Clinical Neurophysiology Overview
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Clinical Neurophysiology Overview

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Questions and Answers

What is an example of an evoked response?

  • Mechanical stimulation of the skin
  • Visual stimulation of the eyes
  • Acoustic stimulation of the ears
  • Electrical stimulation of a peripheral nerve (correct)

    • Electrical recordings are the only way to measure the activity of neurons and muscle cells.

    False

    What are excitable cells?

    Cells that can change their membrane potential to transmit information, including neurons and muscle cells.

    The resting membrane potential is commonly abbreviated as ______.

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

    Match the types of stimulation with their corresponding applications:

    <p>Electrical stimulation = Peripheral nerve analysis Visual stimulation = Sensory pathway assessment Acoustic stimulation = Hearing and auditory processing Mechanical stimulation = Muscle contraction measurement</p> Signup and view all the answers

    Which tool is NOT used in clinical neurophysiology?

    <p>Acoustic tones</p> Signup and view all the answers

    Neurophysiology only examines the central nervous system.

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

    What occurs during the action potential (AP)?

    <p>A change in membrane potential that propagates an information signal along the cell.</p> Signup and view all the answers

    What happens to sodium channels during repolarization?

    <p>They close.</p> Signup and view all the answers

    The duration of an action potential (AP) is the same in all excitable cells.

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

    What is the role of the Na+/K+-ATPase during the refractory period?

    <p>It restores the resting state distributions of Na+ and K+ ions.</p> Signup and view all the answers

    During the ______ period, the membrane cannot generate a further action potential.

    <p>absolute refractory</p> Signup and view all the answers

    Match the following types of cells with the duration of their action potentials:

    <p>Nerve cells = 1 ms Muscle cells = 10 ms Heart muscle cells = 500 ms</p> Signup and view all the answers

    Which ions are predominantly affected during the action potential process?

    <p>Sodium and potassium</p> Signup and view all the answers

    Local anesthetics block calcium channels permanently.

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

    What is the all-or-none principle in action potentials?

    <p>An action potential is triggered only if the depolarization threshold is exceeded.</p> Signup and view all the answers

    Refractory periods help determine the maximal ______ rate of action potentials.

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

    Which component is responsible for stabilizing the membrane of excitable cells?

    <p>Extracellular calcium</p> Signup and view all the answers

    Which type of efferent fiber is responsible for innervating the main contractile muscle cells?

    <p>Aα-fibers</p> Signup and view all the answers

    Afferent Ia-fibers carry information about the absolute length of the muscle.

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

    What is the primary function of Ib-fibers?

    <p>They carry information about the tension in the tendons.</p> Signup and view all the answers

    The contractile elements within muscle spindles are called __________.

    <p>intrafusal muscle cells</p> Signup and view all the answers

    Match the following fibers to their functions:

    <p>Ia = Velocity of length change II = Absolute length Ib = Tension in tendons Aα = Main contractile muscle cells</p> Signup and view all the answers

    How do afferent fibers from the tendons protect muscles?

    <p>By inhibiting motoneurons</p> Signup and view all the answers

    The elastic center of intrafusal muscle cells helps preserve the sensitivity of the muscle spindle.

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

    What is the formula for signal-to-noise ratio (SNR)?

    <p>Psignal/Pnoise</p> Signup and view all the answers

    What is the role of α-motoneurons in muscle innervation?

    <p>They innervate the main contractile muscle cells.</p> Signup and view all the answers

    Electrocerebral silence has a typical SNR of 10:1.

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

    Afferent fibers from the spindle form the circuit for the __________ reflex.

    <p>deep tendon</p> Signup and view all the answers

    What is the typical SNR range for spontaneous activity in EMG?

    <p>5:1 - 10:1</p> Signup and view all the answers

    Which fibers are part of the muscle spindle that measure the length of the muscle?

    <p>Aγ-fibers</p> Signup and view all the answers

    The typical SNR for CMAP in ENG is greater than ______:1.

    <blockquote> <p>100</p> </blockquote> Signup and view all the answers

    Match the following SNR values with their corresponding types:

    <p>Eng CMAP = &gt; 100:1 EEG with EMG artifacts = &lt; 1:10 Evoked Potentials (SEP/VEP) = 1:2 – 1:20 EMG Interference pattern = &gt; 100:1</p> Signup and view all the answers

    What does the evoked response from motor nerve stimulation called?

    <p>Compound muscle action potential (CMAP)</p> Signup and view all the answers

    The nerve conduction velocity is determined by the diameter of the fibers and their myelination.

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

    What should be done to ensure that nerve stimulation activates the whole motor pool?

    <p>Increase stimulus strength until no further increase in response is recorded.</p> Signup and view all the answers

    The ______ latency is observed to measure the time from stimulation to the response onset.

    <p>distal motor</p> Signup and view all the answers

    Match the following conduction velocities with their corresponding fiber classification:

    <p>100 m/s = Aα fibers 20 m/s = Aβ fibers 1 m/s = C fibers 75 m/s = Aγ fibers</p> Signup and view all the answers

    What factor makes it unreasonable to calculate nerve conduction velocity directly from stimulation to recording?

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

    Stimulation should occur with submaximal stimuli.

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

    What is the relationship between the distance between stimulation sites and latency difference?

    <p>Nerve conduction velocity is calculated by dividing the distance by the latency difference.</p> Signup and view all the answers

    Increasing the stimulus strength by 2 mA ensures that the stimulation is ______.

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

    Which of the following is associated with the slowest conduction velocity?

    <p>C fibers</p> Signup and view all the answers

    What primarily generates the EEG recordings?

    <p>Subsynaptic potentials in the uppermost layer of the cortex</p> Signup and view all the answers

    Which frequency band in the EEG is primarily associated with cortical inhibition?

    <p>Alpha band</p> Signup and view all the answers

    The ascending reticular activating system (ARAS) primarily regulates which aspects of neural function?

    <p>Consciousness and attention</p> Signup and view all the answers

    What does beta activity in the EEG indicate?

    <p>Cortical activation focusing attention</p> Signup and view all the answers

    Which statement accurately describes the relationship between frequency bands and synaptic activity in the EEG?

    <p>Lower frequency bands express cortical inhibition from various modulating influences.</p> Signup and view all the answers

    Which of the following symptoms is NOT a cardinal sign of Parkinson's disease?

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

    What is the primary target for deep brain stimulation (DBS) in Parkinson's disease?

    <p>Subthalamic nucleus (STN)</p> Signup and view all the answers

    What type of recording shows potential input data in the context of DBS?

    <p>Local field potentials (LFP)</p> Signup and view all the answers

    Which of the following strategies is NOT aimed at reducing adverse effects during DBS?

    <p>Repetitive shock therapy</p> Signup and view all the answers

    In the context of Parkinson's disease, what physiological change occurs due to the loss of dopaminergic neurons?

    <p>Hyperactivity of the subthalamic nucleus</p> Signup and view all the answers

    What symptom is associated with the bradykinesia aspect of Parkinson's disease?

    <p>Impaired facial expression</p> Signup and view all the answers

    Which of the following best describes the role of the vestibulocerebellum?

    <p>Maintenance of posture and equilibrium</p> Signup and view all the answers

    Which of the following is NOT considered an adverse effect of deep brain stimulation?

    <p>Memory enhancement</p> Signup and view all the answers

    What is the primary focus of neurophysiology?

    <p>The function of the nervous system</p> Signup and view all the answers

    Which of the following techniques is primarily used for analyzing the electrical activity of single neurons?

    <p>Intracellular microelectrode recordings</p> Signup and view all the answers

    What type of electrical activity does the electromyogram (EMG) primarily measure?

    <p>Electrical activity of muscle cells</p> Signup and view all the answers

    How is the assessment of heart-rate variability most commonly extracted from ECG recordings?

    <p>By measuring the intervals between heartbeats</p> Signup and view all the answers

    What does spontaneous electrical activity in the nervous system refer to?

    <p>Unprovoked electrical signals</p> Signup and view all the answers

    Which of the following statements about neurophysiological findings is accurate?

    <p>Knowledge of nervous system architecture is often crucial for interpretation.</p> Signup and view all the answers

    Which of the following describes the electroencephalogram (EEG)?

    <p>An assessment of brain's spontaneous electrical activity</p> Signup and view all the answers

    In clinical practice, which measurement is typically excluded from neurophysiology despite its relevance?

    <p>Electrocardiogram (ECG)</p> Signup and view all the answers

    Which physiological characteristic is primarily analyzed using patch clamp techniques?

    <p>Single neuron ionic currents</p> Signup and view all the answers

    What effect does a decrease in the diameter of the motor nerve branches have on action potential propagation velocity?

    <p>Propagation velocity decreases correspondingly.</p> Signup and view all the answers

    In neuromuscular junctions, what is the primary role of the synapse known as the motor end plate?

    <p>To facilitate signal transmission with a delay.</p> Signup and view all the answers

    Which of the following best defines a motor unit?

    <p>A single motoneuron and all muscle fibers it innervates.</p> Signup and view all the answers

    What is the impact of changing the polarity during direct nerve stimulation when recording responses?

    <p>It can cause an increased latency of the recorded responses.</p> Signup and view all the answers

    What defines the relationship between the size of motor units and the muscles demonstrating well-graded force development?

    <p>Smaller motor units contribute to finer control.</p> Signup and view all the answers

    What type of current is typically used to stimulate nerves with bipolar electrodes?

    <p>Square-wave current.</p> Signup and view all the answers

    When recording from a nerve with many fibers, what shape do the recorded responses typically differ from?

    <p>Biphasic or triphasic shape.</p> Signup and view all the answers

    What is a common misconception about the anodal block during nerve stimulation?

    <p>It is a fictional concept in neurophysiology.</p> Signup and view all the answers

    What is the relationship between the distance between stimulation sites and the latency difference?

    <p>Increased distance results in increased latency difference.</p> Signup and view all the answers

    What is the purpose of an electrode's cathode placement during nerve stimulation?

    <p>To ensure depolarization occurs where needed.</p> Signup and view all the answers

    What is the primary characteristic of sensory nerve conduction in carpal tunnel syndrome?

    <p>Slowing of the median sensory nerve conduction</p> Signup and view all the answers

    What treatment is recommended for carpal tunnel syndrome with minor symptoms?

    <p>Splinting during the night</p> Signup and view all the answers

    Which of the following symptoms is most commonly associated with cubital tunnel syndrome?

    <p>Weakness of the hand</p> Signup and view all the answers

    What is a common diagnostic procedure for carpal tunnel syndrome when nerve conduction studies are inconclusive?

    <p>Ultrasound of the wrist</p> Signup and view all the answers

    How is muscle atrophy in cubital tunnel syndrome typically evaluated?

    <p>Comparison of muscle strength with both hands</p> Signup and view all the answers

    What is a specific finding in nerve conduction tests that indicates Guyon's canal syndrome?

    <p>Prolongation of distal motor latency</p> Signup and view all the answers

    What is the surgical intervention for carpal tunnel syndrome referred to in the content?

    <p>Open or endoscopic decompression</p> Signup and view all the answers

    Which nerve root levels are primarily involved in muscle atrophy associated with cubital tunnel syndrome?

    <p>C8-T1</p> Signup and view all the answers

    What distinguishes the symptoms of Guyon's canal syndrome from cubital tunnel syndrome?

    <p>Numbness in the fourth and fifth fingers</p> Signup and view all the answers

    Which treatment strategy is ineffective if carpal tunnel syndrome symptoms are major or refractory to initial therapy?

    <p>Night splinting</p> Signup and view all the answers

    Match the components of the basal ganglia pathways with their respective functions:

    <p>Striatum = Input from the cortex Globus pallidus interna = Output to thalamus Substantia nigra pars reticularis = Output to thalamus GPe = Indirect pathway modulation</p> Signup and view all the answers

    Match the types of dopamine receptors with their effects in the striatum:

    <p>D1 receptors = Excitation D2 receptors = Inhibition Dopaminergic projections = Modulation of pathways Str -&gt; SNret/GPi = Direct pathway function</p> Signup and view all the answers

    Match the phases of cortical stimulation response with their descriptions:

    <p>First phase = Inhibition of thalamocortical projections Second phase = Disinhibition and movement release Third phase = Inhibition stopping movement release Delay = Increased activity after first phase</p> Signup and view all the answers

    Match the pathways with their corresponding outcomes:

    <p>Direct pathway = Facilitation of thalamocortical projections Indirect pathway = Inhibition of thalamocortical projections Disinhibition = Facilitation of impulse transmission Thalamic output = Influenced by basal ganglia activity</p> Signup and view all the answers

    Match the anatomical features of the basal ganglia with their specific roles:

    <p>Striatum = Major input structure Substantia nigra = Dopaminergic modulation Globus pallidus = Regulates output to thalamus STN = Component of indirect pathway</p> Signup and view all the answers

    Match the types of evoked responses with their corresponding stimulation methods:

    <p>Electrical stimulation = Contraction of innervated muscles Visual stimulation = Assessing visual pathways Acoustic stimulation = Testing auditory pathways Mechanical stimulation = Measuring bladder pressure</p> Signup and view all the answers

    Match the neurophysiological tools with their applications:

    <p>Calcium imaging = Studying metabolic processes in neurons fMRI = Examining brain activity Electrical recordings = Measuring neuronal activity Mechanical transducers = Assessing muscle contractions</p> Signup and view all the answers

    Match the types of cells with their primary characteristics:

    <p>Neurons = Information processing via action potentials Muscle cells = Contraction in response to stimulation Secretory cells = Secretion of neurotransmitters Excitable cells = Change in membrane potential</p> Signup and view all the answers

    Match the physiological terms with their definitions:

    <p>Resting Membrane Potential (RMP) = Baseline membrane potential of cells Action Potential (AP) = Membrane change during signal propagation Neurophysiology = Study of nerve functions and pathways Clinical Neurophysiology = Application of neurophysiological techniques in humans</p> Signup and view all the answers

    Match the types of neurophysiology with their primary focus:

    <p>Peripheral neurophysiology = Assessment of peripheral nerve diseases Central neurophysiology = Study of the central nervous system Autonomous neurophysiology = Diagnosis of autonomic nervous system disorders Clinical neurophysiology = Diagnostic and therapeutic applications in humans</p> Signup and view all the answers

    Match the types of reflex pathways with their characteristics:

    <p>Stretch reflex = Monosynaptic reflex action Withdraw reflex = Polysynaptic reflex action Tendon reflex = Protection from muscle injury Neural reflex = Response via neuronal connections</p> Signup and view all the answers

    Match the types of ion channels with their roles during action potential:

    <p>Sodium channels = Depolarization phase Potassium channels = Repolarization phase Calcium channels = Neurotransmitter release Chloride channels = Inhibitory postsynaptic potentials</p> Signup and view all the answers

    Match the definitions with their corresponding physiological processes:

    <p>Excitability = Ability of cells to generate action potentials Conductivity = Propagation of electrical signals along neurons Neuromuscular transmission = Communication between nerves and muscles Synaptic transmission = Transfer of signals across synapses</p> Signup and view all the answers

    Match the type of muscle fiber with its primary function:

    <p>Aα-fibers = Innervate main contractile muscle cells Aγ-fibers = Innervate contractile elements of muscle spindles Ia-fibers = Carry information of velocity of length change II-fibers = Carry information about absolute length</p> Signup and view all the answers

    Match the type of sensory fiber with its corresponding origin:

    <p>Ia-fibers = Muscle spindle Ib-fibers = Tendon receptors Aα-fibers = α-motoneurons Aγ-fibers = γ-motoneurons</p> Signup and view all the answers

    Match the reflex pathway with its associated function:

    <p>Deep tendon reflex = Assesses muscle spindle afferents Inhibitory reflex = Protects muscle from damage Voluntary movement = Modifies reflex circuit Length change reflex = Monitors muscle length alterations</p> Signup and view all the answers

    Match the component of muscle spindles with its description:

    <p>Intrafusal muscle cells = Contractile elements within spindles Extrafusal muscle cells = Outer muscle cells responsible for contraction Elastic center = Preserves sensitivity of the receptor Contractile ends = Compensate for length changes during contraction</p> Signup and view all the answers

    Match the afferent fiber type with their specific role:

    <p>Ia-fibers = Velocity of length change II-fibers = Absolute muscle length Ib-fibers = Tension in tendons Afferent fibers = Establish synaptic contacts with motoneurons</p> Signup and view all the answers

    Match the type of nerve fiber with its conduction velocity:

    <p>Aα-fibers = Fastest conduction velocity Aγ-fibers = Moderate conduction speed Ia-fibers = Intermediate conduction velocity Ib-fibers = Slowest conduction speed</p> Signup and view all the answers

    Match the following types of refractory periods with their characteristics:

    <p>Absolute refractory period = Membrane cannot generate a further action potential Relative refractory period = Depolarization threshold is increased Refractory period = Determines maximal AP repetition rate Resting state = Ions return to resting state distributions</p> Signup and view all the answers

    Match the following cell types with their action potential duration:

    <p>Nerve cells = Usually lasts 1 ms Muscle cells = Lasts about 10 ms Heart muscle cells = Can last up to 500 ms CNS neurons = Can exhibit slow calcium spikes</p> Signup and view all the answers

    Match the term with its corresponding definition in muscle innervation:

    <p>Electroneurography = Measures nerve conduction Afferent fibers = Sensory signals to CNS Efferent fibers = Motor signals from CNS Muscle spindles = Receptors measuring muscle length</p> Signup and view all the answers

    Match the ion channels with their roles during an action potential:

    <p>Sodium channels = Open during depolarization Potassium channels = Open during repolarization Calcium channels = Influence plateau phase in heart muscles Na+/K+ - ATPase = Returns ions to resting distributions</p> Signup and view all the answers

    Match the type of fiber with the aspect of muscle they innervate:

    <p>Aα-fibers = Main contractile elements Aγ-fibers = Intrafusal muscle components Ia-fibers = Muscle spindle receptors Ib-fibers = Tendon tension receptors</p> Signup and view all the answers

    Match the sensory fiber type with the information it carries:

    <p>Ia-fibers = Velocity of muscle length change Ib-fibers = Tension in tendons II-fibers = Absolute muscle length Aγ-fibers = Contractile information to spindles</p> Signup and view all the answers

    Match the following terms with their definitions related to action potentials:

    <p>All-or-none principle = Action potential independent of stimulus current Depolarization threshold = Minimum potential to trigger an AP Voltage-dependent inactivation = Occurs during refractory periods Calcium spikes = Provide driving force for sodium spikes in CNS</p> Signup and view all the answers

    Match the following drugs with their effects on ion channels:

    <p>Local anesthetics = Block sodium channels reversibly Calcium channel blockers = Inhibit calcium influx Potassium channel blockers = Prolong depolarization phase Sodium channel activators = Increase ease of depolarization</p> Signup and view all the answers

    Match the following phases of action potential with their characteristics:

    <p>Depolarization = Sodium influx raises membrane potential Repolarization = Potassium efflux lowers membrane potential Plateau phase = Caused by voltage-gated calcium channels Refractory phase = Limits frequency of action potentials</p> Signup and view all the answers

    Match the following cellular activities with their respective ions:

    <p>Sodium (Na+) = Rising phase of action potential Potassium (K+) = Falling phase of action potential Calcium (Ca++) = Prolonged plateau phase in cardiac myocytes Sodium-potassium pump = Restoration of resting ion concentrations</p> Signup and view all the answers

    Match the following anatomical features of neurons with their functions:

    <p>Dendrites = Receive synaptic input Axon = Conducts action potentials away from the cell body Synapse = Site of neurotransmitter release Myelin sheath = Increases conduction velocity of action potentials</p> Signup and view all the answers

    Match the following physiological concepts with their implications in excitable cells:

    <p>Increased extracellular calcium = Raises depolarization threshold Absolute refractory period = Prevents immediate second action potential Relative refractory period = Requires stronger stimulus for second action potential Ion channel inactivation = Contributes to the timing of action potentials</p> Signup and view all the answers

    Match the EEG frequency bands with their corresponding frequency ranges:

    <p>Gamma = &gt; 31 Hz Beta = 13 – 30 Hz Alpha = 8 – 12 Hz Theta = 4 – 7 Hz</p> Signup and view all the answers

    Match the EEG findings with their descriptions during normal conditions:

    <p>Alpha waves = Regular and individual-specific frequency Beta waves = Dominated by beta-activity in all channels Theta waves = Increased during some sleep stages Delta waves = Pathologically slowed EEG activity</p> Signup and view all the answers

    Match the factors affecting normal EEG findings with their descriptions:

    <p>Individual factors = Variability due to personal characteristics Age = Can influence EEG patterns External stimuli = Environmental influences on EEG Degree of attention = Contributes to changes in frequency bands</p> Signup and view all the answers

    Match the abnormal EEG conditions with their potential causes:

    <p>Pathologically slowed EEG = Elevated intracranial pressure Burst-suppression EEG = Severe brain dysfunction Electrocerebral silence = Criteria for diagnosing brain death Focal abnormalities = Circumscribed slowing or epileptic activity</p> Signup and view all the answers

    Match the EEG activity changes with their triggers:

    <p>Alpha activity = Blocked by eye opening Beta activity = Observed during drowsiness Theta activity = Dominates during sleep stages Delta activity = Increases pathology of consciousness</p> Signup and view all the answers

    Match the EEG frequencies with their typical characteristics:

    <p>Gamma = Associated with cognitive processing Beta = Indicates active concentration or engagement Alpha = Calm, relaxed state often present with closed eyes Delta = Slow-wave activity during deep sleep</p> Signup and view all the answers

    Match the abnormal EEG patterns with their implications:

    <p>Alpha-coma = Absence of alpha waves with normal background Focal slowing = Localized brain injury or lesions Electrocerebral silence = Potential indication of brain death Burst suppression = Severe neurologic impairment</p> Signup and view all the answers

    Match the EEG states with their resting conditions:

    <p>Awake = Presence of alpha and beta activity Non-REM sleep = Presence of theta and delta activity REM sleep = Active brain function with eye movements Drowsy state = Transitional phase before deeper sleep</p> Signup and view all the answers

    Match the EEG findings with their locations in the brain:

    <p>Alpha rhythm = Accentuated over occipital and temporal lobes Central mu rhythm = Prominent in the central region Beta waves = Widespread across all channels Theta waves = Commonly seen during emotional turmoil</p> Signup and view all the answers

    Match the stimulus factors with their effects on EEG activity:

    <p>Eye opening = Blocks alpha waves Eyes closed = Restores alpha activity Drowsiness = May induce beta and alpha planes intermittently Straining = Can introduce EMG artifacts in the recording</p> Signup and view all the answers

    What are the frequency ranges for the Delta and Beta EEG bands?

    <p>Delta is &lt; 4 Hz and Beta is 13 – 30 Hz.</p> Signup and view all the answers

    How does lateral inhibition contribute to the localization of a damaging stimulus?

    <p>Lateral inhibition enhances the contrast of impulses, limiting propagation to only the afferent signals from the damaged site.</p> Signup and view all the answers

    How does eye opening affect Alpha EEG activity?

    <p>Alpha activity is blocked by eye opening and restored after eye closing.</p> Signup and view all the answers

    What are potential causes of pathologically slowed EEG activity?

    <p>Causes include elevated intracranial pressure and pathologically impaired consciousness.</p> Signup and view all the answers

    What role do small interneurons play in the neural circuitry related to pain stimuli?

    <p>Small interneurons establish inhibitory contacts that facilitate lateral inhibition, contributing to pain processing.</p> Signup and view all the answers

    Explain how the convergence-divergence circuitry functions in response to sensory input like a pain stimulus.

    <p>This circuitry acts like an amplifier, allowing for a quick orientation response to potentially harmful stimuli.</p> Signup and view all the answers

    What distinguishes the Alpha rhythm in an EEG?

    <p>The Alpha rhythm is very regular, specific to the individual, and accentuated over the occipital and temporal lobes.</p> Signup and view all the answers

    What does 'electrocerebral silence' indicate in an EEG?

    <p>Electrocerebral silence may indicate brain death and requires careful validation to avoid false results.</p> Signup and view all the answers

    In the context of clinical neurophysiology, what is a significant challenge in extracellular recordings?

    <p>Extracellular recordings often have a poor signal-to-noise ratio due to the large distance between excitable cells and the recording electrodes.</p> Signup and view all the answers

    Why is it important to consider the relationship between stimulus strength and activation of the motor pool?

    <p>Proper stimulation strength ensures that the entire motor pool is activated for effective muscle response.</p> Signup and view all the answers

    What is the consequence of setting recording electrodes too far from excitable cells in neurophysiological studies?

    <p>It leads to a large distance affecting the signal quality, resulting in a complex relationship between the extracellular field and cellular activity.</p> Signup and view all the answers

    Describe the significance of time-dependent voltage changes in the context of electrophysiological recording.

    <p>These changes reflect the activity of excitable cells and are crucial for understanding their functional state.</p> Signup and view all the answers

    What factors influence the nerve conduction velocity, and how do they relate to fiber diameter?

    <p>Nerve conduction velocity depends on the diameter of fibers and their level of myelination, with larger, myelinated fibers conducting faster.</p> Signup and view all the answers

    What nerve is compressed in meralgia paresthetica?

    <p>The lateral femoral cutaneous nerve.</p> Signup and view all the answers

    What are the roles of the Inner Helmholtz plane (IHP) and Outer Helmholtz plane (OHP) in the electrode-electrolyte interface?

    <p>IHP forms the closest layer of solvent molecules to the electrode, while OHP encompasses additional layers where ionic distribution changes occur.</p> Signup and view all the answers

    What are two common symptoms of polyneuropathy?

    <p>Weakness and burning pain.</p> Signup and view all the answers

    What is the primary mechanism behind distal axonopathy?

    <p>Interrupted function of peripheral nerves.</p> Signup and view all the answers

    Describe the composition and function of mixed nerves.

    <p>Mixed nerves contain both efferent motor fibers and afferent sensory fibers, allowing for the conduction of signals to and from the central nervous system.</p> Signup and view all the answers

    What is the significance of pseudounipolar ganglion cells in nerve fiber anatomy?

    <p>Pseudounipolar ganglion cells have their somata outside the spinal cord and allow sensory fibers to bypass the cell body, facilitating rapid signal transmission.</p> Signup and view all the answers

    What do F-waves signify in neurophysiology?

    <p>They indicate the response of alpha motor neurons after antidromic stimulation.</p> Signup and view all the answers

    What does the H-reflex reflect in the nervous system?

    <p>It reflects the monosynaptic reflex circuit of spinal stretch reflexes.</p> Signup and view all the answers

    How do the spinal roots contribute to nerve function?

    <p>Spinal roots consist of afferent fibers in the dorsal roots and efferent fibers in the ventral roots, mediating sensory and motor pathways between the CNS and peripheral tissues.</p> Signup and view all the answers

    Name one inherited cause of polyneuropathy.

    <p>Charcot-Marie-Tooth disease.</p> Signup and view all the answers

    Explain the role of the skin interface in electrode measurements.

    <p>The skin interface serves as a barrier for electrical signals, affecting the accuracy and quality of electrode recordings during electroneurography.</p> Signup and view all the answers

    What types of fibers are involved in the spinal nerve structure?

    <p>The spinal nerve comprises both sensory afferent fibers and motor efferent fibers, along with vegetative fibers for autonomic functions.</p> Signup and view all the answers

    Which acquired condition is often associated with polyneuropathy?

    <p>Diabetes mellitus.</p> Signup and view all the answers

    Discuss the anatomical locations of somata for afferent somatosensory nerves.

    <p>The somata of afferent somatosensory nerves are located in the spinal ganglions, positioned outside the spine or within the foramina of the vertebral column.</p> Signup and view all the answers

    What is the typical progression pattern of polyneuropathy symptoms?

    <p>They usually begin in the hands and feet and may progress to the arms and legs.</p> Signup and view all the answers

    What role does assessment with somatosensory evoked potentials play in diagnosing peripheral nerve issues?

    <p>It may provide helpful insights into nerve function.</p> Signup and view all the answers

    What type of signals do mixed nerves primarily transmit?

    <p>Mixed nerves primarily transmit both sensory signals from peripheral receptors to the CNS and motor signals from the CNS to skeletal muscles.</p> Signup and view all the answers

    How do efferent motor fibers function in relation to muscle contraction?

    <p>Efferent motor fibers extend from motoneurons in the CNS to voluntary muscles, triggering muscle contractions through the release of neurotransmitters at the neuromuscular junction.</p> Signup and view all the answers

    What distinguishes myelinopathy from other types of polyneuropathy?

    <p>Myelinopathy is specifically caused by a loss of myelin.</p> Signup and view all the answers

    Why are vegetative fibers typically not assessed electrophysiologically in mixed nerves?

    <p>Vegetative fibers are primarily involved in autonomic functions, which are not usually reflected in standard electrophysiological assessments in clinical practice.</p> Signup and view all the answers

    What are the main parts of the neuron involved in action potential propagation?

    <p>The main parts involved are the soma, axon, axon hillock, and dendrites.</p> Signup and view all the answers

    How does myelin affect the speed of action potential propagation?

    <p>Myelin increases the speed of action potential propagation by reducing membrane capacitance and increasing membrane resistance.</p> Signup and view all the answers

    What is the role of nodes of Ranvier in axonal signaling?

    <p>Nodes of Ranvier allow for the saltatory conduction of action potentials, enabling faster transmission along myelinated axons.</p> Signup and view all the answers

    What initiates the release of neurotransmitters at the synapse?

    <p>The arrival of an action potential at the axon terminal triggers the opening of Ca++ channels, which causes neurotransmitter release.</p> Signup and view all the answers

    Describe the primary method of signal transmission between neurons.

    <p>Signal transmission between neurons primarily occurs chemically via neurotransmitters at synapses.</p> Signup and view all the answers

    What factors influence the conduction velocity of nerves?

    <p>Conduction velocity is influenced by the diameter of the axon, temperature, and the myelination of the fibers.</p> Signup and view all the answers

    What does the term 'saltatory conduction' refer to?

    <p>Saltatory conduction refers to the process where action potentials jump from one node of Ranvier to the next along myelinated axons.</p> Signup and view all the answers

    How does the diameter of an axon affect action potential speed?

    <p>A larger axon diameter generally results in faster propagation of action potentials due to lower internal resistance.</p> Signup and view all the answers

    What ensures that two neurons do not connect electrically?

    <p>Two neurons typically do not connect electrically due to the presence of synapses, which facilitate chemical communication.</p> Signup and view all the answers

    What is the significance of the action potential's all-or-none principle?

    <p>The all-or-none principle indicates that an action potential either occurs fully or not at all, ensuring reliable signal transmission.</p> Signup and view all the answers

    What does neurophysiology primarily study?

    <p>Neurophysiology studies the function of the central, peripheral, and autonomic nervous systems.</p> Signup and view all the answers

    What historical approach has dominated the field of neurophysiology?

    <p>The field has been dominated by the analysis of electrical activity of neurons.</p> Signup and view all the answers

    What is spontaneous electrical activity in neurophysiology exemplified by?

    <p>Spontaneous electrical activity is exemplified by the electroencephalogram (EEG).</p> Signup and view all the answers

    How does an electromyogram (EMG) relate to neurophysiology?

    <p>An EMG records the electrical activity of voluntarily innervated muscle cells.</p> Signup and view all the answers

    Why can knowledge of the nervous system architecture be important in neurophysiology?

    <p>Knowledge of architecture is often mandatory to interpret neurophysiological findings.</p> Signup and view all the answers

    What are voltage-clamp and patch-clamp techniques used for in neurophysiology?

    <p>They are used for sophisticated analysis of single neurons' electrical activity.</p> Signup and view all the answers

    What role does heart-rate variability play in neurophysiology?

    <p>Heart-rate variability, assessed from ECG recordings, analyzes the autonomic nervous system.</p> Signup and view all the answers

    What characterizes the distinction between EEG and ECG in terms of neurophysiology?

    <p>EEG focuses on brain activity, while ECG predominantly assesses heart activity.</p> Signup and view all the answers

    What are the main types of acute peripheral nerve lesions?

    <p>The main types are neurapraxia, axonotmesis, and neurotmesis.</p> Signup and view all the answers

    How does temperature affect motor nerve conduction studies?

    <p>Lower temperatures can lead to increased latency and decreased amplitude in nerve conduction.</p> Signup and view all the answers

    What happens during the regeneration process in neurapraxia?

    <p>Regeneration occurs with shorter distances between Ranvier nodes, leading to decreased nerve conduction velocity (NCV).</p> Signup and view all the answers

    What occurs when a neurotransmitter opens sodium channels in the postsynaptic membrane?

    <p>It causes depolarization, resulting in an excitatory postsynaptic potential (EPSP).</p> Signup and view all the answers

    In the context of motor nerve conduction, what is meant by distal motor latency?

    <p>Distal motor latency refers to the time interval between stimulation and response at a distal nerve site.</p> Signup and view all the answers

    What characterizes chronic peripheral nerve damage compared to acute injuries?

    <p>Chronic damage typically involves repetitive degeneration of the myelin sheath and axonal damage due to reduced blood flow.</p> Signup and view all the answers

    How does an inhibitory postsynaptic potential (IPSP) affect the postsynaptic neuron?

    <p>It causes hyperpolarization, making it less likely to generate an action potential.</p> Signup and view all the answers

    What is the significance of the axon hillock in neural signaling?

    <p>The axon hillock is where action potentials are first generated, influenced by the summation of EPSPs and IPSPs.</p> Signup and view all the answers

    Which factors can lead to difficulties in stimulating nerves during conduction studies?

    <p>Difficulties can arise from thick subcutaneous tissue, deep nerve courses, and irradiation of the stimulus to neighboring nerves.</p> Signup and view all the answers

    What are the differences in nerve conduction velocity (NCV) associated with axonotmesis and neurotmesis?

    <p>Axonotmesis shows decreased NCV and partial nerve block, while neurotmesis results in a total block and loss of neuron function.</p> Signup and view all the answers

    What is 'divergence' in the context of neural circuitry?

    <p>Divergence refers to a single presynaptic axon establishing synaptic connections with multiple postsynaptic neurons.</p> Signup and view all the answers

    How does the amplitude of a nerve conduction study change during axonotmesis?

    <p>Initially, the amplitude decreases due to the disruption of axons.</p> Signup and view all the answers

    Describe the process of convergence in neural networks.

    <p>Convergence occurs when multiple presynaptic axons connect to a single postsynaptic neuron, enhancing the signal strength.</p> Signup and view all the answers

    Why is sensory nerve conduction often unsuccessful with skin stimulation?

    <p>Sensory nerve conduction studies may fail because pure sensory nerves have limited response at the skin level.</p> Signup and view all the answers

    How does the convergence-divergence circuitry function in response to a new sensory input?

    <p>It acts like an amplifier, quickly processing and enhancing the response to potentially harmful stimuli.</p> Signup and view all the answers

    What is the main clinical indication for neurotmesis?

    <p>The main indication for neurotmesis is surgical reconstruction due to complete nerve disruption.</p> Signup and view all the answers

    Why do EPSPs and IPSPs last longer than action potentials?

    <p>They involve gradual changes in ionic permeability that persist beyond the rapid spike of an action potential.</p> Signup and view all the answers

    How many synaptic relays are typically involved in the somatosensory pathway?

    <p>Typically, there are three synaptic relays from the periphery to the primary sensory cortex.</p> Signup and view all the answers

    What reflects the dynamic nature of information processing in neural networks?

    <p>The adaptation of postsynaptic potentials to changing inputs illustrates the complex information processing.</p> Signup and view all the answers

    What role do subsynaptic membranes play in a neuron?

    <p>They are critical sites for neurotransmitter reception and shaping the postsynaptic potentials.</p> Signup and view all the answers

    What is the role of the striatum in the direct pathway of the basal ganglia?

    <p>The striatum facilitates thalamocortical projections by disinhibiting the globus pallidus interna and substantia nigra pars reticularis.</p> Signup and view all the answers

    Explain how dopaminergic projections from the substantia nigra affect the striatum.

    <p>Dopaminergic projections from the substantia nigra modulate striatal activity, with D1 receptors promoting excitation and D2 receptors leading to inhibition.</p> Signup and view all the answers

    What are the phases of the triphasic response observed during cortical stimulation?

    <p>The triphasic response includes an initial increase in activity leading to inhibition, a decrease indicating disinhibition, and a final increase that results in inhibition stopping movement release.</p> Signup and view all the answers

    Describe the function of the indirect pathway in the basal ganglia.

    <p>The indirect pathway inhibits thalamocortical projections through a sequence of connections from the striatum to the globus pallidus externus and then to the subthalamic nucleus.</p> Signup and view all the answers

    What effect does the activation of D1 and D2 receptors in the striatum have on thalamocortical transmission?

    <p>Activation of D1 receptors facilitates transmission, while D2 receptors inhibit it, balancing excitation and inhibition within the striatum.</p> Signup and view all the answers

    What is the primary function of the basal ganglia in motor control?

    <p>The basal ganglia primarily control the initiation and termination of movements.</p> Signup and view all the answers

    Describe the role of the extrapyramidal system in muscle movement.

    <p>The extrapyramidal system modulates voluntary movements through polysynaptic projections and continually inhibits spinal reflexes.</p> Signup and view all the answers

    How are the basal ganglia and the thalamus related in the context of neural pathways?

    <p>The basal ganglia are located adjacent to the thalamus and are embedded in complex motor loops that interact with it.</p> Signup and view all the answers

    What processes are modulated by the basal ganglia besides voluntary movement?

    <p>The basal ganglia also modulate procedural learning, conditional learning, eye movements, cognition, and emotion.</p> Signup and view all the answers

    What constitutes the primary role of the N.oculomotorius and N.abducens during intraoperative monitoring?

    <p>They are monitored to assess the integrity of cranial nerves that control eye movements.</p> Signup and view all the answers

    Describe the characteristics of muscle spindle afferent fibers.

    <p>Muscle spindle afferent fibers measure muscle length and adjust muscle tone.</p> Signup and view all the answers

    What does EMG stand for, and what does it measure in intraoperative monitoring?

    <p>EMG stands for electromyography, and it measures the electrical activity of muscle cells.</p> Signup and view all the answers

    In the context of motor pathways, how does the basal ganglia influence reflex arcs?

    <p>The basal ganglia usually inhibit reflex arcs to modulate spinal cord reflex activity.</p> Signup and view all the answers

    What is the significant role of the cranial nerves monitored during surgery?

    <p>Monitoring cranial nerves during surgery helps ensure their functionality is preserved and prevents postoperative complications.</p> Signup and view all the answers

    How do the basal ganglia contribute to the stability of movements?

    <p>The basal ganglia help stabilize movements by coordinating muscle activity and ensuring smooth transitions.</p> Signup and view all the answers

    Which of the following is a cardinal sign of Parkinson's disease?

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

    Deep brain stimulation (DBS) can only be used when all medication options have been exhausted.

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

    What is the main neurotransmitter affected in Parkinson's disease?

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

    In Parkinson's disease, the loss of neurons occurs primarily in the substantia nigra pars __________.

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

    Match the following symptoms of Parkinson's disease with their descriptions:

    <p>Akinesia = Difficulty in initiating movements Bradykinesia = Slowness of movement Tremor = Involuntary shaking Rigidity = Stiffness of muscles</p> Signup and view all the answers

    What is the first line of therapy for managing Parkinson's disease?

    <p>L-Dopa and Dopaminagonists</p> Signup and view all the answers

    Phase amplitude coupling (PAC) is a technique used in DBS optimization to enhance stimulation outcomes.

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

    List one potential adverse effect of deep brain stimulation (DBS).

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

    What does neurophysiology primarily study?

    <p>The function of the nervous system</p> Signup and view all the answers

    The electrocardiogram (ECG) is typically included in neurophysiological assessments.

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

    What is a common technique used to record spontaneous electrical activity in the nervous system?

    <p>Electroencephalogram (EEG)</p> Signup and view all the answers

    Neurophysiology examines not only the central but also the ______ and ______ nervous systems.

    <p>peripheral, autonomous</p> Signup and view all the answers

    Match the following neurophysiological techniques with their primary use:

    <p>EEG = Recording spontaneous brain activity EMG = Recording muscle electrical activity Patch clamp = High-resolution single neuron analysis Voltage clamp = Controlling the membrane potential of a neuron</p> Signup and view all the answers

    Which technique is used to analyze single neurons?

    <p>Patch clamp</p> Signup and view all the answers

    Spontaneous electrical activity can include measurements from muscle cells.

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

    The analysis of the electrical activity of ______ has historically dominated neurophysiology.

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

    What are the electrical measurements typically used in neurophysiology called?

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

    Which of the following statements is true regarding neurophysiological findings?

    <p>They require an understanding of nervous system architecture.</p> Signup and view all the answers

    What is one primary function of the basal ganglia?

    <p>Control of voluntary movements</p> Signup and view all the answers

    The extrapyramidal system consists of only pyramidal tracts.

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

    What is the role of the basal ganglia in motor control?

    <p>Initiation and termination of movements</p> Signup and view all the answers

    The _______ are a group of subcortical nuclei involved in procedural and habit learning.

    <p>basal ganglia</p> Signup and view all the answers

    Match the following types of monitoring with their applications:

    <p>N.oculomotorius = Eye movement control N.abducens = Lateral eye movement N.vagus = Autonomic functions N.VII = Facial expression control</p> Signup and view all the answers

    Which electrode position corresponds to the front of the brain?

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

    Midline electrode positions are indicated by even numbers.

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

    What are the potential differences measured by EEG?

    <p>Electrical activity between pairs of electrodes.</p> Signup and view all the answers

    The __________ electrode position refers to the area of the brain near the ears.

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

    Which type of montage is described as more sensitive?

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

    Match the following EEG montages with their characteristics:

    <p>Bipolar = Localizes signals better Reference = More sensitive to distance Average reference = Uses multiple electrodes for baseline Laplacian = Enhances spatial resolution</p> Signup and view all the answers

    What is the primary disadvantage of bipolar montages?

    <p>Less sensitive than reference montages</p> Signup and view all the answers

    The Laplacian montage is primarily used for long-distance signal monitoring.

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

    What determines how the electrical activity is recorded in EEG?

    <p>The way electrodes are connected to the amplifiers.</p> Signup and view all the answers

    The __________ montages typically use an ear as a reference point.

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

    What is the key factor that leads to a decrease in nerve conduction velocity (NCV) in the case of neurapraxia?

    <p>Segmental degeneration of the myelin sheath</p> Signup and view all the answers

    Axonotmesis is characterized by complete disruption of the entire nerve.

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

    What is the term for the degeneration that occurs with complete nerve disruption?

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

    In chronic nerve damage, the repeated degeneration and regeneration of the ______ sheath occurs.

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

    Match the type of nerve lesion with its characteristic:

    <p>Neurapraxia = Segmental degeneration of myelin Axonotmesis = Disruption of axons with intact sheaths Neurotmesis = Complete nerve disruption Chronic damage = Repetitive degeneration of myelin</p> Signup and view all the answers

    What is a common pitfall that can affect nerve conduction studies?

    <p>Deep, intramuscular nerve course</p> Signup and view all the answers

    Amplitude can be easily assessed due to its consistent variability across stimulation sites.

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

    What is the typical regeneration rate for axonal repair in case of axonotmesis?

    <p>1 mm/day</p> Signup and view all the answers

    The ______ is used to measure the time from stimulation to the response onset in nerve conduction studies.

    <p>distal motor latency</p> Signup and view all the answers

    Which condition does NOT typically involve nerve entrapment syndromes?

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

    Study Notes

    Evoked Responses

    • After a stimulus, the evoked response is an approach to analyzing the nervous system.
    • It's used to evaluate the connections between neurons. (neural pathways)

    Electrical Stimulation

    • This involves applying a stimulus to a peripheral nerve.
    • It triggers a muscle contraction in the area innervated by the nerve.
    • Other than electrical current, techniques like visual, acoustic, mechanical, and magnetic stimulation can also be used to test sensory and motor pathways.

    Clinical Neurophysiology

    • The application of neurophysiological techniques to human subjects for diagnostic and therapeutic purposes.
    • It's used to assess and diagnose diseases of the central, peripheral, and autonomic nervous systems.
    • Also used for therapeutic interventions in suitable neurological disorders or functional disturbances.

    Cellular Level

    • All neurophysiological phenomena are based on the ability of excitable cells to transmit information by changing their membrane potential.
    • These include neurons, muscle cells, and some secretory cells.

    Action Potential (AP)

    • The membrane change associated with signal propagation is called the action potential.
    • During repolarization, sodium channels close, and potassium channels open, returning the membrane potential to a negative value.
    • The refractory period occurs during which the ion channels are inactivated, and sodium and potassium return to their resting state distributions by the Na+/K+-ATPase (sodium-potassium-pump).
    • This period determines the maximum AP repetition rate, limiting the speed of the signal.

    Action Potential Properties

    • The duration of an AP varies for different excitable cells.
    • An AP only triggers when the depolarization threshold is exceeded.
    • In physiological conditions, its shape does not differ and is independent of the stimulus current, following the "all or none principle".

    Calcium Channels

    • Voltage-gated calcium channels have been discovered, influencing cellular activity lasting 100 ms or longer.
    • In heart muscles, they're related to the plateau phase of the action potential.
    • In some CNS neurons, they contribute to long bursts of sodium spikes.
    • They are mediators of cellular activity following the AP in muscle cells.

    Neuron Anatomy

    • The typical anatomy of a neuron includes:
      • Axon
      • Dendrites
      • Soma (cell body)

    Muscle Innervation

    • Muscle innervation is complex, involving:
      • Two different efferent fibers:
        • Aα-fibers from α-motoneurons to the main contractile muscle cells
        • Aγ-fibers from γ-motoneurons to the contractile elements of the muscle spindles
      • Two afferent sensory fibers from the muscle spindle:
        • Ia – fibers carrying information of the velocity of length change
        • II – fibers carrying information about the absolute length
      • Ib – fibers from receptors in the tendons carry information about the tension
    • Afferent fibers establish synaptic contacts directly or via interneurons with the α-motoneurons, crucial for the deep tendon reflexes.
    • Afferents from the tendons inhibit the motoneurons, protecting the muscle from damage.

    Muscle Spindles

    • Contractile elements (intrafusal muscle cells) are located at both ends of the cells. The center is elastic.
    • The contraction of the ends compensates for length changes due to the contraction of the outer (extrafusal) muscle cells, preserving receptor sensitivity.
    • They are involved in modifying reflex circuits for voluntary movements.

    Electroneurography (ENG)

    • ENG measures nerve function by stimulating a nerve and recording the electrical response from a muscle.
    • There are several peaks in the ENG recording, corresponding to fiber groups of different diameters, myelinisation, and AP propagation velocities.

    ENG - Motor Nerve Conduction

    • The CMAP (compound muscle action potential) is the evoked response recorded from a muscle.
    • The distal motor latency is the time between stimulation and the onset of the response.
    • Conduction velocities can be calculated.
    • Stimulation should be supramaximal to activate all motor units.

    Technical Notes - Signal to Noise Ratio (SNR)

    • SNR is the ratio of signal power to noise power.
    • Noise can be technical or biological.
    • Different neurophysiological recordings have different typical SNRs.

    Afferent Pathways

    • Descending modulation is primarily inhibitory.
    • It travels downwards to spinal levels (spinothalamic tract).
    • It's involved in the control of sensitivity in peripheral receptors.

    Basal Ganglia

    • Responsible for a variety of motor functions including initiation and termination of movements, stabilization of movements, and stabilizing muscles at rest
    • Involved in several diseases, including Parkinson's Disease

    Parkinson's Disease

    • Characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta
    • May result in hyperactivity of the SNret and inhibition of thalamocortical projections, inhibiting movement initiation
    • Displays four cardinal signs:
      • Akinesia/Bradykinesia
        • Difficulty with starting and stopping movements
        • Impaired facial expressions
        • Micrography
        • Parkinsonian gait
      • Tremor
      • Rigidity
      • Postural instability
    • Other symptoms include neuropsychiatric and vegetative disturbances

    Parkinson's Disease Therapy

    • First-line treatment involves medications such as L-Dopa and dopamine agonists
    • In case of drug resistance, deep brain stimulation (DBS) is an alternative treatment method

    Deep Brain Stimulation (DBS) in Parkinson's Disease

    • Uses electrodes implanted in the subthalamic nucleus (STN)
    • Records neurophysiological biomarkers via extracellular microelectrodes or implanted DBS electrodes
    • Recording involves:
      • Extracellular recordings of a circumscribed neuron population which are then processed via:
        • High-pass filter to assess neuronal firing and action potentials of local neurons (output)
        • Low-pass filter to assess local field potential
          • Represents pre- and postsynaptic potentials (input)
          • Often transferred in the frequency domain and labeled according to EEG frequency bands

    DBS Optimization

    • The optimal DBS location can be determined by analyzing neuron firing patterns
    • Microelectrodes record from a limited number of neurons compared to DBS electrodes
    • DBS optimization involves analyzing local field potentials (LFPs), which show a peak in the lower beta frequency band
    • Modern DBS systems with multiple electrodes can record LFPs for closed-loop stimulation (aDBS)

    DBS Effect on LFPs

    • DBS can change LFPs and alter neuron firing patterns
    • Phase-amplitude coupling (PAC) describes the interplay between oscillations in different frequency bands

    DBS Segmented Stimulation

    • Stimulates specific brain regions at different times in a controlled manner
    • Used to reduce side effects and improve treatment efficacy

    DBS Adverse Effects

    • Includes infections, hemorrhage, speech arrest, apathy, hallucinations, hypersexuality, cognitive dysfunction, depression, and euphoria
    • Strategies to avoid adverse effects include single-shot antibiotics, electrophysiologically optimized placement of DBS electrodes, closed-loop stimulation, and directional stimulation

    Cerebellum

    • Plays a significant role in coordinating movements and maintaining balance
    • Divided into three main regions:
      • Vestibulocerebellum: Responsible for posture, equilibrium, and muscle tone
      • Spinocerebellum: Responsible for error correction, adjusting posture, and smooth movement coordination
      • Cerebrocerebellum: Responsible for planning, programming, and coordination of complex movements, as well as timing and sequencing of movements

    Evoked Responses and Neurophysiology

    • Evoked responses are used to analyze the nervous system, especially to assess neural pathways.
    • Stimuli like electrical, visual, acoustic, mechanical, and magnetic stimulation are used to assess sensory and motor pathways.

    Electrical and Mechanical Recordings

    • Electrical recordings are not the only way to measure neuron and muscle cell activity.
    • Mechanical transducers can be used to assess muscle contractions, like in bladder or rectal pressure measurements.
    • Neurophysiology uses tools from chemistry, physics, and other fields to examine brain activity.

    Clinical Neurophysiology

    • Clinical neurophysiology applies neurophysiological techniques to humans for diagnostic and therapeutic purposes.

    Cellular Level and Excitable Cells

    • Neurons, muscle cells, and some secretory cells are excitable cells.
    • These cells transmit information through changes in their membrane potential.
    • The baseline membrane potential is called resting (membrane) potential (RMP).
    • The membrane change associated with signal propagation is called action potential (AP).

    Action Potential (AP)

    • AP is made up of four phases: depolarization, repolarization, refractory period, and return to resting state.
    • The duration of an AP varies across excitable cells, lasting 1 ms in nerve cells, 10 ms in muscle cells, and up to 500 ms in heart muscle cells.
    • AP triggers when the depolarization threshold is exceeded.
    • The shape of the AP is cell-specific and independent of the stimulus current, following the all-or-none principle.
    • Ion channels and the Na+/K+ - ATPase can be affected by drugs used for clinical purposes.

    Calcium and AP

    • Extracellular Ca++ is essential for membrane stability in excitable cells.
    • Several voltage-gated Ca++ - channels result in Ca++ - based activity.
    • Ca++ activity is related to the plateau phase of the action potential in heart muscles and slow calcium spikes in CNS neurons.

    Neuron Anatomy

    • Neurons are comprised of a soma (cell body), dendrites (receiving signals), and an axon (transmitting signals).

    Muscle Innervation

    • Muscle innervation involves two types of efferent fibers: Aα-fibers and Aγ-fibers.
    • Aα-fibers from α-motoneurons innervate the main contractile muscle cells.
    • Aγ-fibers from γ-motoneurons innervate the contractile elements of muscle spindles.
    • Muscle spindles also contain two types of afferent sensory fibers: Ia – fibers and II – fibers.
    • Ia – fibers carry information about the velocity of length change.
    • II – fibers carry information about the absolute length.
    • Ib – fibers from receptors in the tendons carry information about tension.

    Muscle Spindles

    • The contractile elements within the muscle spindles (intrafusal muscle cells) are located at both ends of the cells.
    • The center of the cells is elastic.
    • The contraction of the ends compensates for length changes due to contraction of the outer (extrafusal) muscle cells.
    • This ensures the sensitivity of the receptor and modifies the reflex circuit during voluntary movement.

    Electroencephalography (EEG)

    • The brain displays permanent electrical activity.
    • EEG records this activity on the scalp as rhythmic activity within distinct frequency bands: Gamma, Beta, Alpha, Theta, and Delta.

    Normal EEG Findings

    • Normal EEG varies depending on individual factors, normal variants, region of origin, external stimuli, attention level, age, and sleep stage.
    • Alpha-EEG is very regular, with individual-specific frequency.
    • It's accentuated over the occipital and temporal lobes.
    • Side differences in amplitude of less than 50% are normal.
    • Alpha-EEG is often modulated in the form of a spindle.
    • It's blocked by eye opening and restored after eye closing.

    Beta-EEG

    • Beta-activity is present in all channels with alpha-activity seen after eye closing.
    • It indicates drowsiness, sleep, strain, and drug-induced states.

    Abnormal EEG Findings

    • Pathologically slowed EEG is dominated by Theta- and/or Delta-activity.
    • It's associated with elevated intracranial pressure, impaired consciousness, and specific sleep stages.
    • Alpha-coma is a unique condition where alpha-activity is present despite impaired consciousness.
    • Burst-suppression EEG contains alternating periods of high-amplitude bursts and suppression of activity.
    • Electrocerebral silence is a complete absence of EEG activity.
    • Focal abnormalities are circumscribed slowing or epileptic activity.
    • They can indicate tumors, small bleedings, infarctions, etc.

    Basal Ganglia

    • The basal ganglia regulate voluntary movement, learning, and cognition.
    • It receives input from the cortex and projects to the thalamus.
    • The basal ganglia consist of the striatum, globus pallidus, subthalamic nucleus, and substantia nigra.
    • There are two pathways: direct and indirect.
    • The direct pathway facilitates thalamocortical projections, while the indirect pathway inhibits them.
    • The substantia nigra pars compacta provides dopaminergic projections to the striatum.
    • D1 receptors in the striatum cause excitation, while D2 receptors cause inhibition.
    • These dopaminergic projections modulate the balance between the direct and indirect pathways.

    Cortical Stimulation and Basal Ganglia

    • Cortical stimulation yields a triphasic response in the basal ganglia output nuclei (SNret/GPi).
    • The initial response is increased activity, inhibiting thalamocortical projections.
    • This is followed by decreased activity, leading to disinhibition and movement release.
    • The final phase shows increased activity again, inhibiting thalamocortical projections and stopping movement release.

    Neural Networks

    • A pain stimulus activates a convergence-divergence circuitry, amplifying the signal for a rapid response.
    • Lateral inhibition: Interneurons in each relay level create inhibitory connections, refining the localization of the stimulus by enhancing contrast.
    • Lateral inhibition limits impulse propagation to the afferences from the damaged site.

    Electrophysiological Recording

    • Extracellular recording measures voltage changes related to the activity of excitable cells.
    • The potential difference between two electrodes is amplified and converted to a signal for display.
    • Extracellular recordings have a lower signal-to-noise ratio and complex relationship between the extracellular field and cellular processes.

    Action Potential (AP) Propagation

    • APs propagate along the axon membrane, allowing signal transmission.
    • Propagation occurs due to local transmembrane currents that depolarize the membrane, triggering APs in adjacent segments.
    • AP propagation can occur in both directions but is much slower than the current in electric cables.

    Myelination & Conduction Velocity

    • Myelin sheaths accelerate AP propagation by increasing membrane resistance and reducing capacitance.
    • Myelin is made up of Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system.
    • Factors affecting conduction velocity: axon diameter, temperature, length of the inter-node distance.

    Neuron Anatomy

    • The axon typically branches, establishing contact with other neurons or muscle cells at the terminals.
    • Electrical connections between neurons are uncommon.

    Synapses

    • The usual signal transfer between neurons occurs chemically at synapses.
    • Axon terminals contain vesicles filled with neurotransmitters.
    • AP arrival at the presynaptic axon triggers the release of neurotransmitters, opening Ca++ channels.
    • Released neurotransmitters bind to receptors on the post-synaptic membrane, influencing ion channel activity.

    Electrode-Electrolyte Reaction

    • An electrode-electrolyte interface forms between an electrode and an electrolyte solution.
    • The interface is characterized by the formation of an Inner Helmholtz Plane (IHP) and an Outer Helmholtz Plane (OHP).

    Electroneurography (ENG)

    • Most nerves are mixed, containing motor and sensory fibers.
    • Motor fibers are axons of motoneurons, conveying commands to voluntary muscles.
    • Sensory fibers transmit information from sensory receptors to the CNS.
    • Somatosensory neuron cell bodies reside in spinal ganglia.
    • Mixed nerves also contain vegetative fibers, but are not usually assessed electrophysiologically.

    Meralgia Paresthetica

    • Compression of the lateral femoral cutaneous nerve under the inguinal ligament.
    • Causes pain and numbness on the lateral aspect of the thigh.
    • No reliable sensory nerve conduction test for diagnosis.

    Polyneuropathy

    • Damage or disease affecting peripheral nerves bilaterally.
    • Symptoms include weakness, numbness, burning pain.
    • Often begins in hands and feet, progressing to arms, legs, and potentially the autonomic nervous system.
    • Can be acute or chronic.
    • Causes include diabetes, alcoholism, vitamin B12 deficiency, and various genetic conditions.

    Polyneuropathy Classification

    • Distal axonopathy: Interrupted function of peripheral nerves due to metabolic or toxic disturbances.
    • Myelinopathy: Loss of myelin.
    • Neuronopathy: Issues with peripheral nervous system neuron cell bodies.

    F-waves & H-reflex

    • F-waves are evoked by supramaximal electrical stimuli applied to the distal portion of a nerve.
    • The impulse travels orthodromically (towards muscle) and antidromically (towards the cell body).
    • The orthodromic impulse elicits a direct motor response (M).
    • The antidromic impulse reaching the spinal cord cell bodies generates a second AP (F-response) due to persistent dendritic depolarization.

    H-reflex

    • Reflects the monosynaptic reflex circuit of spinal stretch reflexes.

    Electroencephalography (EEG) Frequency Bands

    • The brain exhibits continuous electrical activity, recorded as rhythmic activity within distinct frequency bands.
    • Gamma: > 31 Hz
    • Beta: 13-30 Hz
    • Alpha: 8-12 Hz
    • Theta: 4-7 Hz
    • Delta: < 4 Hz

    Normal EEG Findings

    • The EEG varies based on individual factors, normal variants, recording location, stimuli, attention level, sleep stage, and age.
    • Alpha EEG is regular, individual-specific, accentuated over occipital and temporal lobes, and blocked by eye opening.
    • Beta EEG is dominant when the individual is awake, alert, or stressed.
    • Theta and Delta activity are characteristic of sleep stages.

    Abnormal EEG Findings

    • Pathologically Slowed EEG: Dominated by Theta and/or Delta activity, indicating potential issues such as elevated intracranial pressure or impaired consciousness.
    • Burst-Suppression EEG: Alternating periods of electrical activity and suppression, commonly associated with severe brain injury or coma.
    • Electrocerebral Silence: Absence of electrical activity, considered a sign of brain death.
    • Focal Abnormalities: Localized slowing or epileptic activity, indicating possible underlying pathology.

    Neurophysiology Definition

    • Neurophysiology is a branch of biology focusing on the functionality of the nervous system
    • Neurophysiology studies the central, peripheral, and autonomous nervous systems
    • Analyzing the activity of neurons is a key element of historical neurophysiology
    • The understanding of the nervous system architecture is essential to interpret neurophysiological findings.

    Postsynaptic Potentials

    • Neurotransmitters can open sodium channels, causing depolarization (EPSP)
    • Neurotransmitters can also open potassium channels, causing hyperpolarization (IPSP)
    • EPSPs and IPSPs last longer than action potentials and can add or subtract

    Neural Network Example

    • Sensory pathways typically have three synaptic relays from the periphery to primary sensory cortex neurons.
    • Presynaptic axons establish excitatory synaptic connections with many postsynaptic neurons (divergence).
    • Postsynaptic neurons recieve input from many excitatory presynaptic axons (convergence).
    • This convergence-divergence circuitry acts like an amplifier, enabling a quick response to potentially harmful stimuli.

    Electromyography (EMG) Motor Nerve Conduction

    • Potential difficulties with stimulation include thick subcutaneous tissue and deep, intramuscular nerve courses.
    • Stimulation can be irraditated to neighboring nerves, especially at the wrist.
    • Temperature variations in the extremities are a consideration.

    EMG Motor Nerve Conduction Assessment

    • The assessment involves analysis of distal motor latency, amplitude, and velocity.
    • Side differences and differences between stimulation sites are noted.
    • Absolute amplitude values are difficult to assess due to variability.

    EMG Motor Nerve Conduction Age

    • The values of motor nerve conduction change with age.

    Peripheral Nerve Lesion Types

    • Acute Injuries
      • Neurapraxia: Segmental degeneration of the myelin sheath
      • Axonotmesis: Disruption of axons with intact connective tissue sheaths; partial block, amplitude decreases initially
      • Neurotmesis: Complete disruption of the entire nerve; total block, neuroma/retrograde degeneration with neuron loss
    • Chronic Injuries (Entrapment Syndromes)
      • Repetitive regeneration of the myelin sheath
      • Axonal damage due to reduced blood perfusion

    Intraoperative Monitoring

    • Intraoperative monitoring is used to assess nerve function during surgery.
    • The recording equipment can measure electrical activity.
    • Nerve function can be monitored during procedures on the skull base, as well as other areas.

    Motor Pathways: Extrapyramidal System

    • It's defined as all nuclei/tracts not part of the pyramidal system.
    • Polysynaptic corticospinal projections.
    • The system includes the cerebellum and basal ganglia.
    • The system modulates spinal reflex arcs, usually with inhibitory effects.

    Basal Ganglia

    • A group of subcortical nuclei in the forebrain and midbrain.
    • Numerous functions including:
      • Control of voluntary movements.
      • Procedural learning, habit learning, and conditional learning.
      • Eye movements.
      • Cognition and emotions.

    Basal Ganglia Functions

    • Involved in initiation, termination, and stabilization of movements.
    • Help stabilize muscles at rest.

    Basal Ganglia Connectivity

    • Inputs from the cortex to the basal ganglia are received by the striatum.
    • Output to the thalamus via the globus pallidus interna and substantia nigra pars reticularis.
    • Direct pathway: Striatum –> SNret/GPi –> Thalamus (facilitation of thalamocortical projections)
    • Indirect pathway: Striatum –> GPe –> STN –> SNret/GPi –> Thalamus (inhibition of thalamocortical projections)

    Basal Ganglia: Substantia Nigra Pars Compacta

    • Dopaminergic projections to the striatum.
    • D1 receptors in the striatum lead to excitation.
    • D2 receptors in the striatum lead to inhibition.
    • The different pathways, D1 and D2, facilitate thalamocortical impulse transmission.

    Cortical Stimulation: Effects on Basal Ganglia

    • Cortical stimulation produces a triphasic response in the basal ganglia output nuclei.
    • An initial delay followed by increased activity, inhibiting thalamocortical projections.
    • Decreased activity happens next, leading to disinhibition and movement release.
    • Finally, increased activity resumes, inhibiting thalamocortical projections and stopping movement release.

    Basal Ganglia

    • Part of the extrapyramidal system
    • Located at the base of the forebrain and the top of the midbrain
    • Associated with a variety of functions including:
      • Control of voluntary movements
      • Procedural learning
      • Habit learning
      • Conditional learning
      • Eye movements
      • Cognition
      • Emotion
      • Initiation and termination of movements
      • Stabilization of movements
      • Stabilizing muscles at rest

    Basal Ganglia Diseases

    • Parkinson's disease
      • Loss of dopaminergic neurons in the substantia nigra pars compacta
      • Cortical activation leads to hyperactivity of SNret and an inhibition of thalamocortical projections required for movement initiation
      • Cardinal signs:
        • Akinesia/Bradykinesia
          • Start/Stop disturbances
          • Impaired facial expressions
          • Micrography
          • Parkinsonian gait
        • Tremor
        • Rigidity
        • Postural instability
      • Other Symptoms
        • Neuropsychiatric
        • Vegetative

    Parkinson's Disease Therapy

    • First line: drugs (L-Dopa, Dopamine agonists…)
    • In case of drug resistance: Deep brain stimulation (DBS)

    DBS for Parkinson's Disease

    • Neurophysiological Biomarkers
      • Recorded via:
        • Extracellular microelectrodes (or the inserted DBS electrodes)
      • Extracellular recording of a circumscribed neuron population -> raw data
      • High-pass filter -> neuronal firing:
        • Action potentials of local neurons (Output?)

    DBS for Parkinson's Disease

    • Targeting the optimal DBS location by analyzing neuronal firing
    • Microelectrodes record only from a limited number of neurons around the tip when compared to DBS electrodes

    DBS Optimization with Neuronal Firing

    • Neurophysiological Biomarkers
      • Recorded via:
        • Extracellular microelectrodes (or the inserted DBS electrodes)
      • Extracellular recording of a circumscribed neuron population -> raw data
      • Low-pass filter -> local field potential:
        • Pre- and postsynaptic potentials (Input?)
        • Often transferred in the frequency domain and labeled according to the EEG frequency bands

    DBS Optimization with Local Field Potentials

    • E0 is the common electrode showing a peak in the lower beta frequency band and is chosen for DBS
    • In modern systems with more electrodes, the channels not in use for stimulation may be used to record local field potentials, which are evaluated for an adaptation of DBS (aDBS – closed loop stimulation)

    DBS Effect upon Local Field Potentials

    • PAC – phase amplitude coupling

    DBS for Parkinson's Disease - Segmented Stimulation

    • DBS can be segmented to stimulate specific areas at different times

    DBS for Parkinson's Disease - Adverse Effects

    • Infections
    • Hemorrhage
    • Speech arrest
    • Apathy
    • Hallucinations
    • Hypersexuality
    • Cognitive dysfunction
    • Depression
    • Euphoria

    Strategies to Avoid DBS Adverse Effects

    • Single shot antibiotics
    • Electrophysiologically optimized placement of the DBS electrodes
    • Closed loop stimulation
    • Electrode optimization (directional stimulation)

    Cerebellum

    • Vestibulocerebellum
      • Maintenance of posture and equilibrium
      • Maintenance of muscle tone
    • Spinocerebellum
      • Error correction, adjusts posture
      • Smoothness and coordination of movements
    • Cerebrocerebellum
      • Planning and programming
      • Coordination of complex movements
      • Sequence and precision of movements
      • Timing of movements

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    Clinical Neurophysiology Basics PDF

    Description

    This quiz explores the concepts of evoked responses, electrical stimulation, and the clinical applications of neurophysiology. Learn about how these techniques help analyze and diagnose conditions related to the nervous system. Delve into the cellular mechanisms that facilitate nerve communication.

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