final exam Flashcards
What percent of neural tissue does the brain have?
97%
Be familiar with how the brain develops
This lateral view of the brain of an embryo after 4 weeks of development shows the neural tube, the hollow cylinder that is the beginning of the central nervous system. The internal passageway is called the neurocoel. In the cephalic portion of the neural tube, three areas enlarge rapidly through expansion of the internal cavity. This enlargement creates three prominent divisions called primary brain vesicles. The primary brain vesicles are named for their relative positions.
By week 5 of development, the primary brain vesicles have changed position and the prosencephalon and rhombencephalon have subdivided, forming secondary brain vesicles.
As development continues, the cerebrum enlarges to the point where it covers other portions of the brain
mesencephalon
or “midbrain,” is an expansion caudal to the prosencephalon.
prosencephalon
or “forebrain,” is at the tip of the neural tube.
rhombencephalon
or “hindbrain,” is the most caudal of the primary brain vesicles; it is continuous with the spinal cord
diencephalon
becomes the major relay and processing center for information headed to and from the cerebrum
telencephalon
begins to expand rapidly, eventually becoming the cerebrum, the largest part of the adult brain.
metencephalon
is adjacent to the mesencephalon. The region will form the cerebellum and the pons of the adult brain.
myelencephalon
will become the medulla oblongata
cerebrum
is divided into a pair of large cerebral hemispheres. the surfaces of the cerebral hemispheres are highly folded and covered by a superficial layer of gray matter called the cerebral cortex. Functions include conscious thought, memory storage and processing, sensory processing, and the regulation of skeletal muscle contractions.
Fissures (cerebrum)
deep grooves that subdivide the cerebral hemisphere.
Gyri (cerebrum)
folds in the cerebral cortex that increase its surface area
Sulci (cerebrum)
shallow depressions in the cerebral cortex that separate adjacent gyri
diencephalon
the structural and functional link between the cerebral hemispheres and the rest of the CNS
thalamus (diencephalon)
contains relay and processing centers for sensory information.
hypothalamus (diencephalon)
or floor of the dicencephalon, contains centers involved with emotions, autonomic function, and hormone production.
Brain stem
includes the midbrain, pons, and medulla oblongata
midbrain (brain stem)
contains nuclei that process visual and auditory information and control reflexes triggered by these stimuli. It also contains centers that help maintain consciousness
pons (brain stem)
connects the cerebellum to the brain stem. In addition to tracts and relay centers, the pons also contains nuclei that function in somatic and visceral motor control.
medulla oblongata
relays sensory information to other portions of the brain stem and to the thalamus. The medulla oblongata also contains major centers that regulate autonomic function, such as heart rate and blood pressure.
Ventricles
During development, the neurocoel within the cerebral hemispheres, diencephalon, metencephalon, and medulla oblongata expands to form chambers called ventricles
The ventricles are filled with CSF and lined by ependymal cells.
Ventricles of the brain (lateral ventricle)
Each cerebral hemisphere contains a lateral ventricle
Ventricles of the brain (interventricular foramen)
Each lateral ventricle communicates with the third ventricle through an interventricular foramen
Ventricles of the brain (third ventricle)
The third ventricle is located in the diencephalon
Ventricles of the brain (aqueduct of the midbrain)
the aqueduct of the midbrain is a slender canal within the midbrain that connects the third ventricle to the fourth ventricle.
Ventricles of the brain (fourth ventricle)
The fourth ventricle begins in the metencephalon and extends into the superior portion of the medulla oblongata. It then narrows and becomes the central canal of the spinal cord
How many ventricles are there in the brain?
4
corpus callosum
a thick tract of white matter that interconnects the two cerebral hemispheres
septum pellucidum
a partition that separates the two lateral ventricles.
cranial meninges
The delicate tissues of the brain are protected by mechanical forces with the help of these
[1] Dura Mater (cranial meninges)
The cranial dura mater consists of outer and inner fibrous layers. The outer layer is fused to the periosteum of the cranial bones. As a result there is no epidural space. The outer (endosteal) and inner (meningeal) layers of the cranial dura mater are typically separated by a slender gap that contains tissue fluids and blood vessels, including several large dural sinuses, which collect blood from the veins of the brain.
Dural mater (endosteal layer) Dural sinus Dural mater (meningeal layer)
[2] Arachnoid mater (cranial meninges)
The cranial arachnoid mater consists of the arachnoid membrane and the arachnoid trabeculae (which connect to the pia mater). The arachnoid membrane provides a smooth covering that does not follow the brain’s underlying folds. The subarachnoid space lies between the arachnoid membrane and the pia mater.
Arachnoid membrane
Subarachnoid space
Arachnoid trabeculae
[3] Pia mater (cranial meninges)
Astrocyte processes bind the pia mater to the surface of the brain. The pia mater sticks to the surface of the brain. It extends into every fold and accompanies the branches of cerebral blood vessels as they penetrate the surface of the brain to reach internal structures.
dural folds
sheets that dip inward and then return. These provide additional stabilization and support to the brain
Dural sinuses
large collecting veins located within the dural folds (there are 3 large dural folds)
falx cerebri
a fold of dura mater that projects between the cerebral hemispheres. Its inferior portions attach anteriorly to the crista galli and posteriorly to the internal occipital crest of the occipital bone. The superior and inferior sagittal sinuses lie within this dural fold.
superior sagittal sinus
the largest dural sinus
tentorium cerebelli
separates the cerebral hemispheres from the cerebellum.
falx cerebelli
separates the two cerebellar hemispheres along the midsagittal line inferior to the tentorium cerebelli
cerebrospinal fluid (CSF)
completely surrounds and bathes the exposed surfaces of the CNS.
The CSF circulates from the choroid plexuses through the ventricles and fills the central canal of the spinal cord. As it circulates, materials diffuse between the CSF and the interstitial fluid of the CNS across the ependymal cells.
Choroid plexuses
Each of the ventricles contains an area of choroid plexus, which consists of a combination of specialized ependymal cells and capillaries involved in the production of and maintenance of CSF.