Structures that Support Brain Function

Question 1

Optic Canal

Answer 1

-cranial nerve II (optic nerve) passes

Question 2

Optic Nerve

Answer 2

• CN II

- carries visual information from the retina of the eye back to the brain allowing for vision

Question 3

Superior Orbital Fissure

Answer 3

-CN III (occulomotor), IV (trochlear), IV (abducens), and V1 (branch of trigeminal) pass

Question 4

CN III, IV, VI

Answer 4

• control orbital muscles that move the eye

- constriction of the pupil

Question 5

CN V1

Answer 5

-transmits sensory information from the ipsilateral forehead and scalp to the brainstem

Question 6

Foramen Ovale

Answer 6

-third branch of the trigeminal nerve exits (mandibular)

Question 7

Foramen Spinosum

Answer 7

-entry into the skull of the middle meningeal artery

Question 8

Carotid Foramen

Answer 8

-internal carotid enters the calvaria passig through the bony canal

Question 9

Stylomastoid Foramen

Answer 9

-allows CN VII to enter (internal auditory canal/meatus) and exits the calvaria

Question 10

Jugular Foramen

Answer 10

-permits exit of cranial nerves IX (glossopharyngeal), X (vagus), and XI (accessory)

Question 11

Foramen Magnum

Answer 11

-spinal branches of cranial nerve XI enter calvaria here, join the cranial branches and exit via the jugular foramen

Question 12

Hypoglossal Canal

Answer 12

-lets CN XII (hypoglossal) exit the caldarium

Question 13

Meninges

Answer 13

• protective coverings of the brain
• protect brain from injury by providing mechanical support and to bath it in a fluid solution to buffer it against chemical & mechanical forces

Question 14

Layers of Meninges

Answer 14

-from brain outward they consist of a thin layer of cells tightly approximated to the brain surface called the pia mater, thicker layer called arachnoid mater, and thickest (double membrane) dura mater)

Question 15

Dura Mater

Answer 15

• layer closest to the brain (meningeal layer)
• outer layer just beneath periosteum called periosteal layer
• these 2 layers separate the midline at the lateral aspects of the brain to create large venous sinuses called the superior sagittal sinus and the lateral sinuses

Question 16

Falx Cerebri and Tentorium Cerebelli

Answer 16

-coming together in the midline and lateral aspects of teh brain, the meningeal layers create a thick membrane that separates the left and right cerebral hemispheres

Question 17

Tentorium Cerebelli

Answer 17

• suspends the cerebral hemispheres above the cerebellum

- separates the supratentorial compartment from the infratentoral compartment

Question 18

3 spaces associated with the meninges

Answer 18

-2 are potential spaces and do not exist
(epidural space and subdural space) - head trauma may cause bleding into the epidural space (arterial) called epidural hemorrhage or into the subdural space (venous) called subdural hemorrhage
-Subarachnoid space: true space that is lined by the arachnoid above and the pia mater below
-harbors the bulk of the cerebrospinal fluid that bathes the brain (lined by large blood vessels, arteries & veins positioned at the base of the brain & surrounding it)
-rupture of any of these vessels leads to subarachnoid hemorrhage with accumulation of blood in the subarachnoid space

Question 19

The dur mater forms the?

Answer 19

-epineurium

Question 20

The arachnoid forms the?

Answer 20

-perineurium

Question 21

Trivia Point

Answer 21

-dural membrane surrounding the spinal cord is comprised of only a single layer in contrast to the double layer covering the brain

Question 22

What 2 major pairs of arteries supply the brain?

Answer 22

• right & left internal carotid

- right & left vertebral

Question 23

Right & Left Common Carotid Arteries

Answer 23

-bifurcate in the neck just below the angle of the jaw into external and internal carotid arteries

Question 24

External Carotid Arteries

Answer 24

-supply the face, scalp, and meninges overlying the brain

Question 25

Internal Carotid Arteries

Answer 25

- ascend & travel through the carotid canal, enter the caldarium along side the carvernous sinus - make hairpin turn and continue on as the middle cerebral and anterior cerebral arteries - opthalmic arteries branch off near the apex (first branch)

Question 26

Right & Left Vertebral Arteries

Answer 26

- originate from subclavian arteries - enter vertebral foramen bilaterally at the C6 level and travel upward through these foramen, entering the calvaria through the foramen magnum - 2 vertebral arteries join at the junction of the medulla and pons to form the basilar artery (BA)

Question 27

Circle of Willis

Answer 27

- important structure in the cerebral circulation because it provides the potential for collateral blood flow if one or more of the four major arteries supplying the brain is obstructed or occluded - comprised of the posterior cerebral arteries connected to the internal carotid arteries via the posterior communicating arteries - anterior A1 segment of the anterior cerebral arteries & the anterior communicating artery complete the circle of willis

Question 28

Important Draining Veins of the Brain

Answer 28

- occlusion of any of the major venous sinuses may cause seizures, tissue injury, and blockage of CSF circulation - Cavernous sinus - Straight Sinus - Superior Sagittal Sinus - Transverse Sinus - Great Cerebral Vein - Inferior Sagittal Sinus - Straight Sinus

Question 29

Communication with lateral ventricles with the midline third ventricle through?

Answer 29

-interventricular foramen of Monro

Question 30

Communication b/w the 3rd and 4th ventricles via?

Answer 30

-cerebral aquaduct (aqueduct of Sylvius)

Question 31

How is CSF created?

Answer 31

-in the choroid plexus by specialized epithelial cells that line the lateral, third, & fourth ventricles

Question 32

CSF

Answer 32

- escapes the lateral ventricles into the 3rd ventricle via the foramen of Monro, CSF enters the 4th ventricle by the foramina of Magendie & Luscha - once out in the subarachnoid space some of the CSF circulates down around the spinal cord where approximately 10% is reabsorbed at the egress point of the nerve roots - bulk of CSF travels upward through the opening in the tentorium cerebelli & circulates over & around the brain - bulk (90%) of CSF is reabsorbed into the venous sinuses via the arachnoid granulations that are outpouchings of the arachnoid that protrude into the large venous sinuses

Question 33

How fast is CSF made?

Answer 33

-20 mL/hr

Question 34

Obstructive Hydrocephalus

Answer 34

-blockage of outflow of CSF from the ventricular system

Question 35

Arachnoid Villi

Answer 35

(granulations) - function as a one-way valve to allow CSF to flow out but not back into the ventricular system - obstruction of these one-way valves may cause a backup of CSF and create hydrocephalus

Question 36

Non-obstructive Hydrocephalus

Answer 36

-hydrocephalus caused by blockage of the arachnoid villi

Question 37

Blood Brain Barrier

Answer 37

- brain is highly sensitive to small changes in the ionic and organic chemical milieu - protects brain against fluctuations in blood chemistry & toxic substances or organisms that may circulate in blood - series of brain cells that act as a physical wall b/w the blood capillary lumen and the brain-"tight junctions" such that substances from the capillaries into the brain or ventricular CSF must pass through & not b/w cells lining the capillaries

Question 38

BBB is created by?

Answer 38

-tight junctions b/w capillary endothelial cells

Question 39

How is the choroid plexus created?

Answer 39

- by outpouching of capillaries and the pia mater into the ventricular space - it sandwiches capillary blood vessels b/w layers of the arachnoid membrane & pia mater

Question 40

Blood CSF Barrier

Answer 40

- tight junction, its purpose is to limit egress of potentially toxic substances circulating in the capillaries from egress into the CSF - large and small molecules must pass through and can't pass b/w the chorid epithelial cells to enter the ventricular CSF

Question 41

What substances can go through the BBB?

Answer 41

- water - CO2 - O2 - lipid soluble free forms of steroid hormones

Question 42

When can BBB break down?

Answer 42

- infection - inc. age - Alzheimer disease

Question 43

Drug Access to the CNS

Answer 43

-more lipid soluble a drug, the easier it gets into the CNS

Question 44

Lipid Soluble Drugs

Answer 44

-undergo rapid redistrubution from main site of action to non-acitve sites, making their clinical duration short but increasing the length of elimination from non-active stores, such as fat

Question 45

Polymorphisms in ABCB1 gene predict response to?

Answer 45

-antidepressants