Ch. 12 Self-Quiz

the highly branched receiving or input portions of a neuron

dendrites

form the cytoskeleton of a neuron

neurofibrils

provide myelin sheath for CNS axons

oligodendrocytes

the recovery of the resting membrane potential

repolarization

support neurons in PNS ganglia

satellite cells

What are the two divisions of the autonomic nervous system?

sympathetic and parasympathetic

interstitial fluid-filled space separating two neurons

synaptic cleft

area where nerve impulses arise

trigger zone

Which of the following statements are true? 1. The frequency of impulses and number of activated sensory neurons encode differences in stimuli intensity. 2. Larger-diameter axons conduct nerve impulses faster than smaller-diameter ones. 3. Continuous conduction is faster than saltatory conduction. 4. The presence or absence of a myelin sheath is an important factor that determines the speed of nerve impulse propagation. 5. Action potentials are localized, but graded potentials are propagated.

1, 2, 4

What is a neuron's resting potential established and maintained by?

1. differences in both ion concentrations and electrical gradients 2. the fact that there are numerous large, nondiffusible anions in the cytosol and by the sodium-potassium pumps that help to maintain the proper distribution of sodium and potassium

T of F: Neurons in the PNS are always capable of repair while those in the CNS are not.

False

T or F: at a chemical synapse between two neurons, the neuron receiving the signal is called the presynaptic neuron and the neuron sending the signal is called the postsynaptic neuron.

False

rough ER in neurons; site of protein synthesis

Nissl bodies

provide myelin sheath for PNS axons

Schwann cells

help maintain an appropriate chemical environment for generation of action potentials by neurons; part of the blood-brain barrier

astrocytes

the process that propagates nerve impulses toward another neuron, muscle fiber, or gland cell

axon

area where the axon joins the cell body

axon hillock

the numerous fine processes at the ends of an axon and its collaterals

axon terminals

neurons with one main dendrite and one axon; found in the retina of the eye

bipolar neurons

part of the neuron that contains the nucleus and organelles

cell body

several neurons in the brain sending impulses to a single motor neuron that terminates at a neuromuscular junction is an example of a ______ circuit.

converging

polarization that is less negative than resting level

depolarizing graded potential

extensive neuronal networks that help regulate the digestive system

enteric plexuses

form CSF and assist in its circulation; form blood-cerebrospinal barrier

ependymal cells

a neurotransmitter-caused depolarization of the postsynaptic membrane

excitatory postsynaptic potential

a cluster of neuronal cell bodies located outside the brain and spinal cord

ganglion

a small deviation from the resting membrane potential that makes the membrane either more or less polarized

graded potential

contain neuronoal cell bodies, dendrites, axon terminals, unmyelinated axons, and neuroglia

gray matter

polarization that is more negative than the resting level

hyperpolarizing graded potential

a neurotransmitter-caused hyperpolarization of the postsynaptic membrane

inhibitory postsynaptic potential

first portion of the axon, closest to the axon hillock

initial segment

small phagocytic neuroglia

microglia

neurons having several dendrites and one axon; most common neuronal type

multipolar neurons

a multilayered lipid and protein covering for axons produced by neuroglia

myelin sheath

general term for any neuronal process

nerve fiber

bundles of axons and associated connective tissue and blood vessels in the PNS

nerves

the outer nucleated cytoplasmic layer of the Schwann cell

neurolemma

gaps in the myelin sheath of an axon

nodes of Ranvier

a cluster of cell bodies within the CNS

nucleus

period of time when a second action potential can be initiated with a very long stimulus

relative refractory period

What are the subdivisions of the PNS?

somatic, autonomic, enteric

results from the buildup of neurotransmitter released simultaneously by several presynaptic end bulbs

spatial summation

site of communication between two neurons or between a neuron and an effector cell

synapse

store neurotransmitter

synaptic vesicles

results from the buildup of neurotransmitter from the rapid, successive release by a single presynaptic end bulb

temporal summation

the minimum level of depolarization required for a nerve impulse to be generated

threshold

neurons with just one process extending from the cell body; are always sensory neurons

unipolar neurons

Which of the following statements are true? 1. If the excitatory effect is greater than the inhibitory effect but less than the threshold of stimulation, the result is a subthreshold EPSP 2. If the excitatory effect is greater than the inhibitory effect and reaches or surpasses the threshold level of stimulation, the result is a threshold or suprathreshold EPSP and one or more nerve impulses 3. If the inhibitory effect is greater than the excitatory effect, the membrane hyper polarizes, resulting in inhibition of the postsynaptic neuron and the inability of the neuron to generate a nerve impulse 4. The greater the summation of hyperpolarizations, the more likely a nerve impulse will be initiated.

1, 2, 3

Which of the following are true? 1. The sensory function of the nervous system involves sensory receptors sensing certain changes in the internal and external environments. 2. Sensory neurons receive electrical signals from sensory receptors. 3. The integrative function of the nervous system involves analyzing sensory information, storing some of it and making decisions regarding appropriate responses. 4. Interneurons are located primarily in the PNS. 5. Motor function involves the activation of effectors (muscles and glands).

1, 2, 3, 5

Which of the following statements are true? 1. The basic types of ion channels are gated, leakage and electrical. 2. Ion channels allow for the development of graded potentials and action potentials. 3. Voltage-gated channels open in response to changes in membrane potential. 4. Ligand-gated channels open due to the presence of specific channels. 5. A graded potential is useful for communication over long distances.

2, 3, 4

Neurotransmitters are removed from the synaptic cleft by: 1. axonal transport 2. diffusion away from the cleft 3. neurosecretory cells 4. enzymatic breakdown 5. cellular uptake

2, 4, 5

Place the following events in a chemical synapse in the correct order: 1. release of neurotransmitters into the synaptic cleft 2. arrival of nerve impulse at the presynaptic neuron's synaptic end bulb 3. either depolarization or hyper polarization of postsynaptic membrane 4. inward flow of Ca2+ through activated voltage-gated Ca2+ channels in the synaptic end bulb membrane 5. exocytosis of synaptic vesicles 6. opening of ligand-gated channels on the postsynaptic plasma membranes 7. binding of neurotransmitters to receptors in the postsynaptic neuron's plasma membrane

2, 4, 5, 1, 7, 6, 3

time during which a neuron cannot produce an action potential even with a very strong stimulus

absolute refractory period

a sequence of rapidly occurring events that decreases and eventually reverses the membrane potential and then restores it to the resting state; nerve impulse

action potential

hyperpolarization that occurs after the depolarizing phase of an action potential

after-hyperpolarizing phase