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更多“Electrical impulses cannot pass directly across the gap between two neurons, called the _____ cleft.”相关的问题
Electrical impulses affect ______.
A．long-term memory
B．short-term memory
C．structural changes
D．brain cells
A．The flow of electrical impulses through nerve cells at the site of the injury is broken.
B．The production of substance P traveling through nerve cells to the brain increases.
C．Endorphins begin to speed up the response of nerve cells at the site of the injury.
D．A flood of prostaglandins sensitizes nerve endings at the site of the injury.
E．Nerve cells connected to the spinal cord become electrically quiescent.
Section B
Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C and D. You should decide on the best choice.
A well-established distinction in memory theory is that between short-term and long-term memory. The former refers to our ability to do such things as remember telephone numbers long enough to dial them; the latter concerns the wide range of ways in which experiences can affect behavior. many years later. Given the two different kinds of ability, it is reasonable to hypothesize that each is represented differently, in the brain. An experiment was designed to test the hypothesis that long-term memory implies a chemical change in the brain cells while short-term memory involves patterns of impulses in circuits of nerve cells.
One group of rats were taught to run through a maze. Five minutes after learning the task, they were cooled to 5℃, the temperature at which all electrical activity in the brain ceases. They were then kept at this temperature for 15 minutes before being allowed to return to their normal temperature. They were then run through the maze, again.
A second group of rats were taught to run the same maze, and then immediately cooled to 5℃ for 15 minutes. After being allowed to return to their normal temperature, an attempt was made to run the second group through the maze again. It was found that rats in the first group had no difficulty with the maze the second time, suggesting that they did not have to relearn the task. Rats in the second group which was cooled immediately after learning the maze, on the other hand, could not negotiate the maze successfully, i.e., they apparently could not remember what they had learned.
It was concluded from this experiment that short-term memory (in rats, at least) is unlike long-term memory. Short-term memory involves electrical impulses since at a temperature where electrical activity ceases, there is no memory. Long-term memory, in contrast, is unaffected by the disruption of electrical activity and may involve structural changes in brain cells.
What is the main idea of this passage？
A．The difference between short-term memory and long-term memory.
B．The experiments of two groups of rats.
C．The temperature for rats to lose their memory.
D．The importance of memory.
The Television Camera
The television camera is rather like the human eye. Both the eye and the camera have a lens, and both produce a picture on a screen. In each case the picture is made up of millions of spots of light.
Let us see how the eye works. When we look at an object-a person, a house, or whatever it may be, we do not see all the details of the object in one piece. We imagine that we do, but this is not the case. In fact, the eye builds up the picture for us in our brain, which controls our sight, in millions of separate parts, and although we do not realize it, all these details are seen separately. This is what happens when we look at something. Beams of light of different degrees of intensity, re-fleeted from all parts of the object, strike the lens of the eye. The lens then gathers together the spots of light from these beams and focuses them on to a light-sensitive plate-the retina-at the back of the eyeball. In this way, an image of the object is produced on the retina in the form. of a pattern of lights. The retina contains millions of minute light-sensitive elements, each of which is separately connected to the brain by a tiny fiber in the optic nerve. These nerve fibers, working independently, pick out minute details from the image on the retina and torn the small spots of light into nerve impulses of different strengths. They then transmit these impulses to the brain. They do this all at the same time. All the details of the image are fed to the brain, and as we have taught our brain to add them together correctly, we see a clear picture of the object as a whole.
Television, which means vision at a distance, operates on a similar principle. A television picture is built up in thousands of separate parts. Beams of light reflect from the subject being televised strike the lens of the television camera, which corresponds to the lens of the eye. The camera lens gathers together the spots of light from these beams and focuses an image of the subject on to a plate, the surface of which is coated with millions of photo-electric elements sensitive to light. The spots of light forming the image on the plate cannot be transmitted as light. So they are temporarily converted by an electronic device into millions of electrical impulses ; that is, into charges of electricity. These electrical impulses are then sent through space on a wireless wave to the homes of the viewers. They are picked up by the aerials and conveyed to the receivers to the television set. There, they are finally converted back into the spots of light that make up the picture on the television screen.
We are told that the television resembles the human eye in______.
A．one way
B．two ways
C．three ways
D．four ways
The passage is primarily concerned with
A．analyzing ways that enzymes and other chemicals influence how the body feels pain.
B．describing the presence of endorphins in the brain and discussing ways the body blocks pain within the brain itself.
C．describing how pain signals are conveyed in the body and discussing ways in which the pain signals can be blocked.
D．demonstrating that pain can be influenced by acupuncture and electrical stimulation of the central brain stem.
E．differentiating the kinds of pain that occur at different points in the body" s nervous system.
Controlling Robots with the Mind
Belle, our tiny monkey, was seated in her special chair inside a chamber at our Duke University lab. Her right hand grasped a joystick (操纵杆) as she watched a horizontal series of lights on a display panel. She knew that if a light suddenly shone and she moved the joystick left or right to correspond to its position, she would be sent a drop of fruit juice into her mouth.
Belle wore a cap glued to her head. Under it were four plastic connectors, which fed arrays of microwires-each wire finer than the finest sewing thread- into different regions of Belle's motor cortex (脑皮层), tile brain tissue that plans movements and sends instructions. Each of the 100 microwires lay beside a single motor neuron (神经元). When a neuron produced an electrical discharge, the adjacent microwire would capture the current and send it up through a small wiring bundle that ran from Belle's cap to a box of electronics on a table next to the booth. The box, in turn, was linked to two computers, one next door and the other half a country away.
After months of hard work, we were about to test the idea that we could reliably
translate the raw electrical activity in a living being's brain-Belle's mere thoughts-into signals that could direct the actions of a robot. We had assembled a multi-jointed robot arm in this room, away from Belle's view, which she would control for the first time. As soon as Belle's brain sensed a lit spot on the panel, electronics in the box running two real-time mathematical models would rapidly analyze the tiny action potentials produced by her brain cells. Our lab computer would convert the electrical patterns into instructions that would direct the robot arm. Six hundred miles north, in Cambridge, Mass, a different computer would produce the same actions in another robot arm built by Mandayam A. Srinivasan. If we had done everything correctly, the two robot arms would behave as Belle's arm did, at exactly the same time.
Finally the moment came. We randomly switched on lights in front of Belle, and she immediately moved her joystick back and forth to correspond to them. Our robot arm moved similarly to Belle's real arm. So did Sriniwlsan's. Belle and the robots moved in synchrony (同步), like dancers choreographed (设计舞蹈动作) by the electrical impulses sparking in Belle's mind.
In the two years since that day, our labs and several others have advanced neuroscience, computer science and microelectronics to create ways for rats, monkeys and eventually humans to control mechanical and electronic machines purely by "thinking through," or imagining, the motions. Our immediate goal is to help a person who has been unable to move by a neurological (神经的) disorder or spinal cord (脊髓) injury, but whose motor codex is spared, to operate a wheelchair or a robotic limb.
Belle would be fed some fruit juice if she
A．grasped the joystick.
B．moved the joystick to the side of the light.
C．sat quietly in a special chair.
D．watched lights on a display panel.
Important technological advances such as those already mentioned have encouraged scientists to develop the artificial heart. Early in 1983,in its first use by a human patient, a medical team at the University of Utah Medical Center replaced the diseased heart by a Jarvik-7.
The world watched amazed as television pictures of Dr. Clark showed him as he improved steadily after the surgery. His continued life demonstrated that a bionic device could imitate the action and function of a healthy heart. Dr. Clark lived for 112 days.
Life-like or bionic machines have existed for several centuries. The development of tools by man' s ancestors is a good example of the application of bionics to extend human capabilities. Modern bionic research is especially involved in prosthetics devices that substitute for, or replace lost or diseased body parts such as arms ,legs ,and eyes.
Recent advances in electronics have enabled scientists to make better use of electrical impulses in the control of prosthetic devices. One interesting research project is the development of an artificial eye in which video signals are transformed into light patterns that are sent into nerve receptors in the patient.
The future for applied bionics seems to be promising. Existing bionic devices will become smaller, faster, and more effective. The artificial heart used for Dr. Clark is only one of experimental replacement devices. It is likely to be joined in the future by replacements for other internal systems or organs. Bionic livers, stomachs, and lungs are not impossibilities!
Which of the following does this passage mainly discuss？
A．The application of bionics.
B．The first "open heart" surgery.
C．The development of the artificial heart.
D．The future of applied bionics.
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