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Questions and Answers
Which amino acid neurotransmitter is primarily associated with excitatory synapses?
Which amino acid neurotransmitter is primarily associated with excitatory synapses?
What are the two types of glutamate receptors mentioned?
What are the two types of glutamate receptors mentioned?
Which neurotransmitter is involved in inhibitory synapses?
Which neurotransmitter is involved in inhibitory synapses?
What is the primary effect of calcium ions entering the postsynaptic cell during neurotransmission?
What is the primary effect of calcium ions entering the postsynaptic cell during neurotransmission?
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What role do AMPA receptors play in the process of long-term potentiation (LTP)?
What role do AMPA receptors play in the process of long-term potentiation (LTP)?
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Which process is thought to underlie cellular mechanisms of learning and memory?
Which process is thought to underlie cellular mechanisms of learning and memory?
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Which of the following accurately describes NMDA receptors?
Which of the following accurately describes NMDA receptors?
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Which neurotransmitter binds to AMPA receptors?
Which neurotransmitter binds to AMPA receptors?
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What function is primarily associated with the hypothalamus?
What function is primarily associated with the hypothalamus?
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What is the main difference between electrical and chemical synapses?
What is the main difference between electrical and chemical synapses?
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Which structure is included in the epithalamus?
Which structure is included in the epithalamus?
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Which process facilitates the release of neurotransmitters from vesicles?
Which process facilitates the release of neurotransmitters from vesicles?
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What is the primary role of the cerebellum?
What is the primary role of the cerebellum?
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How is the signal terminated in a chemical synapse?
How is the signal terminated in a chemical synapse?
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What occurs when glutamate-containing cells in the brain die?
What occurs when glutamate-containing cells in the brain die?
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What is the main function of GABA in the brain?
What is the main function of GABA in the brain?
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What does an excitatory postsynaptic potential (EPSP) do to the membrane potential?
What does an excitatory postsynaptic potential (EPSP) do to the membrane potential?
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What is a major function of the reticular formation?
What is a major function of the reticular formation?
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What is the role of autoreceptors in synaptic transmission?
What is the role of autoreceptors in synaptic transmission?
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Which system is primarily involved in emotional experiences and behaviors?
Which system is primarily involved in emotional experiences and behaviors?
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How do benzodiazepine drugs like Xanax® and Valium® exert their effects?
How do benzodiazepine drugs like Xanax® and Valium® exert their effects?
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Which of the following processes does NOT contribute to the removal of neurotransmitters?
Which of the following processes does NOT contribute to the removal of neurotransmitters?
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What overall effect does ethanol have on the brain?
What overall effect does ethanol have on the brain?
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Which function is NOT attributed to the cerebellum?
Which function is NOT attributed to the cerebellum?
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How does the brainstem contribute to the central nervous system?
How does the brainstem contribute to the central nervous system?
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Which statement about inhibitory postsynaptic potentials (IPSPs) is accurate?
Which statement about inhibitory postsynaptic potentials (IPSPs) is accurate?
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What happens to intracellular Ca2+ levels when nearby neurons are excessively stimulated by glutamate?
What happens to intracellular Ca2+ levels when nearby neurons are excessively stimulated by glutamate?
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What specifically does GABA bind to post-synaptically?
What specifically does GABA bind to post-synaptically?
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What happens to receptors in the postsynaptic cell after neurotransmitter binding?
What happens to receptors in the postsynaptic cell after neurotransmitter binding?
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Which of the following is a function of the reticular formation?
Which of the following is a function of the reticular formation?
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What is a consequence of very high doses of ethanol consumption?
What is a consequence of very high doses of ethanol consumption?
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Which compound is a modified form of glutamate?
Which compound is a modified form of glutamate?
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How many pairs of spinal nerves are designated as cervical nerves?
How many pairs of spinal nerves are designated as cervical nerves?
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Which spinal nerves are associated with the lower abdomen, hips, and legs?
Which spinal nerves are associated with the lower abdomen, hips, and legs?
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What neurotransmitters are primarily used at the post-ganglionic synapse in the sympathetic division?
What neurotransmitters are primarily used at the post-ganglionic synapse in the sympathetic division?
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Which division of the peripheral nervous system is responsible for carrying signals out to muscles or glands?
Which division of the peripheral nervous system is responsible for carrying signals out to muscles or glands?
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Where do the sympathetic fibers leave the central nervous system?
Where do the sympathetic fibers leave the central nervous system?
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What is the function of the enteric nervous system in relation to the gastrointestinal tract?
What is the function of the enteric nervous system in relation to the gastrointestinal tract?
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Which type of nerves contain both afferent and efferent fibers?
Which type of nerves contain both afferent and efferent fibers?
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The sympathetic division is often referred to as which division?
The sympathetic division is often referred to as which division?
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What characterizes the parasympathetic division in terms of its synaptic structure?
What characterizes the parasympathetic division in terms of its synaptic structure?
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Which neurotransmitter is primarily associated with both pre-ganglionic and post-ganglionic synapses in the parasympathetic nervous system?
Which neurotransmitter is primarily associated with both pre-ganglionic and post-ganglionic synapses in the parasympathetic nervous system?
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What type of receptors are responsible for acetylcholine's actions on smooth muscle and gland cells?
What type of receptors are responsible for acetylcholine's actions on smooth muscle and gland cells?
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What is the primary role of nonadrenergic and noncholinergic neurons in the autonomic nervous system?
What is the primary role of nonadrenergic and noncholinergic neurons in the autonomic nervous system?
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What is the result upon activation of the adrenal medulla by preganglionic sympathetic axons?
What is the result upon activation of the adrenal medulla by preganglionic sympathetic axons?
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Which statement correctly describes the relationship between the sympathetic and parasympathetic divisions?
Which statement correctly describes the relationship between the sympathetic and parasympathetic divisions?
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What predominates in the adrenal medulla upon activation, and how are these substances classified?
What predominates in the adrenal medulla upon activation, and how are these substances classified?
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In terms of function, what is the role of acetylcholine in autonomic ganglia?
In terms of function, what is the role of acetylcholine in autonomic ganglia?
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Study Notes
Nervous System Overview
- The nervous system has 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 consists of nerves that connect the brain or spinal cord to muscles, glands, and sense organs.
- The neuron is the basic cell type of both systems.
Structure of a Neuron
- Neurons have dendrites, a cell body, an initial segment, axon collateral, and axon terminals.
- Diagrams (Figures 6-13a and 6-13b) illustrate these components.
Neurons
- Neurons are the "nerve cells."
- They are amitotic, meaning they do not divide.
- They have a very high metabolic rate.
- Clusters of neuron cell bodies in the CNS are called nuclei.
- Glial cells are more numerous than neurons in the CNS.
Glial Cells
- Glial cells in the CNS include astrocytes, microglia, ependymal cells, and oligodendrocytes.
- Astrocytes support cells, control the extracellular environment of neurons.
- Microglia are the "immune system" of the CNS.
- Ependymal cells are ciliated and involved in CSF (cerebrospinal fluid) production and movement.
- Oligodendrocytes are responsible for myelin.
- Glial cells in the PNS are satellite cells and Schwann cells.
- Satellite cells surround neuron bodies in the PNS.
- Schwann cells surround and form myelin sheaths around larger nerve fibers.
Axonal Transport
- Axonal transport maintains axon structure and function, moving materials between the cell body and axon terminals via microtubules.
- Kinesin proteins move materials from the cell body to the axon terminal(anterograde).
- Dynein protein moves materials from the axon terminal to the cell body (retrograde).
Functional Classes of Neurons
- Afferent neurons transmit information into the CNS from peripheral receptors.
- Efferent neurons transmit information out of the CNS to effector cells (muscles, glands, other neurons).
- Interneurons function as integrators and signal changers entirely within the CNS, accounting for the majority of neurons.
Development of the Nervous System
- Nervous system development begins in the embryo with stem cells that develop into neurons or glial cells.
- Each neuronal daughter cell differentiates, migrates, sends out processes that will become axons and dendrites.
- The growth cone at the tip of the axon is involved in finding the correct route and target.
- Axonal growth is guided by cell adhesion molecules and neurotrophic factors.
- Synapses form when the growth cone reaches its target.
- Early development is a critical period; substances such as alcohol, drugs, radiation, and/or malnutrition can cause permanent damage.
Injury of the Nervous System
- If axons are severed outside the CNS, they can repair.
- The axon segment separated from the cell body degenerates.
- Regeneration proceeds at a rate of 1mm/day.
- Spinal cord injuries typically crush, not cut the tissue, leaving axons intact.
- Apoptosis of oligodendrocytes in spinal injuries prevents axon regeneration.
New Attempts to Repair Nervous System Damage
- Researchers are studying ways to support axonal regeneration after injury in the CNS.
- These efforts include creating tubes to support severed axonal regrowth and the prevention of apoptosis.
Synapses
- Synapses are junctions between two neurons and can be chemical or electrical.
- In an electrical synapse, electrical activity of the presynaptic neuron affects the postsynaptic neuron.
- Chemical synapses use neurotransmitters.
Anatomy of a Chemical Synapse
- Diagram (Figure 6-26A) illustrates the anatomy of a chemical synapse.
- This includes components like the terminal of the presynaptic axon, synaptic vesicles, synaptic cleft, and postsynaptic density.
Mechanisms of Neurotransmitter Release
- Action potentials reach the terminal, which causes voltage-gated Ca2+ channels to open.
- Calcium entry triggers neurotransmitter release from vesicles via exocytosis.
- Diagram (Figure 6-27) shows the process in detail.
Docking of Vesicles and Release of Neurotransmitters
- Neurotransmitters are produced and stored in vesicles at the axon terminal.
- Intracellular Ca2+ levels increase when the cell is stimulated.
- This stimulates vesicles to translocate and bind to the plasma membrane via SNARE proteins.
- Neurotransmitters are released via exocytosis.
Removal of a Neurotransmitter
- Neurotransmitters must be removed from the synaptic cleft to terminate the signal.
- This is achieved by diffusion, degradation by enzymes, or reuptake into the presynaptic cell.
Activation of the Postsynaptic Cell
- Excitatory synapses generate excitatory postsynaptic potentials (EPSPs), bringing the membrane closer to threshold potential.
- Inhibitory synapses generate inhibitory postsynaptic potentials (IPSPs), making the membrane more negative, making it harder to generate an action potential.
- Diagrams (Figures 6-28 and 6-29) illustrate these potentials.
- Synaptic integration is the process by which the postsynaptic cell sums EPSPs and IPSPs to determine its response (Figure 6-31).
Autoreceptors
- Autoreceptors are built-in brakes, inhibiting further release when neurotransmitter binds to receptors on the presynaptic cell.
Factors That Determine Synaptic Strength
- Factors determining synaptic strength can be presynaptic, postsynaptic, or general factors.
Modification of Synaptic Transmission by Drugs and Disease
- Drugs and diseases can modify synaptic transmission by interfering with or altering normal processes such as neurotransmitter synthesis, release, and receptor activation.
- For example, clostridium tetani (tetanus toxin) prevents vesicle fusion, inhibiting neurotransmitter release.
Types of Neurotransmitters
- Neurotransmitters are classified in many ways. Several chemical classes are summarized in Table 6-6: Acetylcholine (ACh), biogenic amines, amino acids, neuropeptides, gases, and purines.
Acetylcholine
- ACh is found in the PNS and the CNS.
- Several types of ACh receptors exist: muscarinic (G-protein coupled) and nicotinic (ion channels).
- ACh is produced by the enzyme choline acetyltransferase (CAT).
- It is degraded by acetylcholinesterase (AChE).
Biogenic Amines
- Catecholamines (tyrosine): dopamine, norepinephrine, epinephrine
- Serotonin (tryptophan)
- Histamine (histidine).
- Enzymes that degrade biogenic amines are monoamine oxidase (MAO) and catechol-o-methyltransferase.
- Diagrams (Figure 6-35) show the synthesis of catecholamines.
Parkinson's Disease
- Loss of dopamine-releasing neurons in the substantia nigra.
- Symptoms: persistent tremors, slow movements, and postural problems.
- Currently treated with L-dopa (with deprenyl, to slow its breakdown), although not a cure.
- Experimental treatments include deep brain stimulation, and transplantations.
Adrenergic Receptors
- Adrenergic receptors are G protein coupled.
- Used by norepinephrine and epinephrine.
Serotonin
- Often called 5-hydroxytryptamine (5-HT), acting on 5-HT3 receptors (related to vomiting).
- Located in the brainstem.
Histamine
- A CNS neurotransmitter, located primarily in the hypothalamus.
- Acts as a paracrine or peripheral neurotransmitter - associated with allergic reactions, nerve sensitization, and stomach acid production.
Amino Acid Neurotransmitters
- Glutamate (excitatory)
- Aspartate (excitatory)
- Glycine (inhibitory)
- GABA (gamma-aminobutyric acid) (inhibitory).
Glutamate
- Estimated to be the primary neurotransmitter at 50 percent of excitatory synapses in the CNS
- Two types of receptors: metabotropic (G-protein coupled) and ionotropic (AMPA and NMDA).
- Implicated in long-term potentiation (LTP), a cellular process underlying learning and memory (Diagram 6-36 illustrates the process).
- Also involved in excitotoxicity.
GABA (gamma-aminobutyric acid)
- The major inhibitory neurotransmitter in the brain.
- It's a modified amino acid
- Ionotropic receptor increases Cl- flux into the cell, causing hyperpolarization in the postsynaptic membrane.
Glycine
- Major inhibitory neurotransmitter in the spinal cord and brainstem.
- Binds to ionotropic receptors, allowing Cl- entry, leading to hyperpolarization.
- Important for regulating spinal cord activity and skeletal muscle contraction.
- Strychnine poisoning affects glycine receptors.
Neuropeptides
- Short chains of amino acids with peptide bonds.
- Examples include endogenous opioids (enkephalins, endorphins), substance P.
Gas Neurotransmitters
- Examples are nitric oxide (NO), carbon monoxide, and hydrogen sulfide.
- Released from neurons, and bind to proteins rather than receptors.
Purine Neurotransmitters
- Include ATP and adenosine.
- Primarily function as neuromodulators.
Neuroeffector Communication
- Many neurons synapse with muscle or gland cells.
- Neurotransmitters are released from efferent neurons and bind to receptors on the motor endplate to cause muscle contraction.
Peripheral Nervous System
- Transmits signals between the CNS and receptors/effectors throughout the body.
- Includes 12 pairs of cranial and 31 pairs of spinal nerves.
Cranial Nerves
- Detailed descriptions of individual nerves (see Table 6-8).
Spinal Cord
- Structure, organization, and function of the spinal cord; including white matter and gray matter, afferent and efferent neurons, and spinal nerve formation.
- Diagram (Figure 6-41) illustrate.
Somatic & Autonomic Divisions of the Peripheral Nervous System
- The somatic nervous system controls skeletal muscle.
- The autonomic nervous system controls smooth muscle, cardiac muscle, glands, and visceral organs (sympathetic and parasympathetic divisions).
Autonomic Nervous System
- The sympathetic and parasympathetic divisions, controlling diverse functions: "fight-or-flight" response vs. "rest-and-digest" response.
- Many neurotransmitters (e.g. Acetylcholine, norepinephrine, epinephrine).
- Post-ganglionic neurotransmitter release differs.
Protective Mechanisms of The CNS
- Bone (skull and vertebrae) protects the structures.
- Meninges (dura mater, arachnoid mater, pia mater) provide additional protection, support and surround the central nervous system.
- Cerebrospinal fluid (CSF) cushions and protects the delicate brain and spinal cord tissue.
Blood-Brain Barrier
- A protective mechanism regulating substance exchange between blood and brain.
- Specialized capillaries with tight junctions and astrocytic end-feet.
Cerebrovascular Accidents (CVA) or Strokes
- Ischemic strokes (blood clot blockage).
- Hemorrhagic strokes (ruptured blood vessels).
Head Injuries
- Coup and contrecoup injuries, concussions (alterations to brain function with temporary effects), contusions (brain bruising).
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Description
Explore the fascinating world of the nervous system, focusing on its two major divisions: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). This quiz covers the essential structures of neurons and glial cells, providing insights into their functions and characteristics.
