Absolute refractory period The interior of the cell becomes less negative due to an influx of sodium ions. a) motor fibers that conduct nerve impulses from the CNS to smooth muscle, cardiac muscle, and glands This period occurs at the end of action potential and limits the speed at which nerve impulses can be generated in a nerve fibre. Direct diffusion of ions through these junctions allows the action potential to be transmitted with little or no delay or distortion, in effect synchronizing the response of an entire group of neurons. The transmitter molecules are then expelled from the vesicles into the synaptic cleft. a) short distance depolarization Axon- Helps in the propagation of nerve impulses to the target cell. Like the receptor potential, the PSP is a graded response, varying in amplitude according to the duration and amount of stimulation by neurotransmitters. Therefore, repolarization helps in maintaining or restoring the original membrane potential state. Which of the following is true about the movement of ions across excitable living membranes? the membrane potential has been reestablished. The generation of a second action in some neurons can only c) glial cell 1.) The The reverse polarity of active neurons is measured at about +30 mV. C) Specific sodium gates will open. A gap between Schwann cells in the peripheral system is called a(n) ________. This results in a huge influx of sodium ions inside the cells which trigger the nerve impulse conduction. Once an action potential has been generated at the axon hillock, it is conducted along the length of the axon until it reaches the terminals, the fingerlike extensions of the neuron that are next to other neurons and muscle cells (see the section The nerve cell: The neuron). conduction to take place. A second nerve impulse cannot be generated until _____. However, most synapses are chemical synapses. The neurons are said to be in resting phase when there is no nerve impulse. buffering potassium and recapturing neurotransmitters are Which of the following is not a chemical class of neurotransmitters? the membrane potential has been re-established: True or False, Large-diameter nerve fibers conduct impulses much faster than small-diameter fibers. This leaves 0.30 to 3.80 milliseconds for other processes. a) astrocytes We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. Plasma membrane exhibits voltage-gated Ca2+ channels. d) leakage channel, What is the role of acetylcholinesterase? This is essential for altering the resting membrane state to action membrane potential. The transmission of nerve impulses across chemical synapses is more complex. B) A single type of channel will open, permitting simultaneous flow of sodium and potassium. second nerve impulse cannot be generated until proteins have been resynthesized the na ions DismissTry Ask an Expert Ask an Expert Sign inRegister Sign inRegister Home postsynaptic neuron by many terminals at the same time.3.) A second nerve impulse cannot be generated until ________. Neuralgia that control the chemical environment around neurons by buffering potassium and recapturing neurotransmitters are. 3.) - Studocu Neurons and their thresholds, axons, dendrites, and Na+/K+ ATPases. Neurons help in transmitting signals in the form of a nerve impulse from the Central nervous system to the peripheral body parts. a second nerve impulse cannot be generated until___ the membrane potential has been reestablished: an impulse from one nerve cell is communicated to another nerve cell via the___ synapse: neuroglia that control the chemical enviroment around neurons by buffering potassium and recapturing neurotransmitters are___ astrocytes A nerve impulse is thus an important signal transduction mode for triggering a response in major body parts due to a strong stimulus. When one or more presynaptic neurons fire in rapid order it produces a much greater depolarization of the postsynaptic membrane than would result from a single EPSP; this event is called ________ summation. If a motor neuron in the body were stimulated by an electrode placed about midpoint along the length of the axon ________. Hence, more time is taken in generating and then transmitting nerve impulses during an action potential. In myelinated neurons, myelinated sheaths are present. 4.) Which group of fibers spreads impulses at up to 1 meter per second? What is the expected frequency of heterozygotes in the progeny of the self-fertilized plants? B) are crucial in the production of neurotransmitters, C) are crucial for the development of neural connections. Depolarization The specific period during which potassium ions diffuse out of the neuron due to a change in membrane permeability. The role of acetylcholinesterase is to ________. They are generated when the nerve True or False, A graded potential that is the result of a neurotransmitter released into the synapse between two neurons is called a postsynaptic potential. are crucial for the development of neural connections. Synaptic vesicles. A second nerve impulse cannot be generated until _____. In what way does the interior surface of a cell membrane of a resting (nonconducting) neuron differ from the external environment? True or False, In myelinated axons the voltage-regulated sodium channels are concentrated at the nodes of Ranvier. the Na+ ions have been pumped back into the cell. True or False, Voltage is always measured between two points and may be called the potential between these two points. That is, the membrane potential has to reach a certain level of depolarization, called the threshold, otherwise, an action potential will not start. The generation of a second action in some neurons can only happen after a refractory period, when the membrane potential has returned it's base level or even more . A) The release of neurotransmitter molecules gives cells the c) ependymal cells The resting membrane potential refers to the non-excited state of the nerve cell at rest when no nerve impulse is being conducted. As a result of this, the membrane becomes hyperpolarized and have a potential difference of -90 mV. analyzes sensory information, stores information, makes decisions. The nerve impulse travels at a speed of 100 m/s in saltatory conduction. What event is depicted in the structure labeled A? In electrical synapses, two neurons are connected through channel proteins for transmitting a nerve impulse. The part of a neuron that conducts impulses away from its cell body is called a(n) ________. An excitatory neurotransmitter secreted by motor neurons innervating skeletal muscle is ________. 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When information is delivered within the CNS simultaneously by different parts of the neural pathway, the process is called ________ processing. An inhibitory postsynaptic potential (IPSP) is associated with ________. membrane would produce an inhibitory postsynaptic potential (IPSP). A second nerve impulse cannot be generated until _____. the membrane potential has been reestablished In what way does the interior surface of a cell membrane of a resting (nonconducting) neuron differ from the external environment? Following are some major factors that affect the speed of nerve impulse: Myelin sheath is present around the neuron and functions as an electrical insulator. d) generator potential, Which of the following describes the excitatory postsynaptic potential? a) the synaptic cleft prevents an impulse from being transmitted directly from one neuron to another c) sensory neurons that convey information from somatic receptors in the head, body wall, and limbs and from receptors from the special senses of vision, hearing, taste, and smell to the CNS c) action potential 33) A second nerve impulse cannot be generated until _____. True or False, Reflexes are rapid, automatic responses to stimuli. True or False, Enkephalins and endorphins are peptides that act like morphine. In what way does the interior surface of a cell membrane of a resting (nonconducting) . The polarization state is also known as the Unstimulated or non-conductive state. A stimulus traveling toward a synapse appears to open calcium ion Join over 22,000 learners who have passed their exams thanks to us! A teacher walks into the Classroom and says If only Yesterday was Tomorrow Today would have been a Saturday Which Day did the Teacher make this Statement? The frequencies of the alleles A and a are 0.60.60.6 and 0.40.40.4, respectively, in a particular plant population. The first factor is the outside diameter of the nerve fibre. Neurotransmitter inactivation is carried out by a combination of three processes. Figure 11.4. Saltatory conduction is made possible by ________. As is stated above, the lipid bilayer of the neuronal membrane tends to repel electrically charged, hydrated ions, making virtually impossible the movement across the membrane that is necessary for the generation of nerve impulses. The refractory phase is a brief period after the successful transmission of a nerve impulse. This threshold potential varies but is generally about 15 millivolts (mV) more positive than the cell's resting membrane potential. Saltatory is faster than continuous conduction and occurs in myelinated neurons. At the neuromuscular junction, brief depolarizations measuring no more than one millivolt can be observed in the postsynaptic muscle membrane, even when it is at rest. The neuron cannot respond to a second stimulus, no matter how strong. Unmyelinated axons do not have nodes of Ranvier, and ion channels in these axons are spread over the entire membrane surface.