WEEK 3 Nervous System - OBJECTIVES exam with complete solutions.

Describe the structures and functions of neurons. Neurons are specialized cells that transmit signals to different parts of the body. The main parts of a neuron include the cell body, the axon, and the dendrites. The neuron receives a signal at the dendrites. The signal is transmitted along the axon and eventually passes to another neuron. Explain the roles of glial cells in the nervous system. Glial cells assist neurons, providing nutrition and insulation. It is speculated that glial cells may have other roles as well, but this is an area of active research. Which neuron structure receives signals directly from other neurons? dendrite What is a major role of glial cells in the nervous system? Glial cells provide nourishment to neurons. Which of the following organisms would likely have the least intricate nervous system? 1) flatworms 2) jellyfish 3) bivalves 4) insects 5) All of these organisms have equally complex nervous systems. jellyfish In which of the following should the rate of action potential conduction be the fastest? a myelinated, large-diameter nerve Which of the following is an example of a glial cell that develops in the CNS? astrocyte What is the difference between a sensory neuron and a motor neuron? Sensory neurons take in information and send it to the CNS. Describe the electrical potential across a neuron membrane. Membrane potential is a measure of the electrical potential resulting from the unequal distribution of ions on the inside and outside of a cell membrane. For a cell at rest, that membrane potential is known as resting potential. The resting potential of neurons ranges from about -60 mV to about -80 mV. Membrane potentials can be measured by inserting microelectrodes into the interior of a cell and the extracellular environment. The difference in the readings from those two microelectrodes is the membrane potential. Summarize the role of ions in neuron membrane potentials. Ions move into and out of cells through channel proteins in the cell membrane. Gated ion channels open or close in response to stimuli such as heat, pressure, light, chemicals, or a change in the membrane potential. Membranes also transport ions actively into and out of cells by means of ion pumps, which operate using energy supplied by the hydrolysis of ATP. In hyperpolarization, the inside of the cell becomes more negatively charged; a common method of hyperpolarization involves the efflux of potassium ions via K+ ion channels. Conversely, depolarization is the decrease in the negative charge inside the cell, and one common way this happens is by the influx of sodium ions into a cell. These changes produce a graded potential, so nam