Chapter 12 Neurons Multiple Choice – Flashcards

They jump from gap to gap in between the myelin sheaths Explanation: The tiny gaps in between myelin sheaths are referred to as nodes of Ranvier. The action potential will jump from node to node as it moves down the axon.

Dendrites Explanation: Neurotransmitters from presynaptic cells are recieved by the dendrites of postsynaptic cells. There are myriad dendrites on each neuron that then propagate this signal to the some (cell body), allowing the signal to be passed down the axon to another neuron.

D. The axon carries action potentials away from cell body of a neuron Explanation:The axon carries action potentials away from the cell body of a neuron via a sequence of continuous depolarization. The cell body, or soma, however, is the site of neurotransmitter production and the location of the nucleus and other organelles . Every single neuron contains only one axon.

B. Schwann cells and oligodendrocytes Explanation: Schwann cells produce myelin for neurons of the peripheral nervous system, while oligodendrocytes produce myelin for the neurons of the central nervous system.

D. Dendrite, cell body, axon, synaptic terminal Explanation: A neuron receives input from other neurons at the dendrites. Neurotransmitters released by other neurons bind to receptors on the dendrites, which carry the signal to the cell body. The signal is then amplified in the cell body before being transferred to the axon. Once the signal transitions to the axon, it is considered an action potential. The signal eventually reaches the end of the axon, where the synaptic vesicles are located, and stimulates release of neurotransmitters to the next neuron's dendrites.

A. The propagation of signal through a neuron initiates at the dendrite, enters the cell body, and is transferred from the axon. Explanation: Neurons have many dendrites but one cell body, and a single axon with several terminal ranches. A dendrite receives an external stimulus and causes an electrical disturbance in the cell body. This electrical disturbance is transmitted to the axon, where an action potential is generated if the stimulus is large enough. The action potential is propagates through the axon and is transmitted to a neighboring neuron at the synapse. A large enough electrical disturbance will generate an action potential in the axon, but no magnitude of stimulus can create an action potential in the dendrites. Neurons do contain multiple dendrites, but they only contain one cell body and one axon. Finally, neurons transmit electrical signals to other neurons at the synapse, not at the cell body.

D. Gap Junctions Explanation: There are two types of synapses: chemical and electrical. Chemical synapses use chemical signals called neurotransmitter to transmit nerve signals between neurons, whereas electrical synapses use electrical signals. These electrical signals are transmitted through a gap junction that connects adjacent neurons. Intercalated discs in cardiac muscle contain gap junctions for the purpose of propagating electrical signals to cause systole.

C. Schwann cells Explanation: While both oligodendrites and schwann cell produce myelin sheaths that insulate nervous system signals, only the schwann cells are found in the peripheral nervous system. All other cells listed are found only in CNS. Microglia act as immune cells within the cerebrospinal fluid, since lymphoctyes are barred entry by the blood-brain barrier. Astrocytes support the neural cells and provide nutrients. Ependymal cells are responsible for secreting cerebrospinal fluid.

D. Myelin Sheath Explanation: The myelin sheath coats the axon of a neuron and speeds up the transmission of messages. Myelin is a fatty coating that is unable to perpetrate the action potential signal. As a result, the signal jumps over the myelinated areas, bypassing much or the axon and speeding up transmission. This process is known as saltatory conduction. The axon is the long, slender projection of a neuronthat conducts electrical impulses away from cell body. Dendrites are the branched projections of a neuron that recieve electricall stimulation from synapses and convey them to the cell body. The soma is the cell body of the neuron that contains the nucleus. `

A. Myelin Explanation: Myelin is a fatty compound that surrounds the axons of white matter neurons. Its purpose is to increase the speed of action potentials.

D. Sodium Explanation: At rest, there is high concentration of Na outside the neuron and a high concentration of potassium inside the neuron. During an action potential, the gated channels for sodium open and, because there is such a difference in concentration, the sodium rushes int the axon. This makes the axon much more positive in charge . This positivity propagates along the axon until it reaches the end of the axon, where it triggers release of neurotransmitters into the synapse.

A. Sodium and Potasium Explanation: The depolarization of the neural axon durin an action potential is driven by the influx of sodium ions, entering through voltage-gated sodium channels. Following this stage, voltage-gated potassium channels are stimulated, allowing potassium ions to exit the axon and causing hyperpolarization. The sodium-potassium pump restores the ions to their original positions in preparation for the next action potential, known as repolarization.

D. Glucose Explanation: Neurotransmittes are chemical substances that travel across synapses in the nervous system. Acetylchlorine, dopamine, epinephrine, and GABA are all widely-studied neurotransmitters. Glucose, however, is a monosaccharide used for energy in the body. It serves no purpose as a neurotransmitter.

E. Glial Cells Explanation: Glial cells are located in the nervous system, and serve as support and protection for neurons. Schwann cells, Oligodendrocytes, astrocytes, and Ependymal cells are all examples of neuroglia.

D. A chemical that mimics the action of a neurotransmitter. Explanation: Agonists are chemicals that mimic the action of a neurotransmitter. They bind to the same receptor sites as neurotransmitters, but cause their own unique bilogical responses. Agonists activate the receptors to which they bind.