Neuroscience (Purves)
https://www.hse.ru/data/2011/06/22/1215686482/Neuroscience.pdf Notes: the current chapter, didn't properly read before "Short-Term Synaptic Plasticity in the Mammalian Nervous System"
117 flashcards · Biology · by lakesare
Where does the action potential originate from?
Axon hillock. The electrical event that carries signals over such distances is called the action potential, which is a self-regenerating wave of electrical activity that propagates from its point of initiation at the cell body (called the axon hillock) to the terminus of the axon where synaptic contacts are made.
What's a neuropil?
Neuropil (or "neuropile") is any area in the nervous system composed of: axons, dendrites, glial cells LOW number of cell bodies. The neuropil is thus the region between nerve cell bodies where most synaptic connectivity occurs. The most prevalent anatomical region of neuropil is the brain which, although not completely composed of neuropil, does have the largest and highest synaptically-concentrated areas of neuropil in the body. For example, the neocortex and olfactory bulb both contain neuro…
What's extracellular VS intracellular recording used for? Extracellular recording is also called single-unit recording.
Extracellular recordings - detect action potentials, the all-or-nothing changes in the potential across nerve cell membranes. This sort of recording is particularly useful for detecting temporal patterns of action potential activity.Intracellular recordings - can detect the smaller, graded potential changes that trigger action potentials, and thus allow a more detailed analysis of communication between neurons within a circuit. These graded triggering potentials can arise at either sensory rece…
Nerves vs tracts?
nerves - bundle of axons in the peripheral nervous system tracts - bundle of axons in the central nervous system Axons in the central nervous system are gathered into tracts that are more or less analogous to nerves in the periphery.
What's the diffusion: down the concentration gradient VS against the concentration gradient The difference of concentration between the two areas is often termed as the concentration gradient, and diffusion will continue until this gradient has been eliminated.
down the concentration gradient - from high concentration to low. Since diffusion moves materials from an area of higher concentration to an area of lower concentration, it is described as moving solutes "down the concentration gradient".against the concentration gradient - from low concentration to high. Active transport moves material from area of low concentration to area of higher concentration, and therefore referred to as moving the material "against the concentration gradient".
What are ion transporters VS ion channels?
ion transporters - proteins that actively transport ions against their chemical gradients. Transporters create ion concentration differences by actively transporting ions against their chemical gradients.ion channels - proteins that simply allow selected ions to move, via diffusion, down the chemical gradients. Channels take advantage of these concentration gradients, allowing selected ions to move, via diffusion, down their chemical gradients. Thus, channels and transporters basically work aga…
Efflux VS influx?
efflux - material that's flowing out. influx - material that's flowing in. Movement of ions into cells is called influx while movement of ions out of the cells is called efflux.
Mole Vs molar units?
1 mole [mol] - exactly 6.02214076×1023 particles Particles may be atoms, molecules, ions, or electrons.1 molar [M, mol/L] - concentration, means moles per litre. In chemistry, the most commonly used unit for molarity is the number of moles per liter, having the unit symbol mol/L. A solution with a concentration of 1 mol/L is said to be 1 molar, commonly designated as 1 M.
What is mM?
Millimolars 1 Millimolar [mM] = 1 Millimole per liter [mmol/l] Molar concentration [M] measures a concentration of a solute in a solution (substance per unit volume of solution).Molar concentration is also called molarity, amount concentration or substance concentration.
Cations VS anions?
cation - an ion with a net positive charge. Cation is an ion with fewer electrons than protons.anion - an ion with a net negative charge. Anion is an ion with more electrons than protons. Electric charge of an ion = n of protons - n of electrons. There are additional names used for ions with multiple charges. For example, an ion with a −2 charge is known as a dianion and an ion with a +2 charge is known as a dication. A zwitterion is a neutral molecule with positive and negative charges at diff…
Which of these are cations VS anions? Na Cl K
Na+ - cation (positively charged ion) Cl- - anion (negatively charged ion) K+ - cation (positively charged ion) Potassium is the major cation inside animal cells, while sodium is the major cation outside animal cells.
Name an element that can form both a cation and an anion.
Hydrogen can form H+ (cation) and H- (anion). Hydrogen is actually somewhat unusual in that it readily forms both cations and anions. Most elements much prefer to form only one or the other. However, there are other elements that can form both cations and anions, such as arsenic, which can form 3− , 3+, and 5+ ions; and tellurium, which can form 2− and 4 + ions.
What happens when we have compartments with: 1mM of KCL 1mM of KCl membrane ONLY permeable to K+ A membrane permeable only to K+ (yellow spheres) separates compartments 1 and 2, which contain the indicated concentrations of KCl
No electrical potential will be measured across it. If the concentration of K+ on each side of this membrane is equal, then no electrical potential will be measured across it
What happens when we have compartments with: 10mM of KCl 1mM of KCl membrane ONLY permeable to K+ This difference in electrical potential is generated because the potassium ions flow down their concentration gradient and take their electrical charge (one positive charge per ion) with them as they go.Because neuronal membranes contain pumps that accumulate K+ in the cell cytoplasm, and because potassium-permeable channels in the plasma membrane allow a transmembrane flow of K+, an analogous situ…
The electrical potential of compartment 1 will be negative relative to compartment 2: Initially there will be a small movement of K+ from 1 to 2. Until the electromotive force acting on K+ balances the concentration gradient And the net movement of K+ becomes zero (at equilibrium).
What's an electrochemical equilibrium?
When these forces are equal: diffusion - the concentration gradient that causes K+ to move from 1 to 2 (taking along positive charge) Concentration gradient (the 10-fold excess of K+ in 1)electrical repulsion - electrical gradient that stops K+ from moving from 1 to 2 Electrical gradient (the relative positivity of 2)
Log-log VS semi-log plot?
log–log plot - uses logarithmic scales on both the horizontal and vertical axes. Monomials (relationships of the form y = axk) appear as straight lines in a log–log graph, with the power term corresponding to the slope, and the constant term corresponding to the intercept of the line.semi-log plot - uses one axis on a logarithmic scale, the other on a linear scale. It is useful for data with exponential relationships, where one variable covers a large range of values
Linear scale VS logarithmic scale?
linear scale - moving a unit adds +n. log scale - moving a unit of multiplies *n. Such a scale is nonlinear: the numbers 10 and 20, and 60 and 70, are not the same distance apart on a log scale. Rather, the numbers 10 and 100, and 60 and 600 are equally spaced.
[Nernst equation] What's X and EX? Compartment 2 is a reference compartment.
X - ion we're interested in E.g. K+ (potassium)EX - equilibrium potential for our ion X E.g. -58mV Values: X - ion we're interested in E.g. K+ (potassium)EX - equilibrium potential for our ion X E.g. -58mVz - valency of the ion we're interested in (X) E.g. it's 1 for K+T - temperature in K (absolute temperature) E.g. T = 20 °C = 20 + 273 K[X]2 - concentration in mM of ion X in the 2nd container [X]1 - concentration in mM of ion X in the 1st container 1 Millimolar [mM] = 1 Millimole per liter [m…
[Nernst equation] What's z? Compartment 2 is a reference compartment.
z - valency of the ion we're interested in (X) E.g. it's 1 for K+ Values: X - ion we're interested in E.g. K+ (potassium)EX - equilibrium potential for our ion X E.g. -58mVz - valency of the ion we're interested in (X) E.g. it's 1 for K+T - temperature in K (absolute temperature) E.g. T = 20 °C = 20 + 273 K[X]2 - concentration in mM of ion X in the 2nd container [X]1 - concentration in mM of ion X in the 1st container 1 Millimolar [mM] = 1 Millimole per liter [mmol/l]Constants: F - Faraday cons…
[Nernst equation] Name 3 steps to go from: to: Compartment 2 is a reference compartment.
Supersede R (gas constant) and F (Faraday constant) with numbers Take T = room temperature (T = 20 °C = 20 + 273 K) Turn loge into log10
If compartment 2 is a reference point - what's the voltage across our membrane? (Reference point == defined as zero potential)
It's negative, e.g. V = -58mV. This approach is also applied to biological systems. In this case, the outside of the cell is the conventional reference point.
Valency VS molarity?
valency - number of chemical bonds the atoms of a certain element can form. E.g. valency of K+ is 1.molarity [mol/l] - concentration of a solute in a solution Molar concentration [M] measures a concentration of a solute in a solution (substance per unit volume of solution).Molar concentration is also called molarity, amount concentration or substance concentration.
Valency (in linguistics) VS valency (in chemistry)? "Valency" comes from Latin valentia "strength, capacity".
valency (in linguistics) - number of arguments a verb can take. intransitive (0 arguments) - she sleepstransitive (1 argument) - she kicks the ballditransitive (2 arguments) - she gave him a booktritransitive (3 arguments) - I bet her a dollar on a horsevalency (in chemistry) - is the number of chemical bonds the atoms of a certain element can form. The valency of an element is related to how many electrons are in the outer shell.E.g. it's 1 for K+.
How is 1mM read?
1 Millimolar [mM] 1 Millimolar [mM] = 1 Millimole per liter [mmol/l]
#todo The ability to alter ion flux experimentally by changing either the potential imposed on the membrane (Figure 2.5B) or the transmembrane concentration gradient for an ion (see Figure 2.4C) provides convenient tools for studying ion fluxes across the plasma membranes of neurons, as will be evident in many of the experiments described in the following chapters.
This example demonstrates that both the direction and magnitude of ion flux depend on the membrane potential. Thus, in some circumstances the electrical potential can overcome an ionic concentration gradient.
[Goldman equation] What does PK indicate in the Goldman equation?
Permeability of the membrane to potassium (K). If the membrane in Figure 2.6A is permeable to K+ and Na+ only, the terms involving Cl– drop out because PCl is 0.
[Goldman equation] How does the Goldman equation reduce to Nernst equation? Goldman equation Nernst equation
When the membrane is only permeable to one ion, e.g. K+. PNa and PCl become 0. The valence z was eliminated (it's always either 1 or -1) The valence factor (z) in the Nernst equation has been eliminated; this is why the concentrations of negatively charged chloride ions, Cl–, have been inverted relative to the concentrations of the positively charged ions [remember that –log (A/B) = log (B/A)].
What ion is usually inside and outside the cell?
inside: K+ outside: Na+ There is much more K+ inside the neuron than out, and much more Na+ outside than in. Similar concentration gradients occur in the neurons of most animals, including humans
Why are these squid axons so large in diameter? The axons of these nerve cells can be up to 1 mm in diameter—100 to 1000 times larger than mammalian axons.
Squid uses these axons for jet propulsion effect (to escape from predators), and the larger diameter of the axon leads to the faster action potential. Giant neurons evidently evolved in squid because they enhanced survival. These neurons participate in a simple neural circuit that activates the contraction of the mantle muscle, producing a jet propulsion effect that allows the squid to move away from predators at a remarkably fast speed. As discussed in Chapter 3, larger axonal diameter allows…
Name 2 factors that lead to the negative voltage inside the cell during rest.
There is more K+ inside the neuron than outside. During rest, the membrane is mostly permeable to K+ ions. The selective permeability to K+ is caused by K+-permeable membrane channels that are open in resting neurons, and the large K+ concentration gradient is, as noted, produced by membrane transporters that selectively accumulate K+ within neurons.
What happens to the membrane permeability during the action potential?
Membrane temporarily becomes most permeable to Na+. Membrane: starts out being most permeable to K+, and temporarily switches to become most permeable to Na+. and goes back to the decreased Na+ permeability. In the resting state, PK of the neuronal plasma membrane is much higher than PNa; since, as a result of the action of ion transporters, there is always more K+ inside the cell than outside.The transient increase in Na+ permeability causes the membrane potential to become even more positive,…
Why is there much more Na+ outside the cell, and K+ inside the cell?
Both - as a result of the action of ion transporters. Transporters create ion concentration differences by actively transporting ions against their chemical gradients.
What are these?
These are all action potentials! Action potential recorded from a myelinated axon of a frog motor neuron. Action potential recorded from the cell body of a frog motor neuron. The action potential is smaller and the undershoot prolonged in comparison to the action potential recorded from the axon of this same neuron (B).Action potential recorded from the cell body of a neuron from the inferior olive of a guinea pig. This action potential has a pronounced plateau during its falling phase.Action p…
What channels are open at each stage of the action potential? _______ _______ _______ _______
1. Leak K+ channels are open as always (always open)2. Voltage-gated Na+ channels begin to open (Na+ enters into the neuron)3. Voltage-gated Na+ channels begin to close (Na+ conductance starts to decline)4. Voltage-gated K+ channels begin to open (they are normally closed, but open in response to depolarization) Why does the undershoot occur? Because most voltage-gated K channels are still open.
What does the voltage clamp do?
Voltage clamp because it controls, or clamps, membrane potential (or voltage) at any level desired by the experimenter.
What would happen to K+ and Na+ if we change the membrane potential to be more positive (than the resting potential) [using the voltage clamp]? The voltage clamp.
An early influx of Na+ into the neuron Delayed efflux of K+ from the neuron These experiments using the voltage clamp show that changing the membrane potential to a level more positive than the resting potential produces two effects: an early influx of Na+ into the neuron, followed by a delayed efflux of K+.
Membrane conductance VS membrane permeability?
Conductance - reciprocal of resistance. Permeability - what ions the membrane lets through. For present purposes, permeability and conductance can be considered synonymous. When evaluating ionic movements from an electrical standpoint, it is convenient to describe them in terms of ionic conductances rather than ionic permeabilities.
In what way is an action potential a combination of: a fast positive cycle, and a slow negative cycle
Action potential (black curve), together with the underlying changes in Na+ (red curve) and K+ (yellow curve) conductance.
When does the explosion VS action potential start happening?
explosion - when exogenous heat is bigger than the escaping heat. As a result of this positive feedback loop, the rate of the reaction builds up exponentially - the definition of an explosion.action potential - when the rate of increased Na+ entry is bigger than the rate of K+ exit. Remember there's an increased Na+ entry because (for some reason) the membrane has been depolarized, opening the voltage-gated Na+ channels. In any such process there is a threshold, that is, a point up to which hea…
What's a passive current flow?
Current flow in the absence of action potentials. Current conduction by wires, and by neurons in the absence of action potentials, is called passive current flow. The progressive decrease in the amplitude of the induced potential change occurs because the injected current leaks out across the axonal membrane; accordingly, less current is available to change the membrane potential farther along the axon. Thus, the leakiness of the axonal membrane prevents effective passive transmission of electr…
What's shown on these 2 graphs?
1. Passive current flow Membrane doesn't reach its threshold, and current dissipates through the axon.2. Propagation of the action potential An action potential occurs without decrement along the entire length of the axon, which in humans may be a distance of a meter or more. Thus, action potentials somehow circumvent the inherent leakiness of neurons. Remember that both the passive current flow and action potential participate in
[Passive membrane properties] What's Vx and x in the formula for the decrement of voltage with distance? Vx - ___ x - ___ V0 - voltage where the current was applied λ - 'length constant' of the axon. The decrement of the voltage with distance
Vx - voltage at distance x x - distance away from the application of the current The length constant λ depends upon the physical properties of the axon, in particularthe relative resistances of the plasma membrane (rm),the intracellular axoplasm (ri), andthe extracellular medium (r0).
The speed of the passive current flow VS action potential?
passive current flow - nearly instantaneous action potential - it's chemical and is much slower, we wait for the Na+ channels to open. Action potential has a measurable rate of transmission, called the conduction velocity.The rate of action potential conduction limits the flow of information within the nervous system.
Why action potentials do not propagate back to the point of their initiation?
Because of the refractory period. As the action potential spreads, the membrane potential repolarizes due to K+ channel opening and Na+ channel inactivation, leaving a "wake" of refractoriness behind the action potential that prevents its backward propagation.
Name 2 ways to increase the speed of the action potential. Because action potential conduction requires passive and active flow of current, the rate of action potential propagation is determined by both of these phenomena.
increase the diameter of an axon - decreases resistance Increased diameter decreases the resistance to passive current flow.The consequent increase in action potential conduction velocity presumably explains why giant axons evolved in invertebrates such as squid, and why rapidly conducting axons in all animals tend to be larger than slowly conducting ones.myelinate the axon - acts as an insulator Myelination prevents the current from leaking out of the axon and thus increases the distance along…
Exactly how does myelination speed up the action potential conduction. Whereas unmyelinated axon conduction velocities range from about 0.5 to 10 m/s, myelinated axons can conduct at velocities of up to 150m/s.
Time-consuming process of action potential generation occurs only at nodes of Ranvier, where there is a gap in the myelin wrapping. An action potential generated at one node of Ranvier elicits current that flows passively within the myelinated segment until the next node is reached.
What are nodes of Ranvier?
Periodic gaps in the myelination of axons where action potentials are generated. Nodes of Ranvier (axon is blue, and myelin is gold)
What's saltatory propagation?
Propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials. An action potential generated at one node of Ranvier elicits current that flows passively within the myelinated segment until the next node is reached. From the Latin saltare, to hop or leap.
What's an integral membrane protein (IMP)?
A membrane protein that is permanently attached to the membrane of a cell.
[Types of integral membrane proteins (IMP)] What's the difference between: Integral polytopic protein Integral monotopic protein Integral membrane protein (IMP) is a protein that is permanently attached to the membrane of a cell.
Integral polytopic protein - spans the entire membrane Single-pass membrane proteins cross the membrane only once, while multi-pass membrane proteins weave in and out, crossing several times.Polytopic proteins are also called transmembrane protein (TM).Integral monotopic protein - is only on one side of the membrane Integral monotopic proteins are associated with the membrane from one side but do not span the lipid bilayer completely.
Name any 2 ways a neurotoxin might affect the neuron. A toxin is a harmful substance produced within living cells or organisms; synthetic toxicants created by artificial processes are thus excluded.Neurotoxins is a toxin that primarily affects the nervous systems of animals.
Tetrodotoxin produces a potent and spe-cific obstruction of the Na+channelsresponsible for action potential genera-tion, thereby paralyzing the animalsunfortunate enough to ingest it. Other peptides inscorpion venom, called b-toxins, shift thevoltage dependence of Na+channel acti-vation (Figure B). These toxins cause Na+channels to open at potentials muchmore negative than normal, disruptingaction potential generation. (A) Effects of toxin treatment on frog axons.(1) α-Toxin from the scorpion L…
Name 2 types of active transporters (depending on where they take energy for ion transportation). Moving ions uphill requires the consumption of energy, and neuronal transporters fall into two classes based on their energy sources.
ATPase pumps ATPase pumps use hydrolysis of ATP as an energy source.The most prominent example of an ATPase pump is the Na+ pump (or, more properly, the Na+/K+ ATPase pump), which is responsible for maintaining transmembrane concentration gradients for both Na+ and K+.Ion exchangers Ion exchanger channels do not use ATP directly, but depends instead on the electrochemical gradients of other ions as an energy source. This type of transporter carries one or more ions up its electrochemical gradie…
What's a protein domain?
A protein domain is a part of the protein that's self-stabilizing and folds independently. A protein domain is a region of the protein's polypeptide chain that is self-stabilizing and that folds independently from the rest. Each domain forms a compact folded three-dimensional structure. Pyruvate kinase, a protein with three domains.
Where's a domain in an ion channel? Schematic diagram of an ion channel.
1 - channel domains (typically four per channel) Pyruvate kinase, a protein with three domains.
Name 2 types of synapses.
chemical synapses electronic synapses
Name 2 interesting features of electrical synapses. Electrical synapses thus work by allowing ionic current to flow passively through the gap junction pores from one neuron to another. This arrangement has a number of interesting consequences.
extremely fast Another important feature of the electrical synapse isthat transmission is extraordinarily fast: because passive current flow across the gap junction is virtually instantaneous, communication can occur with-out the delay that is characteristic of chemical synapses.Example: Such synapses interconnect many of the neurons within the circuit that allows the crayfish to escape from its predators, thus minimizing the time between the presence of a threatening stimulus and a potentially…
What's an axon terminal? Axon terminals, also knows as synaptic boutons, terminal boutons, or end-feet.
Distal terminations of the branches of an axon.
[Chemical synapses] What are synaptic vesicles filled with?
With neurotransmitters. The key feature of all chemical synapses is the presence of small, membrane-bounded organelles called synaptic vesicles within the presynaptic terminal. These spherical organelles are filled with one or more neurotransmitters.
[Chemical synapses] What's the role of voltage-gated Ca2+ channels in chemical synapses?
Increased Ca2+ concentration causes synaptic vesicles to fuse with the presynaptic membrane. 1. Depolarization of presynaptic terminal opens voltage-gated Ca2+ channels, and2. Increased Ca2+ concentration causes vesicles to fuse with the presynaptic membrane, and3. this allows neurotransmitters to be released into the synaptic cleft. Elevation of the presynaptic Ca2+ concentration allows synaptic vesicles to fuse with the plasma membrane of the presynaptic neuron. The Ca2+-dependent fusion of s…
[Chemical synapses] In what way does the release of neurotransmitter affect the postsynaptic neuron?
Neurotransmitters bind to specific receptors Transmitters diffuse across the synaptic cleft and bind to specific receptors on the membrane of the postsynaptic neuron.This causes channels to open (or close!) The binding of neurotransmitter to the receptors causes channels in the postsynaptic membrane to open (or sometimes to close), thus changing the ability of ions to flow into (or out of) the postsynaptic cells.This changes membrane potential. The resulting neurotransmitter-induced current flo…
Why is striate cortex called so? Stria - a stripe or line distinguished from the surrounding area by color, texture, or elevation.
Because of the stria visible to the naked eye (line of Gennari). The primary visual cortex (or V1) is sometimes also called the striate cortex due to the presence of a large band of myelinated axons that runs along the edges of the calcarine sulcus. Micrograph showing the visual cortex (predominantly pink). The blue, horizontal band in the lower half of the image are the bands of Baillarger/the line of Gennari.
[Chemical synapses] Name 3 criteria for the substance to be considered a neurotransmitter. Over the years, a number of formal criteria have emerged that definitively identify a substance as a neurotransmitter.These have led to the identification of more than 100 different neurotransmitters.
1. Presence in the presynaptic cell. The substance must be present within the presynaptic neuron.2. Substance is released in response to presynaptic depolarization. The substance must be released in response to presynaptic depolarization, and the release must be Ca2+-dependent.3. It activates some receptor on the postsynaptic cell. Specific receptors for the substance must be present on the postsynaptic cell.
[Chemical synapses] Name 2 ways in which different neurotransmitters may do different things. There are more than 100 different neurotransmitters. Having more than one transmitter diversifies the physiological repertoire of synapses.
A neuron can be excited by one type of neurotransmitter and inhibited by another type of neurotransmitter. The speed of postsynaptic responses produced by different transmitters also differs, allowing control of electrical signaling over different time scales. In general, small-molecule neurotransmitters mediate rapid synaptic actions, whereas neuropeptides tend to mod-ulate slower, ongoing synaptic functions.
[Chemical synapses] What's meant by co-transmitters?
Different neurotransmitters synthesized and released from the same neuron. Until relatively recently, it was believed that a given neuron produced only a single type of neurotransmitter. It is now clear, however, that many types of neurons synthesize and release two or more different neurotransmitters. Neuropeptides and small-molecule co-transmitters.Because different types of transmitters can be packaged in different populations of synaptic vesicles, co-transmitters need not be released simult…
Name 2 categories of neurotransmitters. There are more than 100 different neurotransmitters.
small-molecule neurotransmitters The synthesis of small-molecule neurotransmitters occurs locally within presynaptic terminals (Figure 5.5A). The enzymes needed to synthesize these transmitters are produced in the neuronal cell body and transported to the nerve terminal cytoplasm at 0.5–5 millimeters a day by a mechanism called slow axonal transport.Most small-molecule neurotransmitters are packaged in vesicles 40 to 60 nm in diameter, the centers of which appear clear in electron micrographs;…
Name 3 ways in which neurotransmitter can be removed from the synaptic cleft. After a neurotransmitter has been secreted into the synaptic cleft, it must be removed to enable the postsynaptic cell to engage in another cycle of synaptic transmission.
The removal of neurotransmitters involves: diffusion away from the postsynaptic receptors, reuptake into nerve terminals or surrounding glial cells, degradation by specific enzymes. Or a combination of these mechanisms. Specific transporter proteins remove most small-molecule neurotransmitters (or their metabolites) from the synaptic cleft, ultimately delivering them back to the presynaptic terminal forreuse.
What does ACh stand for?
Acetylcholine (аситоко'лин) Acetylcholine is an organic chemical that functions in the brain and body of many types of animals (including humans) as a neurotransmitter—a chemical message released by nerve cells to send signals to other cells, such as neurons, muscle cells and gland cells
What's exocytosis VS endocytosis?
exocytosis - when a cell transports molecules (e.g., neurotransmitters and proteins) out of the cell. E.g. when synaptic vesicles fuse with the membrane and secrete neurotransmitters.endocytosis - when molecules are brought into the cell. Secretion is a fundamental cellular process involving the regulated release of intracellular products from cells.
What does cyto- stand for in biology?
A cell. cytosis - mechanism for the movement of large quantities of molecules in and out of cells.cytoplasm - the contents of a cell except for the nucleus. It includes cytosol, organelles, vesicles, and the cytoskeleton. Borrowed from Ancient Greek κύτος (kútos, "container, receptacl").
What's meant by a precursor in biochemistry?
Substance from which a more mature substance is formed. In biological processes, a substance from which another, usually more active or mature substance is formed.
What's meant by a synaptic vesicle cycle?
Calcium-regulated fusion of vesicles with the membrane, and Recycling of the vesicular membrane to make new vesicles. During the synaptic vesicle cycle, calcium-regulated fusion of vesicles with the presynaptic membrane is followed by endocytotic retrieval of vesicular membrane via coated vesicles and endosomes, and subsequent re-formation of new synaptic vesicles.
What's meant by first VS second messengers?
first messengers - extracellular signaling molecules First messengers are extracellular molecules, often hormones or neurotransmitters.second messengers - intracellular signaling molecules released by the cell in response to extracellular signaling molecules. Second messengers are intracellular molecules that transmit signals from cell membrane receptors to targets within the cell.
How is it possible to release one neurotransmitter but not the other? Differential release of neuropeptide and small-molecule co-transmitters.Big blue circles - neuropeptides.Small green circles - small-molecule neurotransmitters.
With low-frequency stimulation - small amount of Ca2+ is released, only small-molecule neurotransmitters are released. Low-frequency stimulation preferentially raises the Ca2+ concentra-tion close to the membrane, favoring the release of transmitter from small clear-core vesicles docked at presynaptic spe-cializations.With high-frequency stimulation - a lot of Ca2+ is released both small-molecule neurotransmitters, and neuropeptides are released. High-frequency stimulation leads to a more gener…
What exactly is an excititory VS inhibitory postsynaptic potential (PSP)? Postsynaptic potential (PSP) - the potential change produced in a postsynaptic neuron by the binding of neurotransmitter released from a presynaptic neuron.
excititory (EPSP) - increase the likelihood of the postsynaptic action potential inhibitory (IPSP) - decrease the likelihood of the postsynaptic action potential One way receptors can react to being bound by a neurotransmitter is to open or close an ion channel, allowing ions to enter or leave the cell. It is these ions that alter the membrane potential. EPSPs and IPSPs are transient changes in the membrane potential, and EPSPs resulting from transmitter release at a single synapse are generall…
What's meant by the reversal potential of some neurotransmitter [in the context of postsynaptic neurons]? The reversal potential is often called the "Nernst potential", as it can be calculated from the Nernst equation.
In the case of post-synaptic neurons, the reversal potential is the membrane potential at which a given neurotransmitter causes no net current flow of ions through that neurotransmitter receptor's ion channel.
Why is the equillibrium potential also called the reversal potential?
Because the direction of ion flow will be opposite on either side of Erev. If Erev is -80mV:At -12 mV, the net flow of K+ will still be OUT At -100 mV, the net flow of K+ will be IN.This occurs because the inward electrical force is now larger than the outward concentration gradient
How to distinguish postsynaptic excitation from inhibition?
An EPSP has areversal potential more positive than the action potential threshold, whereas an IPSP has a reversal potential more negative than threshold. Intuitively, this rule can be understood by realizing that an EPSP will tend todepolarize the membrane potential so that it exceeds threshold, whereas anIPSP will always act to keep the membrane potential more negative than thethreshold potential. The general rule of postsynaptic action is: If thereversal potential is more positive thanthresho…
Name 2 families of postsynaptic receptors. These two families of postsynaptic receptors give rise to PSPs with very different time courses, producing postsynaptic actions that range from less than a millisecond to minutes, hours, or even days.
ionotropic receptors - two in one, both a receptor and an ion channel. They are also called ligand-gated ion channels.Ligand-gated ion channels combine receptor and channel functions in a single protein complex.metabotropic receptors - a receptor that produces G-proteins that in their turn open the ion channels. Metabotropicreceptors usually activate G-proteins, which modulate ion channels directly or indi-rectly through intracellular effector enzymes and second messengers.
Name one interesting difference between: ionotropic receptors Aka ligand-gated ion channelsmetabotropic receptors Aka G-protein-coupled receptors
ionotropic receptors - mediate rapid postsynaptic effects (milliseconds) Examples are the EPP produced atneuromuscular synapses by ACh, EPSPs produced at cer-tain glutamatergic synapses, and IPSPs produced at certainGABAergic synapses.In all three cases, the PSPs arise within a millisecond or two of an action potential invading the presynaptic terminaland last for only a few tens of milliseconds or less.metabotropic receptors - produces much slower responses (minutes, days) The comparative slow…
Why are postsynaptic receptors named: ionotropic receptors Aka ligand-gated ion channelsmetabotropic receptors Aka G-protein-coupled receptors
ionotropic receptors - receptor is linked directly to the ion channel. Aka ligand-gated ion channelsmetabotropic receptors - eventual movement of ions depends on many metabolic steps. Aka G-protein-coupled receptors The Greek tropos means to move in response to a stimulus
What are the names of these receptors: those in which the receptor is also an ion channel, and those in which the receptor and ion channel are separate molecules.
ionotopic - those in which the receptor is also an ion channel, and Ionotropic receptors or ligand-gated ion channels, and give rise to fast postsynaptic responses that typically last only a few milliseconds.metabotropic - those in which the receptor and ion channel are separate molecules. Metabotropic receptors or G-protein-coupled receptors, produce slower postsynaptic effects that may endure much longer.
What was the first substance identified as a neurotransmitter?
Acetylcholine (ACh) As mentioned in the previous chapter, acetylcholine (ACh) was the first substance identified as a neurotransmitter. Individual amino acids, such as glutamate and GABA, as well as thetransmitters acetylcholine, serotonin, and histamine, are much smaller than neuropeptides and have therefore come to be called small-molecule neurotransmitters.
What's a peptide? In general, small-molecule neurotransmitters mediate rapid synaptic actions, whereas neuropeptides tend to mod-ulate slower, ongoing synaptic functions.
Peptides - chains of between 2 and 50 amino acids, linked by peptide bonds. From Greek language πεπτός, peptós "digested".
Name 3 examples of: small-molecule neurotransmitter neuropeptide neurotransmitter
small-molecule neurotransmitter acetylcholine (ACh) GABA ATP Dopamine Serotonin Histamine neuropeptide neurotransmitter Methionine enkephalin Notice how the neuropeptide molecule is bigger!
Is acetylcholine (ACh) excititory or inhibitory?
ACh is usually excititory, however the same transmitter can elicit any postsynaptic effect depending on the bound ion channel. The most common postsynaptic effect is indicated; the same transmitter can elicit postsynaptic excitation or inhibition depending on the nature of the ion channels affected by transmitter binding.
What's another name for adrenaline?
Epinephrine. Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions.The adrenal medulla is a minor contributor to total circulating catecholamines (L-DOPA is at a higher concentration in the plasma), though it contributes over 90% of circulating adrenaline. Little adrenaline is found in other tissues, mostly in scattered chromaffin cells, and in a small number of neurons which use adrenaline as a neurotransmitter.
What's agonist VS antagonist of a receptor?
agonist - binds to a receptor and activates the receptor to produce a biological response. antagonist - binds to a receptor and doesn't activate it.
What's another name for antagonist of a receptor?
Blocker. Antagonist drugs interfere in the natural operation of receptor proteins. They are sometimes called blockers.Examples include alpha blockers, beta blockers, and calcium channel blockers.
If ACh (acetylcholine) makes the heart rate go down, what do ACh agonists do to heart rate?
ACh agonists make the heart rate go down, too.
What's a receptor called if it responds to ACh? Although all acetylcholine receptors, by definition, respond to acetylcholine, they respond to other molecules as well.
Acetylcholine (or cholinergic) receptor. Cholinergic receptors are receptors on the surface of cells that get activated when they bind a type of neurotransmitter called acetylcholine.
What are 2 types of acetylcholine receptors?
ACh receptors can be divided into: nicotinic receptors, and Because they are sensitive to nikotine, derived from the dried leaves of the tobacco plant Nicotinia tabacum.muscarinic receptors Because these are sensitive to muscarine, derived from the poisonous red mushroom Amanitamuscaria.
Name the most widespread: excititory neurotransmitter inhibitory neurotransmitter
excititory neurotransmitter - glutamate. Glutamate is abundant in the human body, but particularly in the nervous system and especially prominent in the human brain where it is the body's most prominent neurotransmitter, the brain's main excitatory neurotransmitter.3 glutamate receptors (named after the agonists that activate them)inhibitory neurotransmitter - GABA, glycine Most inhibitory synapses in the brain and spinal cord use either γ-aminobutyric acid (GABA) or glycine as neurotransmitter…
What's NMDA?
One of the 3 agonists for the glutamate receptor. N-Methyl-D-aspartic acid or N-Methyl-D-aspartate (NMDA) is an amino acid derivative that acts as a specific agonist at the NMDA receptor mimicking the action of glutamate, the neurotransmitter which normally acts at that receptor. 3 glutamate receptors (named after the agonists that activate them)
Name 3 types of intercellular communication.
synaptic transmission paracrine signaling Secretion of chemical signals onto a group of nearby target cells, which acts over a longer range than synaptic transmission.endocrine signaling Secretion of hormones into the bloodstream where they can affect targets throughout the body.
Name 2 elementary forms of behavioral plasticity. Aplysia, a genus of medium to large sea slugs.
Habituation - animal becomes less responsive to repeated stimulus. Aplysia example: a light touch to the siphon of an Aplysia results in withdrawal of the animal's gill, but habituation causes the gill withdrawal to become weaker during repeated stimulation ofthe siphon.Sensitisation - animal generalizes an aversive response elicited by a noxious stimulus to a variety of other, non-noxious stimuli. Aplysia example: In Aplysia that have habituated to siphon touching, sensitization of gill withdr…
What's synaptic plasticity?
Modification of synaptic strength. Synaptic plasticity is the ability of synapses to strengthen or weaken over time, in response to increases or decreases in their activity.Since memories are postulated to be represented by vastly interconnected neural circuits in the brain, synaptic plasticity is one of the important neurochemical foundations of learning and memory
What's a synaptic strength?
How much an action potential in the presynaptic neuron affects voltage in the postsynaptic neuron. Synaptic strength is the average amount of voltage excursion produced in the postsynaptic neuron by an action potential in the presynaptic neuron. Synaptic strength is not a static quantity, and can be modified rapidly.
What's a receptor modulator?
Any chemical that binds to the receptor (with varying degrees of efficacy). A receptor modulator (or receptor ligand), is a general term for a substance, endogenous or exogenous, that binds to and regulates the activity of chemical receptors.Receptor modulators can act on different parts of receptors and regulate activity in a positive, negative, or neutral direction with varying degrees of efficacy.
[Short-term plasticity at the synapse] Why does the synaptic facilitation happen? Synaptic facilitation - transient increase in synaptic strength when multiple action potentials invade the presynaptic terminal in close succession. Short-term plasticity at the neuromuscular synapse.Electrical recording of EPPs elicited in a muscle fiber by a train of electrical stimuli applied to the presynaptic motor nerve.
Ca2+ repeatedly enters the presynaptic terminal, but is slow to leave, resulting in a Ca2+ build up. This allows more neurotransmitter to be released. Synaptic facilitation is most likely the result of prolonged elevation of presynaptic calcium levels following synaptic activity.Although the entry of Ca2+ into the presynaptic terminal occurs within a millisecond or two after an action potential invades, the mechanisms that return Ca2+ to resting levels are much slower.Thus, when action potentia…
[Short-term plasticity at the synapse] Why does the synaptic depression happen? Synaptic depression - transient decrease in synaptic strength when multiple action potentials invade the presynaptic terminal in close succession. Short-term plasticity at the neuromuscular synapse.Electrical recording of EPPs elicited in a muscle fiber by a train of electrical stimuli applied to the presynaptic motor nerve.
Not enough synaptic vesicles available for fusion anymore. Depression arises because of the progressive depletion of the pool of synaptic vesicles available for fusion in this circumstance.During synaptic depression, the strength of the synapse declines until this pool can be replenished via the mechanisms involved in recycling of synaptic vesicles.