Action Potential in Neurons
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Questions and Answers

What is a characteristic of an action potential?

  • It is an all-or-none response. (correct)
  • Its size varies depending on the strength of the incoming signal.
  • It only occurs at the dendrites of a neuron.
  • It is a graded potential.

    • What happens to the membrane potential when the sodium channels open during an action potential?

  • It becomes positive.
  • It becomes less negative. (correct)
  • It becomes more negative.
  • It remains the same.

    • What is the purpose of the sodium-potassium pump?

  • To generate action potentials.
  • To close potassium channels.
  • To restabilize the membrane potential. (correct)
  • To open sodium channels.

    • What is the absolute refractory period?

    <p>The duration in which no amount of stimulation can stimulate another action potential.</p> Signup and view all the answers

    What is the membrane potential when the potassium channels open during an action potential?

    <p>+50 mV</p> Signup and view all the answers

    What happens to the membrane potential after the absolute refractory period?

    <p>It returns to its resting state.</p> Signup and view all the answers

    What triggers the release of neurotransmitters and exocytosis in the presynaptic neuron?

    <p>An influx of calcium ions in the presynaptic membrane</p> Signup and view all the answers

    Where are small neurotransmitters often aggregated?

    <p>Near the voltage-gated calcium channels in the presynaptic membrane</p> Signup and view all the answers

    What type of receptors are ion channels?

    <p>Ionotropic receptors</p> Signup and view all the answers

    What is the characteristic of the release of small neurotransmitters?

    <p>It is a rapid, pulsing release</p> Signup and view all the answers

    What is the primary advantage of functional magnetic resonance imaging (fMRI) over MRI?

    <p>No need for injection of contrast agents</p> Signup and view all the answers

    What is necessary for the release of neuropeptides?

    <p>A gradual increase in the firing rate of action potentials</p> Signup and view all the answers

    What is the primary function of the capacitor in a Transcranial Magnetic Stimulation (TMS) machine?

    <p>To prevent the flow of current</p> Signup and view all the answers

    What is the term for anything that binds to a protein?

    <p>Ligand</p> Signup and view all the answers

    What type of signal is emitted by water molecules in the blood supply with high oxygen levels?

    <p>A stronger radio frequency signal</p> Signup and view all the answers

    What is the effect of ionotropic receptors on the postsynaptic neuron?

    <p>They lead to a quick, short-lasting change in the postsynaptic potential</p> Signup and view all the answers

    What is the primary limitation of functional magnetic resonance imaging (fMRI)?

    <p>Low temporal resolution</p> Signup and view all the answers

    What is the purpose of Transcranial Magnetic Stimulation (TMS)?

    <p>To stimulate specific regions of the cerebral cortex</p> Signup and view all the answers

    What type of receptors are more common than ionotropic receptors?

    <p>Metabotropic receptors</p> Signup and view all the answers

    What happens when the capacitor in a TMS machine is discharged?

    <p>All of the current flows through the circuit</p> Signup and view all the answers

    What is the name of the signal emitted by water molecules in the blood supply?

    <p>The BOLD signal</p> Signup and view all the answers

    What is the result of the magnetic field around the coils in a TMS machine?

    <p>It induces an electrical current in neural tissue</p> Signup and view all the answers

    What is the purpose of a stereotaxic atlas in lesion technique?

    <p>To map the location of structures in the brain</p> Signup and view all the answers

    What is the role of the head holder in a stereotaxic instrument?

    <p>To hold the brain in place during surgery</p> Signup and view all the answers

    What is the term for lesioning a structure on both sides?

    <p>Bilateral</p> Signup and view all the answers

    What is the significance of the 'bregma' landmark in stereotaxic surgery?

    <p>It provides a reference point for the z-axis</p> Signup and view all the answers

    What is the primary advantage of intracellular unit recording?

    <p>It provides moment-by-moment changes in the membrane potential of a single neuron</p> Signup and view all the answers

    In extracellular unit recording, what is the purpose of the ground electrode?

    <p>To provide a neutral reference point for the recording</p> Signup and view all the answers

    What is the primary purpose of lesion technique in neuroscience research?

    <p>To damage or destroy specific areas of the brain</p> Signup and view all the answers

    What can be done to either side of the brain in lesion technique?

    <p>Lesions can be done to either side of the brain</p> Signup and view all the answers

    What type of information can be obtained from extracellular unit recording?

    <p>Signals about electrical disturbances in the extracellular environment</p> Signup and view all the answers

    What is the purpose of the microelectrode in intracellular unit recording?

    <p>To measure the charge around the microelectrode with respect to the ground electrode</p> Signup and view all the answers

    What is the relationship between different stages of sleep and EEG activity?

    <p>Different stages of sleep are associated with distinct patterns of EEG activity</p> Signup and view all the answers

    What is NOT a type of electrophysiological recording method?

    <p>Neuropsychological testing</p> Signup and view all the answers

    What is the function of myelination in axons?

    <p>To allow action potentials to jump over large distances</p> Signup and view all the answers

    Which type of neuron has either no axons or small axons?

    <p>Interneuron</p> Signup and view all the answers

    What is a characteristic of action potentials?

    <p>The size is not graded and is always the same</p> Signup and view all the answers

    What is the term used to describe the instantaneous conduction of an action potential from one node of Ranvier to another?

    <p>Saltatory conduction</p> Signup and view all the answers

    How does the diameter of an axon affect the speed of conduction?

    <p>The larger the diameter, the faster the conduction</p> Signup and view all the answers

    What is the primary difference between action potentials and postsynaptic potentials?

    <p>Action potentials are not graded, while postsynaptic potentials are</p> Signup and view all the answers

    What is the minimum membrane potential required to generate an action potential?

    <p>-65 mV</p> Signup and view all the answers

    What type of integration occurs when EPSPs and IPSPs are generated at the same time but in different locations?

    <p>Spatial summation</p> Signup and view all the answers

    How do action potentials provide indication of strength of signal?

    <p>By frequency of stimulation</p> Signup and view all the answers

    What is the maximum frequency of stimulation that can be achieved by an action potential?

    <p>1000 hertz</p> Signup and view all the answers

    What type of conduction occurs when an action potential travels in the opposite direction it normally would?

    <p>Antidromic conduction</p> Signup and view all the answers

    How do myelination and conduction velocity relate?

    <p>Myelination increases conduction velocity</p> Signup and view all the answers

    What happens to the resting membrane potential of a neuron when neurotransmitters bind to postsynaptic receptors?

    <p>It becomes more positive (depolarization)</p> Signup and view all the answers

    What is the result of a net excitation at the axon initial segment?

    <p>The neuron is stimulated to produce an action potential</p> Signup and view all the answers

    What happens to the action potential as it travels away from the site of origin?

    <p>It remains the same amplitude</p> Signup and view all the answers

    What is the direction of travel for an action potential under normal conditions?

    <p>Away from the cell body</p> Signup and view all the answers

    What is the significance of the threshold (-65 mV) in a neuron?

    <p>It is the minimum potential required for an action potential to occur</p> Signup and view all the answers

    How do postsynaptic potentials travel in the cell membrane?

    <p>They travel fast and decrease in size</p> Signup and view all the answers

    What is the significance of integrating postsynaptic potentials?

    <p>To decide whether to activate an action potential or not</p> Signup and view all the answers

    What is the effect of inhibitory postsynaptic potentials on the membrane potential?

    <p>It becomes more negative</p> Signup and view all the answers

    What is the significance of neurotransmitters in chemical communication between cells?

    <p>They are the chemical messengers that communicate between cells</p> Signup and view all the answers

    What is the result of a single postsynaptic neuron receiving thousands of signals?

    <p>A net effect that is either excitatory, inhibitory, or no response</p> Signup and view all the answers

    What occurs during the relative refractory period of an action potential?

    <p>The action potential can be generated, but requires more stimulation than normal.</p> Signup and view all the answers

    What type of synapse occurs when an axon contacts the dendrites of a neuron?

    <p>Axodentritic synapse</p> Signup and view all the answers

    What is the primary characteristic of directed synapses?

    <p>The site of release and reception of neurotransmitters are close together.</p> Signup and view all the answers

    What is the term for the swelling on the postsynaptic site of contact in an axodentritic synapse?

    <p>Dendritic spine</p> Signup and view all the answers

    What type of synapse occurs when an axon contacts the soma of a neuron?

    <p>Axosomatic synapse</p> Signup and view all the answers

    What is the primary characteristic of non-directed synapses?

    <p>The site of release and reception of neurotransmitters are far apart.</p> Signup and view all the answers

    What is the term for the swelling along the axon where neurotransmitters are released in non-directed synapses?

    <p>Varicosity</p> Signup and view all the answers

    What is the region between two cells where chemical communication takes place?

    <p>Synapse</p> Signup and view all the answers

    What is the precursor molecule for catecholamines?

    <p>Tyrosine</p> Signup and view all the answers

    What is the role of retrograde transmission in the nervous system?

    <p>Transmitting signals from postsynaptic to presynaptic neurons</p> Signup and view all the answers

    What type of neurotransmitters are nitric oxide and carbon monoxide?

    <p>Soluble gas neurotransmitters</p> Signup and view all the answers

    What is the primary function of computed tomography (CT) scans in neuroscience research?

    <p>Visualizing internal brain structures</p> Signup and view all the answers

    What is the characteristic of neuropeptides?

    <p>They are named based on their location in the body</p> Signup and view all the answers

    What is the role of acetylcholine in the nervous system?

    <p>Causing muscle contraction</p> Signup and view all the answers

    What is the precursor molecule for serotonin?

    <p>Tryptophan</p> Signup and view all the answers

    What is unique about unconventional neurotransmitters?

    <p>They affect presynaptic neurons</p> Signup and view all the answers

    What is the main difference between small and large neurotransmitters?

    <p>Their site of synthesis in the neuron</p> Signup and view all the answers

    What is the role of microtubules in neurotransmitter transport?

    <p>To transport vesicles from the cell body to the synaptic terminal</p> Signup and view all the answers

    What is the characteristic of varicosities in axons?

    <p>They give axons a beaded appearance</p> Signup and view all the answers

    What is the term for the coexistence of a neuropeptide and a small neurotransmitter in a single neuron?

    <p>Coexistence</p> Signup and view all the answers

    What is the process by which synaptic vesicles release their contents into the synapse?

    <p>Exocytosis</p> Signup and view all the answers

    What type of receptors are activated by neuropeptides?

    <p>Metabotropic receptors</p> Signup and view all the answers

    What is the site of small neurotransmitter synthesis?

    <p>Synaptic terminals</p> Signup and view all the answers

    What is the purpose of Electroencephalography (EEG)?

    <p>To look at the pattern of compound brain activity across different regions of the scalp</p> Signup and view all the answers

    What is picked up by a single electrode in Electroencephalography (EEG)?

    <p>The sum of any neural activity present underneath it</p> Signup and view all the answers

    What is the function of golgi complexes in neurotransmitter synthesis?

    <p>To package neurotransmitters in vesicles</p> Signup and view all the answers

    What is stimulated by eddy currents in the brain?

    <p>Neural tissue</p> Signup and view all the answers

    What is the significance of standardized positions of electrodes in Electroencephalography (EEG)?

    <p>It enables the comparison of results across different participants</p> Signup and view all the answers

    What does the machine in Electroencephalography (EEG) pick up?

    <p>Electrical signals, action potentials, and postsynaptic potentials of the skin, eye, and brain</p> Signup and view all the answers

    What do different patterns of activity in Electroencephalography (EEG) reflect?

    <p>Different states of consciousness</p> Signup and view all the answers

    What happens to the protons in a water molecule when a strong magnetic field is applied?

    <p>They align themselves instantly in the direction of the magnetic field</p> Signup and view all the answers

    What is the signal emitted by the protons in an fMRI scan based on?

    <p>The amount of oxygenated blood supplied to active areas of the brain</p> Signup and view all the answers

    Why do different areas of the brain have different signal strengths in an MRI scan?

    <p>Because of differences in water amount in different areas of the brain</p> Signup and view all the answers

    What is the primary advantage of functional magnetic resonance imaging (fMRI) over MRI?

    <p>Non-invasive and provides functional and structural imaging</p> Signup and view all the answers

    What happens when the capacitor in a TMS machine is discharged?

    <p>A quick flow of current through the coils</p> Signup and view all the answers

    What is the main difference between the signal emitted by protons in an MRI and an fMRI scan?

    <p>The origin of the signal (water molecules or oxygenated blood)</p> Signup and view all the answers

    What is necessary for an fMRI scan to be taken?

    <p>A strong magnetic field and a task to be performed by the person</p> Signup and view all the answers

    What type of signal is emitted by water molecules in the blood supply with high oxygen levels?

    <p>A radio frequency signal</p> Signup and view all the answers

    What is the primary limitation of functional magnetic resonance imaging (fMRI)?

    <p>Low temporal resolution</p> Signup and view all the answers

    What do protons in a water molecule emit when they align themselves in a strong magnetic field?

    <p>A signal</p> Signup and view all the answers

    What is the purpose of fMRI?

    <p>To create a functional image of the brain based on oxygenated blood supply</p> Signup and view all the answers

    What is the purpose of Transcranial Magnetic Stimulation (TMS)?

    <p>To stimulate the brain non-invasively</p> Signup and view all the answers

    What is the primary difference between MRI and fMRI?

    <p>The type of image produced (structural vs functional)</p> Signup and view all the answers

    What is the name of the signal emitted by water molecules in the blood supply?

    <p>BOLD signal</p> Signup and view all the answers

    What is the effect of Transcranial Magnetic Stimulation (TMS) on the brain?

    <p>It turns different areas of the brain on or off</p> Signup and view all the answers

    What is the component of a TMS machine that prevents the flow of current?

    <p>Capacitor</p> Signup and view all the answers

    What is the main purpose of a stereotaxic atlas in lesion technique?

    <p>To provide a precise map of the brain for lesioning</p> Signup and view all the answers

    What is the function of the head holder in a stereotaxic instrument?

    <p>To hold the brain in place during surgery</p> Signup and view all the answers

    What is the term for lesioning a structure on both sides of the brain?

    <p>Bilateral lesion</p> Signup and view all the answers

    What is the significance of the 'bregma' landmark in stereotaxic surgery?

    <p>It marks the zero point on the z-axis</p> Signup and view all the answers

    What is the primary advantage of lesion technique in neuroscience research?

    <p>It allows for the study of the effects of lesioning on brain function</p> Signup and view all the answers

    What is the relationship between different stages of sleep and EEG activity?

    <p>Different stages of sleep are associated with different patterns of EEG activity</p> Signup and view all the answers

    Study Notes

    Action Potential

    • Size of action potential is the same regardless of the incoming signal that initiated it
    • Net postsynaptic potential at axon initial segment determines the threshold, which is -65mV
    • Depolarization occurs when sodium channels open, allowing sodium ions to rush inside the cell
    • Repolarization occurs when potassium channels open, allowing potassium ions to leave the neuron
    • Refractory period is the duration in which no amount of stimulation can stimulate another action potential

    Neurotransmitter Release and Activation

    • Release of neurotransmitters (NTs) occurs in response to an influx of calcium ions in the presynaptic membrane
    • Small NTs are released rapidly in pulses due to their proximity to the presynaptic membrane
    • Neuropeptides are released slowly and gradually due to their distance from calcium channels
    • NTs bind to postsynaptic receptors, which are proteins containing the binding site for a few NTs
    • Ionotropic receptors are quick to activate and have short-lasting effects, while metabotropic receptors are more common and have longer-lasting effects

    Functional Neuroimaging

    • Functional magnetic resonance imaging (fMRI) measures changes in blood oxygenation in response to neural activity
    • Blood oxygen level-dependent (BOLD) signal is the change in magnetic signal in response to changes in oxygenation
    • Advantages of fMRI include non-invasiveness, provision of functional and structural imaging, and better spatial resolution
    • Disadvantages include low temporal resolution, making it unsuitable for studying changes in activity over time

    Transcranial Magnetic Stimulation (TMS)

    • TMS stimulates specific regions of the cerebral cortex by inducing a magnetic field
    • Composed of a capacitor that holds a charge, which is suddenly discharged to create a large current flow
    • The magnetic field around the coils induces a current in the neural tissue underneath

    Lesion Technique

    • Lesion technique involves damaging, destroying, or inactivating part of the brain
    • Stereotaxic surgery is used to precisely position experimental devices into the brain
    • Stereotaxic atlas is a map of the brain used to guide the surgery
    • Lesions can be done unilaterally (on one side) or bilaterally (on both sides)

    Electrophysiological Recordings

    • Intracellular unit recording allows researchers to record moment-by-moment changes in the membrane potential of a single neuron
    • Extracellular unit recording records electrical disturbances in the extracellular environment, indicating neural activity but not providing moment-by-moment membrane potential changes

    Chemical Communication between Cells

    • Chemical communication between two cells takes place in the space between the presynaptic neuron and the postsynaptic neuron.
    • Neurotransmitters (chemical messengers) are released by the presynaptic neuron and bind to receptors on the postsynaptic neuron.
    • This binding causes a change in the resting membrane potential of the postsynaptic neuron, which can be either excitatory (less negative or more positive) or inhibitory (more negative or less positive).

    Postsynaptic Potentials

    • Postsynaptic potentials are graded, meaning the size of the potential depends on the strength of the signal.
    • Two characteristics of postsynaptic potentials:
      • They travel very fast.
      • They are decremental, meaning their size decreases as they travel away from the area of origin.

    Integration of Postsynaptic Potentials

    • A single postsynaptic neuron receives thousands of signals from presynaptic neurons, which are a mix of excitatory and inhibitory.
    • These signals are integrated to produce a net effect at the axon initial segment.
    • Integration can occur over space (spatial summation) or time (temporal summation).
    • The purpose of integration is to decide whether to activate an action potential or not.

    Action Potential

    • An action potential is a very short-lasting change in the membrane potential that travels in one direction along the axon.
    • It can travel in one direction due to the absolute refractory period.
    • Action potential frequency, not amplitude, indicates the strength of the signal.
    • Action potentials are non-decremental and can travel long distances without decreasing in size.

    Effects of Myelination

    • Myelination allows for saltatory conduction, where the action potential jumps from one node of Ranvier to another.
    • This increases the speed of conduction and allows the potential to travel long distances quickly.

    Interneurons

    • Interneurons are a special case, with either no axons or small axons.
    • Conduction takes place mostly through postsynaptic potentials rather than action potentials.

    Differences between Action Potential and Postsynaptic Potential

    • Action potential size is not graded and is not dependent on the strength of the incoming signal.
    • Action potentials have a fixed direction of travel, whereas postsynaptic potentials can travel in multiple directions.

    Synaptic Structure

    • Axodendritic synapse: the ends of an axon contact the dendrites of a neuron.
    • Other types of synapses: axosomatic, axoaxonic, axomyelenic, and dendrodendritic.
    • Synapses can be broadly categorized into two types: directed and non-directed.

    Neurotransmitters

    • Monoamines: catecholamines (made from tyrosine) and indolamines (made from tryptophan).
    • Acetylcholine: released from neurons onto skeletal muscles, causing them to contract.
    • Unconventional neurotransmitters: soluble gases (nitric oxide and carbon monoxide), endocannabinoids (anandamide), and neuropeptides.
    • Unconventional neurotransmitters affect the presynaptic neuron rather than the postsynaptic neuron.

    Research Methods

    • Techniques to visualize the brain: computed tomography (CT).
    • CT scans provide researchers with the ability to visualize internal structures of the brain.

    Varicosities and Neurotransmitter Synthesis

    • Varicosities give axons the appearance of beads on a string
    • Two broad categories of neurotransmitters (NTs):
      • Small NTs:
    • Made in the cytoplasm of synaptic terminals
    • Packaged in vesicles by Golgi complexes in the terminals
    • Activate ionotropic receptors
      • Large NTs (neuropeptides):
    • Small chains of amino acids (3-36)
    • Made in the cytoplasm of the cell body using ribosomes
    • Placed in spherical vesicles by Golgi complexes in the cell body
    • Transported from cell body to synaptic terminal through microtubules
    • Activate metabotropic receptors
    • Coexistence: a single neuron usually contains a neuropeptide and a small NT

    Neurotransmitter Release

    • Exocytosis: synaptic vesicles release contents into the synapse
    • Vesicle membrane fuses with the presynaptic membrane
    • Signals are released, generating a structural image

    Functional Magnetic Resonance Imaging (fMRI)

    • Measures signal based on oxygenated blood supply to active areas of the brain
    • Uses magnetic properties of oxygenated blood to create a functional image
    • Advantages:
      • Non-invasive
      • Provides functional and structural imaging
      • Better spatial resolution
    • Disadvantages:
      • Low temporal resolution
      • Not used to look at changes in activity over time

    Technique to Stimulate the Brain

    • Transcranial Magnetic Stimulation (TMS):
      • Turns different areas of the brain on or off
      • Stimulates regions of the cerebral cortex
      • Uses a capacitor to hold a charge, then releases it quickly
      • Creates a magnetic field, inducing electrical currents (eddy currents) in the brain
      • Eddy currents stimulate neural tissue

    Psychophysiological Recording

    • Electroencephalography (EEG):
      • Used to study compound brain activity across different regions of the scalp
      • Participant wears a cap with electrodes placed at standardized positions
      • Electrodes pick up neural activity, action potentials, and postsynaptic potentials
      • Purposes: look at pattern of activity, not individual activities
      • Different patterns reflect different states of consciousness (e.g., sleep stages)

    Lesion Technique

    • Part of the brain is damaged, destroyed, or inactivated
    • Stereotaxic surgery:
      • Used to precisely position experimental devices into the brain
      • Requires a stereotaxic atlas (map of the brain) and stereotaxic instrument
      • Instrument contains a head holder and an electrode holder
      • Electrode can be moved in the x, y, and z directions
    • Lesions can be done to the brain on either side

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    Description

    Learn about the mechanisms of action potential in neurons, including the threshold, depolarization, repolarization, and refractory period.

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