The Nervous System-The Brain
Identify the specific dural sinuses found in each dural meninges. What are their functions, where do they drain their content?
-Superior sagittal sinus -inferior sagittal sinu -transverse sinus -occipital sinus They drain CSF back into venous circulation
Name the six regions of the brain.
-cerebrum -diencephalon (thalamus and hypothalamus) -mesencephalon -pons -medulla oblongata -cerebellum
What are the six division of the adult brain? Name the function of each region and the cranial nerve associated with each region (as outlined in class).
1. cerebrum: frontal (primary motor cortex, control of skeletal muscle), parietal (primary sensory cortex, perception of senses), occipital (visual cortex, perception of vision), temporal (auditory/olfactory cortex, perception of auditory and olfactory), CN I (olfactory bulb and tract) 2. diencephalon: thalamus (integration center for sensory and motor info, emotions, audio, visual. CN II, optic chiasm near hypothalamus) and hypothalamus (controls autonomic nervous system like thirst, hunger, sexual desire, emotions, regulates pituitary gland) 3. mesencephalon integrate visual and auditory info, involutary muscle tone, (CN III, IV) 4. pons: modify respiratory output from medulla oblongata (CN V, VI, VII, VIII, border with medulla oblongata) 5. cerebellum subconscious coordination of body movements 6. medulla oblongata: reflex center of brain (cardiac, vasomotor, respiratory), (CN VIII, IX, X, XI, XII)
Name the four general tracts/fasciculi of the brain and their purpose.
1. longitudinal (lengthwise) go from lobe to lobe in same hemisphere 2. arcuate fibers connects gyri to gyri 3. commissural fibers: hemisphere to hemisphere (corpus callosum) 4. projection fibers: brain stem to cerebrum
Identify the 12 cranial nerves. a. How are they numbered? b. Identify their general function as sensory, motor, or both. c. Identify where they originate from the brain
1. olfactory nerve (NI) sensory, cerebrum 2. optic nerve (NII) sensory, diencephalon 3. Oculomotor nerve (NIII) motor, mesencephalon 4. Trochlear nerve (NIV) motor, mesencephalon 5. Trigeminal Nerve (NV) sensory and motor, pons 6. Abducens Nerve (NVI) motor, pons 7. Facial Nerve (NVII) sensory and motor, pons 8. Vestibulocochlear nerve (NVIII) sensory, medulla oblongata 9. glossopharyngeal nerve (NIX) sensory and motor, oblongata 10. Vagus Nerve (NX) sensory and motor, oblongata 11. Accessory nerve (NXI) motor, oblongata 12. Hypoglossal nerve (NXII) motor , oblongata
How many lobes of the brain? How many cerebrum?
4 lobes in the brain and two hemispheres of cerebrum. Frontal, parietal, temporal, occipital.
What is cerebrospinal fluid (CSF); what is its function and where is it produced?
A filtrate of blood. Nourishes the brain, is found in the ventricles and produced in the choroid plexus.
Define the choroid plexus
An extension of the ventricles that are found in all four but originate in the third and fourth ventricle and then extend into other ventricles. They produce cerebrospinal fluid. Made of choroid plexus endothelial cells. The ependymal cells becomes (are continuous with ) the choroid plexus.
Identify which primary and secondary vesicles develop into the adult regions of the brain.
At birth the telencephalon becomes the cerebrum, the diencephalon stays the diencephalon, the mesencephalon also stays the mesencephalon, the metencephalon becomes the pons and cerebellum, and the myencelphalon becomes the medulla oblongata.
Name the primary brain vesicles and when they appear
At week three, a tube with three primary vesicles has formed. The most superior vesicle is called the prosencephalon, then the mesencephalon, then the rhombencephalon.
Why do we need CSF?
Because too many molecules in blood that could inadvertedly excite nervous tissue.
Describe the 4 different mechanisms to protect and support the brain (cranium, cranial meninges, cerebrospinal fluid and its circulation, blood-brain barrier).
Blood brain barrier made up of astrocytes bound to the capillaries and plugs the holes to block chemicals from entering the cell. This is found everywhere except choracoid plexus, pituitary and pineal glands. Cranial meninges create the space for cerebrospinal fluid and suspend brain in skull to prevent distortion and damage. Cerebrospinal fluid nourishes and cushions the brain. Blood brain barrier prevents exposure of neural tissue to excitatory moleculues.
Name the secondary brain vesicles and when they appear
By week six, the prosencephalon has divided into two secondary vesicles called the telencephalon and diencephalon. The rhombencephalon also divides into two secondary vesicles called the metencephalon and the myelencephalon.
What is the function of arachnoid trabeculae?
Collagen extensions that connect arachnoid mater to pia mater. This creates a framework for subarachnoid space.
Name the functions of the cranial meninges.
Connective tissue membranes that create the space for cerebrospinal fluid and suspend brain in skull.
What is functions of the ventricles?
Contain cerebrospinal fluid and create it.
What is the purpose of the subarachnoid space? What are arachnoid granulations and what is their purpose?
Creates space for cerebrospinal fluid. Arachnoid granulations are fingerlike projection of arachnoid mater that penetrate the dura mater and project into venous sinuses. Here, CSF flows past arachnoid trabeculae, crosses arachnoid mater via diffusion, and enters the venous circulation.
Describe the development of the adult brain. Start at the primary brain vesicles and end at the adult brain. Include the timing during development, name of each vesicle formed during development and what they ultimately become in the adult brain.
Differentiates from ectoderm. At week three, a tube with three primary vesicles has formed. The most superior vesicle is called the prosencephalon, then the mesencephalon, then the rhombencephalon. By week six, the prosencephalon has divided into two secondary vesicles called the telencephalon and diencephalon. The rhombencephalon also divides into two secondary vesicles called the metencephalon and the myelencephalon. At birth the telencephalon becomes the cerebrum, the diencephalon stays the diencephalon, the mesencephalon also stays the mesencephalon, the metencephalon becomes the pons and cerebellum, and the myencelphalon becomes the medulla oblongata.
Name the three cranial meninges
Dura mater Arachnoid Pia matter
Compare and contrast the 3 cranial meninges and explain what happens to the dura mater in the transverse and longitudinal fissures. List the specialized membranes (falx cerebri, tentorium cerebelli, falx cerebelli, diaphragm sellae).
Dura mater Arachnoid Pia matter. Connective tissue membranes that create the space for cerebrospinal fluid and suspend brain in skull. The folds limit movement of brain. -falx cerebri: projects between the cerebral hemispheres in the longitudinal fissure, connecting to the the crista galli and external occipital crest. Has the superior sagittal sinus and inferior sagittal sinus -tentorium cerebelli is at transverse fissure, supports and protects the two occipital lobes of the cerebrum, also separates the cerebellar hemispheres from those of the cerebrum, has the transverese sinus -falx cerebelli at vermis, extens the midsagittal line inferior to the tentorium cerebelli, dividing cerebellar hemispheres, posterior region has the occipital sinus -diaphragma sellae is at sphenoid bone sella turcica, anchors the dura mater to the sphenoid and ensheaths the base of the pituitary gland
What are ventricles?
Empty spaces in the brain that contain cerebrospinal fluid.
Name the two layers of the dura mater. a. How do they differ from each other? b. What is found between these layers?
Endosteal and meningeal layer. Endosteal is fused to the periosteum lining the cranial bones. Often separated by slender gap containing interstitial fluid and blood vessels, including the dural sinuses which drain CSF into blood.
What cells line the ventricles?
Ependymal cells. These monitor the cerebrospinal fluid.
How many ventricles are found in the brain? How many in the cerebrum? How many in the midbrain and brain stem?
Four ventricles. Two lateral, third, and fourth ventricle. Each cerebrum gets a lateral ventricle. The midbrain has the third and the brain stem has the fourth ventricle that covers the pons, medulla and cerebellum. They are all connected. The lateral connects to the third via the interventricular foramen, the third connects to the fourth via the cerebral aquaduct (aquaduct of midbrain) and the fourth divides between two lateral aperatures, a medial aperature, and the central canal of the spinal chord.
How many ventricles are in the brain? What are their names, and where are they located?
Four ventricles. Two lateral, third, and fourth ventricle. Each cerebrum gets a lateral ventricle. The midbrain has the third and the brain stem has the fourth ventricle that covers the pons, medulla and cerebellum. They are all connected. The lateral connects to the third via the interventricular foramen, the third connects to the fourth via the cerebral aquaduct (aquaduct of midbrain) and the fourth divides between two lateral aperatures, a medial aperature, and the central canal of the spinal chord.
Describe the circulation of cerebrospinal fluid around the brain and spinal cord and through the ventricles.
From the choracoid plexus to lateral ventricle to the third ventricle. In the third ventricle theres another choracoid plexus that creates more CSF/ This flows to the fourth ventricle via cerebral aquaduct. The fourth also has a choracoid plexus that creates more CSF. This flows through the central canal of the spinal chord, It also flows through the medial and lateral aperatures that takes it to the subarachnoid space which surrounds the outside of the brain. From there goes to the dural sinus which puts CSF back into blood stream. This allows removal of waste. This creates buoyancy.
Outline the flow of CSF through and out of the ventricles.
From the choroid plexus to lateral ventricle to the third ventricle. In the third ventricle theres another choracoid plexus that creates more CSF/ This flows to the fourth ventricle via cerebral aquaduct. The fourth also has a choroid plexus that creates more CSF. This flows through the central canal of the spinal chord, It also flows through the medial and lateral aperatures that takes it to the subarachnoid space which surrounds the outside of the brain. From there goes to the dural sinus which puts CSF back into blood stream. This allows removal of waste.
What is the difference between gyri, sulci and fissures?
Gyri are elevated regions, shallow depressions are sulci and deep depressions are fissures. The grooves increase surface area.
Discuss of specialization of endothelial cells that form the choroid plexus verses the Ependymal cells that line the brain ventricles. What structural changes occur in these cells that allow for the formation and movement of CSF? Why are these changes important and necessary? How does the presence of blood brain barrier allow for the need for these structural changes?
Instead of astrocytes, endothelial cells have tight junctions that allow them to filter the blood and create cerebrospinal fluid. These cells are more porous.
What are the major functions of cerebrospinal fluid?
Nutrients, and gives buoyancy to the brain.
Name the two primary division of the diencephalon
Thalamus and hypothalamus.
Describe the porous nature of capillaries around the choroid plexus. Describe the porous nature of capillaries in other parts of the brain. What allows for these changes in capillaries to occur without compromising the brain?
The choroid plexus does not have astrocytes to block the capillaries. They have tight junctions. They then filter the blood to create the cerebrospinal fluid. The CSF can flow freely because it doesn't require further filtration, thus the ependymal cells do not require tight junctions. Thus there is passive diffusion across the ependymal cells.
Identify the connection tubes between each ventricle.
The lateral connects to the third via the interventricular foramen, the third connects to the fourth via the cerebral aquaduct (aquaduct of midbrain) and the fourth divides between two lateral aperatures, a medial aperature, and the central canal of the spinal chord.
Identify the lobes each sulcus/fissure separates: Central, Lateral, Longitudinal
The longitudinal fissure separates the cerebral hemispheres of the cerebrum. The central sulcus separates the frontal lobe from parietal. The lateral sulcus separates the temporal from the parietal.
List the 5 encephalons from rostral (superior, anterior end) to caudal (interior, posterior end): telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon. List the brain structures located within each encephalon and explain their function.
The telencephalon becomes the cerebrum, the diencephalon stays the diencephalon, the mesencephalon also stays the mesencephalon, the metencephalon becomes the pons and cerebellum, and the myencelphalon becomes the medulla oblongata.
Name the four meningeal folds and the major dural sinus that travels through them. What is the purpose of the dural sinuses?
These limit movement of brain. -falx cerebri: projects between the cerebral hemispheres in the longitudinal fissure, connecting to the the crista galli and external occipital crest. Has the superior sagittal sinus and inferior sagittal sinus -tentorium cerebelli is at transverse fissure, supports and protects the two occipital lobes of the cerebrum, also separates the cerebellar hemispheres from those of the cerebrum, has the transverese sinus -falx cerebelli at vermis, extens the midsagittal line inferior to the tentorium cerebelli, dividing cerebellar hemispheres, posterior region has the occipital sinus -diaphragma sellae is at sphenoid bone sella turcica, anchors the dura mater to the sphenoid and ensheaths the base of the pituitary gland
Define was white matter is in the brain.
tracts and columns, collections of axons in CNS
