Neuroscience Review

Structure of the Nervous System

• Common misconceptions about the brain include: that we use only part of our brain (incorrect, neurons are used actively to some extent), that neuron loss is only a concern at high age (incorrect, only limited neuron loss of under 5% occurs), and that new neruons are not born after birth (incorrect, neurogenesis occurs still, though at a low rate)
• Gray matter contains cell bodies, while white matter contains myelinated axons.
• A central division (brain and spinal cord) and a peripheral division (nerves) comprise the nervous system of all mammals.
• Gyri (bumps) and sulci (grooves) are on the brain's surface, caused by cerebral cortex expansion in fetal development.
• A fissure is a natural brain separation.
• The major brain structures are the cerebrum (largest part, hemisphere controls contralateral body side), cerebellum (movement control, contralateral control), and brain stem (vital function regulation).
• The cerebrum has four lobes: frontal, parietal, occipital, and temporal.
• The Sylvian fissure separates the frontal and temporal lobes.
• Phrenology relates behavioral traits to skull size.
• Adaptations in structure and function reflect brain evolution across species.
• Animal experiments can relate to humans because nervous systems evolved from common ancestors and mechanisms.

Anatomical References & Brain Structure

• Anterior or rostral points towards rat's nose.
• Posterior or caudal points toward rat's tail.
• Dorsal is pointing up.
• Ventral is pointing down.
• Humans have different anatomical references.
• Bilateral symmetry means the brain and spinal cord's sides mirror each other.
• Viewing the brain's internal structure requires sectioning, often using sagittal, horizontal, and coronal planes.
• A fluid-filled ventricular system consists of lateral, third, and fourth ventricles, and cerebral aqueduct.
• Ventricles contain ~150 ml of cerebrospinal fluid (CSF).
• Choroid plexus produces CSF at ~500 ml/day within the cerebral hemispheres.
• CSF flows from paired cerebral ventricles to connected brain stem cavities, exiting into the subarachnoid space
• Arachnoid villi in the subarachnoid space absorb CSF into blood vessels.
• Hydrocephalus happens if CSF flow to the subarachnoid space is impaired, fluid backs up.
• Hydrocephalus in babies causes head expansion due to skull softness, sparing brain damage.
• In adults, increased intracranial pressure compresses brain tissue leading to impairment/death if untreated.
• Treatment involves draining excess fluid with a tube in the swollen ventricle.

Brain Imaging Techniques

• CT scans generate brain slice images.
• MRI scans provide detailed anatomical views.
• PET scans show brain activity.
• fMRI scans also reveal brain activity.

Learning & Memory Tips

• Maximize short-term and long-term memory use by focusing, using brief learning periods, and taking breaks.
• Facilitate the transition from STM to LTM through sleep.
• Optimize memory retrieval by providing a context to form larger brain networks for learning.
• Reduce unwanted forgetting by repeating study material to strengthen new synapses.

Neurons & Glia

• Neurophilosophy states that understanding brain cell actions equals understanding mental abilities, no need to separate mind and brain.
• Neurons sense changes in the environment, communicate them, and command body responses.
• Glial cells insulate, support, and nourish neighboring neurons.
• In a brain analogy, if neurons were chocolate chips, glia would be the cookie dough.
• Freshly prepared brain tissue is cream-colored, requiring staining for individual cell visualization.
• Nissl stain uses basic dyes to stain neuronal nuclei and Nissl bodies, distinguishing neurons from glia and showing neuron arrangement in the brain.
• Golgi stain makes a small percentage of neurons entirely visible in brain tissue, revealing the distinguishable parts.
• Neurons have neurites: axons and dendrites
• Golgi believed neurites of diffent cells fuse, Cajal argued that eurites of different neurons communicate by contact: neuron doctrine
• A neuron's cell body gives rise to a single uniform diameter axon; branches extend at right angles and can project over great distances.
• Dendrites are rarely longer than 2 mm, extending from cell body and tapering to a fine point
• Neurons are separated from their environment by the neuronal membrane - which depends whether its the soma, the dendrites or the axon.
• A neuron cell body has the same organelles as animal cells.
• The cytoskeleton gives neurons their shape; its components are microtubules, microfilaments, and neurofilaments.
• The cytoskeleton is not static.
• The axon starts at the axon hillock.
• Axons have no protein synthesis, originating in the soma.

Axons, Synapses, and Neuronal Classification

• Axons can range from under a millimeter to more than a meter in length, frequently branching with the branches (axon collaterals) communicating with different regions
• Axon collaterals that communicate with the cell that gave eise or dentrites of neighbouring cells are called recurrent collaterals.
• Axon diameter is variable and crucial; larger diameters increase electrical signal speed.
• Each axon has a beginning (hillock), middle (proper), and end (terminal); the terminal passes information to other neurons via a synapse.
• Axon ends sometimes have short branches collectively called the terminal arbor.
• A neuron making synaptic contact innervates another cell.
• Synaptic vesicles in axon terminals contain neurotransmitters.
• A synapse has presynaptic/postsynaptic sides.
• The space between the synaptic membranes is called the synaptic cleft.
• Synaptic transmission transfers information from one neuron to another.
• Electrical impulses turn into chemical signals (neurotransmitters) at synapses, crossing the synaptic cleft and reversing back into electrical signals at the postsynaptic membrane.
• A single neuron's dendrites form a dendritic tree with each branch being a dendritic branch
• Dendrites have thousands of synapses and specialized spines for synaptic input that isolate chemical reactions
• Spines are sensitive to the type and amount of synaptic activity.
• Neurons are classified by the number of neurites: unipolar (one), bipolar (two), and multipolar (three or more).
• Neuron: stellate or pyramidal.
• Spiny neurons have spines.
• Neurons in the body's sensory surfaces are called primary sensory neurons.
• Motor neurons form synapses connect with muscles are called motor neurons.
• Interneurons only connect with other neurons.
• Projection neurons/Golgi type I neurons have long axons extending to other brain parts.
• Local circuit neurons/Golgi type II neurons have short axons staying within the cell's vicinity.
• Motor neurons commanding voluntary movement release acetylcholine, classifying them as cholinergic.

Glia and Neuronal Diseases

• Astrocytes fill spaces between neurons, influencing neurite growth and regulating the extracellular chemical content.
• Myelinating glia (oligodendroglial in CNS, Schwann cells in PNS) insulate axons with myelin sheath, sheath is interrupted exposing axonal membrane (node of Ranvier.).
• Ependymal cells line brain ventricles, directing cell migration.
• Microglia act as phagocytes, removing debris from dead/degenerating neurons and glia.
• Dendritic tree architecture reflects synaptic connection complexity, crucial for brain function.
• Synaptic connections form during fetal period and refine during infancy/early childhood.
• Intellectual disability is caused by disrupted brain development, subaverage cognitive functioning, and impaired adaptive behavior.
• Individuals with intellectual disabilities have fewer and longer/thinner dendritic spines.
• Alzheimer's disease disrupts neuronal cytoskeleton in the cerebral cortex (cognitive function region) disrupting the cytoskeleton of neurons in the cerebral cortex (region crucial for cognitive function.)
• Neurofibrillary tangles in cortex are caused by paired helical filaments/tau protein.
• Tau normally bridges microtubules in axons, ensuring straight/parallel orientation.
• Hyperphosphorylated tau detaches from microtubules, accumulating in soma, disrupting cytoskeleton and impeding information flow.
• Abnormal amyloid secretion leads to neurofibrillary tangles/dementia, resulting in the formation of plaques or amorphous extracellular deposits of amyloid-ß protein.
• Logic combinations are easier to remember in normal aging, not in Alzheimer's disease.
• Alzheimer's starts after the age of 65 ears, or 35 presenile Alzheimer's.
• Social contacts and stressful events can play a role.
• Patients dont die from teh disease itself, but complications.
• The cholinergic symptom is the first to collapse.
• Hibernation is a unique state with decreased body temperature, periodically interrupted by rewarming periods, in this cycle no brain damage occurs Highly phosphorylated tau forms readily during hibernation but reverses after arousal.

Evolution of the Brain

• Primitive "brains" are collections of body neurons; "real" brains are in the head where most senses are.
• Larger brains mean more nerves, with 40 billion neurons and 100 billion brain cells in humans.
• Human brains are larger than expected based on body size.
• Energetically expensive for larger brain.
• Mammals: a negative correlation of brain size and fat storage
• Aquatic mammals/primates are an exception, combining high fat storage with larger brains due to low movement expenses.
• Evolving a larger apecies, species must either increase net energy intake or reduce energy allocation.
• Humans have large brains due to: walking on two legs (saves energy), efficient food processing (cooking), and fat storage.
• Larger brains correlate with better cognitive skills.
• Neocortex contains sensory/motor areas that are in turn are connected by the association cortex.
• The human association cortex takes up a large part of the neocortex and contains 6 layers.
• Currently, the human brain decreases in size.
• Prefrontal cortex functions include planning, personality expression, decision-making, and social behavior.
• Larger brains have a higher white matter proportion.
• Neuron density is limited, leading to an efficient 3575 cm³ brain size.
• Complex brains have neurons with many spines.
• The two-year-old brain is relatively more complex in connections than adults.
• Less spines mean there is worse mental health.
• Fewer neurons but more synapses per volume.
• Strokes disrupt blood flow.

Neuronal Membrane and Action Potentials

• Action potenitals dont diminish, they are signals that are fixed.
• Information is encoded in the frequency and number of action potentials and the distribution.
• Excitable membranes can generate and conduct potential.
• When cells does not generate the the cell said to be at rest.
• On inside the cell, the cytosol is negative charged compared to the outside
• The difference electrical charge across the membrane is called resting membrane potential.
• Action potential is a simple bref reversal of the condition, and the inside becomes charged in the outside.
• Separation of ions thanks to impermeable lipid membranes and well-controlled exchanve in transmembrane channel.
• Water is the main ingredient in the cytosol and the extra cellular flow.
• The oxygen aqquires negative charge and acquired is more a polar.
• Na+, K, CA2+ and CL are particular importance for cellular neurophisiology.
• lon channels are made from spanning protiens.
• A functional channel accross the membrane requires that 4-6 protein form a poor.
• lon selectively and gating are most important property.
• lon pumps to transport ions actoss the mrembran (ATp).
• Open channel will influence by diffusion and electricity.
• Diffusion is the movement to concentration gradient.
• The voltage accross the membrance is called at any moment.
• Resitng protential is -65%.
• No movement of lons across the membrance.
• Electric forces pulling certain lons inside counts outside.
• lon equibrium protential and miniscule changes increase and decrese changes
• The net is charged occur and it drive accross the lons the more and equibrium
• the rate porportional it
• Voltage-gated sodium channels form a pore selective to sodium ions.
• Pore state depends on membrane voltage.
• Channels open briefly then close, requiring negative potential to reopen.
• Thousands of sodium channels are present per square micrometer of axon membrane.
• Concerted action of all channels generates action potential.
• Stellate cells use steady firing rate with depolarizing current.

The Neural Action Potential

• At rest, the neuronal membrane's inside is negatively charged relative to the outside.
• Action potential is the rapid charge reversal becoming positively charged in relation to the outisde
• Action potentials from the same membrane patch have identical size/duration and do not diminish down the axon.
• Frequency and pattern of action potentials encode information for transfer.
• Rapid depolarization characterizes the rising phase of an action potential, reaching ~40 mV.
• Overshoot is the part where it positive charged
• Rapid repolarization falls until it undershoots, which leads to a gradual restoration.
• Nerves fibers have a type of gated sodium that opens wgeb stretch.
• Nat depolarizes this membrance
• This depolarisation generates the action protential.
• Entry deolarises thr membrance which has to reach a criticlal evel or potential
• Threshold is critical for triggernign the poentiak
• In interneurons, depolarization caused by neurotransmitter-sensitive channels.
• Action potentials are "all-or-none".
• Action potential generation rate relays upon the magnitude of continuous depolarizing current, with the firing frequency reflecting the magnitude
• Neurons have a limited action that is called the absolute refractory period.
• The amount the require elevate the after absolute to de to be able to trigger.
• The after hyperdepolarisation is also important with the memory.
• Sodium current and potassium current are important for the action potential and the changes.

Synaptic Transmision

• The direct ionic cuttent transfer from to another and speacilized call junction.
• Electrical synapses occur to speacilzed sites that they interconect and function as electrifical synapses between neurons.
• Membrances of the cells and sepertade the clusters calls connexins.
• Connexin Subunit is a form in chanel is a called connexion.
• A lot of gap junctions can pass equality in both sides there fore their bidirectional.
• At electricial synapses is very face, action potential the in is very quick and produce, produce the postsynaptic cell at little delay.
• A variety cells are from, astrocytes, microglia, oilgodentrocytes , the brain. -Functionis transport and ATP between cells. If to is electrical coupied, it can flow with the small amount. -Posy synaptical poential and indude potential or fist nurons. -The PSPis a singlesmall but it is enough . If multiple and it is a simentously Electrical synapsis in found were requiers synchronized.
• For visualization and transmembrances their freeze to
• Transmitter.
• Synaptick clift where two mebrance is.
• Transmitter and synapitc vesicles what they do is keep the neurotransminter.
• Also many vesicles contains what is is alos scretory gramules.
• Axon tirminal where active action
• A lot of cells are presnt there.
• Pory Synaptic dense, is just and accumulator.
• CNS is a diffrent type of action cell and depend -On adentrite
  • On ceel body
  • If is on annther anix
• Dendtrintic spane also forms
• There are two type, asynmatrica and sunamticall sinmatricall are inhibitory usually,.
• Synpasis aalso occures between.
• Neuromosular , also one thw synapse is.
• -Always caususe an action potential and that is the must important specillzation. A lots of shallow folds that are packedwith neuro transmistter and zones.
• major neurotransmimtter fall into one of three, amiNO avids amines and peptides. Storage in secratyr, and release into snapatic vasicle.
• Fast transsimision is cna by Gluate Gaba or glynce
• Achyleine is fast and by nueromuscular
• the are synthases diffrent by diffrent ways and to the way .
• Gava are mainlly primmary what release -The contain specfic esnzimes synthesizes the from metaboiluc pescur, synthasizes these enzymes it transpot to exon terminasl.
• A precursor pepitd is esnythesized in thr rougt er and.
• It ckeaved in the golgi apparatus and yield.
• Active neurtransminntert the seceratory can biff out by golgi apparatus. Nerurtranisminetr and actulcal
• Voltage - gate channels , 2 to the cytoplasm is what activate
• Exocytosis is quiucj becaus Ca in the preacisly It occurs wjere vasivles are ready
• Duirns a porid where vasiscles are mobillized the What is is bound to the the sytoskleton thar is on axis teermjnlasl. • Ca is was activate in the end

Neurotransmitters & Synapses

• Calcium-calmodulin kinase phosphorylates synapsin, this help cause exocytosis
• Secretory granules release peptide neurotransmitters by exocytosis, calcium dependant, but not at the active zones
• Because the site of exocytosis is at a distance, release of peptides requires high frequency potentials that is because builds a lvel requiered it
• Vesicular v-SNAREs and outer membrane t-SNAREs bring presynaptic membrane and vesicles together this releases is where action potentiasl happen
• Botox uses this mechanism too, where blocks SNARE resulting botunism causes paralysis
• there are two types of transmitter gate iopwn and gi protien coutpled gates
• transimer gateeon forms proew and it causes conformatinal change and opems.
• they dont have as much selecitivyt because its voltag gated. it is fast bref poewful G proteins longer lasting, and diverse and inbolbve , the reeptorsm the active the proeiteneffecters and enzimes. It riggers metaoprtic with all metaoprtic
• different possyptic action.
• the if open and it helps to Na increase the potential with g protein or e, the it goes and bring with threshold for potentaisl where with help for more. If hyperolarize helps the cell not to create potential. That why its Inhibitory synatoc potential where atach and glycine channels. They then muste be cleared so more can happen with diffussion throht That why they reuputatke in specific reuptake can transptorter and the, It cause by what what
• membrane can be recycled
• what are the neuropharacology the offescts, inhibitors antagonist agonists
• synptic are intergratiom combining multiple potiabtions

Neurotransmitter systems and wiring

• The neurotransmition it the transmistter synthesis ,vesialaur, actikn
• Acetoolicjnee and serotinindopaninne are brain where wotking.
• Nueorns that re us achytocoline are called colongenic which is the where action s called.
• Neurons taht amien are called noradenererifc and is a what is to consider.
• Synthesize and stor in the prsynaptic and released bythe axon with stimulation when applied.
• There are two types or rach reeptors, niconticm.
• and muscain,
• muscarin, acyteline systhesize required
• a protiesn and made
• Cholongeuc nuron contan csht and synthsizes, with the cytotosl
• and the transpot that to the the transprt that, needs a c transprot for the power.

Memory

• adaptibility of brain circuit.
• the learning it the acquired when it.
• the memory of the reataint that it
• the the the are decleratative where it easy to form and get forggoten
• the what we that usually by over longer and less llike too get formton. r
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Memory systems

• following trauma, the memory loss.

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• medula temporal for consolidation. and what temporal. that. What that declarti.

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Questions cover brain anatomy, hydrocephalus, neuroimaging, and memory encoding strategies. It also includes memory retrieval, forgetting, and enzyme function related to spatial navigation.