BIOL 3530 Lecture 12: Chapter 10

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7 Oct 2016

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The nervous system: is the most complex organ system in the animal embryo, provides communication via a network of varied neurons, is connected by a process of action potential propagation and neurotransmitter release. Supporting tissues (glia) include schwann cells (surround peripheral neuron axons), oligodendrites and astrocytes (surround central neurons). Vertebrates have 100s of different types of neurons. The dendrites and axons can be heavily branched (one neuron can receive 100,000 different signals. Specification of cell identity in the nervous system. The neurogenic zone or neurectoderm consisting of cells that can become either neural cells or epidermis form on either side of the ventral mesoderm in the early embryo. In both drosophila and vertebrates, the neuroepithelium is organised into three columns of neural precursors expressing similar genes, on either side of the midline. Proneural gene expression, such as the transcription factor genes of the achaete-scute complex gives the potential to become neural precursors.

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Nerve cells that conduct messages are called (1) ____. (2) _____ cells, which support and nurture the activities of neurons, make up less than half the volume of the nervous system. (3) _______ neurons respond to specific kinds of environmental stimuli, (4) ______ connect different neurons in the spinal cord and brain, and (5) ______ neurons are linked with muscles or glands. All neurons have a (6) _______ ________ that contains the nucleus and the metabolic means to carry out protein synthesis. (7) _______ are short, slender extensions of the (6), and together these two neuronal parts are the neuronsâ âinput zoneâ for receiving (8) _____. The (9) _____ is a single long, cylindrical extension away form the (10) ______; in motor neurons, the (11) ______ has finely branched (12) ________ that terminate on muscle or gland cells and are âoutput zones,â where messages are sent on to other cells. A neuron at rest establishes unequal electric charges across its plasma membrane, and a(n) (13) ____ ____ is maintained. Another name for (13) is the (14) _____ _____ _____; it represents an ability for the membrane to be disturbed. Weak disturbances of the neuronal membrane might set off only slight changes across a small patch, but strong disturbances can cause a(n) (15) _______ ______, which is an abrupt, short-lived reversal in the polarity of charge across the plasma membrane of the neuron. For a fraction of a second, the cytoplasmic side of a bit of membrane becomes positive with respect to the outside. The (16) ______ that travels along the neural membrane is nothing more than short-lived changes in the membrane potential. A. Neurons H. Sensory B. Motor I. Endings C. Interneurons J. Disturbance D. Cell body K. Signals (stimuli) E. Axon L. Voltage differential F. Dendrites M. Resting membrane potential G. Neuroglial N. Action potential

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Santiago Ramon y Cajalâs theory of dynamic polarization refers to the:

(a)membrane potential of a neuron at rest.

(b)membrane potential of a neuron firing action potentials.

(c)opening and closing of gated channels in the membrane.

(d)one way flow of information in neurons from dendrites to axon terminals.

(e)one way flow of information in neurons from axon terminals to dendrites.

Over the course of scientific history, there are many examples of scientists reaching the right conclusion for the wrong reasons. When Schwann first proposed that the nervous system was made of individual cells, he based it on observations of:

(a)synapses.

(b)dendrites

(c)axon terminals.

(d)astrocytes.

(e)Nodes of Ranvier.

The synaptic cleft was finally seen in the 1950s. What prevented scientists from seeing it earlier?

(a)The resolution of the light microscope.

(b)They were looking in the wrong place.

(c)Their tissue was not appropriately stained.

(d)Myelination of the axons.

(e)all of the above

The resting membrane potential of a neuron is approximately:

(a) +65 V

(b) +65 mV

(d) -65 mV

What is largely responsible for the resting membrane potential in a neuron?

(a)Axonal insulation by myelin

(b)Voltage-Gated Sodium Channels

(c)The Action Potential

(d)Potassium Leak Channels

Which of the following would DECREASE the propagation velocity of an action potential down an axon?

(a)Increase in axon diameter

(b)Increase myelination between nodes of Ranvier

(c)Remove myelination between nodes of Ranvier

(d)Decrease density of voltage-gated Na+ channels except at the Nodes of Ranvier

The resting membrane potential of a neuron can be estimated using the:

(a)Nernst equation

(b)Goldman equation

(c)Hodgkin and Huxley equation

(d)Ohmâs law

18. What would happen to the resting membrane potential of a neuron if you added K+ to the extracellular fluid?

(a)Resting membrane potential would increase (become more positive)

(b)Resting membrane potential would decrease (become more negative)

(c)Resting membrane potential would not change

(d)Resting membrane potential would be abolished

. Which of the following statements is FALSE for Graded Potentials

(a)Magnitude changes with magnitude of triggering stimulus

(b)Magnitude decreases with distance from initial site

(c)Cannot be summed

(d)No refractory period

In the nervous system, the strength of the stimulus is coded into:

(a)The frequency of action potentials generated

(b)The amplitude of action potentials generated

(c)Both the frequency and amplitude of action potentials generated

(d)The duration of individual action potentials generated

Ion movement during both the depolarization and repolarization phases of an action potential are the result of:

(a)active transport pumps along the neuron membrane.

(b)diffusion of ions down their electrochemical concentration gradients.

(c)negative feedback loops.

(d)All of the above

At the peak of the action potential, the membrane potential is:

(a)Exactly at the Na+ equilibrium potential

(b)Greater (more positive) than the Na+ equilibrium potential

(c)Above 0 mV but less positive than the Na+ equilibrium potential

(d)0 mV

BIOL 3530 Lecture 12: Chapter 10

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