45. Nervous System

Threshold is of great significance in the physiology of neurons. What happens if threshold is not reached?

Which of the following is caused by the death of specific neurons in the brain that release dopamine?

Taking illegal amphetamines ("speed") can induce symptoms similar to which of the following?

Which of the following neurotransmitters is most closely associated with schizophrenia, addiction, and Parkinson's disease?

What happens when a resting neuron's membrane depolarizes?a. There is a net diffusion of Na+ out of the cell.b. The equilibrium potential for K+(EK) becomes more positive.c. The neuron's membrane voltage becomes more positive.d. The cell's inside is more negative than the outside.

Test your understanding of the nervous system by matching the following labels with their corresponding letters: CNS, effector cells, interneuron, motor neuron, PNS, sensory neuron, sensory receptor, spinal cord, synapse.

Which ion most readily leaks across a neuron's membrane, helping to establish the resting potential?

A common feature of action potentials is that theya. cause the membrane to hyperpolarize and then depolarize.b. can undergo temporal and spatial summation.c. are triggered by a depolarization that reaches threshold.d. move at the same speed along all axons.

The inside of the neuron has a lower concentration of positive ions than the outside of the neuron. Is the membrane potential positive or negative?

Which of these statements about myelination in neurons is/are correct? Select True or False for each statement.T/FIt speeds propagation by increasing the density of voltage-gated channels all along the axon.T/FMultiple sclerosis is characterized by disrupted myelination of certain neurons in the central nervous system.T/FIt speeds propagation by preventing cations from leaking out across the membrane as they spread down the axon.T/FIt is more commonly observed in vertebrates than in invertebrates.

Where are neurotransmitter receptors located?a. the nuclear membraneb. the nodes of Ranvierc. the postsynaptic membraned. synaptic vesicle membranes

In a neuron, what creates the electrochemical gradient favoring the outflow of K+ when the cell is at rest?a. Na+/K+-ATPaseb. voltage-gated K+ channelsc. voltage-gated Na+ channelsd. ligand-gated Na+/K+ channels

Why are action potentials usually conducted in one direction?a. Ions can flow along the axon in only one direction.b. The brief refractory period prevents reopening of voltage-gated Na+ channels.c. The axon hillock has a higher membrane potential than the terminals of the axon.d. Voltage-gated channels for both Na+ and K+ open in only one direction.

What causes a nerve signal to move from one end of a neuron along the length of the neuron to the other end? What is a nerve signal, exactly? Why can't it go backward? How is a nerve signal transmitted from one neuron to the next across a synapse? Write a short paragraph that answers these questions.

Which of the following is the most direct result of depolarizing the presynaptic membrane of an axon terminal?a. Voltage-gated calcium channels in the membrane open.b. Synaptic vesicles fuse with the membrane.c. Ligand-gated channels open, allowing neurotransmitters to enter the synaptic cleft.d. An EPSP or IPSP is generated in the postsynaptic cell.