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Questions and Answers
What is the function of synapses in the nervous system?
What is the function of synapses in the nervous system?
Which component of a neuron is primarily responsible for integrating signals?
Which component of a neuron is primarily responsible for integrating signals?
What occurs to Na+ channels after they close?
What occurs to Na+ channels after they close?
How does the myelin sheath affect nerve impulse transmission?
How does the myelin sheath affect nerve impulse transmission?
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What is the significance of Na+ channel inactivation in cellular activity?
What is the significance of Na+ channel inactivation in cellular activity?
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Which of the following factors does NOT influence the speed of nerve impulses?
Which of the following factors does NOT influence the speed of nerve impulses?
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In what order do signals typically travel through the nervous system?
In what order do signals typically travel through the nervous system?
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Which condition is NOT associated with the closure and inactivation of Na+ channels?
Which condition is NOT associated with the closure and inactivation of Na+ channels?
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What could result from a failure of Na+ channels to inactivate properly?
What could result from a failure of Na+ channels to inactivate properly?
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What structural change occurs in Na+ channels during inactivation?
What structural change occurs in Na+ channels during inactivation?
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What happens to Na+ channels during the action potential process?
What happens to Na+ channels during the action potential process?
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What characterizes the action potential at the threshold of -50 mV?
What characterizes the action potential at the threshold of -50 mV?
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What leads to the brief undershoot observed in the action potential?
What leads to the brief undershoot observed in the action potential?
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How does membrane potential change during an action potential?
How does membrane potential change during an action potential?
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What is the significance of the threshold potential of -50 mV?
What is the significance of the threshold potential of -50 mV?
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What is the maximum speed of nerve impulses in myelinated neurones?
What is the maximum speed of nerve impulses in myelinated neurones?
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What role does the myelin sheath play in nerve conduction?
What role does the myelin sheath play in nerve conduction?
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Which of the following describes saltatory conduction?
Which of the following describes saltatory conduction?
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Which type of ion channel is always open?
Which type of ion channel is always open?
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What triggers the opening of voltage-gated ion channels?
What triggers the opening of voltage-gated ion channels?
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Which of the following is a type of gated ion channel that opens in response to chemical signals?
Which of the following is a type of gated ion channel that opens in response to chemical signals?
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How do temperature and diameter affect the speed of nerve impulses?
How do temperature and diameter affect the speed of nerve impulses?
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What defines the resting membrane potential in a neuron?
What defines the resting membrane potential in a neuron?
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What is the condition of voltage-gated Na+ and K+ channels during the resting state of a neuron?
What is the condition of voltage-gated Na+ and K+ channels during the resting state of a neuron?
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What is the primary state of a neuron during resting potential?
What is the primary state of a neuron during resting potential?
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Which ions primarily contribute to the resting potential of a neuron?
Which ions primarily contribute to the resting potential of a neuron?
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At resting potential, which ion is typically more concentrated outside of the neuron?
At resting potential, which ion is typically more concentrated outside of the neuron?
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Which of the following best describes the magnitude of resting potential?
Which of the following best describes the magnitude of resting potential?
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Why is it important for a neuron to maintain resting potential?
Why is it important for a neuron to maintain resting potential?
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What would likely occur if a neuron's resting potential was disrupted?
What would likely occur if a neuron's resting potential was disrupted?
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What mechanism helps to keep the resting potential stable within the neuron?
What mechanism helps to keep the resting potential stable within the neuron?
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What leads to the initiation of a nerve signal?
What leads to the initiation of a nerve signal?
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During depolarization, which ion's channels are primarily opened?
During depolarization, which ion's channels are primarily opened?
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What happens to potassium channels during repolarization?
What happens to potassium channels during repolarization?
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What is undershoot in terms of membrane potential?
What is undershoot in terms of membrane potential?
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What primarily occurs during the action potential phase of a nerve impulse?
What primarily occurs during the action potential phase of a nerve impulse?
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What is the effect of a stimulus on a nerve's membrane potential?
What is the effect of a stimulus on a nerve's membrane potential?
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What occurs after more Na+ channels open during depolarization?
What occurs after more Na+ channels open during depolarization?
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Which of the following correctly describes the membrane during the action potential?
Which of the following correctly describes the membrane during the action potential?
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In the context of a nerve signal, what does 'repolarization' refer to?
In the context of a nerve signal, what does 'repolarization' refer to?
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Which ion primarily causes the depolarization of the membrane?
Which ion primarily causes the depolarization of the membrane?
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During undershoot, how does the voltage change?
During undershoot, how does the voltage change?
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What is the resting state of K+ and Na+ channels before a stimulus is applied?
What is the resting state of K+ and Na+ channels before a stimulus is applied?
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What is the primary reason for the closure of K+ channels during repolarization?
What is the primary reason for the closure of K+ channels during repolarization?
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Study Notes
Animal Physiology (3rd Level Biology English)
- Course Instructor: Dr. Hiba Allah Abdul Rahman Ahmad
- Course Level: 3rd Level (Biology English)
General Functions of Neuroglia
- Support: Provide supportive scaffolding for neurons.
- Neuron Health Growth: Promote neuron health growth.
- Chemical Guidance: Some neuroglia produce chemicals to guide young neurons to proper connections.
- Speed Up Action Potential Conduction: Others wrap around and insulate neuronal processes to speed up action potential conduction.
Differences Between Neuroglia & Neuron
- Size: Neuroglia are smaller than neurons.
- Quantity: There are 5 to 50 times more neuroglia than neurons.
- Action Potentials: Glial cells do not generate or propagate action potentials.
- Replication: Glial cells can multiply and divide in the mature nervous system.
The Neuron
- Signal Reception: Dendrites receive signals.
- Signal Integration: The cell body integrates signals.
- Signal Transmission: The axon transmits action potentials.
- Speed Increase: The myelin sheath increases the speed of signal transmission.
- Signal Transmission: Synaptic terminals transmit signals.
Nerve Impulse
- Progressive Wave: A progressive wave of electrical and chemical activity along a nerve fiber.
- Action of Nerve Cell: Stimulates or inhibits a muscle, gland, or other nerve cell.
- Information Transmission: Information moves from sensory neurons to interneurons to motor neurons.
Factors Determining Nerve Impulse Speed
- Temperature: Higher temperature leads to faster speed.
- Axon Diameter: Larger diameter results in faster speed.
- Myelin Sheath: Vertebrates have a myelin sheath surrounding their neurons.
- Nodes of Ranvier: Voltage-gated ion channels are found only at these nodes.
- Saltatory Propagation: The myelin sheath isolates the axon, and the impulse jumps between nodes to significantly increase speed, while impulses in unmyelinated neurons only travel at approximately 1 m/s, those in myelinated neurons can reach up to 100 m/s.
Ion Channels
- Plasma Membranes: Contain various ion channels.
- Passive Channels (Leakage Channels): Always open.
- Active Channels (Gated Channels): These channels open and close in response to specific stimuli and include ligand-gated, voltage-gated, and mechanically-gated channels.
Membrane Potential
- Measurement: Measured in millivolts.
- Resting State: When a nerve is inactive (not transmitting a signal), the membrane potential is around -70 mV.
Membrane Potentials
- Separation of Ions: Voltage exists across the plasma membrane due to the separation of oppositely charged ions.
- Resting Membrane Potential: The potential difference in a resting membrane.
- Polarization: The membrane is polarized in a resting neuron.
Changes in Membrane Potential
- Stimuli: Responses to stimuli such as ion concentrations (e.g., temperature, light, or pressure) and chemical stimuli (e.g., neurotransmitters such as dopamine, serotonin, and amino acids)
Resting Membrane Potential
- Charge Differences: Inside and outside of the cell have a difference in charge.
- Ion Concentrations: Sodium is in greater concentration outside the cell, potassium inside, and anions inside.
- Large Molecules: Maintain a negative charge inside the cell..
- Membrane Permeability: Greater for potassium than sodium.
- Active Transport: The Na+/K+ pump moves sodium outside and potassium inside the cell.
Membrane Potentials
- Signals: Neurons use changes in membrane potentials as signals.
- Signal types: Two types of signals: graded potentials and action potentials.
Graded Potentials
- Triggers: Triggered by change in neuron's environment.
- Opens Ion Channels: Opens gated ion channels to change membrane state.
- Depolarization: A small area of the neuron's plasma membrane becomes depolarized (less negative).
- Current Flow: Current flows on both sides of the membrane (+ moves toward − and vice-versa).
Graded Potentials
- Short-lived: Short-lived, local changes in membrane potential (either depolarizations or hyperpolarizations).
- Decreasing Magnitude: Cause current flows that decrease in magnitude with distance.
- Stimulus Strength: Magnitude depends on stimulus strength; stronger stimuli lead to larger voltage changes.
- Current Flow: Larger voltage changes lead to farther current flow..
Graded Potentials
- Short-Distances: Signals over very short distances.
- Action Potential Initiation: Important in initiating action potentials.
Action Potentials
- Phases: Describes four phases of an action potential: resting states, depolarization, repolarization, and undershoot.
- Neuron Response: A nerve signal begins as a change in membrane potential.
- Membrane Permeability Changes: Stimuli alter the membrane permeability, allowing ions to pass through, changing the membrane voltage.
- Action Potential: The nerve signal, termed an action potential, is a change in the membrane voltage that goes through the resting potential to a maximum and back.
Action Potentials
- Phases of Action potential: Different phases of repolarization (e.g. channels close and open) are detailed including the refractory period (absolute refractory period and relative refractory period)
Action Potential Propagation
- Electric Current: Action potential causes an electric current that stimulates adjacent membrane portions.
- Sequential Activation: A series of action potentials occurs sequentially along the axon as a nerve impulse.
Action Potential Propagation
- Self-Propagation: The action potential propagates itself along the neuron.
- One-Way Chain Reaction: Action potentials are self-propagated in a one-way chain reaction along a neuron.
- All-or-None Events: Action potentials are all-or-none events..
Action Potentials
- All-or-Nothing: Action potentials are all-or-nothing phenomena; either they happen completely or not at all.
- Stimulus Strength Independence: Independent of stimulus strength once generated.
- Strong Stimuli: Strong stimuli generate more impulses of the same strength per unit time.
- Intensity Determination: Determined by the number of impulses per unit time
Action Potentials
- Frequency Changes: The frequency of action potentials changes with the strength of the stimulus.
- Strength Stability: The strength of the action potential itself is stable (all-or-none law)
Action Potentials- Refractory Period
- Second Stimulus Response: Neurons cannot respond to a second stimulus while Na⁺ channels are still open from the previous stimulus.
- Absolute Refractory Period: This period is called the absolute refractory period.
- Relative Refractory Period: This is followed by the relative refractory period where repolarization is occurring, and the threshold for impulse generation is elevated.
- Strong Stimuli: Only strong stimuli can generate impulses during this period.
Synapses
- Neuron Connection: Neurons usually do not connect directly, but instead, a junction between dendrites of one neuron and the axon of another, called a synapse, controls signal transmission.
- Neurotransmitters: Neurotransmitters cross the synapse and stimulate the next neuron.
Synapse
- Types: Synapses can be chemical (most common) or electrical.
- Electrical Synapses: Ions flow directly between neurons.
- Chemical Synapses: Neurotransmitters transmit the signal, crossing the synaptic cleft and binding to a receptor, leading to excitation or inhibition.
Synaptic Integration
- Excitatory Postsynaptic Potential (EPSP): Neurotransmitter binding causes depolarization, Na⁺ and K⁺ flow through the membrane, and net depolarization occurs.
- Inhibitory Postsynaptic Potential (IPSP): Neurotransmitter binding reduces a postsynaptic neuron's ability to generate an action potential by increasing permeability to K⁺ and Cl⁻.
Synaptic Integration
- Temporal Summation: Repeated stimulation from a single synapse within a short timeframe leads to summation..
- Spatial Summation: Simultaneous stimulation from separate synapses leads to summation.
Basic Concepts of Neural Integration
- Circuit Patterns: Different patterns of synaptic connections in neuronal pools (e.g., diverging, converging, reverberating, etc.) are shown.
- The diagrams show how signals travel within each circuit type
Synapse
- Function: Mediating information transfer from one neuron to another or to an effector cell..
- Types: Axodendritic, axosomatic, axoaxonal synapses.
Synapse
- Electrical Signals: Pass between cells at electrical synapses, as well as at chemical synapses.
- Chemical Signals: The sending neuron secretes a neurotransmitter, which crosses the synaptic cleft and binds to a receptor on the receiving cell, leading to excitation or inhibition.
Synapse Types
- Electrical synapses: Less common than chemical synapses; correspond to gap junctions; cytoplasm of adjacent neurons are connected through protein channels, allowing ions to flow directly between neurons, and transmission is very rapid.
Neurotransmitters
- Chemicals: Chemicals released from the presynaptic neuron.
- Functions: Assist, stimulate, or inhibit postsynaptic neurons.
- Synthesis Locations: Synthesized in the cytoplasm of synaptic knobs/vesicles.
Neurotransmitters
- Types: Various types including small molecules (e.g., acetylcholine, biogenic amines, amino acids) and neuropeptides (e.g., endorphins).
- Classification: Classified by chemical and anatomical/physiological characteristics.
Criteria for Neurotransmitters
- Synthesis: Synthesized in the presynaptic neuron
- Storage: Stored in vesicles in the presynaptic terminal
- Release: Released upon appropriate stimulus (e.g., action potential)
- Binding: Bind to receptors on the postsynaptic membrane
- Termination: Mechanisms for clearing the neurotransmitter from the synapse.
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Description
This quiz explores the critical roles of synapses, myelin sheaths, and sodium channels in the nervous system's functioning. Test your knowledge on neuronal signal integration, action potential dynamics, and factors influencing nerve impulse transmission. Suitable for students of neuroscience and biology.
