Lecture 3 Flashcards
How much blood circulates to the head?
20-25% of cardiac output each stroke
What two substances does the brain rely on?
glucose and oxygen, only uses amino acids or fatty acids if absolutely necessary
What branch primarily supplies the anterior circulation of the brain?
internal carotid artery
Disease of which artery would be an indicator for disease in the brain?
opthalmic artery
Which artery supplies the lateral convexity of the brain?
middle cerebral artery
In the anterior circulation of the brain, the upper and inferior divisions of the middle cerebral artery supply what areas of the brain?
upper - frontal and parietal lobes; inferior - temporal lobe
Which arteries travel the length of the spinal cord?
anterior and posterior spinal arteries
Which arteries may or may not be present to complete the circle of Willis?
anterior or posteror communicating arteries, if not present you will be more prone to stroke
Which arteries supply irrigation to the pons?
pontine arteries
In the posterior circulation of the brain, which arteries anastomose to form the basilar artery?
vertebral arteries (come through foramen magnum)
The oculomotor nerve lies between which two arteries?
posterior cerebral and superior cerebellar arteries
What are the three meningeal layers covering the brain and spinal cord?
dura, arachnoid, pia
This sinus begins at the Crista Galli and runs to the Inion (external occipital protuberance) through the midline.
superior sagittal sinus
This major vein drains the inside of the brain.
great vein of Galen
This sinus runs in midline straight posteriorly to the Inion, converging with the superior sagittal sinus.
straight sinus
This sinus runs along the falx cerebri (a dural reflection), converges with straight sinus.
inferior sagittal sinus
These sinuses run laterally on both sides of the brain that run to the Inion.
transverse sinuses
What is the confluence of sinuses?
where the superior sagittal sinus, straight sinus, and transverse sinuses all join at the inion
What is the sigmoid sinus?
S-shaped curve the is continuous with internal jugular vein, here there is a change of tissue type: vein (endothelial cells line the inside of veins) and sinus system (fibroblasts)
Which sinus sits on either side of Sella Turcica?
cavernus sinus (facial–>opthalmic vein drain into)
The cavernus sinus provides a direct entry for infection to the brain. What structures could be affected?
oculomotor, trochlear, abducens, and V1 of trigeminal (ophthalmic) can all be directly affected
If the cavernus sinus were infected, what might be some clinical symptoms?
wouldn’t be able to track, affected eye would be dilated, and would have decreased sensation to the forehead
Approximately how much blood is in your brain at any given time?
750 mL….conversation starter
What four types of cells contribute to the BBB?
endothelial, pericytes, neurons, astrocytes
What is the method of transport for anything crossing the BBB?
active transport
These cells act as a physical barrier by surrounding endothelial cells in the BBB.
pericyte cells
The endothelial and pericyte cells are surrounded by what structure?
basal lamina, allow certain structures through and prevent others based on size
These cells surround and act as physical structure to hold the BBB in place (scaffolding).
astrocyte cells
Through this space, infection could spread to the brain (BBB not effective).
Virchow-Robin space (subarachnoid)
Non-Protected CNS Regions
pituitary gland, median eminence of hypothalamus, area postrema, pineal gland, choroidal endothelium
Area Postrema
controls vomiting reflex, no BBB, so any substance potentially toxic you will vomit
This creates the CSF.
choroid plexus (in lateral ventricles)
Normal Flow of CSF
lateral ventricles–>foramina of Monro–>third ventricle–>cerebral aquaduct–>fourth ventricle–>2 foramina of Luschka–>central canal of spinal cord and subarachnoid space
If CSF flows into the brain but it blocked from flowing out will result in what clinically?
hydrocephalus
Why is the potassium level in the CSF less than that of blood?
neurons will not be as excitable
What are the adaptations in CSF to make it less susceptible to bacteria?
more acidic, less glucose/protein/amino acids for energy
What is the significance of the lamina terminalis?
In development it is where the anterior neuropore of neural tube closes, If this doesn’t close during development the child will have anencephaly (no brain) because the brain will not develop
Functions of the BBB
protection from exogenous substance, conservation of endogenous neurotransmitters,
modulation (and/or facilitation) of metabolite fluxes, ionic homeostasis
Factors that control solute flux.
concentration gradient, capillary permeability, capillary surface area, capillary metabolism, response to chemical mediators
How can we administer drugs to bypass the BBB?
intrathecal administration (directly into CSF compartment), carotid artery infusion, specific enzyme inhibitors, enhanced capillary permeability, structural modification of molecules, ommaya reservoir (pumps directly into CSF compartment ventricles of the brain)
The middle cerebral artery runs through which sulcus?
lateral fissure (sulcus)
The primary motor cortex is associated with which gyrus?
precentral gyrus
The primary sensory cortex is associated with which gyrus?
postcentral gyrus
Broca’s area
primary speech
Wernicke’s area
language comprehension area
Learn all the sulcus and gyrus nomenclature.
have fun.
Which artery supplies the basal ganglia?
manticulo strait/choroidal arteries
The superior and inferior petrosal sinuses (from the cavernus sinus) merge with the sigmoid sinus and drain into which vein?
internal jugular
What is the most important determinant of solute flux in the brain?
concentration gradient, drug delivery requires a high concentration or link to a transport molecule for diffusion through BBB
In early development, this forms the lateral, 3rd, and 4th ventricles.
choroid plexus
From these 3 forramina the CSF goes into the subarachnoid space at level of foramen magnum.
foramen of Magendie and 2 foramina of Luschka
CSF returning to the brain will enter which sinus?
superior sagittal
This sulcus separates frontal and parietal lobes from temporal lobes, and looking into the sulcus the insula is visible.
lateral sulcus
This sulcus runs parallel to central sulcus and anterior to the precentral gyrus.
precentral sulcus
This sulcus runs parallel to central sulcus and posterior to the postcentral gyrus.
postcentral sulcus
Two areas of occipital lobe.
cuneus (superior) and lingual (inferior)
What is the significance of the sulcus limitans?
landmark for motor vs. sensory, below the groove is the hypothalamus (motor area), above is the thalamus (sensory relay station)
