Neurons and Action Potentials - AP Psychology

Agonists are chemicals that mimic the action of a neurotransmitter. Agonists bind to the same receptor sites as neurotransmitters, but cause their own unique biological responses. Agonists activate the receptors to which they bind.

Afferent neurons, also known as sensory neurons, are the neurons that relay information to the central nervous system from the sensory organs. Efferent neurons are the motor neurons that carry the nerve impulses away from the central nervous system to the effectors. Interneurons are the neurons that transmit impulses between other neurons.

Efferent neurons are responsible for relaying information from the central nervous system to the muscles or glands. These signals allow for movement.

Cell wall is a cell organelle found in plants, bacteria and archea; it is not found in neurons. The soma is the cells body of the neuron, this is where the nucleus contained but the dendrites and axon are not part of the soma. Dendrites are short branched extensions of a neuron where impulses are received in the synapses and transmitted to the soma. Axons are the long threadlike part of the neuron that conduct the impulses from the soma to other cells.

Glial cells are specialized cells found in the central nervous system. Myelin sheaths are made up of glial cells that insulate the axon of a neuron.

The Myelin Sheath is a fatty substance that covers the axon and helps speed up impulses. A neuron is a nerve cell. Dendrites are the message receiving part of a neuron, and axons are the message sending part. A synapse is the gap between the terminal buttons of the axon of one neuron and the dendrites of another neuron. Soma is a term synonymous with cell body.

Neurons fire according to the All-or-Nothing Principle, meaning that they will either fire completely or not at all. There is no in-between or half-fire.

The time frame when a neuron cannot fire because it has just fired is called the refractory period.

Action potentials travel down the axon to the axon terminal. When an action potential arrives in the axon terminal it signals the synaptic vesicles to move toward the cell membrane. The synaptic vesicle fuses with the cell membrane and releases neurotransmitter.

Reuptake is a term used to describe the process of a neuron absorbing the remaining neurotransmitter back into the axon terminal for release. SSRIs used to treat depression, they function by inhibiting this reuptake process for serotonin.

Acetylcholine affects movement, learning, memory and REM sleep. It has an excitatory affect on skeletal muscle fiber and an inhibitory affect on heart muscle fibers.

Serotonin affects mood, sleep, appetite, impulsivity and aggression. If a person's level of serotonin is too high or too low it could affect mood and aggression. Depression has been directly linked to serotonin levels, and the most regularly prescribed Anti-Depressant drugs (SSRIs) regulat the serotonin re-uptake process, thus elevating the serotonin levels in patients.

The axons of one neuron release neurotransmitters which are received by the dendrites of the adjacent neuron.

Dendrites are the part of the cell that receive information from other neurons and relay it to the cell body. This is easy to remember if you visualize a diagram of the neuron because dendrites look like branches coming out of the cell body.

As for the other answers, axons transmit information to other neurons (as opposed to receiving it), cell branches do not exist (that was a trick answer choice because dendrites look like branches), the synapse is the slight gap between two neurons through which electrical signals pass, and the nucleus is the part of the cell body that contains chromosomes.

Interneurons connect sensory neurons to motor neurons.

It is motor neurons that help produce movement, sensory neurons that convey information from the outside world to the brain, myelin sheaths that insulate axons, and neurotransmitters that transmit information across the synapse.

Dendrites are the little branched hair-like structures attached to the cell body. They play the role of receiving information that will be propagated through the cell body and eventually through the axon hillock as a neural impulse if the stimulus warrants a great enough action potential. The axon is what the neural impulse will travel through to reach the axon terminals and ultimately pass along the message to the next neuron or target tissue via neurotransmitters released into the synapse. The synapse is the space between two neurons. Because action potentials do not propagate backwards (due to refractory periods), a stimulus is not expected to be sensed by the axon terminals. As a result, impulses will travel from cell body to axon terminals with the dendrites responsible for sensing stimuli.

An action potential is a rapid electrical charge that will propagate down through the neuron. This charge causes a continuous chain reaction through the neuron from the dendrites to the axon terminals by creating a threshold stimulus that allows rapid depolarization and repolarization via the movement of ions across the membrane. This represents the basic construct of how neuronal communication is possible. Although stimulus does seem like a viable answer, a neuron may sense a stimulus but may not propagate a neural impulse. In this case, the stimulus may not be strong enough to activate an action potential. This solicits the "all or nothing" behavior of action potentials. If the stimulus is slightly below the necessary threshold to elicit an action potential, then no impulse can be expected. Conversely, if a stimulus is just at the minimal requirement of the neuron's threshold, then an action potential may be expected; therefore, stimulus would be incorrect. Due to the fact that action potentials function on ionic concentration gradients, ionic equilibrium would also be an incorrect answer. While the terms absolute refractory period and hyperpolarization are related to action potentials, these are merely parts of an action potential that may be argued to be the reasoning to prevent an impulse from traveling backwards. This prevents an action potential from travelling back the way it came. These choices would also be incorrect answers because while they are important, they're only components to an action potential.

The synaptic gap is where two neurons meet. Here neurotransmitters will be released from vesicles in the sending neuron to the receiving neuron. The receiving neuron will receive communication via sensing the neurotransmitters at receptor sites specific for that neurotransmitter. The release of neurotransmitter is stimulated once the action potential has propagated to the axon terminal.

The neurotransmitter is released with the purpose of signaling and beginning action potentials for the receiving neuron. This chemical messenger must be quickly removed from the synapse to prevent continuous stimulation of the receiving neuron. The reuptake procedure is done from the sending neuron, meaning the remaining neurotransmitter is reabsorbed by the neuron it came from. This process will not create an action potential for the sending neuron as it would for the receiving neuron and is necessary in order to prevent overstimulation.