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Questions and Answers
Which part of the nervous system is primarily responsible for conveying impulses to the central nervous system?
Which part of the nervous system is primarily responsible for conveying impulses to the central nervous system?
What is the primary function of neuroglia in the nervous system?
What is the primary function of neuroglia in the nervous system?
Which of the following correctly pairs a type of neuroglia with its location?
Which of the following correctly pairs a type of neuroglia with its location?
What is a distinct feature of most neurons regarding their structure?
What is a distinct feature of most neurons regarding their structure?
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In which part of the nervous system would you find a bundle of nerve fibers called a 'nerve'?
In which part of the nervous system would you find a bundle of nerve fibers called a 'nerve'?
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What is the primary role of axon terminals in neurons?
What is the primary role of axon terminals in neurons?
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What type of transport involves ATP-dependent motor proteins moving substances along axons?
What type of transport involves ATP-dependent motor proteins moving substances along axons?
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In the classification of neurons, which type of neuron conducts impulses away from the CNS?
In the classification of neurons, which type of neuron conducts impulses away from the CNS?
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Which structure is responsible for the formation of the myelin sheath in the peripheral nervous system?
Which structure is responsible for the formation of the myelin sheath in the peripheral nervous system?
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What is the primary function of the sodium-potassium pump in resting neurons?
What is the primary function of the sodium-potassium pump in resting neurons?
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What is the resting membrane potential of a typical neuron?
What is the resting membrane potential of a typical neuron?
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What is the role of nodes of Ranvier in myelinated fibers?
What is the role of nodes of Ranvier in myelinated fibers?
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What occurs during depolarization in a neuron?
What occurs during depolarization in a neuron?
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What characterizes an action potential (AP)?
What characterizes an action potential (AP)?
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What happens to the membrane potential if the threshold is not reached?
What happens to the membrane potential if the threshold is not reached?
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What contributes to the repolarization phase of an action potential?
What contributes to the repolarization phase of an action potential?
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What is a significant characteristic of the absolute refractory period?
What is a significant characteristic of the absolute refractory period?
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In terms of stimulus strength, what is true regarding action potentials?
In terms of stimulus strength, what is true regarding action potentials?
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What happens at regions of the axon immediately after they generate an action potential?
What happens at regions of the axon immediately after they generate an action potential?
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How do action potentials propagate in nonmyelinated fibers?
How do action potentials propagate in nonmyelinated fibers?
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What happens during the relative refractory period?
What happens during the relative refractory period?
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What type of receptors are responsible for fast changes in membrane potential?
What type of receptors are responsible for fast changes in membrane potential?
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Which neurotransmitter classification does NOT belong to the category of biogenic amines?
Which neurotransmitter classification does NOT belong to the category of biogenic amines?
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What is the primary mechanism through which G protein–coupled receptors operate?
What is the primary mechanism through which G protein–coupled receptors operate?
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In the reflex arc, which component is NOT part of the minimum five elements?
In the reflex arc, which component is NOT part of the minimum five elements?
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What is a characteristic of serial processing in neural pathways?
What is a characteristic of serial processing in neural pathways?
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Which of the following structures is NOT part of the diencephalon?
Which of the following structures is NOT part of the diencephalon?
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What is the role of second messengers in neurotransmitter signaling?
What is the role of second messengers in neurotransmitter signaling?
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Which part of the adult brain is primarily involved in balance and coordination?
Which part of the adult brain is primarily involved in balance and coordination?
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Which of the following statements about reflexes is correct?
Which of the following statements about reflexes is correct?
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Study Notes
Nervous System Overview
- The nervous system is anatomically divided into central nervous system (brain and spinal cord) and peripheral nervous system (cranial and spinal nerves).
- The major functional divisions of the peripheral nervous system (PNS) are sensory (afferent) and motor (efferent).
- Sensory division conveys impulses to the central nervous system (CNS).
- Motor division carries impulses from the CNS.
Nervous System Components
- The motor division includes somatic (voluntary) and autonomic (involuntary) systems.
- Somatic system serves skeletal muscles.
- Autonomic system innervates smooth and cardiac muscle, and glands.
- The nervous system has two cell types: neuroglia and neurons.
Neuroglia
- Neuroglia (supporting cells) support and insulate neurons.
- CNS neuroglia includes astrocytes, microglial cells, ependymal cells, and oligodendrocytes.
- Astrocytes are the most abundant CNS neuroglia.
- Microglial cells are defensive cells in the CNS.
- Ependymal cells line cerebrospinal fluid-filled cavities.
- Oligodendrocytes have processes forming myelin sheaths around CNS nerve fibers.
- PNS neuroglia includes Schwann cells and satellite cells.
Neurons
- Neurons have a cell body and cytoplasmic processes called axons and dendrites.
- A bundle of nerve fibers is called a tract in the CNS and a nerve in the PNS.
- A collection of cell bodies is called a nucleus in the CNS and a ganglion in the PNS.
- The cell body is the biosynthetic (and receptive) center of the neuron.
- Most neurons have many dendrites, receiving signals from other neurons toward the nerve cell body.
- Neurons typically have one axon that transmits nerve impulses away from the nerve cell body.
- Axon terminals release neurotransmitters.
- Bidirectional transport along axons uses ATP-dependent motor proteins "walking" along microtubule tracks.
Myelinated Fibers
- Large nerve fibers (axons) are myelinated.
- Myelin sheath is formed in the PNS by Schwann cells and in the CNS by oligodendrocytes.
- The myelin sheath gaps are called nodes of Ranvier.
Neuron Classification
- Neurons are classified based on the number of processes issuing from the cell body into multipolar, bipolar, or unipolar types.
- Functionally, neurons are classified as sensory, motor, or interneurons.
- Sensory neurons conduct impulses toward the CNS.
- Motor neurons conduct impulses away from the CNS.
- Interneurons connect sensory and motor neurons.
Basic Principles of Electricity
- Voltage (potential) is the measure of potential energy of separated electrical charges.
- Current is the flow of electrical charge.
- Resistance hinders current flow.
Resting Membrane Potential
- A resting neuron has resting membrane potential at -70 mV (inside negative).
- This potential is due to differences in sodium and potassium ion concentrations, and differences in membrane permeability to these ions.
- The sodium-potassium pump maintains these ion concentration differences.
The Synapse
- A synapse is a functional junction between neurons.
- The information-transmitting neuron is the presynaptic neuron.
- The information-receiving neuron is the postsynaptic neuron.
- Electrical synapses allow ions to flow directly from one neuron to another; the cells are electrically coupled.
Chemical Synapses
- These are sites of neurotransmitter release and binding.
- When an impulse reaches the presynaptic axon terminals, voltage-gated Ca2+ channels open, and Ca2+ enters the cell, mediating neurotransmitter release.
- Neurotransmitters diffuse across the synaptic cleft and attach to postsynaptic membrane receptors, opening ion channels.
- Neurotransmitters are removed from the synapse via diffusion, enzymatic breakdown, or reuptake into the presynaptic terminal or astrocytes.
Postsynaptic Potentials and Synaptic Integration
- Excitatory postsynaptic potentials (EPSPs) are local graded potentials caused by simultaneous passage of Na+ and K+.
- Inhibitory postsynaptic potentials (IPSPs) lead to hyperpolarizations caused by opening K+ or Cl- channels.
- The membrane of the axon hillock acts as a neuronal integrator, summing EPSPs and IPSPs.
- Presynaptic inhibition is mediated by axoaxonal synapses, which reduce the amount of neurotransmitter released by the inhibited neuron.
Classification of Neurotransmitters by Function
- Neurotransmitters can be classified by their function (inhibitory or excitatory, or both) and action (direct or indirect).
- Direct-acting neurotransmitters bind to and open ion channels.
- Indirect-acting neurotransmitters act through second messengers.
Neurotransmitter Receptors
- These can be channel-linked (fast changes in membrane potential) or G protein-coupled (slow synaptic responses).
- Second messengers often activate kinases, which act on ion channels or activate other proteins.
Classification of Neurotransmitters by Chemical Structure
- Main classes include acetylcholine, biogenic amines, amino acids, peptides, purines, dissolved gases, and lipids.
Patterns of Neural Processing
- In serial processing, one neuron stimulates the next sequentially.
- A reflex is a rapid, involuntary motor response to a stimulus mediated by reflex arcs.
- The minimum number of elements in a reflex arc is five: receptor, sensory neuron, information processing center, motor neuron, effector.
The Brain Regions and Organization
- The adult brain is divided into cerebral hemispheres, diencephalon, brain stem, and cerebellum.
- The cerebral hemispheres and cerebellum have gray matter nuclei surrounded by white matter and an outer cortex of gray matter.
- The diencephalon and brain stem lack a cortex.
The Brain Ventricles
- The brain contains four ventricles filled with cerebrospinal fluid (CSF).
- Two are lateral ventricles within the cerebral hemispheres.
- The third ventricle is within the diencephalon.
- The fourth ventricle lies between the brain stem and cerebellum and connects with the central canal of the spinal cord.
Cerebral Hemispheres
- The two cerebral hemispheres are connected by the corpus callosum.
- Each hemisphere receives sensory impulses and dispatches motor impulses from the opposite side of the body.
Blood Brain Barrier
- The blood-brain barrier consists of the least permeable capillaries in the body.
- It excludes many potentially harmful substances.
- Some substances that pass through the blood-brain barrier include fats and fat-soluble molecules, respiratory gases, alcohol, nicotine, and anesthetics.
Spinal Cord
- Extends from the medulla oblongata to the region of T12.
- Below T12 is the cauda equina (collection of spinal nerves).
Spinal Cord Anatomy
- Spinal cord has white matter and central canal, along with dorsal and ventral horns of gray matter, dorsal root ganglion, and spinal nerve.
Peripheral Nervous System: Structure of a Nerve
- Endoneurium surrounds each nerve fiber.
- Groups of fibers are bound into fascicles by the perineurium.
- Fascicles are bound together by the epineurium.
Peripheral Nervous System: Branches of the Efferent System
- The efferent, or motor system, includes somatic (non-autonomic/voluntary control over skeletal muscles) and autonomic (involuntary control over visceral organs). - The autonomic further branches into sympathetic and parasympathetic systems.
Comparison of Efferent Nervous System Branches
- Acetylcholine (ACh) is the neurotransmitter at the preganglionic synapses of both the parasympathetic and sympathetic.
- The postganglionic neuron of the parasympathetic system releases ACh while the postganglionic neuron of the sympathetic system releases norepinephrine (NE).
Function of Autonomic Divisions
- Parasympathetic generally opposes sympathetic efforts.
- Sympathetic division has a widespread effect throughout the body; generally prepares for action and use of energy resources; increases heart rate, blood pressure and glucose levels.
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Description
Explore the intricate structure and function of the nervous system through this quiz. Learn about the central and peripheral nervous systems, their divisions, and the types of cells involved. Test your knowledge on neuroglia and neurons to understand their roles.
