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CNS -PCC
First lecture exam
| Question | Answer |
|---|---|
| What makes up the CNS? | 1. Brain = Encephalon 2. Spinal Cord |
| What makes up the PNS? | 12 Cranial Nerve Pairs, 32 Spinal Nerve Pairs, Ganglia |
| What are the somatic components of the nervous system? | the part of the NS that innervates skeletal muscles, includes CNS and PNS |
| What is a synonym for the somatic component of the NS? | Voluntary component |
| In the somatic component are there efferent and afferent nerve fibers? | Yes, but the efferent or motor oriented fibers receive the most emphasis |
| What is the chemical released by the somatic axon endings of the somatic component of the NS? | Acetylcholine |
| What does the Autonomic (Visceral) Component of the NS innervate? | Glandular epithelium, smooth and cardiac musculature |
| What is a word often associated with the ANS? | Involuntary |
| What are the two division of the efferent nerve fibers of the ANS? | 1. Parasympathetic 2. Sympathetic |
| Parasympathetic Nerve Fibers | The first preganglionic neuron is long and the postganglionic is short. Located both in CNS and PNS. Release of ACH. |
| Sympathetic Nerve Fibers | Fight or Flight component. The preganglionic neuron is short and the postganglionic neuron is long. |
| Which nerve fibers, parasympathetic or sympathetic have a more widespread effect? | The sympathetic because of the ratio of preganglionic to postganglionic neurons. Sympathetic = 1:17 Parasympathetic = 1:2 |
| Which nerve fibers have a more precise response? | Parasympathetic |
| Embryology: 4th week of development: What arises from the spinal cord? | 3 primary brain vesicles |
| Embryology: what arises from the 3 primary vesicles? | 1. Prosencephalon (forebrain) 2. Mesencephalon (midbrain) 3. Rhombencephalon (hindbrain) |
| Embryology: What arises from the Prosencephalon? | 1. Telencephalon 2. Diencephalon |
| Embryology: what arises from the telencephalon? | 1. Cerebral Cortex 2. Basal Ganglia 3. Lateral Ventricle |
| Embryology: what arises from the diencephalon? | 1. Thalamus 2. Hypothalamus 3. Pineal Gland 4. 3rd Ventricle |
| Embryology: what arises from the Mesencephalon? | Mesencephalon (5th week) |
| Embryology: what arises from the mesencephalon (5th week) | 1. Corpora Quadrigemina 2. Cerebral Peduncle 3. Aqueduct of Sylvius |
| Embryology: what arises from the Rhombencephalon? | 1. Metencephalon 2. Mylencephalon |
| Embryology: what arises from the metencephalon? | 1. Cerebellum 2. Pons 3. 4th Ventricle |
| Embryology: what arises from the myelencephalon? | 1. Medualla Oblongata 2. 4th Ventricle |
| Check out figure 2 and 3 on page 10 | Neural plate, neural groove, neuroectoderm, neural fold, flexures in development |
| Does the weight of the brain change as we grow? | Yes. At birth: 10% of body weight (300-400g) In adulthood: 2-2.5% of body weight (1100-1400g) |
| What are neural tube cells? | They give rise to CNS structures. The cells do not divide but they mature. 1. Gliobalsts 2. Astrocyts 3. Oligodendrocytes 4. Ependymal cells 5. Microglia 6. Neuroblasts |
| Glioblast cells | Still fairly undifferentiated cells...they like to divide! divide! divide! They give rise to the astrocytes and the oligodendrocytes. |
| What is the functional connective tissue of the CNS? | The glioblasts |
| Are there more glioblast derivatives or neurons in the brain? | Glioblast derivative... 10 times more |
| Astrocytes ( stellate shape) | Most common cell in the NS. Most mobility potential. Stop dividing around age 5 or 6. |
| 2 types of astrocytes | 1. Protoplasmic Astrocytes (gray mater) 2. Fibrillar Astrocytes (white mater) |
| Function of Astrocytes | 1. Connective tissue-like function 2. Part of the BBB 3. Store (very little) glucose in the CNS 4. Forms a scar like tissue after injury to CNS 5. Are affected by neurotransmitters and maybe even ions (K) |
| Oligodendrocytes: 2 types | 1. Perineuronal Satelites (gray mater) 2. interfascicular (white mater) |
| Primary Function of Oligodendrocytes | Inerfascicular: form myelin sheaths around the CNS neurons 2. Perineural Satelites: unclear... may serve as a type of nutrient role |
| Ependymal cells | They line the central canal and ventricles of the CNS. They serve as the leaky barrier between the CSF and CNS parenchyma. |
| What is the classification of ependymal cells? | Simple cuboidal |
| Are cilia present? | No.. we start loosing our cilia at the time of birth |
| What is a glioma? | General term used to classify solid tumors derived from glioblasts, astrocytes and oligodendrocytes. |
| What is an astrocytoma? | Most common tumor of the brain tissue |
| Microglia | Abundant in numbers, phagocytic function, mediate immune responses |
| Neuroblast | Neuroepithelial origins (along the neural tube). Little mitotic activity but undergo growth and maturation. Depend of glial cells to help guide them as the migrate and spread through the CNS. |
| How does alcohol or radiation affect the fetal neuroblast cells? | This may cause them to under or over shoot their target sites. |
| Neuron classification | 1. Anatomical 2. Physilogical |
| Anatomical neuron classification | Unipolar, bipolar, multipolar |
| Physiological neuron classification | Sensory, motor, internucial |
| Unipolar Neuron | One cell body and one process |
| Bipolar Neuron | One cell body and two processes |
| Multipolar Neuron | One cell body, multiple processes |
| Sensory Neurons | Neurons which carry impulses from the periphery to the cord or brain. 1: Visceral 2. Somatic |
| Motor Neurons | Neurons which carries impulses away from the center toward the major peripheral target sites. 1: Visceral 2. Somatic |
| Internuncial Neurons | All the neurons that are entirely within the CNS structures. Messengers or connectors between incoming sensory and outgoing motor neurons. |
| Internuncial Neurons: Commissural | Runs between equivalent structures on opposite sides of the CNS |
| Internuncial Neurons: Projections | Begins in one structure and terminates in a different structure of the CNS (ipsilateral vs contralateral) |
| Internuncial Neurons: Intra Segmental | Starts in the spinal cord and ends at the same cord level |
| Internuncial Neurons: Inter Segmental | Neuron that starts at one cord level and terminates at another cord level |
| Internuncial Neurons : figure on page 16 | Look at it. Happy day! |
| Nerve cell cytology: | See figure 6 on page 17 |
| Diameter of a neuron's parikaryon | 4 - 130 micrometers |
| What shape does a perikarya take? | 1. Steeple 2. Star like 3. Oval 4. Fusiform |
| How long can a process be? | a few microns to 40 inches |
| How many cells in a neuron? | Trick question: a neuron is a single cell |
| What are the typical organelles and structures present in the neuron? | Cell membrane, nucleus, nucleolus (RNA), Mitochondria (they are long and skinny, unlike myo cells), golgi apparatus, endoplasmic reticulum and ribosomes, centrosome, Barr body |
| Where are mitochondria most abundant? | In the dendrites and the cell body |
| Nerve Fiber structure: Neuron | The anatomical and functional unit of the nervous system |
| Nerve Fiber structure: Neuron process | An extension of the neuron away from its cell body. |
| Nerve Fiber structure: Dendrite | A neuron process conducting an impulse towards the cell body. |
| Nerve Fiber structure: Axon | A single neuron process carrying the impulse away from the cell body towards a synaptic or neuromuscular junction |
| Nerve Fiber structure: Hillock | The gradual boundary between the cell body and its process. In the CNS the axon hillock is the sight of most action potentials. |
| Nerve Fiber structure: Nerve Fiber | A predominately long process, if present, of a neuron |
| Myelin Covering | Composed of a phospholipid-cholesterol and neurokeratin (protein) accumulations. Myelin is made by a surrounding cell (not by the neuron) |
| Can myelin be found in both CNS and PNS fibers? | yes |
| Function of myelin | Alters nerve impulse conduction speeds without taking up much space. |
| Does myelin form on neuron fibers smaller than 1 micron in diameter in the PSN? | No |
| True or false: The thick the myelin covering, the slower the nerve impulse will be carried? | False, the thicker the covering, the quick the transmission of the nerve impulse. |
| Neurilemma | The name given to surrounding Schwann cell coverings. Every PSN structure has this covering... does not mean that it is myelinated. |
| Example of an unmyelinated PNS nerve fiber | Post ganglionic sympathetic neuron |
| Nodes of Ranvier | Where one Schwann covering cell meets another there is a very tiny exposed area called a node of Ranvier |
| Internode | The area where the Schwann cell covers |
| True or False: Nerve fibers of the PNS can be myelinated while other are not but they all have a neurilemma. | True |
| ENdomeurium | Delicate, highly vascular, fibrous cellular matrix is around each neurilemma. It continues even out along the finest telodendric branches. |
| Perineurium | The coat that wraps arpund groups of fibers. Most elastic of the mesodermal covers and it is continuous with the pia and the arachnoid maters as it approaches CNS structures. |
| Epineurium | Highly collagenous outer coat of a nerve. Inelastic and adds protection, streght and support to the fasciculi within. Continuous with the dura mater. |
| Myelin will be found covering what structures in the CNS? | Axons that are usually greater than 1 micrometer in diameter. |
| Is the myelin associated with a Schwann cell? | No! It is an intravasicular oligodendrocyte. |
| Are there unmyelinated CNS fiber? | Yes, some are so small the have no myelin |
| Are nodes of Ranvier present in the CNS? | Yes, but you must substitute the oligodendrocyte in the place of Schwann cells. |
| White matter | Axons grouped together in the CNS |
| Commissures | Midline white matter connectors inside the CNS |
| Peduncles | A stalk or pillar-like formation of CNS white matter. |
| Page 24 to 28 | Read it! There will be a question on the exam! |
| Synonym for Dura Mater | Pachymeninx, Hard Mother, Thick Mother |
| Is the dura mater part of the nervous system? | No, but it is an important accessory structure. |
| What are the two divisions of the dura mater? | 1. Periosteal dura 2. Visceral dura |
| Periosteal Dura | Outer highly vascular layer which servesas a periosteum to the cranial bones. It is fused to the cranial bones. |
| Visceral Dura | Inner more fibrous that is separate only where a falx or dural venous sinus is present. |
| Where are the Periosteal and Visceral Dura located? | In the cranial vault |
| What type of Dura Mater do you find within the vertebral Canal? | More collagenous than its cranial counterpart. |
| How is the dura attached to the vertebral canal? | It forms a loose sac in the canal. It is, however, fused to the rim of the foramen magnum. Slips of dura attach into the ligaments of the periosteum of the axis, lower cervical and thoracic vertebrae. |
| Why is the dura mater of the vertebral canal attached in such a manner? | It is structured this way to be able to move freely but still needs to be anchored (meningovertebral ligaments) |
| Dura in the vertebral Canal : figure 12 | Page 30... look at it. |
| The dural falces | Double layer of visceral dura extending into a few fissures of the brain. |
| Where is the dura of the falces located? | In the great longitudinal cerebral fissure between the right and left cerebral hemispheres. |
| Falx Cerebelli | Where the visceral dura dips between the cerebellar hemispheres in the posterior cerebellar notch. |
| Is there a dural venous sinus in the falx cerbelli? | Yes |
| Tentorium Cerebelli | Visceral dura running laterally and foward from its confluence with the falx cerbrelli and falx cerebri. Built like a tent over the cerebellum and under the occipital lobes of the cerebrum. |
| Tentorium Hiatus | The brain comes through this opening. It is the opening in the middle of the left and right tentorial wings. |
| Diaphrama sellae | Visceral dura that roofs over the sella trurica (pituitary fossa) |
| Is the dura a vascular tissue? | Mostly collagen but it does have a few capillaries. It has vessels going around its outer surface. |
| Do nerve innervate the dura? | Yes, supertentorium: trigeminal and facial and infratentorium: vagus |
| Where are most of our ''throbbing'' headaches located? | The dura, particularly on the cranial floor |
| Is the arachnoid mater vascular? | No, it is a non-vascular membrane |
| Physical features of the arachnoid mater | Thin and transparent (saran wrap). The inner and out walls are composed of a simple squamous cell lining. |
| True or False: It is from the arachnoid mater that many meningeomas arise? | True |
| What is a synonym for arachnoid mater? | Leptomeninx |
| Does the arachnoid mater dip into the fissures and sulci of the brain? | Yes, wherever the dura mater goes, the arachnoid mater is sure to follow. |
| Arachnoid Trabeculae | Aid in maintaining the shape and add some support in combination with the cerebrospinal fluid. |
| Subarachnoid space | The space between the dura and the arachnoid mater |
| Figure 15 on page 34 | Know it. |
| What is a cistern? | A little reservoir, a well. The deeper than normal gap between the arachnoid and pia mater. |
| Figure 16 on page 35 | Know it. |
| Cerebellomedually cistern (cisterna magna) | Posterior location to the foramen magnum. The largest of all CRANIAL cisterns. |
| What opens into the cerebellomedually cistern and from where? | The fourth ventricle opens to the cisterna magna via the median formamen of Magendie. |
| Superior Cistern | Deep within the transverse cerebral fissure. |
| What are the important blood vessels that are found on the floor of the superior cistern? | 1. Great Vein of Gallen 2. Posterior and superior cerebral artery |
| Pontine Cistern | Anterior aspect of the pons. |
| Lateral Foramina of Lushka | A pair of openings that enter the pontine cistern from the fourth ventricle. |
| Lumbar cistern | It extends around the tapering end of the spinal cord all the way down to the upper sacral canal. |
| What fills the so called lumbar cul-de-sac? | The lumbar cistern |
| From where do we get a spinal tap? | The lumbar cistern |
| Interpeduncular cistern | region between the cerebral peduncles on the anterior aspect of the midbrain. |
| Where can you find much of the vascularization for the circle of willis? | Along the epipia of the interpeducular cistern |
| What is another term for Arachnoid Villi? | Pcchinonion bodies |
| Arachnoid Villi | Tuffed prolongations of arachnoid mater that herniate into the dura mater and associate with the lining of the dural venous blood sinuses |
| Where can you fin most of the arachnoid villi? | In the superior sagittal dural sinus |
| The function of the arachnoid villi | Allows used CSF to enter the bloodstream and be removed from the cranial vault. |
| Another term for Pia Mater | Tender Mother |
| Pia Mater | The inner most meninx (leptomeninx). Vascular are transparent membrane |
| Does the Pia dip into all fissures and sulci of the brain and the cord? | No |
| Parts of the Pia: Epipial Layer | A complex of cells and collagen bundles continuous with the arachnoid tuberculae. Blood vessels going or coming from the CNS structures are generally conducted by this layer. |
| Name 2 structures formed by the epipial layer | 1. Dendate Ligament 2. Filum terniale interum |
| Parts of the Pia: Inner Pia Intima | It has a fine reticular and elastic fiber which sticks to the CNS tissue within. |
| What percentage of the body weight is the adult brain? | 2-2.5% |
| What percentage of the normal cardiac output does the brain consume? | 14-17% |
| What percent of oxygen and sugar does the brain consume at rest? | 20% |
| Do larger people consume more or less oxygen and glucose at rest than smaller people? | Less |
| How much blood is perfused through the brain per minute? | 800ml |
| CVA | Blood loss to a brain area that results in a prolonged or permanent loss of function. |
| What is one of the most common areas in the brain for a stroke to occur? | The middle cerebral artery and its branches |
| Brain and brainstem blood supply : the circle of Willis | 1. Get out a blank piece of paper 2. Draw the circle of Willis 3. Label it. |
| Where is the most likely port for aneurysms in the circle of Willis? | The Anterior Communicating Artery |
| Where is the most common anomaly found in the circle of Willis? | The Anterior Communicating Artery |
| Through what structure does all the blood supply to the medualla oblongata and the pons go through? | The Circle of Willis |
| Why is the circle of Willis so important? | 1. Lewellen wants us to learn how to draw it for the exam. 2. One third of all the blood to the brain passes through it. |
| Spinal Cord Blood Supply: Major contributing vessels | 1. Anteromedial longitudinal artery trunk (anterior spinal artery) 2. Posterolateral longitudinal artery trunks (posterior spinal) |
| Vasocorona Anastomosis | These vessels enter via the IVF at the various levels. They supply more total blood to the cords that do the three longitudinal vessels. |
| Pia-glia cuff | The blood vessels to the brain penetrate inward from the pia mater with a slight cuff of pia |
| Virchow Robin Space | The space between the blood vessels and the pia. |
| How are the arteries and veins of the cerebrum different? | They have a thinner wall and the internal elastic membrane is reduced or absent. The veins also lack valves. |
| Capillaries of the CNS: Gray mater vs White mater | Extremely dense capillary beds are found in the gray mater compared to the white mater |
| How much blood is present in the brain? | 75 ml |
| How much blood passes through the brain at any one minute? | 800 ml |
| What is the most common type of capillary found in the CNS? | The continuous capillary |
| Continuous capillary | Lacks holes, does not have fenestrae, the junction between the cells are tight and the basement membranes are thick |
| BBB | Substances do not easily find access into the CNS structures via the bloodstream thanks to the BBB. |
| Blood Drainage from the CNS | Veins of the CNS usually do not flow back the same course the arteries followed inward. They form pial plexuses of veins. |
| Most cerebral veins penetrate the arachnoid mater and visceral dura to drain into what? | The dural venous sinuses |
| How does the blood get from the scalp to the dural venous sinus? | Emissary veins |
| How does the blood get from the scalp to the bones of the skull? | Diploic veins |
| Vault drainage of the dural venous sinus blood happens into what? | Right or left internal jugular veins at the jugular foramina |
| Dural venous sinuses | 1. Large 2. Lack valves 3. Have a simple endothelial lining |
| Function of the dural venous sinus | Serves as support tissue |
| List the dural venous sinuses | 1. Superior Sagittal 2. Inferior Sagittal 3. Occipital 4. Transverse 5. Superior petrosal 6. Inferior petrosal |
| Superior Sagittal Dural Venous Sinus | Runs along attached border of the falx cerebri from the cecum to the confluens sinuum |
| Blood supply to supperior saggital DVS | Scalp, bones and cerebrum |
| Flow pattern of superior sagittal DVS | Flows into te right transerves DVS after passing through the confluens sinuum |
| Inferior Sagittal DVS | Runs along the posterior two thirds of the falx cerebri |
| Flow pattern of the inferior sagittal DVS | Empties blood into the straight DVS (along with the vein of Galen) |
| Straight (Rectus) DVS | At the junction of the falx cerebri, tentorium cerebelli and the falx cerebelli. Runs in a posterior inferior direction to the confluens sinuum |
| confluens sinuum | The superior sagittal sinus, straight sinus, and occipital sinus connect at a series of channels that comprise the confluence of sinuses |
| Flow pattern of the straight DVS | Drains into the left transverse DVS. Blood from the vein of Galen and inferior sagittal DVS flows the same route. |
| Occipital DVS | Very small DVS. Runs along the attached margin of the falx cerebelli into the confluens siuum |
| Flow pattern of the occipital DVS | Flows into the left transvers DVS |
| Transverse DVS | Largest DVS and bilateral. They run along the occipital bone margins of the tentorium cerebelli. |
| Superior Petrosal DVS | Small, bilateral sinus. Runs along the crest of the petrous parts of the temporal bones at the attached margin of the tentorium cerebelli. |
| What two structures does the superior petrosal DVS connect? | The cavernous DVS with the ipsilateral transverse DVS |
| Blood flow of the superior petrosal DVS | Middle ear veins penetrate into the vault and drain into the superior petrosal sinuses. |
| Inferior petrosal DVS | Small, bilateral sinus. Carries blood along the petrooccipital suture from the cavernous sinus to the lower sigmoid extension of the transverse DVS. |
| Circular Dural Sinus | Look at the picture on page 47 |
| Where is the CSF produced? | In each of the 4 ventricles, CSF is produces in specialized ependymal structures called choroid plexuses. |
| Right and Left Lateral Ventricles | Largest of the ventricles. Each lateral ventricle is totally separate from the other. Location is entirely within the right or left cerebral hemisphere. |
| How do the right and left lateral ventricle communicate with the third ventricle? | Via the Foramina of Monro (interventricle foramina) |
| The five basic parts or the right and left lateral ventricles: | 1. Anterior horn 2. Ventricle body 3. Collateral trigone (atrium) 4. Inferior horn 5. posterior horm |
| Where is the choroid plexus located? | Along the roof of the anterior horn, through the atrium and along the floor of the body. It continues through the faramen of Monroe, spreading onto the roof the third ventricles. |
| Third ventricle | A narrow opening in the substance of the diencephalon |
| From where does the third ventricle receive CSF? | From the foramina of Monroe |
| Does the third ventricle produce CSF? | Yes, from the choroid plexus |
| What denotes the third ventricle inferiorly? | The cerebral aquaduct of Sylvius |
| Fourth Ventricle | An irregular shaped expansion between the cerebellum and the pons and the medualla oblongata |
| List the 5 openings into or out of the fourth ventricle | |
| Cerebral Spinal Fluid: when is it first produced? | 5th or 6th month of fetal developemnt |
| Cerebral Spinal Fluid: what is it mostly made up of? | Water |
| Cerebral Spinal Fluid: What are the physical caracteristics | Clear and colorless |
| Cerebral Spinal Fluid: functions | 1. Shock absorber 2. Buoyancy for the brain 3. Vitamin C |
| Cerebral Spinal Fluid: Quantity of fluid | 80 to 150 ml |
| Cerebral Spinal Fluid: is it overturned every day? | Yes, a little is overturned at any given moment. 500ml is produced per day |
| Cerebral Spinal Fluid: By what is it reabsorbed? | The arachnoid villi |
| Cerebral Spinal Fluid: site of production | 70 to 80 % in the choroid plexus |
| Cerebral Spinal Fluid: factors involved in production | 1. high hydrostatic pressure in blood vessels 2. fenestrated capillary beds 3. active transport in microvilli 4. Sympathetic innervation |
| Cerebral Spinal Fluid: causes for obstructions | Neoplasmic growths, small or absent openings |
| Cerebral Spinal Fluid: sites of obstruction | 1. Foramina of monroe 2. Foramina of Luchka 3. Foramina of Magendie 4. Cerebral Aquaduct |
| Cerebral Spinal Fluid: symptoms of obstruction | Hydrocephalus (cranial enlargement), Nausea, Explosive vomiting, Headache, Blurred or altered vision |
| Cerebral Spinal Fluid: Surgical shunts | Shunt are used to redirect the CSF from the blocked region to another region. |
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LrB
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