Support Systems Flashcards
between the arachnoid and dura mater
Subdural space
- virtual space, not an actual space in healthy brains - can fill up with things like hematomas that make a space
between arachnoid and Pia mater; Space filled with CSF and blood vessels
subarachnoid space
between dura mater and skull
epidural space
- virtual space, not an actual space in healthy brains
what are the two layers of the dura mater?
- Periosteal layer- attaches to skill
2. meningeal layer - attaches to arachnoid
The two layers of dura matter are attached except at ________.
Dural venous sinuses
Projection of meningeal layer of dura matter that separates L and R cerebral hemisphere
Falx cerebri
Projection of meningeal layer of dura matter that separates cerebellum and posterior cerebellum
Tentorium cerebelli
What is the order of mater from superficial to deep
- Dura
- Arachnoid
- Pia
bars of tissue deep to arachnoid membrane
Trabeculae
Thin layer
Firmly attached to brain and spinal cord
Pia mater
Where are the lateral ventricles?
Telencephalon
Where is the 3rd ventricle?
Diencephalon
Where is the 4th ventricle?
Pons/medulla/ cerebellum
- opens to subarachnoid space
Where is the cerebral aqueduct?
Midbrain
What is CSF made by? how does it travel?
Choroid plexus
Made in lateral vent –> 3rd –> cerebral aqueduct –> 4th –> subarachnoid space (surrounds outside brain and spinal cord)
Where does CSF go after the subarachnoid space?
Arachnoid villi into dural venous sinuses and enters general circulation
How many seconds of O2 deprivation does it take to lose conscious ness? how long until electrical activity stops? low long until irreversible injury occurs?
10s
20s
few minutes
Arteries supply Superior spinal cord brainstem, cerebellum, posterior occipital and temporal lobes of the cerebrum; most of telencephalon and diencephalon
vertebral arteries
- travels along medulla, branches in medulla to supply the spinal cord (Post/ ant spinal arteries)
What are the branches of the vertebral arteries?
- Posterior spinal arteries – posterolateral cord; Posterior 1/3rd of cord
- Anterior spinal artery – just one; anterior median cord; Anterior 2/3rd of cord
- Posterior inferior cerebellar artery (PICA); Inferior cerebellum
Supplement vascular supply (not enough blood supply by A and P spinal arteries); Most are small, only a few are significant; Blockage can damage the spinal cord at that level, but also axons passing through that region
Radicular arteries
- enter the SC with the nerve roots
The 2 vertebral arteries join at the pons is called the ____. what are the branches of this artery? What do they supply?
Basilar
1. Anterior inferior cerebellar artery (AICA)
2. Superior cerebellar artery
Supply: pons and most of cerebellum
At the rostral pons the basilar artery forks to form the ______ arteries. What do they supply?
2 posterior cerebral; supply: 1. Midbrain 2. Occipital lobe 3. Medial and inferior temporal lobes
Around the optic chasm, the Internal carotid artery (ICA) splits into?
Anterior cerebral artery (ACA) - travels in longitudinal fissure
Middle cerebral artery (MCA) - passes through lateral sulcus
What is supplied by the ACA? by the MCA?
ACA = Primary motor and somatosensory cortex for LE MCA = Supplies most of lateral cerebral hemispheres
What does the circle of Willis connect (3 communicating arteries)?
Anterior communicating artery - L and R anterior cerebral artery
Posterior communicating arteries - PCA and ICA on each side
Regions where small anastomoses link the ends of the cerebral arteries; regions are relatively spared with strokes; when blood supply in two adjacent arteries is affected, these regions are most affected
Watershed regions
Where are common sites for aneurysms?
circle of willis (branches points are weak)
Why isn’t there a lot of blood flow in the circle of willis? What’s the point of the circle of willis if it doesn’t allow a lot of blood flow?
- blood vessels are small; similar pressure on each end of the artery
- arteries can expand to adapt to slowly developing occlusions in one of the MCA (long term adaptation)
What events can affect blood flow in two (or more) adjacent arteries, affecting watershed regions?
- Severe drop in systolic blood pressure
2. Blockage or restriction in internal carotid artery (Supplies both ACA and MCA)
Where are impairments when there is damage to watershed regions?
- For ACA and MCA - Often includes the trunk and proximal limbs (Man in a barrel syndrome); Transcortical aphasia syndromes
- Between MCA and PCA -Difficulties in higher order visual processing
Supplies choroid plexus in lateral ventricles; Parts of optic tract, putamen, thalamus, internal capsule and hippocampus
Anterior choroidal artery
Supplies choroid plexus in third ventricle; Parts of hippocampus and thalamus
Posterior choroidal artery
What are the deep cerebral blood supply structures?
- Branches of cerebral arteries
- Anterior choroidal artery
- Posterior choroidal artery
What are the unique features of veins of the brain?
- Not paired with arteries
- Valvless - can carry infections into brain
- frequent anastomoses
- Superficial and deep veins
Superficial veins are on the surface of cerebral hemispheres. Bridging veins that connect to dural sinuses can be damaged with shearing forces. What is the result?
blood moving into subdural space (subdural hematoma)
Where do most superficial veins drain into?
Superior sagittal sinus
- Some connect to other sinuses located between the two layers of the dura
Where are the deep veins?
Drain deeper regions of telencephalon and diencephalon
What causes blood vessels to dilate?
- Low BP, Oxygen or pH
- High CO2 or lactate
What causes blood vessels to constrict?
- High pH, Oxygen or BP
- Low CO2 or lactate
Autoregulation important to ensure adequate blood flow and prevent ____.
edema
The amount of blood flow to the brain depends on how much activity is going on in that area. The brain requires glucose and oxygen but can’t store either. Is the CC or brainstem more sensitive to hypoxia?
CC
- results in persistent vegetative state
