Neurons - GRE Subject Test: Psychology

This can seem like a "which is the best response" type of question where more than one of these choices could be correct. Do not be fooled. The exchange of information or "impulses" in which dendrites and axons are involved is straightforward. Axons send out neural "messages" and dendrites receive. Sometimes it can be helpful to use a mnemonic device to remember: Axon has four letters like send. Dendrite has eight letters like receives.

An action potential describes the event of an electrical impulse being activated by a given neuron once it is sufficiently polarized. We may think of an experience such as pain. If I prick my finger with a needle, I feel a small amount of pain. If, however, I unfortunately lose my fingertip due to a mechanical accident of some sort, I will feel much more pain. This difference in pain is not due to the strength of any one given action potential. An action potential either leads to an electrical impulse or it does not (in other words, it is all-or-none). There are no gradients in strength or degree; however, the number of action potentials occurring across neurons can have a cumulative effect (e.g., greater number of nerve cells involved in the more serious injury of losing a finger tip equates to a greater experience of pain).

The tiny space between a synapse of one neuron and the synapse of another is called the synaptic gap. It is also known as the synaptic cleft. It is in this space where neurotransmitters can be exchanged between neurons. It is important to note that not all neurotransmitter molecules emitted by a given synapse or necessarily received by the synapse across the synaptic gap. Multiple variables are at play. The gap is not needed for the neurons to have space to grow nor is the brain kept moist via these clefts.

While potassium—alongside sodium—plays a vital role in the functioning of neurons and in the exchange of neurotransmitters, it is not a neurotransmitter. Rather, it is involved in the shifting of polarity in the neuron that leads to an action potential. In other words, the amount of potassium present in a given neuron directly impacts meeting the threshold of an action potential. Serotonin, dopamine, and norepinephrine are neurotransmitters released by these action potentials.

In reading popular articles on brain science or, perhaps, by watching a documentary on brain injuries, we might have come across the terms sensory and motor neurons. Just as they sound, a sensory neuron passes along sensory information. Motor neurons, which are located close to the spine, assist with our motoric abilities (e.g., walking, grasping, pushing). Interneurons play the role of circuitry connectors between sensory and motor neurons. Because of this, they are also sometimes referred to as relay neurons. Finally, “outer neurons” are not one of the three major classifications of neurons. In fact, there are no such things as outer neurons.

The human brain is incredibly complex. “One or multiple neurotransmitters can result in one or multiple behaviors” is the best answer to this question. As an example, serotonin and dopamine both play an intimate role in the mood state and contingent behaviors associated with depression. While neurotransmitters can be difficult to balance, especially in people with a psychiatric disorder, there are real and predictable relationships at work between neurotransmitters and our behavior.

This question is closely associated with the nature vs. nurture debate. Let us be reminded that both nature and nurture are at play in development including neuronal development. With that in mind, we can successfully conclude that the false statement in this series is, “by birth, neurons are fully developed including axons, dendrites and myelin.” While most of the neurons we will have throughout our life are present at birth, these neurons are in nascent form. That is, they are still building neural pathways and connections while other neural pathways and connections are being pruned away if left unused. This process is most prolific in the first three years of life, but continues across the lifespan.

Glial cells, which are also known as neuroglia cells or sometimes simply glia, serve the function of supporting, nourishing and protecting the neurons. They are not involved in the breakdown or removal of unused neural pathways, nor are they any type of parasite. As for the function of a sheath, that better describes myelin that glial cells help to form.

The corpus callosum performs the task of communicating between the brain’s two hemispheres. It is the large band of neural fibers, which connects the two brain hemispheres and carries messages between them. The sympathetic and parasympathetic nervous systems are divisions of the autonomic nervous system and involve both hemispheres of the brain. The sensory cortex, while it spans both hemispheres, does not directly aid in communication between the two sides.

From studies of feral children seriously neglected in childhood who cannot speak or engage with others socially to investigations of kittens who have been permanently blinded by having their eyes covered for an extended period of time after birth, researchers have demonstrated that critical learning periods exist. In these critical periods, if the environment does not permit exposure, then some losses in social learning cannot be regained even if the environment provides those learning exposures later. Saltation refers to the process of actually regressing in small steps during normal development. While phyletic gradualism and punctuated equilibrium refer to theories about the rate of development.

On both micro and macro levels from the development of neurons to our actual body length, we experience small regresses or steps backward as part of normal healthy development. This process is called saltation. Phyletic gradualism and punctuated equilibrium refer to theories about the rate of development. In the instances of critical periods, if the environment does not permit exposure, some losses in social learning cannot be regained even if the environment provides those learning exposures later.

Just as it sounds, phyletic gradualism refers to a slow and steady pace of development. Punctuated equilibrium, on the other hand, best captures the theory described in this question. In the instances of critical periods, if the environment does not permit exposure, some losses in social learning cannot be regained even if the environment provides those learning exposures later. Saltation refers to the process of actually regressing in small steps during normal development.

The correct answer is that dendrites are the sole receiver of stimulation because the soma of the neuron can also receive input from other cells. The other answers were wrong because they are true characteristic of the nervous system. Summation can be temporal or spatial depending on the amount of cells communicating with the neuron. One pre-synaptic cell can send input to the neuron multiple times to result in temporal summation, and multiple cells can send input to the same cell resulting in spatial summation. The total amount of input received by the dendrites and soma will sum in the initial segment of the axon, if the axon reaches the depolarization threshold, voltage gated sodium channels will open and set off a chain reaction that propagates the action potential to the axon terminal. This process is faster in cells with myelin because less of the axon needs to be stimulated to send the action potential to the terminal due to the insulation of segments by the myelin.

The correct answer is voltage gated sodium channels. These cells are in the axon of the neuron and are only opened when the cell reach the depolarization threshold. Voltage-gated potassium channels are responsible for the re-polarization of the cell or the hyper-polarization. Voltage-gated calcium channels are apparent in the axon terminal of the neuron and play a role in the release of neurotransmitters. Sodium channels and potassium channels are in the dendrites and soma of the neuron. They interact to keep the cell at it's resting potential and inputs to the cell can affect the amount of sodium or potassium entering the cell. This can lead to the cell becoming depolarized or hyper-polarized, but do not themselves lead to the surge of activity that generates the action potential.

The action potential begins at the axon hillock, a specialized region connecting the dendrite and the axon. Before the action potential may occur, an energy threshold must be surpassed. The axon hillock acts like a gateway, permitting the action potential to begin only once this minimum has been reached. From there, the action potential propagates down the axon of the neuron. This is the long, tail-like extension of the cell which connects to the dendrites of other neurons. At the end of the axon are the terminal buttons. It is here that neurotransmitters are released from the neuron, which travel across the synaptic cleft to bind to neighboring dendrites of other neurons. If these dendrites receive sufficient excitation, then they will release their own action potentials, and repeat the process; thus, the action potential sends information between nerve cells.

The "soma" is the name for the cell body of a neuron. This refers to the part of the neuron that houses the cell nucleus, and other organelles necessary for the life of the cell. This region is distinct from the dendrites, which are the branch-like structures that protrude from the soma. It is also distinct from the axon, the long tail-like structure which extends away from the cell body. "Myelin" is the name of a fatty substance which coats the axons of some nerve cells in order to insulate them. "Nerve" is a word that may be used interchangeably with 'neuron', particularly when referring to those in the peripheral nervous system. However it is not an alternate name for the cell body_._

Myelin is a fatty coating that develops around the axons of some nerve cells in order to insulate them. This insulation serves to aid in the completion of action potentials. Glial cells exist in the brain, and aid in nourishing the neurons. Myelin does not serve this purpose. Myelin also does not protect against viral attack, nor that of other pathogens. Although myelin insulates the cells, it is not capable of speeding their rate of firing. Finally, myelin has no interaction with neurotransmitters, and does not increase the receptivity of a nerve cell to stimulation.

The nerve impulse within a neuron is primarily an electrical event. This is due to the fact that the cell becomes polarized and then proceeds through rapid depolarization and repolarization during and following the action potential. All of this is achieved through electrical gradients, which are maintained across the cell membrane in order to create potential energy. Communication between neurons, on the other hand, is achieved through the transmission of chemical information. Neurotransmitters released from the terminal button of one neuron cross the syaptic cleft to bind to receptor sites on neighboring dendrites of other nerve cells. The transmission of these chemicals delivers information, leading to excitation or inhibition of the receiving cells. "Axon and dendrite" does not correctly describe this relationship. "Neurotransmitter and action potential" seems more appropriate, but these two items are in the incorrect order to describe nerve impulse and interneuronal communication, respectively.

The symptoms of alertness, stress, physical excitation and readiness, rapid breathing and so forth all describe the 'fight or flight' response to danger, which would be appropriate to the example of fleeing from a predator. This response is controlled by the sympathetic nervous system. The sympathetic nervous system is responsible for such involuntary behaviors as increasing heart rate, constricting blood vessels and raising blood pressure. These behaviors serve to benefit the organism in events demanding physical exertion and focus (e.g. hunting, fighting, or fleeing). The parasympathetic nervous system controls the opposing involuntary behaviors, which contribute to relaxing, digesting, and other states. The central nervous system refers to those neurons housed within the brain and spinal cord. This is not an applicable response to the question. The neurotransmitter dopamine is a part of the brain's reward system. It does not play a role in the fight or flight response.