Exam 1 lecture 6 Flashcards
(16 cards)
1-arterial supply of brain
2-internal carotid artery
3-vertebral artery
4-course of internal carotid artery
1-derived from 2 pairs of vessels: internal carotid artery & vertebral artery
2-anterior circulation & supply 80% of blood to brain
3-posterior circulation & supply 20% of blood to brain
4-courses through the petrous portion of the temporal bone & through cavernous sinus, giving off hypophysical branches
Internal Carotid Branches
1-opthalmic artery
2-anterior choroidal artery
3-posterior communicating artery
1-given off once ICA enters subarachnoid space
—supplies eyeball & other contents of orbit
2-goes caudally & laterally to supply: optic tract, choroid plexus of inferiour horn of lateral ventricle, ventromedial portion of temporal, globus pallidus, & thalamus, & ventral portion of internal capsule
3-goes posterior & inferior to optic tract to anastomose w/ posterior cerebral artery…branching pt of posterior communicating artery= common site for aneurysms
1-Main Bifurcation of ICA
2-Anterior Cerebral Artery
a-anterior communicating artery
b-medial striate artery
1-anterior cerebral & middle cerebral artery
2-smaller of the 2 terminal branches—goes medial from point of origin to go superor to optic nerve
-goes into longitudinal fissue to supply the superior surface of the corpus callosum (anterior 4/5) &&& anterior 3/4 of medial surface of cerebral hemisphere (medial/orbital of front, medial of parietal & dorsomedial of primary motor/sensory cortices)
a-joins l & r anterior cerebral at midline
b-given off by prximal part of anterior cerbral artery—supplies anteromedial of basal ganglia & internal capsule
Middle Cerebral Artery
a-lateral striate (lenticulostriate) artery
- larger of 2 term branches—direct continuation of ICA
- goes laterally to enter lateral fissure of sylvius
- distal branches of MCA emerge from lateral fissure in a fan like fashion
supplies: most of lateral surface of cerebral hemisphere (frontal, parietal, temporal, & occipital)
& function areas: primary motor, somatosensory, premotor cortex, frontal eye, primary auditory, broca & wernickes speech, parietal association, & optic radiation
a-supplies: deep parts of diencephalon & telencephalon
parts of striatum
anterior & posterior limbs of internal capsule
—damage= neurological deficits
Vertebral Artery
- provides posterior circulation & supplies 20% of blood to brain
- comes from subclavian artery & goes through transverse foramina of vertebral column
- enters posterior cranial fossa through foramen magnum & runs on ventrolateral surface of medulla & unites w/ counterpart of opposite side at caudal border of pons to form basilar artery
Vertebral Artery Branches
1-posterior inferior cerebellar artery (PICA)
2-posterior spinal artery
3-anterior spinal artery
1-largest branch of vertebral
supplies: posterior & inferior aspects of cerebellum, choroid plexus of 4th ventricle, & dorsolateral medulla
2-runs on dorsolateral surface of spinal cord as plexiform network of small arteries
supplies: dorsal horns & dorsal funiculi (dorsal columns)
3-formed by joining of small contributions from each vertebral artery, just before vertebral arteries fuse to make basilar artery—runs in anterior median fissure
supplies: anterior 2/3 of spinal cord
Basilar Artery Branches
1-anterior inferior cerebellar artery (AICA)
2-Labyrinthine (internal acoustic)
3-Pontine Arteries
4-superior Cerebellar Artery (SCA)
5-Posterior Cerebral Artery (PCA)
6-Calcarine Artery
1-rostral to formation of basilar artery
Supplies: lateral caudal pons &&& anterior/inferior aspects of cerebellum, including flocculus & middle cerebellar peduncle
2-branch of AICA, goes through internal acoustic meatus
Supplies: Middle ear, occlusion= vertigo & ipsilateral deafness
3-small branches of basilar artery
some penetrate pons as paramedian branches= short circumferential branches & long circumferential branches
4-right before bifurcation into the posterior cerebral arteries
Supplies: Lateral rostral pons & caudal midbrain
superior aspect of cerebellum: vermis, deep cerebella nuclei & cerebellar white matter
5-terminal branch of basilar artery, goes laterally around midbrain
Supplies: rostral midbrain, caudal diencephalon, & medial/inferior surfaces of temporal & occipital lobes
6-branch of PCA
supplies: primary visual cortex &&& occlusion of vessul= homonymous hemianopsia w/ macular sparing
1-Circle of Willis
Blood Supply to Spinal Cord
2-anterior spinal artery
3-posterior spinal artery
1-arterial polygon at base of brain
- formed by anterior & poster comm arteries & proximal portions of anterior, middle & posterior cerebral
- encircles optic chiasm & mammillary bodies
- parts of diencephalon, basal ganglia & internal capsule are supplied by vessels that make up Willis
- no blood flow around the circle bc of pressure
- if major vessel is near circle and becomes occluded, neuro damage can be prevented bc of anastomotic flow
2-single artery located in ventromedian fissure
-supplies anterior (ventral) 2/3 of spinal cord
3-located medial to dorsal root entry zone
-supply posterior (dorsal) 1/3 of spinal cord
Blood Supply to Brainstem
1-to medulla
2-caudal medulla
3-Rostral Medulla
1-depends on primarily the vertebral-basilar system for its blood supply
- caudal medulla resembles spinal cord w/ blood
- rostral medulla= varying blood
2-ventral & lateral areas of caudal medulla supplied by branches of anterior spinal artery (ASA) & vertebral artery (VA)
-dorsal areas of caudal medulla supplied by branches of posterior spinal arteries (PSA) & Posterior inferior cerebellar artery (PICA)
3-ventral & medial areas supplied by branches of anterior spinal artery & vertebral artery
-lateral & dorsal areas by PICA, PSA, & VA
Blood Supply to Brainstem
1-to pons
2-to midbrain
3-watershed zones
1-by branches of basilar artery (BA)
-dorsal & lateral pontine tegmentum, middle & superior cerebellar peduncles supplied by anterior inferior cerebellar artery (AICA) & superior cerebellar artery (SCA)
2-from posterior cerebreal artery (PCA)
- caudal midbrain —superior cerebellar artery SCA & BA
- crus cerebri—Posterior communiating artery (PCoA) & anterior choroidal artery (ANTChA)
3-areas of brain located between terminal distributions of adjacent arteries
- under norm conditions, supplied by end arteries= under low arterial pressure
- if cerebral perfusion drops (Dec BP), blood flow to watershed zone= diminished
1-blood brain barier
2-anatomic basis
3-movement through endothelial cells
1-CNS capillaries are specialized to preventm ovement of chemical substances between blood & CNS
=optimal microenvironment for neurons & glial cells
2-adjacent endothelial cells are joined by tight junctions = high electrical resistance
- lack fenestrations & pinocytotic vesicles
- macromolecules cant move from blood to brain by intra or transcellular movement
3-selective—lipid soluble substances diffuse across, glucose crosses by facilitated diffusion, &&& AA cross by carrier mediated transport
1-circumventricular organs (CVOs)
- certain brain regions that dont have BBB
- highly vascular & fenestrated capillaries…CNS response to blood borne macromolecules (direct secretion)
- Neurohypophysis—posterior pituitary- releases ocytocin & vasopressin into capillaries
- Area Postrema- monitors blood for toxins & triggers vomiting
- Pineal Gland-secretes melatonin, circadian rhythm & sleep
CSF
1-choroid plexus
2-hisotology
3-Blood-CSF barrier
4-CSF Formation
1-rich capillary network w/ ependymal & pial cells
-produces & secretes CSF into ventricles
2-formed by collection of pial capillaries invaginates into ventricle, pushing thin covering of pial & ependymal cells in from= macro folds (villi), ependymal w/in villi become choroid plexus which will secrete CSF
ONLY CHOROID PLEXUS MAKES CSF
3-apical regions of adjacent choroid epithelial cells are connected by continuous tight junctions…anatomic & physiological barrier to seal off extracellular space of villi from ventricular lumen
4-choroid plexus makes 75% of all CSF, while 25% derived via diffusion from CNS interstitial fluid or BV in subarachnoid space
CSF produced at rate of 500-700 mL/day
-total volume of CSF replaced 3-4 times a daye
-avg human body has 140 mL CSF, occupies the subarachnoid space
1-CSF Comp
2-hydrocephalus
1-clear & colorless—mostly water
- acellular
- isotonic w/ plasma
- minimal protein
- low glucose conc
- higher Na, Cl, & Mg
- lower K & Ca
2-dilation of ventricles inc CSF volume bc of overproduction of CSF, blockage of CSF through system, or deficiency in CSF reabsorption
CSF formation occurs relatively independently of pressure w/in ventricles & subarachnoid space
-elevation of intracranial pressure= reduce arterial blood supply to brain & lead to irreversible CNS injury if untreated
CT & MRI=best diagnostic for hydrocephalus
CSF Circulation
- energy needed to move fluid w/in ventricular system is derived from arterial pulsations of choroid plexus & movement of cilia from apical surface of choroidal epithelium
- CSF in lateral ventricle:
- –lateral ventricles–>foramina of monro–>3rd ventricle–>cerebral aqueduct–>4th vent—>exits ventricular via foramina of luschka & magendie–>into subarachnoid space–>goes rostrally & caudally
- –CSF returned to venous via arachnoid granulations (tufted projections through dura mater into lumen of superior sagittal sinus)
- arachnoid granulations=passive, pressure dependent, 1 way flow valves
- hydrostatic pressure of CSF+greater than venous pressure in dural sinuses…1 way of CSF=bulk flow bc all constitutents of CSF leave w/ fluid
CSF functions
1-Buoyancy effect= fluid is incompressible
- –prevents weight of brain from compressing nerve roots and BV against internal surface of skull
- –cushions from trauma by reducing momentum and minimizing shearing & tearing w/ reduction in damage
2-intracranial volume adjustment & stabilization of intracranial pressure
—CSF vol change in response to intracranial BV change
3-micronutrient transport—essential substantial, transported by choroid plecus to CSF then across walls to brain cells
4-buffers sudden changes in brain fluid solute conc
5-choroid pleux synthesizes & secretes into CSF substanced needed for brain cell growth & development
6-excretion of metabolites & toxins from CSF to blood…man are reabsorbed by choroid plex into blood or cleared by bulk flow of CSF via arachnoid granulations
7-drug delivery—drugs dont pass through BBB, may be administered intraventricularly or intrathecally infused into subarachnoid fluid
