1. Sensory neurons follow which kind of pathway to the Central Nervous System? (choose a or b) a. Afferent b. Efferent 2. A stimulus to a neuron initiates an action potential by (choose a. or b.) a. opening a gated sodium (Na+) channel. b. closing a gated sodium (Na+) channel. 3. Depolarization of a neuron membrane occurs when (choose a. or b.) a. gated sodium (Na+) channels open. b. gated potassium (K+) channels open. 4. Repolarization of a neuron membrane occurs when (choose a. or b.) a. gated sodium (Na+) channels open. b. gated potassium (K+) channels open. 5. A neuron membrane is depolarized when (choose a. or b.) a. sodium ions (Na+) rush out of the neuron. b. sodium ions (Na+) rush into the neuron. 6. A neuron membrane is repolarized when (choose a. or b.) a. potassium ions (K+) rush out of the neuron. b. potassium ions (K+) rush into the neuron. 7. Vesicles containing neurotransmitter molecules fuse with the membrane of the pre-synaptic cell—and release the neurotransmitter into the synaptic cleft—when (choose a. or b.) a. calcium ions (Ca++) are released into the pre-synaptic cell at the axon terminal. b. calcium ions (Ca++) leave the post-synaptic cell.
Added by James B.
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1) Sensory neurons follow the afferent pathway to the Central Nervous System. Show more…
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Nerve signals travel in the following manner: A dendrite of a sensory neuron receives the signal; its cell body transmits the signal to a motor neuron's axon, and the signal is sent to the target. b. An axon of a motor neuron receives the signal; its cell body transmits the signal to a sensory neuron's dendrite, and the signal is sent to the target. c. Efferent neurons conduct nerve impulses toward the cell body of sensory neurons, which send them on to interneurons and, ultimately, to afferent motor neurons. d. A dendrite of a sensory neuron receives the signal; the cell's axon transmits the signal to an interneuron, and the signal is transmitted by efferent neurons to effectors. The axons of oligodendrocytes transmit nerve impulses to the dendrites of astrocytes.
19. Dendrites: A) carry impulses from ganglia to organs B) are found only in the peripheral nervous system C) carry impulses toward a nerve cell body D) are solely responsible for sodium flux 20. The primary function of the spinal cord is: A) simple reflexes B) to help integrate incoming and outgoing signals to and from the brain C) to act as a link between the brain and the body D) all are correct 21. The autonomic nervous system: A) regulates only organs on the left side of the body B) has preganglionic but no postganglionic fibers C) is only part of the central nervous system D) has cell bodies in both the spinal cord and in ganglia 22. The cell bodies of the postganglionic neurons of the sympathetic system lie in the: A) chain of ganglia running alongside the spinal cord B) gray matter of the brain C) the gray matter of the spinal cord D) ventral root ganglia 23. Which type of neuron conducts information away from the central nervous system out to effectors in the periphery? A) sensory neuron B) interneuron C) motor neuron 24. Which type of neuron conducts information from receptors in the periphery to the central nervous system? A) sensory neuron B) interneuron C) motor neuron 25. The portion of the neuron that conducts impulses away from the cell body is the: A) dendrite B) axon C) peripheral process
Madhur L.
Axons. Neurons are the basic units of the nervous system. They contain long tubular structures called axons that propagate electrical signals away from the ends of the neurons. The axon contains a solution of potassium $\left(\mathrm{K}^{+}\right)$ ions and large negative organic ions. The axon membrane prevents the large ions from leaking out, but the smaller $\mathrm{K}^{+}$ ions are able to penetrate the membrane to some degree (Fig. E23.37). This leaves an excess negative charge on the inner surface of the axon membrane and an excess positive charge on the outer surface, resulting in a potential difference across the membrane that prevents further $K^{+}$ ions from leaking out. Measurements show that this potential difference is typically about 70 $\mathrm{mV}$ . The thickness of the axon membrane itself varies from about 5 to $10 \mathrm{nm},$ so we'll use an average of 7.5 $\mathrm{nm}$ . We can model the membrane as a large sheet having equal and opposite charge densities on its faces. (a) Find the electric field inside the axon membrane, assuming (not too realistically) that it is filled with air. Which way does it point: into or out of the axon? (b) Which is at a higher potential: the inside surface or the outside surface of the axon membrane?
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