mod 2 - 15-17 cns, orbit ear

for the brain, superior is synonymous with

dorsal

for the brain, inferior is synonymous with

ventral

cephalic flexure

80 degree curve between forebrain and midbrain

neural tube

an embryonic fluid-filled tube that gives rise to the central nervous system

rostral end of neural tube

becomes the head

primary vesicles

3 bulges that form at the rostral end of the neural tube by the 4th week of embryonic development. Prosencephalon, Mesencephalon, & Rhombencephalon

Prosencephalon

The embryonic portion of the brain that becomes the forebrain.

Mesencephalon

The embryonic portion of the brain that becomes the midbrain. Doesn't undergo further subdivision. Becomes the tectum (with superior colliculi and inferior colliculi), cerebral peduncles, substantia nigra, red nucleus, & cerebral aqueduct. Contains CNs III & IV.

Rhombencephalon

the embryonic portion of the brain that becomes the hindbrain. Contains CNs V - XII.

secondary vesicles

futher subdivisions that occur in 2 of the 3 primary vesicles (the prosencephalon & the rhombencephalon) during the 5th week of embryonic development. telencephalon, diencephalon, metencephalon, myelencephalon

Telencephalon

subdivision of the prosencephalon that becomes the cerebral cortex, olfactory cortex, basal ganglia, hippocampus, lateral ventricles, & portions of third ventricle. Contains CN I.

Diencephalon

subdivision of the prosencephalon that becomes the thalamus, hypothalamus, epithalamus (w/pineal body), mammillary bodies, & portions of the third ventricle. Contains CN II.

Metencephalon

subdivision of the rhombencephalon that becomes the cerebellum & the pons (including its dorsal component the pontine tegmentum)

Myelencephalon

subdivision of the rhombencephalon that becomes the medulla oblongata

brainstem

a structural, NOT developmental, subdivision that refers collectively to non-cerebellar portions of the hindbrain (medulla & pons) together with the midbrain

frontal pole

Most anterior part of the frontal lobe. near midline.

temporal pole

Most anterior part of the temporal lobe. lateral from midline.

occipital pole

most posterior part of the occipital lobe. near midline.

central sulcus

Separates frontal lobe from parietal lobe. Runs uninterrupted from the dorsal surface of the cerebral hemisphere to the lateral sulcus.

lateral sulcus/fissure

Separates temporal lobe from parietal and frontal lobes. Very deep.

parieto-occipital sulcus

separates the parietal lobe from the occipital lobe

preoccipital notch

indentation that marks the start of the occipital lobe & end of the temporal lobe

frontal lobe boundaries

anterior to central sulcus, superior to lateral sulcus

parietal lobe boundaries

posterior to central sulcus, anterior to parieto-occipital sulcus, superior to lateral sulcus

occipital lobe boundaries

posterior to the parieto-occipital sulcus & preoccipital notch

temporal lobe boundaries

inferior to lateral sulcus, anterior to preoccipital notch

insula

deep lobe covered by operculums of 3 of the 4 other lobes

frontal operculum

The part of the frontal lobe that sits over the insula.

parietal operculum

Part of the parietal lobe that overlies the insula

Temporal operculum

part of the temporal lobe that sits over the insula.

limbic lobe

a not universally recognized "lobe" located in the center of the brain beneath the other lobes

falx cerebri

large, crescent-shaped fold of dura mater that descends vertically in the longitudinal fissure between the cerebral hemispheres

tentorium cerebelli

A fold of dura mater that separates the cerebrum from the cerebellum.

falx cerebelli

fold of dura mater that separates the left & right hemispheres of the cerebellum

the frontal lobe sits in the

anterior cranial fossa

the temporal lobe sits in the

middle cranial fossa

the cerebellum & brainstem sit in the

posterior cranial fossa

the brainstem runs through the

foramen magnum

brain ventricles

hollow, fluid-filled reservoirs of CSF in the brain that developed in the embryo as primary and secondary vesicles grew

lateral ventricles

A set of paired ventricles lying within the cerebral hemispheres. Originate in the telencephalon.

third ventricle

The midline ventricle that conducts cerebrospinal fluid from the lateral ventricles to the fourth ventricle. Originates in the diencephalon.

fourth ventricle

the ventricle located between the cerebellum and the pons that drains CSF to the central canal of the spinal cord. Originates in the metencephalon.

cerebral aqueduct

a narrow tube connecting the third and fourth ventricles of the brain

Septum pellucidum

thin membrane that separates lateral ventricles

central canal of spinal cord

center of spinal cord that contains cerebrospinal fluid, which is received from the 4th ventricle

Anterior (frontal) horn of lateral ventricle

Anterior-most part of a lateral ventricle that projects into the

frontal lobe

Inferior (temporal) horn of lateral ventricle

inferior-most part of a lateral ventricle that projects into the temporal lobe

Posterior (occipital) horn of lateral ventricle

posterior-most part of a lateral ventricle that projects into the occipital lobe

interventricular foramen

connects the anterior horn of each lateral ventricle with the third ventricle

choroid plexus

strands of highly convoluted and vascular membranous material in ventricles that serves as the primary site of CSF production

Cerebrospinal Fluid (CSF)

Clear, colorless fluid in the ventricles of the brain & in the subarachnoid space throughout the CNS. Functions:

- Cushions & protects the brain and spinal cord from trauma

- Provides mechanical buoyancy & support for the CNS

- Provides nutrients to, & removes waste products from, CNS

arachnoid granulations

large clusters of villi in the superior sagittal sinus that reabsorb CSF into venous circulation

total volume of CSF

150 ml (25ml within ventricles)

daily production of CSF

500 mL per day

spinal tap

draws CSF from subarachnoid space at L3/4 or L4/5

-can be fatal in patients with increased intracranial pressure, as the rapid equilibration of pressure will pull the brain into the spinal canal

cisternal tap

draws CSF from subarachnoid space at the cisterna magna or cerebellomedullary cistern, between C1 and the foramen magnum

-Done in cases where a spinal tap is contraindicated

Lateral aperture (foramen of Luschka)

2 paired holes in the roof of the fourth ventricle that allow CSF to enter subarachnoid space

median aperture (foramen of Magendie)

1 paired hole in the roof of the fourth ventricle that allow CSF to enter subarachnoid space

cerebellomedullary cistern

An enlargement of the subarachnoid space between the cerebellum and the medulla oblongata that receives CSF directly out of the median aperture

pathway of CSF circulation

choroid plexus -> lateral ventricles -> interventricular foramen -> 3rd ventricle -> cerebral aquaduct -> 4th ventricle -> lateral or median aperture -> subarachnoid space -> arachnoid granulations -> dural venous sinuses

Cerebral Arterial Circle of Willis

anastomoses between the internal carotid artery and vertebral artery on the basal aspect of the brain

vertebral arteries

branches of the subclavian artery that enter the cranial canal via the foramen magnum

basilar artery

Artery formed by the fusion of the 2 vertebral arteries that along the pons. Gives off superior & anterior inferior cerebellar arteries, before splitting into the posterior cerebral artery.

anterior inferior cerebellar artery

branch of basilar artery that supplies cerebellum and pons

superior cerebellar artery

branch of basilar artery that supplies cerebellum and midbrain

posterior cerebral artery

branch of basilar artery that supplies ventral surfaces of temporal & occipital lobes. Found on inferomedial aspect of temporal and occipital lobes.

internal carotid artery

branch of the common carotid artery that enters the cranial canal via the carotid canal. branches into anterior & middle cerebral arteries.

anterior cerebral artery

medial branch of internal carotid artery that supplies frontal & parietal lobes. runs along longitudinal fissure.

middle cerebral artery

lateral branch of internal carotid artery that supplies lateral aspects of the frontal, parietal, and temporal lobes.. Runs along lateral sulcus.

anterior communicating artery

Connection between left and right anterior cerebral arteries.

posterior communicating artery

Connection between posterior cerebral artery & internal carotid artery (and therefore between vertebral and internal carotid circulation)

most superficial cerebral veins drain into

superior sagittal sinus (via bridging veins)

Deep cerebral veins drain into

straight sinus (via great cerebral vein)

Most venous blood from brain ends up in

internal jugular vein

gray matter

collections of neuronal cell bodies (which are unmyelinated)

white matter

Collections of axons (which are myelinated)

cortex of brain

superficial layer of gray matter

basal ganglia of brain

deep layer of gray matter

types of white matter fiber tracts in the brain

Association Tracts, Projection Tracts, Commissural Tracts

association tracts

short white matter fiber tracts connecting different parts of same subdivision of the brain

projection tracts

white matter fiber tracts connecting different subdivisions of the brain, & the brain with the spinal cord

commissural tracts

white matter fiber tracts connecting left & right hemispheres

functions of the brainstem

1. Conduit for ascending (afferent) and descending

(efferent) fiber tracts

2. Acts as an integration center, exerting subconscious control over respiratory and cardiovascular activities, complex motor

patterns, & regulating levels of consciousness (largely via the reticular formation)

3. Site of exit/entry of most cranial nerves (all besides CN I &

CN II)

reticular formation

a nerve network in the brainstem that plays an important role in controlling levels of arousal

cranial nerves that enter/exit the telencephalon/forebrain

CN I

cranial nerves that enter/exit the diencephalon/forebrain

CN II

cranial nerves that enter/exit the mesencephalon/midbrain

CN III & CN IV

cranial nerves that enter/exit the rhombencephalon/hindbrain

CN V - CN XII

(although CN XI emanates from upper cervical segments of the spinal cord, rather than a cranial root)

divisions of the brainstem along an anteroposterior gradient

tectum, tegmentum, base

tectum

area of the brainstem posterior to the ventricular space. prominent only in the midbrain.

tegmentum

area of the brainstem anterior to the ventricular space. Contains the reticular formation, cranial nerve nuclei and tracts, ascending fiber tracts from the spinal cord, & some descending fiber tracts. Spans the whole brainstem.

base

area of the brainstem anterior to the tegmentum, consisting of structures containing only descending fiber tracts from the motor cortex (crura cerebri on anterior peduncle, basal pons on ventral pons, medullary pyramids on ventral medulla)

medulla oblongata

The most inferior part of the brainstem representing a transitional zone between more superior portions of the brainstem and the spinal cord.

-Contains both fiber tracts (white matter) & nuclei (gray matter), with the fiber tracts organized in the same pattern as the spinal cord (sensory tracts on dorsal side & motor tracts on ventral side)

Cuneate fasciculus

ascending fiber tract that carries sensory information from the upper body (T6 & above) to the cerebral cortex along the dorsal side of the medulla. lateral to gracile fasciculus.

Gracile fasciculus

ascending fiber tract that carries sensory information from the lower body (T7 & below) to the cerebral cortex along the dorsal side of the medulla. medial to cuneate fasciculus.

Pyramidal tracts

voluntary motor fiber tracts from the primary motor cortex that

descend toward the spinal cord immediately to the left and right sides of midline along the ventral side of the medulla. medial to olives.

Olives

nuclei with synapses for neurons connecting the cerebellum with the spinal cord along the ventral side of the medulla. Lateral to pyramidal tracts. Function with the cerebellum in motor coordination and learning.

cranial nerves arising from the medulla

CN IX Glossopharyngeal (dorsal aspect of olive), CN X Vagus (dorsal aspect of olive), & CN XII Hypoglossal (between olive and pyramid)

cerebellum

Largest part of the hindbrain accounting for 10% total brain volume but containing as many neurons as there are in all the rest of the CNS.

-Lies in the posterior cranial fossa posterior to the fourth ventricle, pons, & medulla oblongata

-Separated from overlying cerebral hemispheres by the tentorium cerebelli

vermis

Connects the right & left hemispheres of the cerebellum at the midline