Basic Structure And Function Of The Nervous System! Trivia Quiz

Action potentials do not travel decrementally down the membrane. Instead, they propagate in an all-or-nothing manner, meaning that once initiated, they travel along the membrane at a constant amplitude and speed.

The strength of a stimulus is encoded by neurons through the frequency of action potentials. When a stimulus is stronger, it causes the neurons to fire action potentials at a higher frequency. This increased frequency of action potentials allows for more information about the strength of the stimulus to be transmitted to the brain. Therefore, the frequency of action potentials is a key factor in encoding the strength of a stimulus.

The correct answer is C. It is faster in myelinated axons than in nonmyelinated axons. This is because myelin acts as an insulating sheath around the axon, allowing for faster propagation of the action potential. In nonmyelinated axons, the action potential must travel continuously along the entire length of the axon, which is slower compared to myelinated axons where the action potential "jumps" from one node of Ranvier to the next, known as saltatory conduction. This allows for faster and more efficient transmission of the action potential.

During the after-hyperpolarization phase, the permeability of the membrane to potassium ions is greater than its permeability at rest. This is because after an action potential, the membrane potential becomes more negative than the resting potential, known as hyperpolarization. During this phase, potassium channels remain open, allowing potassium ions to flow out of the cell, which increases the permeability of the membrane to potassium ions. This increased permeability to potassium ions contributes to the restoration of the resting membrane potential.

Neuronal axons typically have abundant voltage-gated channels for Na+ that open in response to depolarization. This is because during an action potential, the axon membrane depolarizes, meaning the inside of the axon becomes more positive. The opening of these Na+ channels allows Na+ ions to flow into the axon, further depolarizing the membrane and propagating the action potential along the axon. Therefore, the presence of these voltage-gated Na+ channels is crucial for the transmission of electrical signals in neurons.

The rate of propagation of an action potential down an axon is independent of stimulus strength. This means that once an action potential is initiated, it will travel down the axon at a constant speed regardless of the strength of the stimulus that initiated it. The strength of the stimulus only determines whether or not an action potential will be generated in the first place, but it does not affect the speed at which it travels.

A depolarizing action potential is not an example of a graded potential because it is an all-or-nothing event that does not vary in magnitude. Graded potentials, on the other hand, are variable in magnitude and can be either depolarizing or hyperpolarizing. Examples of graded potentials include receptor potentials in sensory receptor cells, depolarizing excitatory postsynaptic potentials (EPSPs), hyperpolarizing inhibitory postsynaptic potentials (IPSPs), and depolarizing pacemaker potentials.

An action potential in a neuronal membrane is different from a graded potential because it is propagated without decrement, meaning it maintains its strength as it travels along the membrane. In contrast, a graded potential decrements with distance, meaning it becomes weaker the further it travels. This difference in propagation allows action potentials to carry information over long distances in the nervous system, while graded potentials are limited to short distances.

At an excitatory chemical synapse between two neurons, there is increased permeability of the postsynaptic cell to both Na+ and K+. This allows both Na+ and K+ ions to flow into the postsynaptic cell, causing depolarization and making it more likely for an action potential to be generated. This increased permeability is due to the opening of specific ion channels in the postsynaptic membrane in response to the release of neurotransmitters from the presynaptic neuron. This influx of positive ions contributes to the excitatory nature of the synapse.

The binding of nicotine with nicotinic acetylcholine receptors results in various effects, such as signal transmission at neuromuscular junctions, generation of excitatory signals within autonomic ganglia, the release of norepinephrine, dopamine, and epinephrine, and facilitation of the release of multiple neurotransmitters within the brain. However, it does not result in a mild form of skeletal muscle paralysis that creates a more relaxed state.

Temporal summation refers to the phenomenon where a synapse is stimulated a second time before the effect of a first stimulus at the synapse has terminated. This means that the second stimulus is added to the residual effect of the first stimulus, resulting in a cumulative effect on the postsynaptic cell. This process can lead to the generation of an action potential if the cumulative effect reaches the threshold for firing. It is important to note that temporal summation can occur with both excitatory and inhibitory inputs.

Spatial summation refers to the process by which the postsynaptic neuron integrates signals from multiple presynaptic inputs that are spatially separated. In this scenario, when neurons X and Y are stimulated simultaneously and repeatedly, their signals are combined at the postsynaptic neuron, reaching threshold and resulting in an action potential. This demonstrates spatial summation because the signals from X and Y, which are spatially separated inputs, are combined to generate an action potential. On the other hand, when X and Z are stimulated simultaneously, there is no change in the membrane potential of the postsynaptic neuron, indicating that the signals from these inputs do not summate and do not reach threshold. Therefore, the correct answer is C. spatial summation.

Acetylcholine is a neurotransmitter that binds to both nicotinic and muscarinic receptors. Nicotinic receptors are found in the autonomic ganglia, neuromuscular junctions, and the central nervous system, while muscarinic receptors are found in the parasympathetic nervous system and some areas of the central nervous system. Therefore, statement A is correct.

During the falling (repolarizing) phase of the action potential, the permeability to K+ increases greatly while that to Na+ decreases. This allows K+ ions to flow out of the cell, repolarizing the membrane potential and restoring it to its resting state. At the same time, the decreased permeability to Na+ prevents further influx of Na+ ions, helping to bring the membrane potential back to its resting level. This change in permeability is crucial for the repolarization of the action potential.

The reticular formation is a network of neurons located in the brainstem that plays a crucial role in regulating sleep and wakefulness. It receives information from various regions of the central nervous system (CNS) and integrates this information to control arousal, attention, and consciousness. This region is responsible for maintaining wakefulness during the day and promoting sleep at night. Additionally, the reticular formation also contributes to other functions such as motor coordination and balance, but its primary role is in regulating sleep and wakefulness.

A myelinated axon is not shielded from direct contact with the extracellular fluid all along its length. In fact, the myelin sheath, which is made up of fatty substances, acts as an insulating layer around the axon. This insulation helps to increase the speed at which electrical signals can travel along the axon. However, there are small gaps in the myelin sheath called nodes of Ranvier, where the axon is exposed to the extracellular fluid. These nodes play a crucial role in the conduction of nerve impulses. Therefore, the statement that a myelinated axon is shielded from direct contact with the extracellular fluid all along its length is false.

The statement is true because the parasympathetic division of the autonomic nervous system consists of preganglionic fibers that originate from the brainstem and sacral portions of the spinal cord. These fibers then leave the central nervous system (CNS) to synapse with postganglionic fibers in ganglia located near or within the target organs. This allows the parasympathetic division to regulate various bodily functions, such as digestion, relaxation, and restoration, in a rest-and-digest response.

The statement is false because SNARE receptor protein complexes in presynaptic neurons actually function as facilitators of calcium transport. These complexes help in the fusion of neurotransmitter vesicles with the presynaptic membrane, allowing for exocytosis and release of neurotransmitters.

An inhibitory postsynaptic potential (IPSP) is a small hyperpolarization in a postsynaptic cell, not a depolarization as mentioned in option C. It is caused by the opening of ligand-gated ion channels that increase the permeability to K+ ions, leading to an efflux of positive ions and making the cell more negative inside. This hyperpolarization makes it less likely for an action potential to be generated in the postsynaptic cell. Thus, option B correctly describes an IPSP.

The postsynaptic neuron depolarizes when neuron X is stimulated, indicating that neuron X is excitatory. When both X and Y are stimulated, the postsynaptic neuron depolarizes even more, suggesting that neuron Y is also excitatory. However, when both X and Z are stimulated, there is no change in the membrane potential, indicating that neuron Z is inhibitory. Therefore, it is most likely true that presynaptic neuron Y is excitatory and presynaptic neuron Z is inhibitory.

An increase in the extracellular concentration of K+ above normal would result in depolarization of resting nerve cells. This is because K+ plays a crucial role in maintaining the resting membrane potential of nerve cells. An increase in extracellular K+ concentration would disrupt the balance between intracellular and extracellular K+ concentrations, leading to a higher influx of K+ ions into the cell. This influx of positive charge would cause the membrane potential to become less negative, resulting in depolarization of the cell.

The correct answer is A. The cerebellum is a structure located at the back of the brain that is responsible for coordinating body movement. It receives information from the sensory systems, the spinal cord, and other parts of the brain, and uses this information to regulate and fine-tune movement. Damage to the cerebellum can result in problems with coordination, balance, and motor control.

The sympathetic division of the ANS is responsible for the fight-or-flight response, which prepares the body for action. Preganglionic neurons in the sympathetic division are short and synapse in ganglia located near the spinal cord, as stated in option B. Additionally, preganglionic neurons release acetylcholine at synapses with postganglionic neurons, as mentioned in option C. Postganglionic neurons release norepinephrine at their neuroeffector junctions, as stated in option D. Therefore, the characteristic that is NOT true for the sympathetic division is option A, which states that preganglionic neurons tend to be long, with the ganglion located in or near the effector target tissue(s).

During a hyperpolarizing graded potential, the membrane becomes more negative than its resting potential. This occurs when positively charged ions, such as potassium (K+), flow out of the cell or sodium (Na+) channels close. As a result, the positive charge moves away from the site of initial hyperpolarization on the outside of the membrane and towards this site on the inside, leading to a more negative potential. Therefore, the statement is true.

An EPSP (excitatory postsynaptic potential) is a depolarization of the postsynaptic membrane potential that brings the neuron closer to its threshold for firing an action potential. This depolarization is caused by the opening of ligand-gated channels, which are permeable to both Na+ and K+ ions. When these channels open, Na+ ions enter the cell and K+ ions exit the cell, leading to a net positive charge inside the cell and depolarization. Therefore, option A is the correct answer.

The cerebrospinal fluid does not have the same composition as blood plasma. It is produced by the choroid plexus in the ventricles of the brain and has a different composition compared to blood plasma. It acts as a cushion for the brain and spinal cord, circulating within and between brain ventricles and surrounding the spinal cord. It is also in diffusion equilibrium with the extracellular fluid of the central nervous system.

Calcium ions play a crucial role in the process of neurotransmission at chemical synapses. When an action potential reaches the axon terminal of the presynaptic cell, it causes voltage-gated calcium channels to open. This allows calcium ions to enter the axon terminal. The influx of calcium ions then triggers the fusion of synaptic vesicles, which contain neurotransmitters, with the plasma membrane of the axon terminal. This fusion leads to the release of neurotransmitters into the synaptic cleft, allowing them to bind to neurotransmitter receptors on the postsynaptic cell and initiate a response. Therefore, the main role of calcium ions at chemical synapses is to cause fusion of synaptic vesicles with the plasma membrane of the axon terminal.

During the absolute refractory period, the excitable membrane is unable to respond to any additional stimuli. This is because the sodium channels, which are responsible for generating action potentials, are in the process of opening and becoming inactivated. This prevents any further depolarization and action potential generation until the channels have reset and are ready to be activated again. Therefore, the statement that the absolute refractory period corresponds to the period when sodium channels are opening and inactivated is true.

Tyrosine hydroxylase is important for the metabolism of catecholamines. Catecholamines are a group of neurotransmitters that include dopamine, norepinephrine, and epinephrine. Tyrosine hydroxylase is the enzyme responsible for converting the amino acid tyrosine into L-DOPA, which is the precursor for the synthesis of catecholamines. Without tyrosine hydroxylase, the metabolism of catecholamines would be impaired, leading to a decrease in the production of these important neurotransmitters.

The statement is false because not all parts of a neuronal cell body have the same threshold. Different synapses on the cell can have different levels of importance based on their specific functions and connections within the neural network.

Action potentials are described as "all-or-none" because they either occur fully or not at all in response to a suprathreshold stimulus. Once the threshold is reached, an action potential is generated and its amplitude remains constant regardless of the strength of the stimulus. This means that a stronger stimulus will not result in a larger action potential. Therefore, the size of the stimulus does not affect the amplitude of the action potential, leading to the "all-or-none" characteristic.

The question asks for a mechanism that would not explain the effects of Drug X interfering with the action of norepinephrine at synapses. Option C, which states that X blocks reuptake of norepinephrine by the terminal, would actually explain the effects of Drug X. Reuptake is the process by which neurotransmitters are taken back up into the presynaptic neuron, and blocking this process would lead to increased levels of norepinephrine in the synaptic cleft, resulting in prolonged and enhanced effects. Therefore, option C is the correct answer.

Interneurons are a type of neuron that are found entirely within the central nervous system (CNS). They receive synaptic input from other neurons in the CNS (A), summing both excitatory and inhibitory inputs (B), and deliver synaptic input to other neurons (C). However, they do not make synapses on effector organs in the peripheral nervous system (PNS) (D). Instead, interneurons primarily function in transmitting information between afferent neurons (sensory neurons) and efferent neurons (motor neurons) (E).

The action potential elicited by a supra-threshold stimulus is not larger than one elicited by a threshold stimulus. In fact, the amplitude of an action potential is independent of the strength of the stimulus that elicited it. Once the threshold is reached, the action potential will always have the same amplitude. Therefore, the statement is false.

The sympathetic division of the autonomic nervous system functions as a cohesive unit, meaning that its components work together to produce a coordinated response. This allows for a rapid and widespread activation of the sympathetic system in response to stress or danger. On the other hand, the components of the parasympathetic division generally act independently, allowing for more localized and specific control over bodily functions. This distinction in the organization of the two divisions supports the statement that the sympathetic division acts largely as a unit, while the parasympathetic division acts as discreet, independent components. Therefore, the answer is true.

"Dual innervation of effectors" refers to the innervation of the same effector organs by both the sympathetic and parasympathetic divisions of the autonomic nervous system, not by somatic and autonomic nerves. Somatic nerves control voluntary movements and do not innervate the same effector organs as the autonomic nervous system. Therefore, the statement is false.

Nicotine is a cholinergic agonist because it binds to and activates nicotinic acetylcholine receptors in the brain and peripheral nervous system. This leads to the release of neurotransmitters such as dopamine, norepinephrine, and acetylcholine, resulting in various physiological and psychological effects.

Glutamate is one of the most abundant excitatory neurotransmitters in the central nervous system (CNS). It plays a crucial role in transmitting signals between nerve cells, enhancing neuronal activity, and promoting synaptic plasticity, which is important for learning and memory. Glutamate is involved in various physiological processes, including motor control, sensory perception, and cognitive functions. It is also essential for the development and function of the brain.

The frequency of action potentials in a postsynaptic cell refers to how often action potentials occur in that cell. Depolarization of the postsynaptic cell refers to a decrease in the difference in electrical charge between the inside and outside of the cell, making the cell more positive. The statement suggests that there is a direct relationship between the degree of depolarization and the frequency of action potentials. In other words, as the postsynaptic cell becomes more depolarized, the frequency of action potentials increases. Therefore, the correct answer is true.

EPSPs, or excitatory postsynaptic potentials, are graded potentials that occur in the postsynaptic membrane of a neuron. These potentials are produced by the opening of chemically-gated sodium channels (A), which allow sodium ions to enter the cell and depolarize the membrane (C). EPSPs are able to summate (D), meaning that multiple EPSPs can add together to reach the threshold for an action potential. However, EPSPs do not always have the same amplitude (E). The amplitude of an EPSP can vary depending on factors such as the strength of the stimulus and the number of synapses activated.

The initial segment of an axon is the region where the action potential is initiated. It contains a high density of voltage-gated sodium channels, which are responsible for depolarizing the membrane and generating an action potential. The threshold potential is the membrane potential at which an action potential is triggered. In order for an action potential to be generated, the membrane potential at the initial segment must reach a certain level, which is more negative than the threshold potential of the cell body and dendrites. Therefore, option B is the correct answer.

Alzheimer's disease is a neurodegenerative disorder characterized by the progressive loss of cognitive function. It is primarily associated with the accumulation of beta-amyloid plaques and neurofibrillary tangles in the brain. Cholinergic neurons, which release the neurotransmitter acetylcholine, play a crucial role in memory and cognitive function. In Alzheimer's disease, there is a significant loss of cholinergic neurons in specific regions of the brain, particularly the basal forebrain and hippocampus. This loss of cholinergic neurons leads to a deficiency in acetylcholine, contributing to the cognitive decline observed in Alzheimer's disease.

Postganglionic sympathetic neurons are not generally cholinergic. Cholinergic neurons release acetylcholine as their neurotransmitter, while sympathetic postganglionic neurons release norepinephrine. Therefore, postganglionic sympathetic neurons are not cholinergic.

The limbic system is best described as "an interconnected group of brain structures including parts of the frontal lobe-cortex, temporal lobe, thalamus, and hypothalamus, that is associated with learning, emotional experience, and behavior." It plays a crucial role in regulating emotions, memory formation, and various behaviors such as motivation and aggression. The limbic system also helps in processing and interpreting sensory information.

The most common neurotransmitters for neuroeffector communication are not dopamine and acetylcholine. While dopamine and acetylcholine are important neurotransmitters, they are not the most common ones. Other neurotransmitters such as norepinephrine, serotonin, and glutamate also play significant roles in neuroeffector communication. Therefore, the statement is false.

The statement is false because dorsal root ganglia actually contain the cell bodies of sensory neurons, not efferent neurons. Efferent neurons have their cell bodies in the ventral horn of the spinal cord. The dorsal root ganglia are located on the dorsal side of the spinal cord and are responsible for transmitting sensory information from the body to the central nervous system.

A presynaptic synapse refers to a synapse where the signal transmission occurs from the axon terminal of one neuron to the terminal of another neuron. Option B correctly states that a presynaptic synapse is between an axon terminal and another axon's terminal. It also mentions that this type of synapse can be either excitatory or inhibitory, which is accurate as the release of neurotransmitters at the synapse can either increase or decrease the likelihood of an action potential in the postsynaptic neuron.

When action potentials are stimulated in neuron X, it will make inhibitory axon-axon synaptic contact with neuron Y at the synapse of Y and neuron Z. This means that the release of neurotransmitter by neuron Y will be inhibited. Inhibitory synapses prevent the postsynaptic neuron from firing an action potential by hyperpolarizing the postsynaptic membrane or decreasing its excitability. Therefore, in this scenario, the release of neurotransmitter by neuron Y will be inhibited, preventing it from transmitting signals to neuron Z.

Postganglionic neuron cell bodies of the autonomic nervous system have nicotinic acetylcholine receptors. These receptors are ion channels that respond to the neurotransmitter acetylcholine. When acetylcholine binds to nicotinic receptors, it causes the opening of ion channels, leading to the depolarization of the cell membrane and the generation of an action potential. This allows for the transmission of signals from the postganglionic neuron to the target organ or tissue.

The correct answer is B. takes place in the cell bodies of neurons. Neuropeptides are synthesized in the cell bodies of neurons, specifically in the endoplasmic reticulum and Golgi apparatus. Unlike other neurotransmitters, neuropeptides are not synthesized in the axon terminals of neurons. Neuropeptides are larger molecules that are derived from precursor proteins and are then transported to the axon terminals for release. This process of synthesis in the cell bodies allows for the production and packaging of neuropeptides before they are transported to their target sites.

Motor signals transmitted by the parasympathetic nervous system do not tend to be displayed throughout the body simultaneously. This is because there is not much divergence of nerve pathways and there is not a close anatomical association between presynaptic neurons and their ganglia. Additionally, there is no accessory activity with the adrenal glands.

Acetylcholine is the main neurotransmitter released by preganglionic sympathetic neurons and motor neurons.

Epinephrine is not a precursor to norepinephrine. Instead, norepinephrine is a precursor to epinephrine. Norepinephrine is converted into epinephrine through a series of enzymatic reactions. Therefore, the statement that epinephrine is a precursor to norepinephrine is false.