NSCI175 Exam 1

Steps in synaptic transmission

1. Synthesis and Storage 2. Release 3. Postsynaptic Receptors 4. Inactivation.

Glutamate

Primary excitatory Receptor subtype: AMPA, NMDA Agonist: AMPA, NMDA Antagonist: CNQX, AP5 mGlut receptor. Kainate receptors exist on presynaptic and postsynaptic membranes.

Describe the key molecular (i.e., ionic) events that underlie each phase: threshold; rising phase; peak; falling phase; afterhyperpolarization; refractory period

Rising phase characterized by a rapid depolarization of the membrane. Continues until membrane potential reaches +40 mV. Voltage-gated sodium channels open for depolarization. Overshoot: part of action potential where the inside of the neuron is positively charged with respect to the outside. The membrane potential goes to a value that is close to the Equilibrium potential for sodium. The driving force pushes potassium out of the cell/as the membrane potential reaches +30 mV, other voltage-gated channels are opening in the membrane. These channels are specific for the potassium ion. Falling phase is a rapid repolarization until the membrane is more negative than the resting potential. Undershoot: last part of the falling phase. Also called afterhyperpolarization. Sodium channels go from inactive to close.

Differentiate neurotransmitter-gated ion channels from g-protein-coupled receptors

Transmitter-gated ion channels: membrane-spanning proteins consisting of 4 or 5 subunits that come together to form a pore between them. Pore usually closes in absence of neurotransmitters. Do not show the same degree of ion selectivity as do voltage-gated ion channels. Can be permeable to multiple ions. Ionotropic. Faster. G-protein-coupled receptors can trigger widespread metabolic effects. Often referred to as metabotropic receptors. Muscarinic. Metabotropic. Slower. Activate second messengers.

Discuss the three mechanisms for termination of chemical synaptic transmission

1. diffusion. Having more particles in the cleft than outside is a highly-ordered state, and so the particles move until the concentrations are equal. 2. enzymatic degradation. The breakdown of the neurotransmitter acetylcholine into its constituent parts, acetate and choline, by the enzyme acetylcholinesterase (AChE). 3. reuptake. This mechanism is common to all of the classical "small-molecule" neurotransmitters except acetylcholine. The pre-synaptic neuron (or possibly a glial comrade-in-arms) expresses a reuptake transporter, or a protein that pushes the neurotransmitter against its concentration gradient and ferries it across the cell membrane.

Identify factors that influence conduction velocity

Action potential conduction velocity increases with increasing axonal diameter. If the axon is narrow, and there are many open membrane pores, most of the current will flow across the membrane. If the axon is wide, and there are few open membrane pores, most of the current will flow down inside the axon. Wide axons conduct action potentials faster. The farther the current goes down the axon, the farther ahead of the action potential the membrane will be depolarized. Axonal size: smaller axons require greater depolarization to reach threshold. They are more sensitive to being blocked by local anesthetics. Number of voltage-gated channels in the membrane.

Describe the main types of glial cells, including the main function of each

Astrocytes: the most numerous glia in the brain. Fill most of the spaces between neurons. Regulate the chemical content of the extracellular space. Can restrict neurotransmitters. Have special proteins that actively remove many neurotransmitters from the synaptic cleft. Oligodendroglial and Schwann cells provide layers of membrane that insulate axons. Node of Ranvier: part of axon membrane exposed/not covered by myelin sheath. Oligodendroglia are only found in the central nervous system. Schwann cells are only found in the peripheral nervous system. Ependymal cells: cells that line fluid-filled ventricles within the brain and play a role in directing cell migration during brain development. Microglia: cells that function as phagocytes to remove debris left by dead or degenerating neurons and glia. Remodel synaptic connections.

Explain why a neuron needs a resting potential

Can't always be firing. Need a "recharge."

Goldman equation

Changes in resting potentials

Stimulants

Cocaine and amphetamine exert their effects at synapses made by dopaminergic and noradrenergic systems Dopamine and norepinephrine are catecholamines because of their chemical structure. Catecholamines released into the synaptic cleft are normally terminated by specific uptake mechanisms. Cocaine and amphetamine block this catecholamine uptake. Cocaine targets dopamine reuptake more selectively Amphetamine blocks norepinephrine and dopamine reuptake and stimulates the release of dopamine. Amphetamine causes the transporters to spill neurotransmitters into the synaptic cleft. Cocaine binds to the transporters at the presynaptic cleft.

Sketch a hippocampal slice and explain its microcircuitry

Consists of two thin sheets of neurons folded onto each other: dentate gyrus and Ammon's horn. Ammon's horn has four divisions. Entorhinal cortex: major input to the hippocampus. Sends information to the hippocampus by way of a bundle of axons (perforant path). Perforant path axons synapse on neurons of the dentate gyrus. Dentate gyrus neurons give rise to axons (mossy fibers) that synapse on cells in CA3. CA3 cells give rise to axons that branch One branch leaves the hippocampus via the fornix The other branch (Schaffer collateral) forms synapses on the neurons of CA1. The trisynaptic circuit is a neural circuit in the hippocampus, which is made up of three major cell groups: granule cells in the dentate gyrus, pyramidal neurons in CA3, and pyramidal neurons in CA1. The hippocampal relay involves 3 main regions within the hippocampus which are classified according to their cell type and projection fibers. The first projection of the hippocampus occurs between the entorhinal cortex and the dentate gyrus. The entorhinal cortex transmits its signals from the parahippocampal gyrus to the dentate gyrus via granule cell fibers known collectively as the perforant path. The dentate gyrus then synapses on pyramidal cells in CA3 via mossy cell fibers. CA3 then fires to CA1 via Schaffer collaterals which synapse in the subiculum and are carried out through the fornix. Collectively the dentate gyrus, CA1 and CA3 of the hippocampus compose the trisynaptic loop. EC → DG via the perforant path (synapse 1), DG → CA3 via mossy fibres (synapse 2), CA3 → CA1 via schaffer collaterals (synapse 3)

Discuss methods for studying neurotransmitter systems including immunohistochemistry, in situ hybridization, neuropharmacological analysis (agonists, antagonists, etc), and ligand binding methods

Cre technology: Allows scientists to manipulate DNA in model organisms. Allows us to insert or delete genes in particular cells. Immunocytochemistry: method used to anatomically localize particular molecules to particular cells. Applied to thin sections of tissue. Once the neurotransmitter candidate has been chemically purified, it is injected under the skin or into the blood-stream where it stimulates an immune response. The best antibodies for immunocytochemistry bind very tightly to the transmitter. Optogenetics make it possible to activate one specific type of synapse at a time. Microiontophoresis: method used to assess the postsynaptic actions of a transmitter candidate. Neurotransmitter candidates are dissolved in solutions that cause them to acquire a net electrical charge. Pipette with ionized solution is positioned next to the postsynaptic membrane. Transmitter candidate is ejected in very small amounts by passing electrical currents through the pipette.

Explain how demyelination affects action potential conduction

Demyelination: failure of action potential conduction. Can lead to numerous diseases that affect coordination, movement, etc. because of the failure of action potential conduction.

Compare convergence and divergence of neurotransmitter systems

Divergence: one neurotransmitter activates more than one subtype of receptor, allowing it to elicit different postsynaptic responses. Convergence: several neurotransmitters can influence one effector system via activation of their specific receptors.

Opioids

Each class of opioid peptide is liberated from an inactive pre-propeptide derived from distinct genes Opioid precursor processing is carried out by tissue-specific processing enzymes that are packaged into vesicles, along with the precursor peptide, in the Golgi apparatus Widely distributed throughout the brain Often co-localized with small-molecule neurotransmitters, such as GABA and 5-HT (Serotonin). Opioids tend to be depressants. Act as analgesics when injected intracerebrally in experimental animals. Analogs of morphine.

Compare the similarities and differences between electrical and chemical synapses

Electrical synapses: synaptic transmission is an electrical current flowing from one neuron to the next. Common in brains of invertebrates and vertebrates, including mammals. Relatively simple in structure and function. Allow direct transfer of ionic current from one cell to the next Occur at gap junctions. The membranes of two cells are separated about 3 nm which is spanned by clusters of connexin proteins. The channel that forms from these connexons allows ions to pass directly from the cytoplasm of one cell to the cytoplasm of the other. Cells are said to be electrically coupled Chemical synapses: chemical neurotransmitters transfer information from one neuron to another at the synapse.

Nernst equation

Equilibrium potentials

Describe how EPSPs and IPSPs contribute to the generation of an action potential in the post-synaptic cell

Excitatory postsynaptic potential (EPSP): a transient postsynaptic membrane depolarization caused by the presynaptic release of neurotransmitters. EPSP summation: the simplest form of synaptic integration in the CNS. As the current proceeds down the dendrite and farther from the synapse, the EPSP amplitude will diminish because of the leakage of ionic current through membrane channels. May eventually approach 0. Inhibitory postsynaptic potential (IPSP): a transient hyperpolarization of the postsynaptic membrane potential caused by the presynaptic release of neurotransmitters.

Discuss the importance of animal research in the field of neuroscience

Genetically close to humans to help treat diseases.

Discuss important histological procedures and how they contributed to the advancement of neuroscience

Immunocytochemistry: method that anatomically localizes particular molecules to particular cells. When applied to thin sections of tissue, it's often called immunohistochemistry. Once the neurotransmitter candidate has been chemically purified. It is injected under the skin or into the bloodstream of an animal where it stimulates an immune response, such as the generation of antibodies. In situ hybridization: method useful in confirming that a cell synthesizes a particular protein or peptide. Uses complementary strands of mRNA (probes) to localize a certain peptide in a neuron. Can chemically tag the probes. Autoradiography: method using digital electronic imaging devices to detect radioactivity if the probe is made radioactive. FISH: fluorescence in situ hybridization.

Acetylcholine

In most cases is an excitatory neurotransmitter but is also a neuromodulator The primary neurotransmitter secreted by efferent neurons of the CNS Receptor subtype: Nicotinic receptor, muscarinic receptor Agonist: Nicotine, muscarine Antagonist: Curare, atropine Nicotinic ACh receptor at neuro muscular junction Cholinergic neurons. First neurotransmitter to be discovered. Primary neurotransmitter secreted by efferent neurons of the CNS. Memory, learning, reward, stress, etc.

Describe what factors determine each neuron's unique physiology

In most neurons in the CNS, depolarization of the dendrites and soma caused by synaptic input from other neurons leads to the generation of axon potentials if the axon hillock membrane is depolarized beyond threshold. In most sensory neurons, the action potential is generated near the sensory nerve endings, where depolarization caused by sensory stimulation leads to the generation of action potentials that propagate along the sensory nerves. Cerebral cortex has two major types of neurons: aspinuous stellate cells and spiny pyramidal cells. Aspinuous stellate cells fire at a relatively steady frequency because of a steady depolarizing current injected into its soma. Most pyramidal cells cannot sustain a steady firing rate and instead fire rapidly at the beginning and slow down even if the stimulus remains strong. Some neurons fire rapidly and then pause. Diverse behavior results from each neuron's physiology, which is determined by the properties and numbers of ion channels in its membrane. Some potassium ion channels activate very slowly.

List factors that can influence synaptic plasticity and neurogenesis

Increased neurogenesis facilitates learning and memory in the adult brain Pathological conditions, diet, stress, etc. can affect it. Think positive effect --> increase neurogenesis Negative effect --> decrease neurogensis

Compare and contrast input specificity and cooperativity

Input specificity: only active inputs show the synaptic plasticity. Synapses must be stimulated at frequencies high enough to cause summation of the EPSPs, and enough synapses must be active simultaneously to cause significant spatial summation of EPSPs (cooperativity).

Describe the properties and mechanisms of LTD in CA1

Long-term synaptic depression (LTD) Active synapses are decreased in effectiveness. Caused by lower levels of Ca2+ under lower levels of NMDA receptor activation and less Ca2+ influx. Results in a loss of AMPA receptors and synapse elimination. Synaptic transmission occurring at the same time as weak or modest polarization of the postsynaptic neuron causes LTD of the active synapses.

Discuss how synaptic homeostasis impacts LTP/LTD induction at active versus silent synapses

Metaplasticity: the rules of synaptic plasticity change depending on the history of synaptic or cellular activity. Synaptic scaling: adjustment of absolute synaptic effectiveness that preserves the relative adjustment of absolute synaptic effectiveness that preserves the relative distribution of synaptic weights. When activity is too high for too long, metaplasticity and scaling kick in to promote LTD and scale down synaptic weights. When activity is too low, they promote LTP and scale up synaptic weights. Silent synapse: a synaptic contact between two neurons where a presynaptic action potential fails to evoke a detectable postsynaptic signal. A synapse can be presynaptically silent if the action potential invading the presynaptic bouton or terminal fails to evoke release of neurotransmitter.

Compare different levels of analysis in neuroscience research (molecular, cellular, systems, behavioral, and cognitive neuroscience)

Molecular neuroscience: brain matter consists of a variety of molecules, many of which are unique to the nervous system. Cellular neuroscience: focuses on how all the molecules work together to give neurons their specific properties. Systems neuroscience: how different neural circuits analyze sensory information, form perceptions of the external world, make decisions, and execute movements. Behavioral neuroscience: how neural systems work together to produce integrated behaviors. Cognitive neuroscience: focuses on neural mechanisms responsible for the higher levels of human mental activity, such as self-awareness, imagination, and language. How the activity of the brain creates the mind.

Identify the criteria used to determine if a substance in the brain is a neurotransmitter and be able to determine if a substance is a neurotransmitter based on these criteria

Molecule must be synthesized and stored in the presynaptic neuron. Molecule must be released by the presynaptic axon terminal upon depolarization. When experimentally applied, the molecule must produce a response in the postsynaptic cell that mimics the response produced by the release of neurotransmitter from the presynaptic neuron. Have a mechanism to terminate the biological effect/feedback mechanism to control its activity.

Serotonin

Nine raphe nuclei Each nucleus projects to different regions of the CNS Those more caudal, in the medulla, innervate the spinal cord, where they modulate pain-related sensory signals Those more rostral, in the pons and midbrain, innervate most of the brain in much the same diffuse way as do the locus coeruleus neurons. Neurons fire most rapidly during wakefulness, when an animal is aroused and active. Manipulated by SSRIs Ionotropic and G-protein. ascending reticular activating system

Describe the methods used to classify neurons and glia

Number of neurites: Unipolar: neuron with one neurite Bipolar: neuron with two neurites Multipolar: neurons with more than three neurites Dendrites: Stellate cells: star-shaped dendritic trees Pyramidal cells: pyramid shaped trees Spiny or aspinous Connections: Primary sensory neurons: neurons with neurites on the sensory surfaces of the body. Deliver information to the nervous system. Motor neurons: neurons with axons that form synapses with the muscles and command movements. Interneurons: neurons that form connections only with other neurons. Majority of neurons. Axon length: Golgi type I neurons or projection neurons: neurons with long axons that extend from one part of the brain to the other. Golgi type II neurons or local circuit neurons: neurons with short axons that do not extend beyond the vicinity of the cell body.

List and define the four essential steps in the scientific process, including examples

Observation: includes making a hypothesis, designing an experiment, etc. to make an observation about the question being asked. Replication: there is always the possibility that something is due by chance. At the individual research level. The researcher repeats their own experiments. Interpretation: going beyond the observations. How is this important? How does it explain what was observed? Verification: other people doing similar work.

Describe the structure and functional properties of the sodium channel

Opened and closed by changes in membrane voltage. Created from a single long polypeptide. 4 domains numbered I-IV; each domain consists of 6 transmembrane alpha helices, number S1-S6. The domains clump together to form the pore that opens and closes. Has pore loops that assemble into a selectivity filter, making it 12 times more permeable to Na+ than K+. Na+ molecules are stripped of most of their associated water molecules when passing through the channel. The water is necessary for the ion to pass the selectivity filter. Voltage sensor in S4. Pattern of behavior: they open with little delay, stay open for about 1msec and then close, and cannot be opened again by depolarization until the membrane potential returns to a negative value near threshold. A membrane can include thousands of sodium channels, and many can be required to generate an action potential.

Describe post-synaptic potentials

Postsynaptic potential (PSP): an electrically mediated potential in the other neuron. Occurs when two neurons are electrically coupled, and an action potential in the presynaptic neuron causes a small amount of ionic current to flow across the gap junction channels into the other neuron.

GABA

Primary inhibitory Receptor subtype: GABAA, GABAB Agonist: muscimol, baclofen Antagonist: bicuculline, phaclofen GABA receptors are GABA-gated permeable to Cl- or G-protein coupled receptors.

Compare primary sensory neurons, motor neurons, and interneurons

Primary sensory neurons: neurons with neurites on the sensory surfaces of the body. Deliver information to the nervous system. Motor neurons: neurons with axons that form synapses with the muscles and command movements. Interneurons: neurons that form connections only with other neurons. Majority of neurons.

Differentiate agonists from antagonists

Receptor agonists: drugs that bind to receptors and mimic the actions of the naturally occurring neurotransmitter. Receptor antagonists: inhibitors of neurotransmitter receptors that bind to the receptors and block the normal action of the transmitter.

Explain why the progress of science is often slow

Repetition and verification.

Define the resting membrane potential, how it is measured and its value in a "typical" neuron

Resting membrane potential: the cytosol along the inside surface of the membrane has a negative electrical charge compared to the outside in a resting neuron. -65 mV. The resting membrane potential (EK) is approximately -65 mV and not -80 mV because the membrane is also somewhat permeable to Na+.

Describe the factors that enable saltatory conduction to occur

Saltatory conduction: action potentials skipping from node to node in myelinated axons. Myelin sheath and nodes of Ranvier.

Explain what Golgi and Cajal disagreed about

Santiago Ramón y Cajal argued that neurites of different neurons are not continuous with each other and communicate by contact and not continuity. Became known as the neuron doctrine. Camillo Golgi believed that the neurites of different cells are fused together to form a continuous network (reticular theory). Made the brain an exception to the cell theory. Santiago Ramón y Cajal argued that neurites of different neurons are not continuous with each other and communicate by contact and not continuity. Became known as the neuron doctrine.

Discuss how the resting membrane potential is maintained, including the role of ions and physical forces involved

Sodium-potassium pump: enzyme that breaks down ATP in the presence of internal Na+. Exchanges internal Na+ for external K+. Ensures that K+ is concentrated inside the neuron, ad Na+ is concentrated outside the neuron. The sodium-potassium pump is essential for maintaining the resting membrane potential because it moves ions against their concentration gradient and allows the neuron to maintain its typical membrane potential and prepare to fire action potentials. It's important to regulate external potassium concentration because the neuronal membrane at rest is mostly permeable to K+, so the membrane potential is close to EK. High K+ permeability is that the membrane potential is particularly sensitive to changes in the concentration of extracellular potassium.

Compare and contrast spatial summation and temporal summation

Spatial summation: adding together of EPSPs generated simultaneously at many different synapses on a dendrite. Temporal summation: adding together of EPSPs generated at the same synapse if they occur in rapid succession, within about 1-15 msec of one another. The synaptic current can either go down the inside of the dendrite or across the dendritic membrane.

Define LTP and how the EPSP change after LTP in the CA1

Strong NMDA receptor activation strengthens LTP. Strong NMDA receptor activation results in a flood of Ca2+ into the postsynaptic dendrite and the insertion of new AMPA receptors into the synaptic membrane, which makes transmission stronger. Synapses can split in half and form two different sites of synaptic contact. High-frequency stimulation is not an absolute requirement for LTP. Synapses must be active at the same time that the postsynaptic CA1 neuron is strongly depolarized for LTP. To achieve this necessary depolarization with a tetanus, synapses must be stimulated at frequencies high enough to cause summation of the EPSPs, and enough synapses must be active simultaneously to cause significant spatial summation of EPSPs (cooperativity). Following LTP, synaptic structure changes. Postsynaptic dendritic spines bud and form new synaptic contacts with axons. Increases probability that an action potential will trigger presynaptic glutamate release on CA1.

Explain the purpose of synaptic integration

Synaptic integration: process by which multiple synaptic potentials combine within one postsynaptic neuron.

Understand the difference between induction mechanisms and expression mechanisms of LTP in the CA1

Tetanus usually induces LTP. It's a brief burst of high-frequency stimulation.

Dopamine

The Dopaminergic Substantia Nigra and Ventral Tegmental Area Precursor of tyrosine Substantia nigra cells project axons to the striatum (the caudate nucleus and the putamen), where they facilitate the initiation of voluntary movements. Degeneration of the dopamine-containing cells can lead to Parkinson's disease. Axons from neurons in the ventra; tegmental area innervate a circumscribed region of the telencephalon that includes the frontal cortex and parts of the limbic system. Dopaminergic projection from the midbrain is sometimes called the mesocorticolimbic dopamine system Only G-protein

Norepinephrine

The Noradrenergic Locus Coeruleus: section of the pons with about 12,000 neurons Neurons use norepinephrine (NE). Axons leave the locus coeruleus in several tracts but then fan out to innervate just about every part in the brain. The locus coeruleus makes some of the most diffuse connections in the brain. One of its neurons can make more than 250,000 synapses and can have one axon branch in the other cerebral cortex and another in the cerebellar cortex. Cells seem to be involved in the regulation of attention, arousal, sleep-wake cycles, learning, memory, anxiety, pain, mood, and brain metabolism. Only G-protein. ascending reticular activating system

Summarize how an action potential is propagated along an axon

The axon is essentially the fuse; when a patch of axonal membrane is depolarized sufficiently to reach threshold, voltage-gated sodium channels open and initiate the action potential. The action potential does not turn back on itself. It goes in one direction only because of the refractory period and the inactivation of the sodium ion channels.

Explain why action potentials move away from the cell body

The flow of the sodium ions goes in one direction—away from the cell body. The areas that have had the action potential are refractory to a new action potential.

Explain the concept of driving force and calculate the driving force for an ion

The net force driving molecules down a concentration gradient is the chemical driving force. Net Driving Force: NDF = Vm - Eion -NDF → the direction of net current flow is inward +NDF → the direction of net current flow is outward

Discuss why resting membrane potential does not match the equilibrium potential

The resting membrane potential is not exactly equal to the equilibrium potential for potassium because the membrane has some resting permeability to species other than potassium.

Describe how vesicles fuse with the membrane

Vesicles release contents through exocytosis. Exocytosis: membrane of synaptic vesicle fuses to the presynaptic membrane at the active zone, allowing the contents of the vesicle to spill out into the synaptic cleft. The vesicle membrane is later recovered by endocytosis.

Differentiate animal rights and animal welfare views

Welfare: Animals are used only in worthwhile experiments that promise to advance our knowledge of the nervous system. All necessary steps are taken to minimize pain and distress experienced by the experimental animals (use of anesthetics, analgesics, etc.). All possible alternatives to the use of animals are considered. Adherence to ethical code is monitored Research proposals must pass a review by the Institutional Animal Care and Use Committee (IACUC), as mandated by federal law. Consists of a veterinarian, scientists in other disciplines, and nonscientist community representatives. After passing, proposals are evaluated for scientific merit by a panel of expert neuroscientists. Ensures only the most worthwhile projects are carried out. Papers out for publishing are carefully reviewed by other neuroscientists for both scientific merit and animal welfare concerns. Rights: Animal welfare: animals should be treated well but do not have the same legal and moral rights as humans. Animal rights: animals have the same legal and moral rights as humans.

Describe what it means if K+ ions are at equilibrium

When K+ ions are at equilibrium, it is due to potassium channels in the phospholipid bilayer. Potassium channels allow K+ to pass freely across the membrane and outside the cell. The A- left behind acquires a net negative charge, and an electrical potential difference is established across the membrane. The resulting electrical force pulls K+ ions inside the cell to counterbalance the force of the diffusion that is pushing the K+ ions outside of the cell. An equilibrium state is reached.

Reductionist approach

breaking the problem into smaller pieces for systematic experimental analysis to reduce the complexity of the problem.

Explain the ways in which neurons are specialized for communication

morphology: extensive branching of neurons, presence of axon and arborization of dendrites as branches. The number of inputs a particular neuron receives depends on the complexity of its dendrites. structural and functional intricacies of the synaptic contacts between neurons: pre and postsynaptic components communicate via the secretions of molecules from the presynaptic terminals that bind to receptors in the postsynaptic cell. organization in their membrane components for long-distance signaling: projection neurons have axons that extend long distances.

Explain why the action potential is referred to as all-or-none

neurons only fire when crossing the threshold. Depolarization has no effect until it crosses the threshold.

Endocannabinoids

small lipid molecules that can be released from postsynaptic neurons and act on presynaptic terminals. Retrograde messengers. Not packaged in vesicles like most other neurotransmitters. Manufactured rapidly and on demand. Small and membrane permeable. Bind selectively to the CB1 type of cannabinoid receptor, which is mainly located on certain presynaptic terminals. CB1 receptors are G-protein-coupled receptors. Main effect of CB1 receptors is often to reduce the opening of presynaptic calcium channels. Retrograde signaling: pre to post direction of communication.

Golgi stain

soaking material in a silver chromate solution. Makes neurons become darkly colored in their entirety. Shows that neurons have at least two distinguishable parts: the cell body and the neurites (axon branches and dendrites).

Explain what happens to the membrane potential when the brain is deprived of oxygen

the mitochondria within neurons cease producing ATP. The Sodium-Potassium pump requires ATP to function, so it would no longer be able to keep the resting membrane potential negative and pump out the Na+ as it flows in from the ion channels. The membrane potential would depolarize.

Define neurogenesis and identify where it can occur in the adult brain

the process by which neurons are formed or born. Takes place in the subventricular zone (SVZ) that forms the lining of the lateral ventricles and the subgranular zone that forms part of the dentate gyrus of the hippocampus area.

Nissl stain

uses basic dyes to stain the nuclei of all cells and clumps (Nissl bodies) of material surrounding the nuclei of neurons. Useful because it distinguishes between neurons and glia and enables histologists to study the arrangement (cytoarchitecture) of neurons in different parts of the brain.