Neuroscience Action Potentials and Graded Potentials
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Questions and Answers

What primarily determines the amplitude of a graded potential?

  • The distance from the trigger zone
  • The type of ion channels involved
  • The duration of the stimulus
  • The strength of the stimulus (correct)

Which statement describes action potentials accurately?

  • They can vary in frequency but not amplitude
  • Action potentials occur in a single, fixed amplitude
  • They can only occur if the membrane potential reaches a threshold (correct)
  • They consist of phases of hyperpolarization and depolarization

During which phase of an action potential does the membrane potential become more positive?

  • Resting phase
  • Hyperpolarization
  • Repolarization
  • Depolarization (correct)

What type of channels are primarily involved in grading potentials?

<p>Mechanically gated or ligand-gated ion channels (D)</p> Signup and view all the answers

How do graded potentials propagate?

<p>They exhibit decremental conduction over short distances (C)</p> Signup and view all the answers

What occurs during repolarization of an action potential?

<p>The membrane potential becomes more negative (D)</p> Signup and view all the answers

What is a key difference between graded potentials and action potentials?

<p>Graded potentials can be initiated at any part of the neuron (D)</p> Signup and view all the answers

What type of channels are responsible for the generation of action potentials?

<p>Voltage-gated channels for sodium and potassium (A)</p> Signup and view all the answers

What triggers ligand-gated channels to open in neurons?

<p>Binding of a chemical ligand (B)</p> Signup and view all the answers

Which of the following channels opens in response to mechanical stimuli?

<p>Mechanically gated channels (B)</p> Signup and view all the answers

What primarily determines the resting membrane potential in a non-conducting neuron?

<p>Selective permeability and ion distribution (C)</p> Signup and view all the answers

Which of the following statements about graded potentials is true?

<p>Graded potentials result from the opening of mechanically or ligand-gated ion channels. (C)</p> Signup and view all the answers

What is a characteristic of voltage-gated channels?

<p>They open when the membrane potential changes. (D)</p> Signup and view all the answers

Which of the following best explains why the inside of a non-conducting neuron is negative?

<p>Anions within the cell are unable to leave. (D)</p> Signup and view all the answers

How do Na+/K+ pumps contribute to the resting membrane potential?

<p>They create a higher concentration of Na+ outside the cell. (B)</p> Signup and view all the answers

Which statement regarding the distribution of ions across the plasma membrane is correct?

<p>The distribution of ions is uneven across the membrane. (D)</p> Signup and view all the answers

What is a necessary condition for repair in the peripheral nervous system (PNS)?

<p>Intact cell body (D)</p> Signup and view all the answers

Which of the following is NOT a step involved in the repair process of the PNS?

<p>Neurogenesis (C)</p> Signup and view all the answers

What is a primary characteristic of multiple sclerosis?

<p>Destruction of myelin sheath (C)</p> Signup and view all the answers

Which symptom is most commonly associated with depression?

<p>Lack of interest in activities (C)</p> Signup and view all the answers

What class of medication is commonly used to treat depression?

<p>Selective serotonin reuptake inhibitors (SSRIs) (D)</p> Signup and view all the answers

What initiates the episodes of epilepsy?

<p>Abnormal synchronous electrical discharges (A)</p> Signup and view all the answers

What causes excitotoxicity in the central nervous system?

<p>High levels of glutamate (C)</p> Signup and view all the answers

What is a symptom of seasonal affective disorder (SAD)?

<p>Mood changes related to seasons (B)</p> Signup and view all the answers

What is the typical amplitude of action potentials?

<p>Typically about 100 mV (D)</p> Signup and view all the answers

How does the refractory period differ between graded potentials and nerve impulses?

<p>Graded potentials have no refractory period (A)</p> Signup and view all the answers

Which factor does NOT affect the propagation speed of action potentials?

<p>Distance from the heart (B)</p> Signup and view all the answers

Which statement best describes graded potentials?

<p>They can be both hyperpolarizing and depolarizing (A)</p> Signup and view all the answers

What is a key characteristic of action potentials during propagation?

<p>They maintain their strength while traveling (D)</p> Signup and view all the answers

Which characteristic distinguishes nerve impulses from graded potentials?

<p>They only consist of depolarizing phases (A)</p> Signup and view all the answers

How does the diameter of an axon influence the propagation of action potentials?

<p>Larger diameter axons propagate faster (B)</p> Signup and view all the answers

What happens to action potentials during the trigger zone?

<p>They begin to propagate along the axon (C)</p> Signup and view all the answers

What is the primary result of summation in the context of neurotransmitter release?

<p>It increases the likelihood of creating a nerve impulse. (D)</p> Signup and view all the answers

What distinguishes spatial summation from temporal summation?

<p>Spatial summation involves multiple presynaptic neurons, whereas temporal summation involves one neuron firing multiple times. (D)</p> Signup and view all the answers

Which neurotransmitter is classified as a small molecule neurotransmitter?

<p>Amino acids (C)</p> Signup and view all the answers

What is the primary role of endorphins in the nervous system?

<p>Inhibit pain impulses. (D)</p> Signup and view all the answers

Which of the following neuropeptides is primarily associated with pain perception?

<p>Substance P (C)</p> Signup and view all the answers

Which neurotransmitter is likely to play a role in memory and learning, according to its classifications?

<p>Enkephalins (C)</p> Signup and view all the answers

What could be a potential function of dynorphins in the nervous system?

<p>They may control pain and register emotions. (B)</p> Signup and view all the answers

Which of the following is NOT considered a small molecule neurotransmitter?

<p>Substance P (C)</p> Signup and view all the answers

What is the primary function of gap junctions in electrical synapses?

<p>To synchronize the activity of a group of cells (D)</p> Signup and view all the answers

What characterizes a chemical synapse as opposed to an electrical synapse?

<p>It involves the release of neurotransmitters (A)</p> Signup and view all the answers

Which type of postsynaptic potential is associated with depolarization?

<p>Excitatory postsynaptic potential (D)</p> Signup and view all the answers

What is the role of ionotropic receptors at chemical synapses?

<p>To bind neurotransmitters and open ion channels (C)</p> Signup and view all the answers

How can neurotransmitters be removed from the synaptic cleft?

<p>By diffusion, enzymatic degradation, or uptake into cells (B)</p> Signup and view all the answers

What is a characteristic of metabotropic receptors?

<p>They are coupled to a separate ion channel via G proteins (C)</p> Signup and view all the answers

What typically happens to a postsynaptic neuron that receives multiple excitatory inputs simultaneously?

<p>It can become depolarized (D)</p> Signup and view all the answers

Which of the following statements about neurotransmitter action at chemical synapses is correct?

<p>Neurotransmitters cause either excitatory or inhibitory graded potentials (B)</p> Signup and view all the answers

Flashcards

Ligand-gated Channels

Ion channels that open when a specific chemical messenger binds to them. This binding can be triggered by neurotransmitters, hormones, or other signaling molecules.

Mechanically-gated Channels

Ion channels that open in response to a physical force, such as touch, pressure, vibration, or tissue stretching. They are critical for sensory perception.

Voltage-gated Channels

Ion channels that open when the membrane potential changes around them. This change in voltage is a vital signal in nerve impulse transmission.

Resting Membrane Potential

The difference in electrical charge across the plasma membrane of a neuron when it is not actively signaling. Usually, the inside of the neuron is negatively charged, and the outside is positively charged.

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Graded Potentials

A temporary change in the resting membrane potential, caused by the opening or closing of ion channels. These changes are small and localized.

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Unequal Ion Distribution

The uneven distribution of ions across the neuron’s membrane. Potassium ions (K+) are more concentrated inside the neuron, while Sodium ions (Na+) are more concentrated outside.

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Sodium-Potassium Pump

A protein pump that actively moves sodium ions (Na+) out of the neuron and potassium ions (K+) into the neuron. It requires energy to maintain the resting membrane potential.

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Membrane Potential

The electrical potential difference across the neuronal membrane at rest. It is measured in millivolts (mV) and is typically around -70 mV.

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Graded Potential: Stimulus Strength

The strength of a stimulus directly influences the amplitude of a graded potential. A stronger stimulus leads to a larger graded potential.

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Graded Potential: Summation

Multiple graded potentials can combine, or summate, to create larger potentials. This occurs when stimuli arrive close together in time or space.

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Action Potential

An action potential is a rapid sequence of events that quickly alters the membrane potential, reversing it temporarily and then restoring it to its resting state.

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Action Potential: Depolarization

Depolarization is the initial phase of an action potential where the membrane potential becomes less negative, moving towards a more positive value.

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Action Potential: Repolarization

Repolarization follows depolarization and brings the membrane potential back to its resting, negative value.

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Action Potential: Threshold

An action potential can only occur if the membrane potential reaches a certain threshold level. This threshold is the minimum stimulation required to trigger an action potential.

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Voltage-Gated Channels in Action Potentials

Action potentials rely on voltage-gated sodium (Na+) and potassium (K+) channels. These channels open and close in response to changes in membrane potential.

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Comparison of Graded and Action Potentials

Graded potentials degrade over distance and are local in nature, while action potentials are propagated and can travel long distances without losing strength.

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What is a synapse?

A synapse is a junction between two neurons or between a neuron and an effector cell, allowing communication between these cells.

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What is an electrical synapse?

Electrical synapses use gap junctions to allow the direct transfer of information between cells, synchronizing their activity.

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Propagation of Action Potentials

The movement of an action potential along the axon of a neuron. It allows signals to travel from one part of the neuron to another.

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What is a chemical synapse?

Chemical synapses involve a one-way transfer of information from a presynaptic neuron to a postsynaptic neuron using neurotransmitters.

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What is an excitatory postsynaptic potential (EPSP)?

An excitatory postsynaptic potential (EPSP) causes a depolarization in the postsynaptic neuron, making it more likely to fire an action potential.

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Saltatory Conduction

A type of action potential propagation in which the signal jumps from one node of Ranvier (unmyelinated gap) to the next, making the signal travel much faster.

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Continuous Conduction

A type of action potential propagation in which the signal travels continuously along the entire axon membrane.

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What is an inhibitory postsynaptic potential (IPSP)?

An inhibitory postsynaptic potential (IPSP) causes a hyperpolarization in the postsynaptic neuron, making it less likely to fire an action potential.

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What is an ionotropic receptor?

Ionotropic receptors have a neurotransmitter binding site and an ion channel, allowing for rapid responses.

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Axon Diameter and Propagation Speed

The diameter of an axon affects the speed of action potential propagation. Larger axons conduct signals faster because they have less resistance.

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Myelination and Propagation Speed

The presence of myelin around the axon increases the speed of action potential propagation. Myelin acts as an insulator, preventing signal leakage.

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What is a metabotropic receptor?

Metabotropic receptors have a neurotransmitter binding site and are coupled to a separate ion channel through a G-protein, resulting in slower, longer-lasting responses.

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Temperature and Propagation Speed

Temperature affects the speed of action potential propagation. Higher temperatures increase the speed because ion movements are faster at higher temperatures.

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How are neurotransmitters removed from the synapse?

Neurotransmitter removal from the synaptic cleft can occur through diffusion, enzymatic degradation, or uptake into cells.

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Spatial Summation

The combined effect of multiple presynaptic neurons releasing neurotransmitters simultaneously, resulting in a stronger signal.

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Temporal Summation

The combined effect of multiple signals from the same presynaptic neuron arriving in rapid succession, increasing the signal strength.

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Summation of Postsynaptic Potentials

The summation of postsynaptic potentials (EPSPs and IPSPs) that can lead to either depolarization (excitation) or hyperpolarization (inhibition) of the postsynaptic neuron.

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Small Molecule Neurotransmitters

Small molecules that act as chemical messengers in the nervous system, transmitting signals across synapses.

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Acetylcholine

A type of neurotransmitter that is involved in muscle contraction, memory, and learning.

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Amino Acid Neurotransmitters

A type of neurotransmitter that includes glutamate, GABA, and glycine, which are involved in various brain functions, such as learning, memory, and mood regulation.

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Biogenic Amine Neurotransmitters

Neurotransmitters derived from amino acids, such as dopamine, norepinephrine, and serotonin, which are involved in various functions, including mood, sleep, and motivation.

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Neuropeptides

Larger molecules that act as chemical messengers in the nervous system, often involved in slower, more long-lasting signaling.

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Chromatolysis

A process where the neuron's cell body swells and its nucleus shifts to the periphery, occurring after an axon is damaged.

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Wallerian Degeneration

The breakdown and degeneration of the distal portion of a damaged axon, beginning at the injury site and proceeding to the axon terminal.

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Regeneration Tube

A tube formed by Schwann cells, guiding the regrowing axon to its original target after injury.

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Multiple Sclerosis

A chronic, progressive autoimmune disease that attacks the myelin sheath of neurons in the central nervous system.

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Bipolar Depression

Characterized by abnormal moods and emotions that fluctuate between periods of intense energy (mania) and periods of profound sadness (depression).

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Epilepsy

A disorder marked by abnormal synchronous electrical discharges in the brain, causing recurrent seizures of varying severity and duration.

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Excitotoxicity

A process where neurons are damaged or destroyed as a result of excessive stimulation by neurotransmitters, particularly glutamate.

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Seasonal Affective Disorder (SAD)

A type of depression characterized by sadness, lack of interest, and low energy, often linked to changes in seasons, especially in the fall and winter, often treated with light therapy.

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Study Notes

Nervous Tissue Overview

  • The nervous system maintains homeostasis, controlling conditions within healthy limits.
  • Learning about the different branches and cell types is important.

Nervous System Overview

  • Neurons (nerve cells) are electrically excitable, transmitting information through action potentials.
  • Sensory neurons receive information from receptors (e.g., in skin).
  • Interneurons (in brain or spinal cord) process information.
  • Motor neurons transmit signals to effectors (e.g., muscles). The diagram on page four displays these components.

Nervous System Organization

  • The central nervous system (CNS) comprises the brain and spinal cord.
  • The peripheral nervous system (PNS) includes cranial nerves, spinal nerves, enteric plexuses, and sensory receptors. A diagram on page six illustrates this.

Functions of the Nervous System

  • Sensory function: Detects sensory stimuli.
  • Integrative function: Processes sensory information and decides on appropriate actions.
  • Motor function: Initiates actions in response to the integrative functions.

Nervous Tissue Histology

  • Neurons, the conducting cells, and nerve neuroglia, the supporting cells.

Neurons (Structure and Types)

  • Neurons are electrically excitable cells.
  • Action potential is the nerve impulse.
  • Neurons are characterized by their processes; multipolar, bipolar, and pseudounipolar.
  • Diagrams on pages twelve and thirteen depict the parts of a neuron including the dendrites, cell body, axon and axon terminal.

Neuron Types

  • Sensory (afferent) neurons carry information to the CNS.
  • Motor (efferent) neurons carry signals from the CNS.
  • Interneurons (association neurons) connect sensory and motor neurons, processing information.

Neuroglia (Supporting Cells)

  • Neuroglia are not electrically excitable.
  • They make up about half the volume of the nervous system.
  • They are capable of dividing.
  • There are six main types, four in the CNS (astrocytes, oligodendrocytes, microglia, ependymal cells) and two in the PNS (satellite cells and Schwann cells). Page twenty details these.

Myelination

  • Myelin sheath is produced by Schwann cells (PNS) and oligodendrocytes (CNS) surrounding axons. Myelination increases propagation of action potentials, increasing speed. Pages twenty-three and twenty-four show diagrams of myelinated axons.

White Matter vs. Gray Matter

  • White matter consists of myelinated axons.
  • Gray matter consists of neuron cell bodies, dendrites, and unmyelinated axons.

Electrical Signals in Neurons

  • Excitable cells communicate via action potentials or graded potentials.
  • Action potentials transmit signals over short and long distances
  • Graded potentials transmit signals over short distances.

Ion Channels in Neurons

  • Leak channels alter between open and closed states
  • Ligand-gated channels open/close according to chemical stimulus.
  • Mechanically gated channels open according to mechanical stimulation
  • Voltage gated channels open/close according to membrane potential.

Postsynaptic Potentials

  • Excitatory postsynaptic potentials (EPSPs) are depolarizations—increasing the chances of an action potential.
  • Inhibitory postsynaptic potentials (IPSPs) are hyperpolarizations—decreasing the chances of an action potential.

Neurotransmitters

  • Small molecule neurotransmitters (e.g., acetylcholine, amino acids, biogenic amines, ATP/purines, nitric oxide, carbon monoxide) and neuropeptides (e.g., substance P, enkephalins, endorphins, etc.) are released at chemical synapses to transmit signals.
  • Pages 75-80 detail the various neurotransmitters, and their functions.

Summation

  • Summation is the addition of postsynaptic potentials (EPSPs and IPSPs) to determine if an action potential will occur.
  • Spatial summation refers to the simultaneous input from multiple sources on a postsynaptic neuron.
  • Temporal summation refers to the addition of sequential inputs received from a single source.

Neural Circuits

  • Neural circuits are groups of neurons that perform specific information processing.
  • Examples include simple series, diverging, converging, reverberating, and parallel after-discharge circuits (pages 81-84).

Regeneration

  • The nervous system can exhibit plasticity, changing in response to experience.
  • Regeneration of neurons in the CNS is limited, compared to the PNS, primarily due to inhibitory neuroglial influences and lack of growth cues.

Neural Disorders

  • Multiple sclerosis is an autoimmune condition that destroys myelin sheaths.
  • Depression is a neurological condition with various types, including major depression, dysthymia, bipolar disorder, and seasonal affective disorder.
  • Other disorders like epilepsy and excitotoxicity—damage to neurons from excessive excitation are also mentioned. Pages 89-92 detail these disorders.

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Test your understanding of action potentials and graded potentials in neuroscience. This quiz covers key concepts such as membrane potentials, channel types, and the differences between graded and action potentials. Perfect for students looking to solidify their knowledge of neuronal function.

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