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Questions and Answers
What role do sodium ions play in establishing the resting membrane potential?
What role do sodium ions play in establishing the resting membrane potential?
During action potential, when does the depolarization of the membrane occur?
During action potential, when does the depolarization of the membrane occur?
What happens during the refractory period of an action potential?
What happens during the refractory period of an action potential?
What is the primary reason that the cell membrane is more permeable to potassium ions than sodium ions?
What is the primary reason that the cell membrane is more permeable to potassium ions than sodium ions?
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Which component is NOT involved in generating the action potential?
Which component is NOT involved in generating the action potential?
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What is the primary function of voltage in an electric circuit?
What is the primary function of voltage in an electric circuit?
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What type of current is characterized by a one-directional flow of electrons?
What type of current is characterized by a one-directional flow of electrons?
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How do negative ions flow in relation to the electrodes?
How do negative ions flow in relation to the electrodes?
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Which factor primarily influences the body’s electrical impedance?
Which factor primarily influences the body’s electrical impedance?
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Which of the following best describes capacitive reactance?
Which of the following best describes capacitive reactance?
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Study Notes
Overview of the Nervous System and Neuron Function
- Nervous system consists of sensory, motor, and interneurons that facilitate communication and processing of information.
- Neurons are specialized cells responsible for transmitting signals throughout the body.
Types of Neurons
- Sensory Neurons: Transmit sensory information from receptors to the central nervous system (CNS).
- Motor Neurons: Convey signals from the CNS to muscles or glands, facilitating movement.
- Interneurons: Connect sensory and motor neurons, playing a critical role in reflex arcs and processing information.
Neuron Structure
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Components:
- Dendrites: Receive signals from other neurons.
- Axon: Conducts impulses away from the neuron's cell body.
- Myelin Sheath: Insulates axons to speed up signal transmission.
Resting Membrane Potential
- Maintains a net positive charge outside and negative charge inside the neuron.
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Mechanisms:
- Sodium-potassium pumps move three Na+ ions out for every two K+ ions in.
- Membrane permeability allows K+ to diffuse outward faster than Na+ influx.
- Large negatively charged anions inside the neuron create an imbalance, contributing to the resting potential.
Action Potential
- Initiated when a stimulus depolarizes the membrane toward the threshold potential.
- If the threshold is met, Na+ channels open, causing rapid depolarization.
- Following peak action potential, K+ channels open allowing K+ to exit, leading to hyperpolarization.
- The refractory period follows, during which the neuron's ability to fire is temporarily inhibited, restoring the resting potential.
Current Flow
- Electric Current: Movement of charged particles; involves both electron and ion flow.
- Electron Flow: Moves through electrical conductors between generators and electrodes.
- Ion Flow: Occurs in tissues, with negative ions towards the anode and positive ions towards the cathode.
Electrical Impedance
- Refers to the resistance to current flow in biological tissues.
- Impedance arises from combinations of resistive and capacitive properties of tissues.
- High water content in tissues facilitates better conductance and lower impedance.
Types of Electrical Currents
- Direct Current (DC): Unidirectional flow; used for iontophoresis and wound care.
- Alternating Current (AC): Bidirectional flow, required to change direction at least once per second; frequency measured in hertz (Hz).
Modes of Electrical Currents
- Continuous Mode: Steady current flow.
- Interrupted or Pulsed Mode: Current flow is periodically interrupted.
Electrical Current Classification by Frequency
- Low Frequency Currents: Range 1-1000 Hz; effective for sensory and motor nerve stimulation.
- Medium Frequency Currents: Around 1 kHz; requires modulation for nerve stimulation.
- High Frequency Currents: Greater than 1 MHz; generally non-stimulatory to sensory and motor nerves.
Current Characteristics
- Current Amplitude: Peak distance the wave rises above/below baseline.
- Pulse Attributes: Include amplitude, phase duration, pulse duration, and intervals affecting muscle contraction types.
Pulse Frequency
- Measured in pulses per second (pps); higher frequencies lead to different contraction types (e.g., twitch vs. tonic contraction).
- Low pulse frequency allows for greater resistance than high frequency.
Rise and Decay Times
- Rise time: how quickly a pulse reaches maximum amplitude.
- Decay time: time taken for the pulse to drop from max to zero.
- Significant for understanding nervous tissue excitability during stimulation.
Duty Cycle
- Ratio of current ON time to total cycle time; calculated as a percentage.
- Affects muscle stimulation patterns, starting low to prevent fatigue, gradually increasing for effectiveness.
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Description
This quiz covers the physiological background of electrotherapy, focusing on the nervous system and neuron function. Topics include types of neurons, neuron structure, and resting membrane potential. Test your understanding of these fundamental concepts in neurophysiology.
