Neuroscience Exam 1

glycine

inhibitory neurotransmitter (spinal cord and brain stem) increases the Cl- conductance of the postsynaptic membrane (hyperpolarizes)

what three factors maintain the flow of CSF?

rhythmic pulsations of brain blood flow slight variation in pressure of CSF action of ependymal cilia

role and associated problems of serotonin

role: alertness, mood elevation, breathing control, temperature regulation problems: OCD, depression, anxiety, aggression, eating disorders, SIDS (sudden infant death syndrome)

role and associated problems of noradrenergic projection system

role: attention, sleep-wake states, mood elevation problems: attention-deficit disorders, narcolepsy, depression, anxiety

role and associated problems of dopaminergic projection system (CNS)

role: movement, initiative, working memory problems: parkinson's disease, addiction, and hallucination

describe the physiological properties of the true BBB

- no transcytosis (where macromolecules enter the cell and then exit) - under neural control, capillary endothelial cells ACTIVELY regulate the passage of substances by various transport mechanisms (transport glucose, sodium, oxygen, Cl-,).

How are PNS nerve fibers classified?

- pharmacological classification: by the type of neurotransmitter released in chemical synapse - anatomical classification: by the information transmitted (sensory vs motor) and the nature of organ being innervated (visceral vs somatic) - physiological classification: by the axon diameter and the speed of impulse conduction

Where does the CSF flow?

1. CSF secreted by choroid plexus in each lateral ventricle 2. CSF flows through interventricular foramina into 3rd ventricle 3. choroid plexus in 3rd ventricle adds more CSF 4. CSF flows down cerebral aqueduct to 4th ventricle 5. choroid plexus in 4th ventricle adds more CSF 6. CSF flows out two lateral apertures and one median aperture 7. CSF fills subarachnoid space and bathes external surfaces of brain and spinal cord 8. at the arachnoid villi, CSF is reabsorbed into venous blood of dural venous sinuses.

In the brain, what two fluids must be shielded from blood? and what is the shield for each?

1. brain extracellular fluid (BECF) - the microenvironment of the actual brain cells (parenchyma of brain). protected by true blood-brain barrier 2. cerebrospinal fluid - protection by a blood-CSF barrier.

what are the four types of neurotransmitters?

1. choline esters: (acetylcholine (Ach)) 2. biogenic amines: (dopamine, epinephrine, histamine, serotonin) 3. amino acids: (GABA, glutamate, glycine) 4. neuropeptides: ACTH,

what are the three types of synaptic arrangements?

1. one-to-one synapse (neuromuscular junction) 2. one-to-many synapses (motoneuron-renshaw cells) 3. many-to-one synapses (nervous system)

Describe the two types of astrocytes.

1. protoplasmic astrocytes: have short, branching processes. More common in gray matter (associated with soma) 2. fibrous astrocytes: have fewer, relatively straight processes. More common in white matter (associated with axons) there is also a third category: radial glia

How does glucose travel from blood vessels to neurons?

1. the direct route: glucose diffuses from blood to BECF to neuron, where it is oxidized. 2. the indirect route: glucose enters astrocytes, stored as glycogen (or immediately metabolized to lactate), diffused to neuron, and oxidized there.

Primary CNS tumors arise from what?

1/3 arise from glia (these naturallly proliferate) - gliomas 1/3 arise from arachnoid: meningiomas: benign neoplasm of arachnoid origin 1/3 arise from a variety, most common is pituitary adenomas and schwannomas they rarely arise from neurons (neuronal tumors) because neurons do not proliferate. for them to divide, they must revertt o an undifferentiated stem cell-stage. so these tumors are generally not aggressive and more treatable.

what are the two general causes of demyelinating diseases?

2 main causes: 1. hereditary: alexander disease and canavan disease - mutations in genes encoding these proteins (P0 myelin protein zero) 2. Immune-mediated: multiple sclerosis, Guillain-Barre syndrome - myelin proteins (MBP myelin basic protein) are targeted by various leukocytes. the critical result for both is that axons conduct action potentials slowly, unreliably, or not at all.

how many ventricles are in the brain?

4 2 lateral ventricles, a third ventricle, and a fourth ventricle. each lateral ventricle is located on a cerebral hemisphere and communicates with the third ventricle by an inter-ventricular foramen (of monroe) the third ventricle lies in the diencephalon and communicates with the fourth ventricle via cerebral aqueduct the fourth ventricle is located between cerebellum and the pons. the third ventricle communicates with the fourth ventricle via the diencephalon.

Which of the following layers is a thick membrane that provides strength? What gives it strength? a. Dura Mater b. Arachnoid Mater c. Pia Mater

A. Dura mater. the reason it is strong is because it has a sparse population of fibroblasts and consists mostly of layered collagen bundles running in different directions.

which of the following creates the supratentorial compartment (cerebrum) and infratentorial compartment (brainstem and cerebellum)? a. Falx cerebri b. Falx cerebelli c. tentorium cerebelli d. diaphragma sellae

C. tentorium cerebelli is the correct answer. it separates cerebellum & brainstem from the cerebrum. Falx cerebri divides the cerebral hemispheres along the longitudinal fissure. The falx cerebelli divides the CEREBELLAR hemispheres the diaphgrama sellae covers the hypophyseal fossa, the fossa that contains the pituitary gland. Dural infoldings are taut (tight) and firmly attached to the skull. So, in cases of increased intracranial pressure, (resulting from hemorrhage or tumor), the brain may herniate from one compartment into another. tentorium cerebelli is especially sharp (remember Dr. jaynes was saying).

What are satellite cells?

Cuboidal cells that cover large neuronal cell bodies in PNS ganglia. They support the neurons, nourishing them, insulating them, and regulating their microenvironment.

Electrical synapse

Direct spread of electrical impulse from one cell to another via gap junctions (ions flow through gap junctions) particular to muscle cells (heart, uterus, bladder) FAST, but reduced possibility for modulation

What are other ways that synaptic activity is altered where the repeated stimulation causes the postsynaptic response to be greater than expected?

Facilitation Augmentation Post-tetanic potentiation accumulation of calcium in the presynaptic terminal increases the release of neurotransmitters.

inhibitory neurotransmitters

GABA glycine

Lecture 3

Lecture 3

Lecture 4

Lecture 4

Lecture 6

Lecture 6

what's more common - primary CNS tumors or metastatic CNS tumors?

Metastatic CNS tumors (80-90% of CNS tumors)

What are the glial cells in the PNS (peripheral glia)?

Schwann cells and satellite cells

What is the difference between spatial summation and temporal summation?

Spatial summation is when two or more presynaptic inputs arrive at the postsynaptic cell at the same time. they will either create greater depolarization or cancel each other out. Temporal summation is when two presynaptic inputs arrive at the postsynaptic cell rapidly.

what is endoneurium?

The connective tissue sheath that wraps around the individual nerve fiber. the myelin sheath is deep to endoneurium.

What are the different effects of ionotropic and metabotropic receptors?

The effect of a neurotransmitter is determined by the receptor it binds. ionotropic receptors are fast-acting ligand-gated ion channels. - nicotinic ACh receptor (only at the neuromuscular junction) metabotropic receptors are slow; neurotransmitter binding leads to changed concentration of secondary messengers. - muscarinic Ach receptor: G protein-coupled (smooth0and cardiac muscle fibers, neurons)

where does the CSF exit from the ventricles?

There are four exit points: 2 lateral apertures and 1 median aperture empty into the subarachnoid space. the inferior apex of the fourth ventricle is continuous with the central canal of the spinal cord.

what are reactive astroctyes?

They are astrocytes that are responding to CNS damage by undergoing hypertrophy and hyperplasia. They wall off an injured area, preventing the spread of inflammation. In doing so, they form an astrocytic scar (this is thought to block regrowing axons, but recent research shows this is not true).

What are Inhibitory postsynaptic potentials (IPSPs)?

They are inputs that hyper-polarize the post-synaptic cell membrane by opening Cl- channels

What are subarachnoid cisterns?

They are large pockets of subarachnoid space filled with CSF. These are useful for CSF sampling and for radiological landmarks. a great example of a subarachnoid cistern is the lumbar cistern (exists bc dural sac extends more distally than the spinal cord does). This space is ideal for CSF sampling another CSF collection site is the cisterna magna, which is rarely used but may be needed if a person has a back deformity, an infection, or a spinal tumor. Using this space for sampling is more risky, because important centers in the medulla can be hit by the needle.

What are choroid plexuses?

They are tufts of capillaries that produce CSF that are found in the four ventricles. Each ventricle is lined by ependymal cells (collectively known as the choroid epithelium). Some of these ependymal cells are specialized that produce CSF.

what is long-term potentiation?

When we repeatedly stimulate a particular synapse, the synaptic connection gets stronger. this was initially discovered in the hippocampus, functions in memory and learning. this depends on the activation of the glutamate receptor.

one to one synapse

a single action potential in the presynaptic cell, the motoneuron, causes a single action potential in the postsynaptic cell, the muscle fiber Neuromuscular junction

what causes cranial subarachnoid hemorrhage?

a subarachnoid hemorrhage is the leaking of blood into the subarachnoid space. This leaking is either caused by a ruptured aneurysm in the cerebral artery, or from a cut of the cerebral artery due to head trauma. what causes ruptured aneurysm? a sudden increase in blood pressure (straining, lifting)

lipofuscin

a wear and tear pigment

which of the following layers consists of two fused layers? a. cranial dura mater b. cranial arachnoid mater c. cranial pia mater d. spinal pia mater

a. cranial dura mater. it is tightly stuck to the skull, especially along suture lines and the base of the cranium. It is made up of two layers - the periosteal layer: creates tight adhesion to cranium the meningeal layer: forms infoldings the periosteal layer is the inner periosteum of the skull (continuous with the outer periosteum) and the layer that creates the tight adhesion to the cranium. these two layers are tightly fused, and there are no known conditions that separate the two dural layers from each other. The entire dura mater may only separate from the skull , so like a brain hemorrhage would separate the dura mater from the skull. HOWEVER, along certain parts of the skull, the two fused layers exhibit a normal separation, thus forming dural venous sinuses. Also, along certain divisions of the brain, the MENINGEAL LAYER of cranial dura mater projects inward to form infoldings (or reflections, or partitions, or septa). These infoldings' main purpose is to reduce movement of the brain (such as rotary displacement). The infoldings divide also partially divide the cranial cavity into compartments, which are useful for clinical reference.

excitatory neurotransmitters

acetylcholine norepinephrine and epinephrine dopamine glutamate serotonin

curare alters neuromuscular function how?

acts as a competitive inhibitor - it competes with Ach for receptors on motor end plates effect: decreases the end plate potential, in maximal doses produces paralysis of respiratory muscles --> death

neostigmine alters neuromuscular function how?

acts as an AChE inhibitor effect: prolongs and enhances the action of Ach at the motor end plate.

what area monitors blood for presence of toxins and triggers vomiting if necessary?

area postrema this is a circumventricular organ

why is hemorrhage in the brain more problematic than in the spinal cord?

because cranial cavity is closed, whereas the vertebral cavity is relatively open. In the brain, when hemorrhage occurs, the blood has nowhere to go in the skull, so it pools, creating two related problems: 1. pooling blood is depleted of oxygen fast, which the brain requires almost continuously. and 2. pooling blood squishes the brain against the hard skull.

Which of the three layers of the meninges are continuous with each other? a. Dura Mater and arachnoid mater b. Arachnoid Mater and Pia mater c. Pia Mater and dura mater

b. arachnoid mater and Pia mater is the correct answer. they are continuous with each other, so they are sometimes referred to together as the leptomeninges. The dura mater is the outermost layer and makes up the pachymeninx (thick membrane). next comes the arachnoid and then the pia. These make up the leptomeninges (a slender, thin, fine membrane). The pia mater adheres to the brain and is not dissectible, it is visible by the shine it imparts to the surface of the brain. the spinal cord is also enclosed by three layers of meninges. The cranial and spinal meninges are continuous at the foramen magnum (so they are very similar) BUT, there are some minor differences between cranial and spinal dura and cranial and spinal pia. However, there are no significant differences between cranial and spinal arachnoid mater.

Which of the following correctly lists the drainage route of the middle meningeal vein? a. internal jugular vein --> sigmoid sinus --> superior petrosal sinus --> cavernous sinus --> middle meningeal vein b. middle meningeal vein --> cavernous sinus --> superior petrosal sinus --> sigmoid sinus --> internal jugular vein c. internal jugular vein --> superior petrosal sinus --> sigmoid sinus --> cavernous sinus --> middle meningeal vein d. middle meningeal vein --> cavernous sinus --> sigmoid sinus --> superior petrosal sinus --> internal jugular vein

b. is the correct answer. the flow of drainage is: middle meningeal vein --> cavernous sinus --> superior petrosal sinus --> sigmoid sinus --> internal jugular vein.

What is the dural sac? a. the periosteal layer of the spinal dura Mater b. the meningeal layer of the spinal dura mater c. the curve of the dura mater as it transitions from cranial to spinal d. the epidural space that houses the spinal dura mater

b. is the correct answer. the meningeal layer of the cranial dura mater becomes the spinal dura mater, while the periosteal dura mater stays attached to the and reflects onto tthe exterior surface of the cranium (becoming continious with the external periosteum of the cranium) Thus, the spinal dura mater consists of only a meningeal layer, which is also referred to as the dural sac. A periosteal layer of dura mater does exist in spinal canal, it is the periosteum that lines the vertebral foramina. However, in the spinal canal (unlike the skull) this periosteal layer is separated from the meningeal layer to create a natural epidural space.

which of the following is not derived from the neural tube? a. ependymal cells b. microglia c. macroglia d. schwann cells

b. microglia is the correct answer Microglia is the only CNS cell type that is not derived from the neural tube. They are derived from hematopoeitic stem cells instead. microglia are phagocytes related to macrophages, osteoclasts, dendritic cells, etc. macroglia (oligodendrocytes and astrocytes and ependymal cells) are derived from neural tube. schwann cells and other pns neurons and glia are indirectly derived from the neural tube via the neural crest.

Cranial Dura mater is mainly supplied by what vessels? a. cranial dura mater artery b. middle meningeal artery c. the internal carotid artery d. the subclavian artery

b. middle meningeal artery is the correct answer. this artery travels in the periosteal layer of dura (the middle meningeal artery's principal function is to supply bone). As for the veins, the cranial dura mater is drained by the middle meningeal vein, which runs along the middle meningeal artery. Now let me describe the vessels: the arch of aorta supplies the head, neck, and upper limbs. the right subclavian artery and left subclavian artery supply the upper limbs. from the arch of aorta, we have the right and left common carotid arteries. The common carotid artery splits into the external carotid artery (head and neck) and the internal carotid artery (brain). the internal carotid artery becomes the middle meningeal artery and runs on the periosteal layer of the dura.

why is an immune reaction (swelling) very dangerous in the brain? How does the BBB prevent that?

because swelling in the brain can crush irreplaceable post-mitotic neurons. BBB Prevents that because it prevents blood, which likely has pathogens and immune cells, from entering the CNS.

why is a blood-CSF barrier needed? Where is it needed?

because there are 3 areas in the brain where capillaries do not form a true blood-brain barrier and where CSF could be exposed to blood plasma, so a blood-CSF barrier is needed: These areas are: 1. along the superficial aspect of arachnoid mater (here, tight junctions between cells of the arachnoid protect CSF from extracerebral capillaries (which do not form tight junctions). 2. at the choroid plexuses (we need real blood to make CSF out of it). 3. at the circumventricular organs (organs like the pineal and pituitary gland that sample the blood and check for any toxins).

Why are astrocytes able to accomplish a wide range of functions?

because they communicate with each other by gap junctions, forming a coordinated network that spans the entire brain astrocytes are involved in glia limitans (they extend the entire surface of the brain and spinal cord) astrocytes are involved in the true BBB (they contact blood vessels) they also contact most dendrites and nerve cell body surfaces. They can also associate with over one million synaptic sites.

Hemicholinium alters neuromuscular function how?

blocks re-uptake of choline effect: depletes presynaptic terminal's Ach storage

What are the two steps in converting blood to CSF?

blood goes from the blood capillaries into the ventricle. To get to ventricle, it passes through capillary wall, pia mater, and the choroid epithelium (the specialized ependymal cells). so the two steps are: 1. ultrafiltration of plasma as it goes through the fenestrated capillary wall: the fenestrations are small enough to prevent passage of proteins, many amino acids, and cells. Ultrafiltration also occurs via the choroid epithelium bc the cells are bound to one another by tight junctions, which further hinder the passage of all but the smallest molecules into the ventricular space. 2. Transport processes: the ependymal cells of the choroid epithelium use regulated transport processes to ensure a specific and constant composition of CSF.

a freshly isolated brain is soft and mushy, with a jello-like consistency, and tears and collapses under its own weight because... a. it contains fixatives b. it does not contain fixatives c. it lacks internal connective tissue d. the blood brain barrier prevents entrance of molecules/chemicals necessary to make it more stiff.

c is the correct answer - a brain lacks the internal connective tissue framework (e.g. fascia) seen in most organs.

Which statement is not part of the primary purpose of the meninges? a. the meninges physically protects the brain & sc from the hard surfaces b. the meninges physiologically protects the brain & sc by isolating these structures from the rest of the body c. the meninges physically protects the brain by separating it from the spinal cord d. the meninges contains CSF, which baths the brain and sc (CSF plays a role in both physical and physiological protection of the CNS)

c is the correct answer because it is a false statement. the primary purpose of the meninges is to physically and physiologically protect the brain and sc. the meninges also contains CSF, which further protects the brain and spinal cord. the meninges also have. secondary purpose, which is to provide a framework for vasculature.

What intracranial structure is the main pain-sensitive structure? a. leptomeninges b. nerves in the brain c. the dura mater

c. dura mater is the correct answer. the brain and leptomeninges do not have nociceptors and are thus not sensitive to pain dura mater is the main pain-sensitive intracranial structure. Dura mater is especially sensitive to pain where the dural sinuses receive cerebral veins. Deformation of blood vessels is generally related to changes in blood flow.

What layer projects inward to form infoldings, which acts to reduce movement of the brain? a. the periosteal layer b. pia mater c. the meningeal layer d. arachnoid mater

c. the meningeal layer it creates infoldings that reduce the movmenet of the brain and partially divide the cranial cavity into compartments, such as dividing cerebrum from cerebellum, dividing right cerebellar hemisphere from left cerebellar hemisphere through the longitudinal fissure.

what are the symptoms of cranial subarachnoid hemorrhage?

cardinal signs of sudden excruciating headache, stiff neck, and loss of consciousness.

What are mitotic figures?

cells that are undergoing mitosis. clinicians might misinterpret the presence of mitotic figures for a neoplasm, when it is actually the proliferation of macrophages.

Cranial subdural hemorrhage (aka subdural hematoma, or dural border hematoma) occurs due to laceration of _____.

cerebral vein at the point where it penetrates the arachnoid. This type of hematoma is usually not emergent. it occurs due to head trauma, particularly the kind seen in rapid acceleration/deceleration. The dural sinuses move with the skull, but the brain lags, tearing the cerebral vein.

which synapse can be modulated?

chemical synapse

How is the glia limitans basement membrane attached to the pia mater basement membrane?

collagen fibers passing through the subpial space. this attachment via collagen fibers has two purposes: 1. the brain can be secured to the skull (because tightly attached pia mater is tightly attached to the meninges. Similarly, this is how the spinal cord is secured to the dural sac. 2. they create a capsule for the brain and spinal cord. This is because the glia limitans and firmly attached pia form a relatively impermeable barrier.

Which of the following is false regarding dural venous sinuses? a. they are blood channels b. they are mostly located along free and attached borders of falx cerebri and tentorium cereblli c. they mainly collect blood from the brain via cerebral veins d. Most often, the sinuses drain blood from the diploe of the skull (diploic veins) and from the scalp (emissary veins) to the dural venous sinuses

d is the correct answer because it is a false statement. Everything else is a true statement. D is false because although blood does flow to sinuses from the skull (via diploic veins) and the scalp (via emissary veins) to the sinuses, it does not occur "most often". Most often, the blood flows from the sinuses to the scalp. emissary veins constitute a possible route for the spread of infection from scalp to brain.

What is the main sensory nerve of the head? a. CN I b. CN II c. CN III d. CN V

d. CN V is the correct answer Cranial nerve 5, the trigeminal nerve, is the main sensory nerve of the head. It innervates the cranial dura mater. It's got three branches: CN V_1: innervates the front of the brain and the back. CN V_2: small part of the front of the brain, behind and more lateral to the area covered by the anterior meningeal branch of CN V_1 CN V_3: covers the most lateral and more front part of the brain.

Which of the following is a normal space? a. cranial subdural space b. spinal subdural space c. cranial extradural space d. spinal extradural space

d. spinal extradural space is the correct answer. extradural space is aka the epidural space. This is the space above the dura mater. This space is present in both the cranium and the spine. It is pathological when present in the cranium, but normal in the spine. the normal cranial spaces are: subarachnoid space. pathological cranial spaces: epidural/extradural space, subdural space. the normal spinal spaces: subarachnoid space, epidural space/extradural space pathological spinal spaces: subdural space

Chemical synapse

electrical impulse spread from one cell to another indirectly via a chemical agent (neurotransmitter). separated by synaptic cleft

which synapse can't be modulated?

electrical synapse

what is the difference between extracerebral and intracerebral hemorrhages?

extracerebral occurs between skull and brain, whereas intracerebral occurs within brain tissue or ventricles. there are three types of extracerebral hemorrhages, one in each of the 3 cranial meningeal spaces: epidural (extradural space), subdural space, and subarachnoid space.

True or false: hematomas in the spinal epidural space are rare, but when they occur, there is nothing to worry about

false. hematomas in the spinal cord are in fact rare. However, when they occur, that is a problem because it can cause compression of the spinal cord. This diagnosis should be considered if there is back pain with unknown etiology.

what is the difference between filum terminale internum and filum terminale externum?

filum iterminale internum is the top part of the filum terminale whereas the filum terminale externum is the bottom part of the filum terminale. the internum is a continuation of the spinal cord and consists mainly of pia mater and some neural tissue. whereas externum consists of dura (because it perforates the dural sac) and continues downward to attach to the coccyx.

what is the single most common primary CNS tumor?

glioblastoma. Also most aggressive cells of origin are probably astrocytes but also other progenitor cells.

What complicates SSH?

hematoma formation, which can compress the spinal cord. Normally, the flow of CSF can wash away blood, preventing hematoma formation. However, in certain patients, flow of CSF is compromised, and a hematoma may form.

A schwann cell wraps around how many axons?

if the axon has an intermediate-sized diameter or a large diameter, it wraps only one. If the axon has a small-diameter, a schwann cell can embed up to 20 of these axons.

when do microglia become reactive?

in response to injury (trauma or pathology) when they are reactive microglia, they rapidly proliferate, retract their processes, elongate their nuclei, and become motile and phagocytic. They secrete toxins, which are harmful to neurons. - without trauma or injury, they stay in place, extending processes to do immune surveillance

botulinum toxin alters neuromuscular function how?

it blocks Ach release from presynaptic terminals effect: total blockade, muscle paralysis (including respiratory muscles) --> death

What determines which neurotransmitter is secreted between Norepinephrine, epinephrine, and dopamine?

it depends on which enzymes are present in the particular location. ex: dopaminergic neurons are released in locations where there is tyrosine hydroxylase and dopa decarboxylase.

Does wallerian degeneration happen in the CNS?

it does, but it is much slower - months or years. Also, it is not really effective because astrocytes and oligodendrocytes do not spur regrowth of neurons (in contrast to schwann cells). in fact, astrocytes and oligodendrocytes actually impede the growth of neurons

What is glial fibrillary acidic protein (GFAP)?

it is an intermediate filament that is highly present in reactive astrocytes and neoplastic astrocytes. You cannot distinguish between the two by using GFAP alone, other markers such as differentiation (less in neoplastic astrocytes) and the nature of intracellular signaling pathway molecules may be necessary

What is hydrocephalus?

it is buildup of CSF in the brain; can be overproduction of CSF, blockage of CSF flow, or blockage of CSF reabsorption. result: dilated ventricles, thinned cerebral cortex, and separated calvaria in the skull. treatment: artificial drainage systems. These systems can by-pass the blockages.

what is wallerian degeneration?

it is the process where the neuron degrades its axon distal to the injury (transection) After this degeneration, Schwann cells proliferate and serve as a guide for growing axons - they increase secretion of growth factors but downregulate housekeeping functions (so muscle atrophy actually occurs). So regeneration occurs in PNS, in CNS this is different.

How does CSF return to blood?

it returns via the arachnoid villi. an arachnoid villus is basically a herniation of arachnoid mater through the meningeal layer of dura mater. These herniations are filled with CSF. The CSF can travel out of the villus but the venous blood cannot go into it. arachnoid villi are located within the dural sinuses - the superior sagittal sinus and its lateral lacunae.

If a patient has meningitis, what does a CSF glucose ratio of less than 0.6 tell us?

it tells us that the meningitis is bacterial. This is because bacteria consume glucose.

the blood clot of an epidural hematoma typically has a ____ shape the blood clot of a subdural hematoma typically has a ____ shape.

lentiform/bi-convex crescenteric/bi-concave

What are the causes of long-term depression?

long-term depression is where a synaptic connection is weakened the 2 causes are (1) strong synaptic stimulation in the cerebellum (motion sickness?) and (2) persistent weak synaptic stimulation (hippocampus)

GABA: what is it? What is it synthesized from? what receptors does it bind?

main inhibitory neurotransmitter widely distributed in the CNS synthesized from glutamic acid receptors are ionotropic (hyperpolarizes) and metabotropic (hyperpolarizes)

glutamate

major excitatory neurotransmitter in the CNS (spinal cord and cerebellum) ionotropic and metabotropic receptors

How does the CSF serve mechanical, chemical, and circulatory functions?

mechanical: CSF provides cushion Chemical: CSF provides a stable chemical environment that is needed for proper function of the CNS. circulatory: bc the CSF circulates, it is able to distribute substances and removes waste products from parenchymal cells. CSF helps avoid compression of the brain with each heartbeat.

Cranial epidural hemorrhage occurs from laceration of ____ artery

middle meningeal artery. Cranial epidural hemorrhage occurs from a skull fracture that lacerates the middle meningeal artery. This bleeding strips away the dura from the skull. Usually, there is an initial loss of consciousness, then a lucid interval (1-5 hours) and then a decline of consciousness again.

one-to-many synapse

motoneuron-renshaw cells an action potential in presynaptic cell (motoneuron) causes a burst of action potentials in the postsynaptic cells (amplification of activity)

many-to-one synapse

nervous system an action potential in the presynaptic cell is insufficient to produce an action potential in the postsynaptic cell. Instead, many presynaptic cells converge on the postsynaptic cell, the inputs summate, and the sum of the inputs determines if postsynaptic cell fires or not. these inputs can be excitatory or inhibitory

Where is acetylcholine released?

neuromuscular junction, parasympathetic neurons: preganglionic and postganglionic sympathetic neurons: all preganglionic presynaptic neurons of the adrenal medulla

list the cells that are found in the nervous system

neurons glia (about same number as neurons but a bit more) neural stem cells blood vessel cells (endothelial cells, fibroblasts, etc.)

What are the glial cells in the CNS (Central glia)?

oligodendrocytes astrocytes microglia ependymal cells

why is it important that astrocytes can uptake potassium?

recall that to to repolarize the neuron, potassium release occurs. but repeated action potentials can elevate extracellular potassium to the point where brain functions are compromised (such as neuron excitation). so astrocytes help prevent that. Also, because they act as a syncytium, accumulation of K can be distributed to distant astrocytes (spatial buffering). finally, the accumulation of K can serve as a signal for astrocytes to increase glucose metabolism and provide more lactate for neurons.

The spinal dura mater is innervated by...

recurrent meningeal (sinuvertebral) nerves. these nerves arise from all 31 spinal nerves. They are called "recurrent" because they follow a recurrent course back through the intervertebral foramina. Pain from spinal dura mater is similar to pain from headache - they are regular, poorly localized, and often referred. Along with innervating dura mater, the recurrent meningeal nerves supply IV disks, periosteum of the vertebral arch, and ligaments of the vertebral column. So recurrent meningeal nerves convey pain sensations arising from IV disk herniations, sprains, contusions, and fractures. however, such pain sensations are not like headaches, but are intermittent and localized.

describe the process of CNS myelination

similar to PNS myelination by schwann cells 1. they recognize cell-surface proteins on appropriate axons 2. the edge of an oligodendrocyte process flattens out sheet-like and wraps itself around the axon multiple times. 3. compaction: the cytoplasm is then extruded out of all the layers, but the remaining tightly rolled membrane stays continuous with the oligodendrocyte, which nourishes it. CNS myelination occurs during late fetal period into the 1st year.

Do microglia ever recruit other immune cells to the CNS?

so sometimes they do. When it's a minor insult to brain parenchyma, microglia are enough to counter the threat. They secrete ILs to recruit T cells and macrophages to the CNS in cases of larger lesions. - interleukin secretion loosens the BBB (endothelial cell tight junctions), allowing macrophages and t cells to enter - microglia present Ag to T cell

both the choroid plexuses and circumventricular organs feature...

specialized ependymal cells that separate blood from CSF. these ependymal cells usually have tight junctions

most CSF is contained in the ____ space

subarachnoid space CSF is a clear watery liquid that bathes brain and spinal cord. It is derived from blood and it circles the brain and then returns to blood. Though both CSF and plasma are derived from blood and don't have cells, they're pretty different.

For neurons to transmit electrical signals throughout the nervous system, they need to manipulate the ionic gradients for action potentials, synthesis of neurotransmitters, control the environment for proper transmission of action potentials. What cells help do this?

supporting cells, known as neuroglial cells/glial cells/neuroglia/glia

describe the anatomical properties of the true BBB

the capillaries of the true BBB have endothelial cells that are linked by tight junctions and that overlie a thick basement membrane. The tight junctions are maybe stimulated by astrocytes (whose end-feet provide a continuous covering of the capillaries).

How are Pia and arachnoid different? a. arachnoid closely adheres to all contours of the CNS whereas the pia closely loosely covers the surface of the brain b. the arachnoid is avascular whereas the pia is vascular c. the arachnoid has subpial spaces whereas pia does not d. there are no differences between arachnoid and pia, they are exactly the same and there is no space between them

the correct answer is B. All the other statements are false. a. is false because this is mixed up. the arachnoid loosely covers the surface of the brain, whereas the pia closely adheres to all contours of the CNS. b. is correct: the arachnoid is avascular because it doesn't have any blood vessels trunning within it. both the dura and the pia are vascular. the dura has the middle meningeal artery and branches, and the pia has the cerebral arterioles. c. is very false. the subpial space falls under the pia, between the pia and the CNS. Cranial pia wraps around arterioles (but not venules) as they enter the parenchyma of the brain, but a perivascular space called the SUBPIAL space exists betwee pia and these arterioles.

The following dural venous sinuses are associated with _____ and _____ infoldings Describe where each of the sinuses are located: a. inferior sagittal sinus b. superior sagittal sinus c. straight sinus d. confluence of sinuses e. Right transverse sinus f. Superior petrosal sinus

the falx cerebri and tentorium cerebelli a. inferior sagittal sinus is the inferior border of the falx cerebri until it becomes straight sinus b. superior sagittal sinus is the superior border of the falx cerebri c. straight sinus is where the falx cerebri and the tentorium cerebelli intersect d. confluence of sinuses is the connecting point of the superior sagittal sinus, straight sinus, and occipital sinus. e. right transverse sinus is the edghe of the tentorium cerebelli f. superior petrosal sinus is the anterior part of the tentorium cerbelli

The meningeal branches of C2 and C3 innervate what?

the floor of the posterior cranial fossa.

What is a neuropil?

the meshwork of cellular processes emerging from neurons (axons and dendrites) and glial cells. This literarly means "nerve felt". Special staining methods (not H&E) are needed to see the neuropil.

What two CNS barriers do astrocytes contribute to?

the true BBB: - formed by tight junctions of the endothelium and astrocytes mediate the formation of these junctions, and also the astrocytic end-feet contributes physically to the barrier. glia limitans: formed by astrocytic end-feet

How does the Meninges physically protect the brain? Choose at least one a. Though CSF adds weight to the brain, CSF provides a "cushioning" barrier b. The brain floats in the CSF, which drops the weight of the brain, thus allowing the brain to be suspended c. the brain is tied by the meninges in a way that suspends them. d. the brain is tethered by the meninges but not the spinal cord

the two correct answers are b and c. the CSF allows to decrease the weight of the brain, thus allowing the brain to be suspended. the brain is tethered by the meninges in a way that suspends them.

the neural cavity of the neural tube becomes _____

the ventricles of the brain and the central canal of the spinal cord. there are 4 ventricles in the brain, and that is where CSF is formed.

Neuropeptides act as what?

they act as neuromodulators, neurohormones, and neurotransmitters neuromodulators act on the presynaptic cell to change the amount of neurotransmitter released in response to stimulation or is co-secreted with a neurotransmitter and changes the response of the postsynaptic cell neurohormones are released from secretory neurons into the blood to act at a distant site

what are glia limitans?

they are astrocytic end-feet lining the outermost parenchyma of the brian and spinal cord. these astrocytic end-feet are arranged very closely together (they are also joined by tight junctions).

What are denticulate ligaments?

they are extensions of the pia mater that attach on either side of the spinal cord. They each have 20-22 sawtooth processes that anchor the spinal cord to the dura mater.

From what are choroid plexuses formed embryologically?

they are formed by an invagination of well-vascularized pia mater and the adjacent (specialized) ependyma into the ventricles.

What are Excitatory postsynaptic potentials (EPSPs)?

they are inputs that bring the postsynaptic membrane potential closer to threshold they open sodium and potassium channels, driving the membrane potential to depolarization

What are arachnoid granulations?

they are large clusters of arachnoid villi that are located within the dural sinuses. particularly found in the superior sagittal sinus and its lateral lacunae. arachnoid granulations are visible to the naked eye.

how do astrocytes influence neurotransmission?

they are present at synapses and participate in neurotransmitter metabolism. for example, they can stop synaptic transmission by taking up glutamate (neurotransmitter) and converting it to glutamine (amino acid), which can be taken up by the presynaptic neuron again and converted back to glutamate.

what do oligodendrocytes do and where do they predominate?

they myelinate neurons, acting as insulators of CNS axons they are the predominant glial cells in white matter (where they produce and maintain the myelin sheaths around axons). * they are also present in gray matter, but their significance (function) seems debatable. How they look: they have a central cell body that extends to 50 processes that myelinate individual neurons. They are arranged in rows, regularly interspersed, with processes radiating outward to axons.

What is the function of microglia?

they provide widespread immunological surveillance of the CNS. They are the endogenous immune cells of the CNS. Also found in optic nerve and retina. - they are the smallest glia, proliferate fast, make up 5% of all glial cells in the CNS. - they do not overlap with neighboring microglia (but unlike astrocytes, microglia are not jointed by gap junctions).

what is synaptic delay?

time from the arrival of a signal at the axon terminal of a presynaptic cell to the beginning of an action potential in the postsynaptic cell

What causes spinal subarachnoid hemorrhage (SSH)?

trauma (often due to lumbar puncture), arteriovenous malformations, aneurysms, tumors, and even spontaneously (this is rare) Spinal subarachnoid hemorrhage is much more rare than cranial subarachnoid hemorrhage (SSH makes up <1% of all subarachnoid hemorrhage cases). This is because blood flow to spinal cord is much less than to the brain. Also, there is room to accommodate hemorrhage in spinal cavity.

true or false: the composition of interstitial fluid reflects the composition of blood plasma in the body, but this is not the case for nervous tissue.

true. generally in the body, the only limitation to exchange through capillaries is the physical properties of the capillary wall (fenestrations, intercellular clefts). But this free exchange is not present in nervous tissue.

True or False: spinal epidural space is normal

true. recall that the two dural layers in the spine are not fused. in between the two layers is a natural space (the epidural space). this space can be accessed by a needle.

what is serotonin produced from and where?

tryptophan in the brain and GI tract

What 4 arteries provide the blood supply to the brain?

two vertebral arteries and two internal carotid arteries. these arteries pierce the dura and arachnoid and then course through the subarachnoid space (where they are invested in a leptomeningeal coat)

Norepinephrine, epinephrine, and dopamine are synthesized from what?

tyrosine

how do spinal subdural hematomas occurs?

we are not really sure. in contrast to cranial subdural hematomas, which occur due to laceration of cerebral vein, spinal subdural hematomas etiology is not fully known. This is very rare. symptoms are: back pain and/radiculopathy with variable neurological deficit. about 1/2 of these patients develop complete sensorimotor deficits.