Kapitel 4: Neural konduktion og synaptisk transmission

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Questions and Answers

Hvordan registreres membranpotentialet?

Membranpotentialet registreres ved at placere spidsen af en elektrode inde i neuronen og spidsen af en anden elektrode uden for neuronen i den ekstracellulære væske.

Hvad er hvilemembranpotentialet?

Hvilemembranpotentialet er -70 millivolt (mV) for neuroner.

Hvilke tre faktorer påvirker fordelingen af Na+ og K+ ioner over cellemembranen?

Koncentrationsgradient, diffusion og elektrolytisk tryk

Osmosis, diffusion og kemisk gradient

Koncentrationsgradient, elektrostatisk tryk og natrium-kaliumpumper (correct)

Elektrostatisk tryk, diffusion og osmosis

Hvad er de to vigtigste typer af postsynaptiske potentialer?

De to vigtigste typer af postsynaptiske potentialer er excitatoriske postsynaptiske potentialer (EPSP) og inhibitoriske postsynaptiske potentialer (IPSP). Signup and view all the answers

Hvordan summeres postsynaptiske potentialer?

Postsynaptiske potentialer summeres både temporalt og rumligt. Temporalt betyder at de summeres over tid ved at flere PSPs indtræffer hurtigt efter hinanden. Rumligt betyder at de summeres over forskellige steder på neuronen. Den samlede effekt af alle de summerende EPSPs og IPSPs bestemmer om neuronen aktiveres eller ej. Signup and view all the answers

Hvad er det ioniske grundlag for et aktionspotentiale?

Aktionspotentialet starter med en depolarisering af cellemembranen, når tilstrækkelig mange natriumkanaler åbnes, og natriumionerne strømmer ind i cellen. Denne depolarisering udløser åbningen af kaliumkanaler, og kaliumionerne strømmer ud af cellen, hvilket genopretter cellens hvilemembranpotentiale. Under repolariseringen bliver cellen kortvarigt hyperpolariseret, og det er den periodiske udblænding af aktionspotentialet. Signup and view all the answers

Hvad er refraktærperioden?

Refraktærperioden er en periode efter et aktionspotentiale, hvor det er vanskeligt eller umuligt at udløse et nyt aktionspotentiale. Signup and view all the answers

Hvordan ledes et aktionspotentiale langs en axon?

Aktionspotentialer ledes langs en axon ved at hoppe fra en Ranvier-knude til den næste. I myeliniserede axoner ledes aktionspotentialet meget hurtigere end i umyelinerede axoner. Signup and view all the answers

Hvad er forskellen mellem excitatoriske og inhibitoriske neurotransmittere?

Excitatoriske neurotransmittere øger sandsynligheden for at neuronen aktiveres, mens inhibitoriske neurotransmittere mindsker sandsynligheden for at neuronen aktiveres. Signup and view all the answers

Hvordan syntetiseres og pakkes neurotransmittere?

Neurotransmittere syntetiseres i cytoplasmaet af den terminale knap og pakkes i synaptiske vesikler af Golgis apparat. Signup and view all the answers

Hvad er exocytose?

Exocytose er processen hvor ved en neuron frigiver neurotransmittermolekyler fra den synaptiske knap ind i den synaptiske kløft. Signup and view all the answers

Hvordan fjernet neurotransmittere fra synafsen?

Neurotransmittere fjernes fra synafsen ved hjælp af reuptage og enzymatisk nedbrydning. Signup and view all the answers

Hvad er forskellen mellem ionotrope og metabotrope receptorer?

Ionotrope receptorer er direkte forbundet med en ionkanal der åbner eller lukker når neurotransmitteren binder sig til receptoren. Metabotrope receptorer er forbundet med en signalproteinkæde, der aktiverer en sekundær messenger der åbner ionkanalen. Signup and view all the answers

Hvad er en autoreceptor?

En autoreceptor er en metabotrop receptor der reagerer på samme neurotransmitter som neuronen frigiver. Signup and view all the answers

Study Notes

Chapter Overview and Learning Objectives

Resting Membrane Potential (LO 4.1): Describes how the membrane potential is measured.
Resting Membrane Potential (LO 4.2): Details the resting membrane potential, its ionic basis, and the three factors influencing the distribution of sodium (Na+) and potassium (K+) ions across the neuronal membrane.
Generation, Conduction, and Integration of Postsynaptic Potentials (LO 4.3): Outlines the different types of postsynaptic potentials and their conduction mechanisms.
Generation, Conduction, and Integration of Postsynaptic Potentials (LO 4.4): Explains how postsynaptic potentials summate and action potentials are generated.
Conduction of Action Potentials (LO 4.5): Describes the ionic basis of an action potential.
Conduction of Action Potentials (LO 4.6): Explains how the refractory period influences neuronal activity.
Synaptic Transmission (LO 4.7): Describes how action potentials are conducted along axons (both myelinated and unmyelinated).
Synaptic Transmission (LO 4.8): Discusses the limitations of Hodgkin-Huxley model when applied to mammalian neurons.
Synaptic Transmission (LO 4.9): Describes the structure of different types of synapses.
Synaptic Transmission (LO 4.10): Explains how neurotransmitter molecules are synthesized and packaged in vesicles.
Synaptic Transmission (LO 4.11): Explains the process of neurotransmitter exocytosis.
Synaptic Transmission (LO 4.12): Discusses the differences between ionotropic and metabotropic receptors.
Synaptic Transmission (LO 4.13): Explains how neurotransmitters are removed from a synapse.
Synaptic Transmission (LO 4.14): Describes the roles of glia and gap junctions in synaptic transmission.
Neurotransmitters (LO 4.15): Names the major classes of neurotransmitters.
Neurotransmitters (LO 4.16): Identifies and describes the functions of each neurotransmitter class.
Pharmacology of Synaptic Transmission and Behavior (LO 4.17): Provides a general overview of how drugs influence synaptic transmission.
Pharmacology of Synaptic Transmission and Behavior (LO 4.18): Describes examples of how drugs are used to influence neurotransmission.
The Lizard: A Case of Parkinson's Disease: Presents a case study of Parkinson's disease.

Resting Membrane Potential

Recording: Membrane potential is measured by placing electrodes inside and outside the neuron.
Ionic Basis: Resting potential is predominantly maintained by the unequal distribution of Na+ and K+ ions. More Na+ is outside, and more K+ is inside the neuron.
Factors: Electrostatic pressure, concentration gradients, and the sodium-potassium pump are important factors.

Generation, Conduction, and Integration of Postsynaptic Potentials

Postsynaptic Potentials (PSPs): They are graded potentials, meaning their magnitude depends on the strength of the stimulus. They are either excitatory (EPSPs) or inhibitory (IPSPs).
Summation: EPSPs and IPSPs summate (add up) at the axon hillock; if the sum reaches threshold, an action potential is generated.
Conduction: PSPs are conducted passively, decreasing in amplitude as they travel. Action potentials are conducted actively and do not decrease in amplitude.

Conduction of Action Potentials

Ionic Basis: Action potentials result from the rapid influx of Na+ ions followed by efflux of K+ ions.
Phases: Action potential has three phases: rising phase, repolarization phase, and hyperpolarization phase.
Refractory Periods: The absolute refractory period prevents backward action potential propagation, while the relative refractory period limits the firing rate.

Synaptic Transmission

Structure of Synapses: Synapses are junctions between neurons where neurotransmitters are released. Common types: axodendritic, axosomatic, axoaxonic and more.
Neurotransmitter Synthesis/Packaging: Neurotransmitter molecules are synthesized and packaged into vesicles by the neuron's Golgi apparatus.
Neurotransmitter Exocytosis: Action potentials trigger the release of neurotransmitters from synaptic vesicles into the synaptic cleft by the process of exocytosis.
Receptors: Neurotransmitters bind to receptors on the postsynaptic membrane, either ionotropic (directly on ion channels) or metabotropic (second messenger system).
Removal of Neurotransmitters from Synapse: Neurotransmitters are deactivated by reuptake, enzymatic degradation or diffusion away from the synaptic cleft.
Glia and Gap Junctions: Glial cells and gap junctions are involved in communication and support of neurotransmission beyond the neuron-neuron synapses.

Neurotransmitters

Amino Acids: Common neurotransmitters including glutamate, aspartate, glycine, and GABA.
Monoamines: Dopamine, epinephrine (adrenaline), norepinephrine (noradrenaline) and serotonin.
Acetylcholine: A neurotransmitter at neuromuscular junctions.
Unconventional Neurotransmitters: Include soluble gases (like nitric oxide) and endocannabinoids.
Neuropeptides: Numerous different peptides serving various roles.

Pharmacology of Synaptic Transmission and Behavior

Drug Effects: Drugs can affect synaptic transmission by acting as agonists (increasing neurotransmitter effects) or antagonists (decreasing neurotransmitter effects).
Examples of Drug Influence: Includes examples of treatments impacting Parkinson's, schizophrenia and more.

Studying That Suits You

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Description

Dette quiz handler om de vigtigste koncepter i kapitel 4 om hvilemembranpotentiale, postsynaptiske potentialer og aktionspotentialer. Det dækker måling af membranpotentiale, ionisk basis, synaptisk transmission samt hvordan aktionspotentialer genereres og ledes. Test din viden om neurale mekanismer og deres funktioner.