granulations

7. venous circulation

arachnoid granulations

• specialized portions of the arachnoid

• protrudes through the inner layer of the dura matter and superior agittal sinus

• CSF passes through here and returned to the venous circulation in the superior agittal sinus

hyrdocephalus

when there is an abnormal buildup (in cerebral abduct) of CSF in the ventricles due to an obstruction

• can lead to an enlargement of the ventricles —> compression of the brain

• commonly found in kids

the brain’s energy consumption

consumes >20% of the ody’s energy at rest

a stroke

sudden loss of brain function caused by a sudden lockage or rupture if a blood brain vessel

stroke symptoms

• loss of balance/headache/dizziness

• blurred vision

• half of face is drooping

• 1 arm/leg weakness

• speech difficulty

how a stroke occurs

blood flow to the brain is blocked/sudden bleeding in the brain

ishchemic strokes

blocked blood vessels

• thrombotic: blockage due to fatty plaque build-up on cerebral vessels

• embolic: blood clots ofmred somewhere else in the body, traveling through bloodstream to the brain

hermorrhagic strokes

rupruted blood vessel

• bleeding within/around the brain

transient ischemic attack (TIA)

warning stroke signs (temporary blockage)

blood supply of the brain and spinal cord from aorta

1. internal carotid

2. verteral arteries

carotid arteries

• ascend up the L and R sides of the neck

• branch into the external and internal carotid arteries

vertebral arteries

1. ascend up eahc side of the cervical vertebrae

2. fuse together within the skull to form the basilar artery

anterior circulation

supplies the forebrain (cerebral hemispheres and diencephalon)

posterior ciurcualtion

supplies the brainstem, cerebellum, and upper portion of the spinal cord 

• also supplies to the brainstem, cerebellum, and upper portion of the spinal cord

they supply 2nd/3rds of the cerebrum (arteries)

the interanl arteries branch to form the anterior cerebral artery (ACA) and middle cerrebral artery (MCA)

anterior cerebral arteries

travel anterior (forward) from the internal carotid artery

• towards the medial longitudinal fissure

middle cerebral arteries

travel out laterally from the internal carotid artery towards the lateral (sylvian) fissure

what do anterior cerebral arteries supply?

supplies regions in the medial aspect and dorsal margins of the frontal lobe

what do middle cerebral arteries supply?

supplies extensive region of the central and lateral cerebral hemispheres

• sensorimotor

• language

posterior cerebral artery (PCA)

supply regions in the posterior partietal, inferior temporal, and occipital lobe

what arteries form the circle of willis?

• posterior cerebral artery

• posterior communicating artery

• internal carotid artery

• anterior cerebral artery

• anterior communicating artery

where is the circle of willis located?

at the base of the brain

what is found within the center of the circle of willis?

the optic chaism

lenticulostriate arteries

deep-penetrating branches of the middle cerebral artery (MCA) that supplies MOST of the basal ganglia

• small diameter & sharp R angle —> easy for rupture/occlusion —> stroke symptoms

posterior cerebral arteries

supplies posterior hypothalamus, most of thalamus

why lenticulostriate arteries are referred to as “end arteries”

the regions they supply do not have significant alternative supply to rely on

the artery from the vertebral supply that goes to the cerebral hemispheres

posterior cerebral artery

• + also supplies midbrain of the brainstem

the artery that can also supply medial regions of midbrain and pons

basilar artery

the arteries caudal to the posterior cerebral artery (PCA) that supply regions of the brainstem on their way to supplying blood to the cerebellum

• superior cerebellar artery (SCA): midbrain + cerebellum

• anterior inferior cerebellar artery (AICA): pons + cerebellum

• posterior inferior cerebellar artery (PICA): medulla + cerebellum4

what spaces are considered “potential spaces”

subdural space & epidural space

hemorrhage

occurs when an artery in the brain ursts and causes localized bleeding

epidural hemorrhage

blood between the skull and dura mater due to injury

• epi = above —> “above the dura”

subdural hemorrhage

blood between the dura mater and arachnoid mater

• sub = below —> “below the dura”

subarachnoid hemorrhage

blood within the subarachnoid space and pia mater

• due to brain aneurysm

intracerebral hemorrhage

leeding with the brain tissue itself

a series of dural ____ return blood from the brain back to the heart via internal juglar veins

venous sinuses

superior sagittal sinus

runs along the dorsal midline of the hemispheres & drains into the confluence of sinuses

transverse sinus

• oriented on horizontal plane

• extending laterally from the confluence sinuses

• traveling briefly anterior before turning to sigmoid sinuses

list of dural venous sinuses

• superior sagittal sinus

• inferior sagittal sinus

• straight sinus

• confluence sinuses

• transverse sinus

• sigmoid sinuses

• cavernous sinus

confluence of sinuses

found at the posterior end of the longitudinal fissure & drains into the L and R transverse sinus

purpose of venous sinuses

to drain blood and CSF from the brain

the blood-brain barrier (BBB)

makes the movement of substances from blood vessels into brain cells difficult

• provides protection and homeostasis in the brain

can only cross the blood-brain barrier if

• soluble in lipids

• special transporters

what the blood brain-barrier allow through it to maintain homeostasis

• oxygen

• glucose

• other critical molecules

glymphatic system

a lymphatic system in the brain to remove wastes and aid movement of nutrients

glymphatic system draining process

1. CSF flows from subarachnoid space to periarterial space

2. CSF enters brain tissue via specialized chanels

3. CSF drains into perivascular space - joining the cirulatory system