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What is a characteristic of an action potential?
What happens to the membrane potential when the sodium channels open during an action potential?
What is the purpose of the sodium-potassium pump?
What is the absolute refractory period?
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What is the membrane potential when the potassium channels open during an action potential?
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What happens to the membrane potential after the absolute refractory period?
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What triggers the release of neurotransmitters and exocytosis in the presynaptic neuron?
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Where are small neurotransmitters often aggregated?
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What type of receptors are ion channels?
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What is the characteristic of the release of small neurotransmitters?
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What is the primary advantage of functional magnetic resonance imaging (fMRI) over MRI?
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What is necessary for the release of neuropeptides?
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What is the primary function of the capacitor in a Transcranial Magnetic Stimulation (TMS) machine?
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What is the term for anything that binds to a protein?
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What type of signal is emitted by water molecules in the blood supply with high oxygen levels?
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What is the effect of ionotropic receptors on the postsynaptic neuron?
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What is the primary limitation of functional magnetic resonance imaging (fMRI)?
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What is the purpose of Transcranial Magnetic Stimulation (TMS)?
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What type of receptors are more common than ionotropic receptors?
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What happens when the capacitor in a TMS machine is discharged?
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What is the name of the signal emitted by water molecules in the blood supply?
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What is the result of the magnetic field around the coils in a TMS machine?
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What is the purpose of a stereotaxic atlas in lesion technique?
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What is the role of the head holder in a stereotaxic instrument?
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What is the term for lesioning a structure on both sides?
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What is the significance of the 'bregma' landmark in stereotaxic surgery?
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What is the primary advantage of intracellular unit recording?
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In extracellular unit recording, what is the purpose of the ground electrode?
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What is the primary purpose of lesion technique in neuroscience research?
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What can be done to either side of the brain in lesion technique?
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What type of information can be obtained from extracellular unit recording?
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What is the purpose of the microelectrode in intracellular unit recording?
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What is the relationship between different stages of sleep and EEG activity?
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What is NOT a type of electrophysiological recording method?
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What is the function of myelination in axons?
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Which type of neuron has either no axons or small axons?
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What is a characteristic of action potentials?
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What is the term used to describe the instantaneous conduction of an action potential from one node of Ranvier to another?
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How does the diameter of an axon affect the speed of conduction?
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What is the primary difference between action potentials and postsynaptic potentials?
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What is the minimum membrane potential required to generate an action potential?
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What type of integration occurs when EPSPs and IPSPs are generated at the same time but in different locations?
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How do action potentials provide indication of strength of signal?
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What is the maximum frequency of stimulation that can be achieved by an action potential?
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What type of conduction occurs when an action potential travels in the opposite direction it normally would?
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How do myelination and conduction velocity relate?
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What happens to the resting membrane potential of a neuron when neurotransmitters bind to postsynaptic receptors?
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What is the result of a net excitation at the axon initial segment?
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What happens to the action potential as it travels away from the site of origin?
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What is the direction of travel for an action potential under normal conditions?
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What is the significance of the threshold (-65 mV) in a neuron?
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How do postsynaptic potentials travel in the cell membrane?
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What is the significance of integrating postsynaptic potentials?
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What is the effect of inhibitory postsynaptic potentials on the membrane potential?
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What is the significance of neurotransmitters in chemical communication between cells?
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What is the result of a single postsynaptic neuron receiving thousands of signals?
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What occurs during the relative refractory period of an action potential?
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What type of synapse occurs when an axon contacts the dendrites of a neuron?
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What is the primary characteristic of directed synapses?
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What is the term for the swelling on the postsynaptic site of contact in an axodentritic synapse?
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What type of synapse occurs when an axon contacts the soma of a neuron?
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What is the primary characteristic of non-directed synapses?
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What is the term for the swelling along the axon where neurotransmitters are released in non-directed synapses?
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What is the region between two cells where chemical communication takes place?
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What is the precursor molecule for catecholamines?
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What is the role of retrograde transmission in the nervous system?
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What type of neurotransmitters are nitric oxide and carbon monoxide?
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What is the primary function of computed tomography (CT) scans in neuroscience research?
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What is the characteristic of neuropeptides?
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What is the role of acetylcholine in the nervous system?
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What is the precursor molecule for serotonin?
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What is unique about unconventional neurotransmitters?
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What is the main difference between small and large neurotransmitters?
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What is the role of microtubules in neurotransmitter transport?
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What is the characteristic of varicosities in axons?
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What is the term for the coexistence of a neuropeptide and a small neurotransmitter in a single neuron?
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What is the process by which synaptic vesicles release their contents into the synapse?
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What type of receptors are activated by neuropeptides?
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What is the site of small neurotransmitter synthesis?
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What is the purpose of Electroencephalography (EEG)?
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What is picked up by a single electrode in Electroencephalography (EEG)?
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What is the function of golgi complexes in neurotransmitter synthesis?
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What is stimulated by eddy currents in the brain?
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What is the significance of standardized positions of electrodes in Electroencephalography (EEG)?
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What does the machine in Electroencephalography (EEG) pick up?
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What do different patterns of activity in Electroencephalography (EEG) reflect?
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What happens to the protons in a water molecule when a strong magnetic field is applied?
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What is the signal emitted by the protons in an fMRI scan based on?
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Why do different areas of the brain have different signal strengths in an MRI scan?
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What is the primary advantage of functional magnetic resonance imaging (fMRI) over MRI?
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What happens when the capacitor in a TMS machine is discharged?
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What is the main difference between the signal emitted by protons in an MRI and an fMRI scan?
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What is necessary for an fMRI scan to be taken?
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What type of signal is emitted by water molecules in the blood supply with high oxygen levels?
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What is the primary limitation of functional magnetic resonance imaging (fMRI)?
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What do protons in a water molecule emit when they align themselves in a strong magnetic field?
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What is the purpose of fMRI?
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What is the purpose of Transcranial Magnetic Stimulation (TMS)?
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What is the primary difference between MRI and fMRI?
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What is the name of the signal emitted by water molecules in the blood supply?
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What is the effect of Transcranial Magnetic Stimulation (TMS) on the brain?
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What is the component of a TMS machine that prevents the flow of current?
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What is the main purpose of a stereotaxic atlas in lesion technique?
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What is the function of the head holder in a stereotaxic instrument?
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What is the term for lesioning a structure on both sides of the brain?
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What is the significance of the 'bregma' landmark in stereotaxic surgery?
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What is the primary advantage of lesion technique in neuroscience research?
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What is the relationship between different stages of sleep and EEG activity?
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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.