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Questions and Answers
What is the primary role of myelination in neurons?
What is the primary role of myelination in neurons?
What characterizes an action potential in neurons?
What characterizes an action potential in neurons?
Which type of neural tissue is characterized by having a high density of neurons and is involved in processing information?
Which type of neural tissue is characterized by having a high density of neurons and is involved in processing information?
What distinguishes white matter from gray matter in the nervous system?
What distinguishes white matter from gray matter in the nervous system?
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How do ion concentration gradients influence action potentials?
How do ion concentration gradients influence action potentials?
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Which statement about neuroglia is correct?
Which statement about neuroglia is correct?
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What is the role of dendrites in a neuron?
What is the role of dendrites in a neuron?
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What is an effector in the context of motor neurons?
What is an effector in the context of motor neurons?
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What is the primary reason the inside of the cell is negatively charged compared to the outside?
What is the primary reason the inside of the cell is negatively charged compared to the outside?
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What initiates the depolarization phase during an action potential?
What initiates the depolarization phase during an action potential?
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What is the threshold level that must be reached to trigger an action potential?
What is the threshold level that must be reached to trigger an action potential?
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During the repolarization phase of an action potential, what is occurring?
During the repolarization phase of an action potential, what is occurring?
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What characterizes an action potential in terms of its response?
What characterizes an action potential in terms of its response?
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What prevents another action potential from occurring immediately after one?
What prevents another action potential from occurring immediately after one?
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In terms of ion concentration differences, which ions are more concentrated outside the neuron compared to inside?
In terms of ion concentration differences, which ions are more concentrated outside the neuron compared to inside?
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Which cellular structure is responsible for maintaining the ion concentration gradients necessary for action potentials?
Which cellular structure is responsible for maintaining the ion concentration gradients necessary for action potentials?
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Which neuroglial cell type is responsible for myelinating axons in the CNS?
Which neuroglial cell type is responsible for myelinating axons in the CNS?
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What is the primary function of astrocytes in the CNS?
What is the primary function of astrocytes in the CNS?
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Which statement correctly describes the myelin sheath?
Which statement correctly describes the myelin sheath?
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How do Schwann cells support PNS neuronal regeneration?
How do Schwann cells support PNS neuronal regeneration?
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What comprises white matter in the central nervous system?
What comprises white matter in the central nervous system?
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Which part of the nervous system contains ganglia?
Which part of the nervous system contains ganglia?
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What do Nodes of Ranvier facilitate?
What do Nodes of Ranvier facilitate?
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What critical role do ependymal cells play in the CNS?
What critical role do ependymal cells play in the CNS?
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Study Notes
The Nervous System
- The nervous system is divided into two major divisions: the central nervous system (CNS) and the peripheral nervous system (PNS).
- The CNS consists of the brain and spinal cord.
- The PNS contains nerves that connect the brain and spinal cord to muscles, glands, and sense organs.
Nervous System Overview
- The brain (100 billion neurons) is involved in information processing.
- The spinal cord (100 million neurons) transmits information to and from the brain and performs some information processing (reflexes).
- Cranial nerves provide sensory and motor functions for the face and vital organs (e.g., heart, respiratory muscles).
- Spinal nerves provide sensory and motor functions to specific body regions.
- Enteric plexuses are networks of neurons within digestive organs that regulate digestion.
- Sensory receptors monitor internal and/or external environmental changes.
Peripheral Nervous System (PNS)
-
Somatic nervous system: Voluntary control of movements
- Afferent neurons bring signals from receptors to the CNS.
- Efferent neurons carry signals from the CNS to skeletal muscles.
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Autonomic nervous system: Involuntary control of smooth and cardiac muscle, and glands
- Contains sensory neurons from visceral organs and motor neurons conveying impulses from the CNS to smooth muscle tissue, cardiac muscle tissue, and glands.
- Works with the endocrine system to maintain homeostasis.
- Enteric nervous system: Regulates the gastrointestinal system(part of the autonomic nervous system.)
Classification of Neurons
- Structural: Multipolar, bipolar, unipolar
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Functional:
- Sensory (afferent) neurons: Bring sensory information to the brain
- Motor (efferent) neurons: Carry signals from the brain to effectors (muscles and glands)
- Interneurons (association neurons): Connect sensory and motor neurons within the CNS; integrate and process information.
Histology of Nervous Tissue
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Neurons:
- Possess electrical excitability.
- Three parts: cell body, dendrites, axon.
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Neuroglia:
- Smaller than neurons, more numerous (5–25 times);
- Support, nourish, and protect neurons.
- Types: astrocytes, oligodendrocytes, microglia, ependymal cells (in CNS).
- Types: Schwann cells, satellite cells (in PNS).
Neuroglia
- Two types of neuroglia produce myelin sheaths:
- Oligodendrocytes myelinate axons in the CNS.
- Schwann cells myelinate axons in the PNS.
Myelination
- The myelin sheath is a fatty substance that insulates axons, increasing the speed of nerve impulses.
- Nodes of Ranvier are gaps in the myelin sheath that allow for faster signal propagation.
Collections of Nervous Tissue
- Ganglia: Clusters of neuronal cell bodies in the PNS, associated with cranial and spinal nerves.
- Nuclei: Clusters of neuronal cell bodies in the CNS.
- Nerves: Bundles of axons in the PNS(cranial or spinal).
- Tracts: Bundles of axons in the CNS, connecting neurons in the brain and spinal cord.
Gray and White Matter
- White matter: Primarily myelinated neurons; white color from myelin.
- Gray matter: Neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia; grayish color from cellular organelles.
Action Potentials
- Resting membrane potential (~-70mV): The inside of the cell is more negative than the outside.
- Threshold potential (~-55mV): The stimulus needed to initiate an action potential.
- Depolarization (+30mV): Sodium (Na+) ions rush into the cell, making the inside more positive.
- Repolarization: Potassium (K+) ions rush out of the cell, returning the inside to a negative charge.
- Hyperpolarization: The membrane potential temporarily becomes more negative than the resting potential. This prevents further immediate action potentials.
Synaptic Transmission
- A synapse is a junction between two neurons or a neuron and an effector cell (e.g., a muscle or gland).
- The presynaptic neuron sends the signal, and the postsynaptic neuron receives it.
- Neurotransmitters are released at the synapse to transmit the signal across the synaptic cleft.
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Description
Explore the structure and function of the nervous system, including its two main divisions: the central nervous system (CNS) and peripheral nervous system (PNS). Understand the roles of the brain, spinal cord, cranial nerves, and sensory receptors in processing information and controlling bodily functions.
