nervous system and nervous tissue

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8)wWhich structural and functional type of neuron is activated first when you burn your finger? Which type is activated last to move your finger away form the source of heat?

first activated is unipolar (pseudounipolar) neurons that are sensory(afferent) neurons. The impulse to move your away from the heat will be carried by multipolar neurons that are motor (efferent) neurons.

2

measure of potential energy generated by separated charge? Measured between two point.

voltage

3

potential difference?

Which gated are always open?

voltage is always measured between two points

leakage or nongated channels

4

Open and closes in response to membrane potential?

Open in response to physical deformation of the receptor (as in sensory receptors for touch and pressure)

voltage-gated channels

mchanically gated channels

5

electrical and concentration gradients constitute the

amount of charge that moves between the two points depends on two factors:

electrochemical gradient

current

6

what are the 3 different neuron types

mutltipolar
bipolar
unipolar

7

which neuroon type are interneurons that conduct impulses within the CNS, initegrating sensory input or motor output; may be one of a chain of CNS neurons; some multipolar neurons are motor neurons that conduct impulses along the fferent pathways form the CNS to an effector (muscle/gland)

multipolar

8

which neuron type are sensory neurons that are located in some special sense organs such as retina

bipolar

9

which neuron type are sensory neurons that conduct impulses along afferent pathways to lthe CNS for interpretation. these sensory neurons are called primary or first-order sensory neurons

unipolar

10

define resting membrane potential

potential diffference across the membrane of a resting cell -70mV in neurons (cytoplasmic side of membrane is negatively charged relative to outside)

11

9)For an open channel,what factors determine in which direction ions will move through that channel?

The concentration gradient and the electrical gradient --- together called the elctrochemical gradient -- determine the direction in which ions flow through an open membrane channel.

12

10)For which cation is there the greatest amount of leakage channels) across the plasma membrane?

there are more leakage of K+ than any other cations

13

11)Comparing graded potentials and action potentials, which is bigger? Which travels farthest? Which initiates the other?

Action potentials are larger than graded potentials and travel furter. Graded potentials generally initiate action potential

14

12)An action potential does not get smaller as it propagates along an axon. Why not?

an action potential is regenerated anew at each membrane patch.

15

13) Why is conduction of action potentials faster in myelinated than in unmyelinated axons?

because myelin allows the axon membrane between nodes to change its voltage rapidly, and allows current to flow only at the widely spaced nodes

16

14)If an axon receives two stimuli close together in time, only one AP occurs. why?

If a second stimulus occurs before the end of the absolute refractory period, no AP can occur because Na+ channels are still inactivated.

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15) What is the structure that joins two neurons at an electical synapse?

At an electical synapse, neurons are joined by gap junctions

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16)Events at a chemical synapse usually involve opening of both voltage-gated ion channels and chemically gated ion channels. Where are these ion channels located and what cause each to open?

Voltage-gated ion (Ca+) channels are found in the presynaptic axon terminal and open when an action potential reaches the axon terminal. Chemically gated ion channels are found in the postsynaptic membrane and open when neurotransmitter binds to the receptor protein.