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Questions and Answers
What percentage of neurons in the human brain are classified as multipolar neurons?
What percentage of neurons in the human brain are classified as multipolar neurons?
Which part of the neuron is primarily responsible for receiving signals from other neurons?
Which part of the neuron is primarily responsible for receiving signals from other neurons?
What structure insulates the axon and plays a crucial role in the conduction of electrical signals?
What structure insulates the axon and plays a crucial role in the conduction of electrical signals?
Which statement reflects a limitation of the neuron doctrine?
Which statement reflects a limitation of the neuron doctrine?
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What is the primary role of the cell body (soma) in a neuron?
What is the primary role of the cell body (soma) in a neuron?
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What is a defining characteristic of a bipolar neuron?
What is a defining characteristic of a bipolar neuron?
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Which type of neuron is primarily responsible for integrating neural activities within a single brain structure?
Which type of neuron is primarily responsible for integrating neural activities within a single brain structure?
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What is a primary component of a synapse?
What is a primary component of a synapse?
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What function do sensory neurons serve in the peripheral nervous system (PNS)?
What function do sensory neurons serve in the peripheral nervous system (PNS)?
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What occurs during the process of exocytosis at the presynaptic neuron?
What occurs during the process of exocytosis at the presynaptic neuron?
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Interneurons can be classified into local and relay categories. What distinguishes relay interneurons?
Interneurons can be classified into local and relay categories. What distinguishes relay interneurons?
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What is the role of neurotransmitters at the synapse?
What is the role of neurotransmitters at the synapse?
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What role do neurotransmitters play in communication at the synapse?
What role do neurotransmitters play in communication at the synapse?
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What is the primary function of the axon hillock in a neuron?
What is the primary function of the axon hillock in a neuron?
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What distinguishes anterograde axoplasmic transport from retrograde axoplasmic transport?
What distinguishes anterograde axoplasmic transport from retrograde axoplasmic transport?
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What structural components primarily constitute the neuron’s cell membrane?
What structural components primarily constitute the neuron’s cell membrane?
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How does the cytoskeleton contribute to the function of the neuron?
How does the cytoskeleton contribute to the function of the neuron?
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What is the role of kinesin in the neuron?
What is the role of kinesin in the neuron?
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What is the function of channel proteins embedded in the neuron's cell membrane?
What is the function of channel proteins embedded in the neuron's cell membrane?
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What internal feature of the neuron is specifically responsible for producing ribosomes?
What internal feature of the neuron is specifically responsible for producing ribosomes?
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How do dendritic spines contribute to neural plasticity?
How do dendritic spines contribute to neural plasticity?
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What is the primary function of Schwann cells in the peripheral nervous system (PNS)?
What is the primary function of Schwann cells in the peripheral nervous system (PNS)?
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Which statement correctly describes oligodendrocytes compared to Schwann cells?
Which statement correctly describes oligodendrocytes compared to Schwann cells?
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Why is effective axonal regeneration restricted to the peripheral nervous system?
Why is effective axonal regeneration restricted to the peripheral nervous system?
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What neurological condition is characterized by immune system attacks on myelin sheaths?
What neurological condition is characterized by immune system attacks on myelin sheaths?
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What occurs to a neuron's membrane potential during an excitatory postsynaptic potential (EPSP)?
What occurs to a neuron's membrane potential during an excitatory postsynaptic potential (EPSP)?
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Which of the following statements about action potentials is true?
Which of the following statements about action potentials is true?
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How does the composition of myelin in the central nervous system (CNS) differ from that in the peripheral nervous system (PNS)?
How does the composition of myelin in the central nervous system (CNS) differ from that in the peripheral nervous system (PNS)?
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What is the resting potential of a neuron typically around?
What is the resting potential of a neuron typically around?
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What are inhibitory postsynaptic depolarizations (IPSPs) characterized by?
What are inhibitory postsynaptic depolarizations (IPSPs) characterized by?
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Study Notes
Neurons
- Neurons are specialized cells for receiving, conducting, and transmitting electrochemical signals.
- There are approximately 80-90 billion neurons in the adult human brain.
- Glial cells support neurons and contribute to information processing.
Neuron Anatomy
- Dendrites: Receive information from other neurons at synapses.
- Cell body (soma): Contains the nucleus and integrates incoming signals.
- Axon: A long, thin tube that carries electrical signals away from the cell body.
- Myelin sheath: Insulating layer around the axon, increasing signal speed.
- Nodes of Ranvier: Gaps in the myelin sheath where the action potential is regenerated.
- Axon terminals (terminal buttons): Release neurotransmitters to communicate with other cells.
Neuron Classification
- Multipolar: Many dendrites, one axon (most common).
- Unipolar: One process extending from the cell body, branching into input and output zones.
- Bipolar: One dendrite and one axon.
- Multipolar interneuron: Short axon or no axon.
Synapses
- Synapse: The junction between two neurons.
- Presynaptic membrane: Axon terminal of the sending neuron.
- Postsynaptic membrane: Dendrite or cell body of the receiving neuron.
- Synaptic cleft: Gap between the presynaptic and postsynaptic membranes.
- Synaptic vesicles: Contain neurotransmitters.
- Neurotransmitters: Chemical messengers.
Synapse Function
- Neurotransmitters are released into the synaptic cleft.
- Neurotransmitters bind to receptors on the postsynaptic membrane.
- Binding of neurotransmitters causes changes in the postsynaptic membrane potential.
Neurons Classifications (by Function)
- Sensory neurons: Gather information from the environment.
- Motor neurons: Control muscle contractions.
- Interneurons: Connect circuits within the CNS.
Additional Notes
- Neural plasticity: Synaptic connections change constantly.
- Axoplasmic transport: Movement of substances along the axon.
- Anterograde: Cell body to axon terminals.
- Retrograde: Axon terminals to cell body.
- Glial cells: Astrocytes, microglia, oligodendrocytes (CNS) and Schwann cells (PNS)
Action Potentials
- Resting potential: Membrane potential of a neuron at rest (-70 mV).
- Polarization: Neuron is polarized at resting.
- Diffusion: Molecules move from high to low concentration.
- Electrostatic pressure: Opposing charges attract, like charges repel.
- Threshold of excitation: The minimum level of depolarization to trigger an action potential.
- Depolarization: Membrane potential becomes less negative (Na+ influx).
- Repolarization: Membrane potential returns to resting potential (K+ efflux).
- Refractory period: Time when a neuron cannot fire another action potential.
- All-or-none principle: Action potentials are always the same size.
- Rate law: Intensity of a stimulus is reflected by the rate of action potentials.
- Saltatory conduction: Action potential jumps between nodes of Ranvier.
Neurotransmitter Release
- Docking: Vesicles are positioned near the membrane.
- Release zone: Portion of the presynaptic membrane where neurotransmitters are released.
- Calcium channels: Opening allows calcium to enter and trigger neurotransmitter release.
- Fusion pore: Formed when vesicles fuse with the presynaptic membrane.
- Neurotransmitter types: Small vs. large molecule neurotransmitters. Small molecule neurotransmitters contain neurotransmitter molecules and are recycled into the nerve terminal via a kiss and run process, other neurotransmitters can be released through merge and recycle process.
- Kiss and run: Vesicles release then reabsorb neurotransmitters.
- Merge and recycle: Vesicles merge, then reform
- Bulk endocytosis: Recycling of vesicle membrane.
Synaptic Integration
- Spatial summation: Multiple synapses at different locations add their effects.
- Temporal summation: Multiple synapses that occur shortly in succession add their effects.
- Inhibitory postsynaptic potentials (IPSPs): Hyperpolarizes the membrane.
- Excitatory postsynaptic potentials (EPSPs): Depolarizes the membrane.
Synaptic Termination
- Reuptake: Neurotransmitters are taken back into the presynaptic neuron.
- Enzymatic deactivation: Neurotransmitters are broken down by enzymes.
Synapse Types
- Axodendritic: Axon to dendrite.
- Axosomatic: Axon to cell body.
- Axoaxonic: Axon to axon.
- Dendrodendritic: Dendrite to dendrite.
Additional Glials
- Astrocytes: Largest glial cell, involved in nutrient exchange, synapse formation and pruning, blood-brain-barrier control.
- Microglia: Smaller glial cells, involved in immune response and clearing debris.
- Oligodendrocytes: Produce myelin in the CNS.
- Schwann cells: Produce myelin in the PNS.
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Description
Explore the fascinating world of neurons and their structures through this quiz. Learn about the different parts of a neuron, their functions, and the classification of neurons based on their anatomy. This quiz is essential for understanding the fundamental building blocks of the nervous system.
