Chapter 11

Front 1

name the structural componenets of a typical neuron.

Back 1

Structural components of a typical neuron include a cell body (including the nucleus and perikaryon, plus neurofilaments and neurotubules), an axon (including the axon hillock, axoplasm, axolemma, telodendria, collateral branches, an synaptic terminals), and dendrites (including dendritic spines).

Front 2

Describe a synapse.

Back 2

A synapse is the site of communication between a neuron and some other cell; if the other cell is not a neuron, the term neuromuscular junction or neuroglandular synapse is often used.

Front 3

Why is a CNS neuron not usually replaced after it is injured?

Back 3

most CNS neurons lack centrioles, which organize the microtubules of the spindle apparatus during mitosis, so these cells cannot divide and replace themselves.

Front 4

Classify neurons according to their structure

Back 4

According to structure, nuerons are classified as anaxonic, bipolar, unipolar, or multipolar.

Front 5

Classify neurons according to their function

Back 5

According to function, neurons are classified as sensory neurons, motor neurons, or interneurons.

Front 6

Are unipolar neurons in a tissue sample of the PNS more likely to function as sensory neurons or motor neurons?

Back 6

Most sensory neurons of the PNS are unipolar, so these neurons most likely function as sensory neurons.

Front 7

Identify the neuroglia of the central nervous system.

Back 7

Central nervous system neuroglia are ependymal cells, astrocytes, oligodendrocytes, and microglia.

Front 8

Which glial cell protects the CNS from chemicals and hormones circulating in the blood?

Back 8

Astrocytes protect the CNS from circulating chemicals and hormones by maintaining the blood-brain barrier.

Front 9

Which type of neuroglia would occur in increased numbers in the brain tissue of a person with a CNS infection?

Back 9

microglia, small phagocytic cells, occur in increased numbers in infected (and damaged) areas of the CNS.

Front 10

Identify the neuroglia of the peripheral nervous system.

Back 10

Neuroglia of the peripheral nervous system are satellite cells and schwann cells.

Front 11

Describe the neurilemma

Back 11

the neurilemma is the outer surface of a schwann cell encircling an axon.

Front 12

In which part of the nervous system does wallerian degeneration occur?

Back 12

Wallerian degeneration occurs in the PNS, where schwann cells participate in the repair of damaged nerves.

Front 13

Define resting potential.

Back 13

The resting potential is the transmembrane potential of an undisturbed (nonstimulated) cell.

Front 14

What effect would decreasing the concentration of extracellular potassium ions have on the transmembrane potential of a neuron?

Back 14

Decreasing the concentration of extracellular potassium ions would cause more potassium to leave the cell, which would make the transmembrane potential of the neuron more negative.

Front 15

What happens at the sodium-potassium exchange pump?

Back 15

The sodium-potassium exchange pump maintains the cell's resting potential by ejecting three sodium ions from the cell for every two potassium ions it revovers from the extracellular fluid.

Front 16

Define gated channels

Back 16

Gated channels are active channels in the plasma membrane that typically open in respoonse to specific stimuli.

Front 17

Identify the three types of gated channels, and state the conditions under which each operates.

Back 17

Chemically gated channels operate when they bind specific chemicals (such as ACh); voltage-gated channels operate in response to change in the transmembrane potential; and mechanically gated channels operate in response to physical distortion of the membrane surface.

Front 18

What effect would a chemical that blocks voltage-gated sodium channels in a neruon's plasma membrane have on its transmembrane potential

Back 18

if the voltage-gatedsodium channels in a neuron's cell membrane could not open, sodium ions could not rush into the cell, and its transmembrane potential would not change.

Front 19

Define graded potential.

Back 19

a graded potential (also called a local potential) is a change in the transmembrane potential that cannot spread from the site of stimulation.

Front 20

Describe depolarization, repolarization, and hyperpolarization.

Back 20

Depolarization is a shift from the resting potential in which the transmembrane potential becomes less negative. Repolarization is the return of the trnasmembrane potential to the resting potential after the membrane has been depolarized. Hyperpolarization is a shift from the resting potential in which the transmembrane potential becomes more negative.

Front 21

What factors account for the local currents associated with graded potentials?

Back 21

Movement of sodium ions parallel to the inner and outer surfaces of the ploasma membrane- after passing through open chemically gated sodium channels- accounts for the local currents associated with graded potentials.

Front 22

Define action potential.

Back 22

An action potential is a propogated change in the transmembrane potential of excitable cells, initiated by a change in the plasma membrane's permeability to sodium ions.

Front 23

List teh events involved in the generation of an action potential.

Back 23

The events involved in the generation of action potentials are (1) depolarization to threshold, (2) activation of sodium channels and rapid depolarization, (3) inactivation of sodium channels and activation of potassium channels, and (4) closing of potassium channels.

Front 24

Compare the absolute refractory period with the relative refractory period.

Back 24

The refractory period is the time between the initiation of an action potential and the restoration of the normal resting potential. The absolute refractory period is the portion of the refractory period during which the membrane cannot respond to further stimulation, no matter its magnitude. The relative refractory period is the time during which the membrane can respond only to a larger-than-normal stimulus.

Front 25

Define continuous propogation and saltatory propagation.

Back 25

Continuous propotation is the propagation of an action potential along an unmyelinated axon, wherein the action potential affects every portion of the membrane surface. Saltatory propagation is the relatively rapid propagation of an action potential between successive nodes of myelinated axon.

Front 26

What is the relationship between myelin and the propogation speed of action potentials?

Back 26

The presene of myelin greatly increases the propagation speed of action potentials.

Front 27

Describe the parts of a chemical synapse.

Back 27

The parts of a chemicla synapse- the site where a neuron communicates with another neuron or with a cell of a different type- are a presynaptic cell and a postsynaptic cell, whose plasma membranes are separated by a narrow gap called the synaptic cleft.

Front 28

Contrast an electrical synapse with a chemial synapse.

Back 28

In chemical synapses, a neurotransmitter crosses a narrow synaptic cleft, whereas in electrical synapses the membranes of the presynaptic and postsynaptic cells are joined together by gap junctions.

Front 29

What is synaptic fatigue, and how does the synapse recover?

Back 29

Synaptic fatigue occurs in a synaptic know when intensive stimulation exceeds the knob's ability to keep pace with the demand for neurotransmitter. It is reversed and eliiminated by the resynthesis of the neurotransmitter.

Front 30

Define excitatory postsynaptic potential (EPSP) and inhibitory postsynaptic potential (IPSP).

Back 30

An excitatory postsynaptic potential (EPSP) is a graded depolarization of a postsynaptic membrane by a chemical neurotransmitter released by a presynaptic cell. An inhibotory postsynaptic potential (IPSP) is a graded hyperpolarization of a postsynaptic membrane after the arrival of a neurotransmitter.

Front 31

Compare temporal summation with spatial summation.

Back 31

temporal summation is the additon of a rapid succession of stimuli occurring at a single synapse. Spatial summation involves the addition of simultaneous stimuli applied at different locations; that is, it involves multple synapses that are active simultaneously.

Front 32

if a single EPSP depolarizes the initial segment from a resting potential of -70mV to -65mV, and threshold is at -60mV, will an action potential be generated

Back 32

No action potential will be generated, because the depolarization did not reach threshold.

Front 33

Describe the role of regulatory neurons.

Back 33

regulatory neurons facilitate or inhibit the activaties of presynaptic neurons by affecting the plasma membrane of the cell body, or by altering the sensivity of synaptic knobs.

Front 34

What determines the frequency of action potential generation?

Back 34

The degree of sustained depolarization at the axon hillock determines the frequency of action potential generation.

Front 35

The greater the degree of sustained depolarization at the axon hillock, the _______(higher or lower) the frequency of generation of action potentials.

Back 35

The greater the degree of sustained depolarization at the axon hillock, the HIGHER the frequency of generation of action potentials.