Neuro Week 3 - Specialized Support Systems of the Brain

what are the three meninges?

• dura mater

• arachnoid mater

• pia mater

what are the three fossa’s of the brain and what parts do they hold?

• anterior fossa: ventral aspects of the frontal lobe

• middle fossa: much of the temporal lobe

• posterior fossa: brainstem and cerebellum

falx cerebri

the fold of the dura matter than descends vertically in the longitudinal fissure separating the two hemispheres

surrounds the corpus collosum

what is the tunnel that connects the lateral ventricles to the third ventricle?

the interventricular foramens

describe where the third ventricle is

in between the two thalami, a narrow midline space between the right and left diencephalon (thalamus + hypothalamus)

what connects the two thalami together?

axonal tract

where is the fourth ventricle?

between the dorsal brainstem and cerebellum

what connects the third and fourth ventricle?

the cerebral aqueduct

what does the choroid plexus do?

modifies vascular structure lining the ventricles that produces CSF by filtering blood

create a flow chart of the circulation of the CSF

lateral ventricles → interventricle foramen → 3rd ventricle → cerebral aqueduct → fourth ventricle → subarachnoid space → arachnoid granulations

Foramen of Magendie

a small midline opening that drains CSF from 4th vent. to the subarachnoid space

Foramina of Luschka

two lateral openings that drains CSF from the 4th vent. to subarachnoid space

arachnoid granulations

specialized portions of the arachnoid that protrude

through the inner layer of dura matter and into the superior sagittal sinus

what region of the ventricular system would be prone to blockage

cerebral aqueduct

what is hydrocephalus?

occurs when there is an abnormal buildup of CSF in the ventricles due to an obstruction

• common in children

• blockage of the cerebral aqueduct

• caused by congenital or aquired due to cerebral disease (ex. meningitis, hemorrhage, traumatic brain injury, brain injury, brain tumors)

what happens with patients Alzheimer’s (brain size and ventricles)

brain can shrink up to 1/3 of normal size

ventricles become larger

• provides more space for the ventricles to expand

how long does it take to loose consciousness when you have no blood supply going to the brain?

10 sec

what is a stroke?

the sudden loss of brain function caused by a sudden blockage or rupture of a blood brain vessel

symptoms of a stroke

• loss of balance

• blurred vision

• one side face drooping

• one side arm or leg weakness

• speech difficulty

FAST

difference between a ischemic stroke vs. a hemorrhagic stroke

blocked blood vessel vs. ruptured blood vessel (caused by high BP)

two types of ischemic strokes

thrombotic stroke: fatty plaque blockage on cerebral vessels

embolic stroke: blood clot somewhere else that then travels the brain

the entire blood supply of the brain and spinal cord depends on which 2 sets of branches of the aorta?

1. internal carotid arteries

• extend from the carotid artery and extends up the neck

2. vertebral arteries

• extends against the side of the cervical vertebrae later fusing together to form the basilar artery

what arteries are part of the circle of willis

• Posterior Cerebral Artery

• Posterior Communicating Artery

• Internal Carotid Artery

• Anterior Cerebral Artery

  • travel anterior from the internal carotid artery,

    towards the medial longitudinal fissure

    • Supplies regions in the medial aspect and dorsal margins of the frontal lobe

• Anterior communicating artery

• middle cerebral arteries

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

  • Supplies an extensive region of the central and lateral cerebral hemispheres (sensorimotor, language)

Lenticulostriate arteries

the deep-penetrating branches of the MCA that supplies most of the basal ganglia

aka the end arteries

prone to blockage and rupture (stroke)

what part of the brain layers is called real space

subaracnoid space

what are the 4 areas that cause localized bleeding (hemorrage/hematomas)

1. epidural hematoma

a collection of blood between the skull and dura mater
- Usually happens due to injury (e.g., skull fracture causes tear to underlying
blood vessels)

2. subdural

a collection of blood between the dura mater and
arachnoid mater
• Symptoms can occur suddenly or take days to weeks to develop

3. subarachnoid

a collection of blood within the subarachnoid space
surrounding the brain (the area between the arachnoid and pia mater)
• Usually happens due to brain aneurysm

4. intracerebral

• bleeding within the brain tissue itself

Medullary arteries

a collection of 6-10 arteries that arise from various branches of the aorta and supply the anterior and posterior spinal arteries along the spinal column

what is the purpose of the BBB

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

what/ how can cross the blood brain barrier

• soluble in lipids

• special transporters

glymphatic system

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

when is the glyphatic flow the fastest

during sleep because the extracellular spaces expand (by about 50%) and the CSF flows faster

immune factors go into the glymphatic system supporting damaged tissue to roles in learning and social behaviour

what does the dura matter consist of?

the outer layer and the inner layer

tentorium cerebelli

U-shaped infolding of dura matter that runs under the occipital lobe dividing the occipital lobe and the cerebellum

what does the tentorial notch provide space for?

the brainstem

falx cerebelli vs. falx cerebri

falx cerebelli is the dura matter that divides the cerebellum (smaller one)

falx cerebri is the dura matter that divides the cerebrum (larger one)

follow the same orientation

tentorium cerebelli

U-shaped fold that runs between the occipital lobe and the cerebellum

tentorial notch

space created by the tentorium cerebelli providing a space for the brainstem to pass

Falx cerebelli

small midline fold that runs in the space between the two cerebellar hemispheres

subarachnoid space

space under the arachnoid layer filled with cerebral fluid

falx cerebri

a crescent shape fold that descends vertically in the longitudinal fissure, separating the two hemispheres

meningiomas

are typically benign tumors arising from the dura mater

meningitis

is an infection and inflammation (swelling) of the two inner meningeal layers

what is the common cause of meningitis?

viral or bacterial infection

what are the major functions of the ventricular system

1. protects brain (shock absorber for brain)

2. provides buoyancy (reduces weight of brain from 1400gm to only 50gm)

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

label the diagram

left side top to bottom:

1. interventricular foraman

2. frontal horn of lateral ventricle

3. third ventricle

4. temporal horn of lateral ventricle

right side top to bottom:

1. occipital horn of lateral ventricle

2. fourth ventricle

3. cerebral aqueduct

what is the cauliflower-like fronds in the lateral and fourth ventricle that produce the CSF by filtering blood

choroid plexus

what is CTE?

chronic traumatic encephlopathy

cause and result of CTE

cause: smaller, repeated, subconcussive hits to the head causing a natural occurring protein known as tau to build up over time in certain patters

diagnosed: diagnosed post-mortem

result: clumps of tau strangle brain cells often causing affect to the dorsolateral frontal cortex, an area critical for cognition and executive function, working memory, planning and abstract reasoning.

how do you measure the amount of deformation of the brain when shaking your head/brain injury

MRI with grid overlap to measure deformation

what protects our brain and spinal cord?

Bone, Meninges, CSF

foramen magnum (area)

a large, oval-shaped opening in the occipital bone of the skull that the spinal cord passes through when exiting the cranial cavity.

explain how the meninges form on the spinal cord

dura is on the outside (not on the actual spine) then the arachnoid part is on the dorsal side (still not on the spine) and then the pia mater will grip on the spine

what happens to the meninges when forming the sinuses?

the dural matter is made up of two parts (the inner and outer layer) that are usually fused together, but when it needs to make the venous sinus, the inner layer creates a dural folding that creates deep fissures to house dural venous sinuses

what space is a frequent site of bleeding following trauma or during rupture of an aneurysm on a cerebral artery

subarachnoid space

where is CSF found?

subarachnoid space under normal conditons, but can be filtered into the venous sinus to remove it

meningiomas

are typically benign tumors arising from the dura mater

• Grows slowly, usually without symptoms for many years

• Symptoms due to compression of the brain and depend on

where tumor is located

meningitis

is an infection and inflammation (swelling) of the two inner meningeal layers (in between the arachnoid pia layers)

cause and result of meningitis

cause: viral or bacterial infection, non-infections conditions like cancer or head injuries

result: swelling in the two inner meningeal layers can interfere with blood flow, resulting in stroke, brain damage, or death

• infects the CSF

symptoms: cold symptoms + double vision, stiffness of neck, rash

major functions of the ventricular system

1. Protects brain – acts as a shock absorber for brain

2. Provides buoyancy – reduces weight of brain from 1400gm

to only 50gm

3. Provides a medium for the exchange of materials between blood vessels and brain tissue

what can enter the CSF and what does the CSF do?

Nutrients and hormones can enter the brain via ventricles. Likewise, excretion of waste can be carried in CFS and then removed by being reabsorbed into the blood stream

Septum pellucidum

(“translucent wall”): a very thin membrane separating the frontal

horns and body of the left and right ventricles

choroid plexus

is a modified vascular structure lining the ventricles that produces CSF by filtering blood

• found in the lateral and fourth ventricles

internal jugular vein

Drainage of venous blood is through sinuses that finally

supply the internal jugular vein and back to the heart

track the branching of the internal carotid artery into the brain

carotid → internal carotid → anterior cerebral and the middle cerebral arteries (supplies middle and dorsal margins of frontal lobe as well as the central and lateral cerebral hemishperes)

why is the circle of willis important

alternative route → if a main artery is damaged or blocked

→ Reduces damage!

Lenticulostriate arteries

• the deep-penetrating branches of the MCA that supplies most of the basal ganglia

• end arteries

• Small diameter and sharp right angles make them highly susceptible to rupture/occlusion

→ Leads to classic stroke symptoms

explain the path of the sinuses

superior sagittal (most) → inferior sagittal (on the bottom of the falx cerebri/ on top of the corpus collosum) → straight sinus → confluence and cavernous → left and right transverse → sigmoid → internal jugular venus

(just look at image tbh)

posterior spinal arteries

supply much of the dorsal horn and the dorsal columns (carries sensory information from the body

endothelial cells

form much tighter junctions than in the rest of the body in the BBB

ways to bypass the BBB

• Mimic chemical structure of something that cross naturally

  • ex. L-DOPA treatment lets dopamine in the brain by mimicking the amino structure of a specific transporter that is already being let into the cell natural

• Temporarily disrupt BBB to allow delivery of larger molecules (e.g., hyperosmotic agents, focused ultrasound)

  • risk of letting anything into the brain, weaking the endothelial cells, not specific weaking to the type of drug you wanna let in

• Intranasal administration to bypass BBB

  • go through olfactory or trigeminal nerves

• Use of nanoparticles to transport drugs

what is the tie between B-amyloid proteins, sleep and AD?

B-amyloid is found in the in fluids of glymphatic system because trying to remove toxic substances

B-amyloid proteins are harmful substances implicated in AD
therefore less sleep = more susceptible to AD