A&P Nervous Tissue Flashcards
The subdivisions of the PNS are the ___, ___ and ___.
Autonomic, somatic, enteric.
The two divisions of the autonomic nervous system are the ___ and the ___ division.
Sympathetic and parasympathetic.
T/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
T/F: Neurons in the PNS are always capable of repair while those in the CNS are not
False
Which of the following statements 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 and 5
A neuron’s resting membrane potential is established and maintained by
(1) a high concentration of K+ in the extracellular fluid and a high concentration of Na+ in the cytosol,
(2) the plasma membrane’s higher permeability to Na+ because of the presence of numerous Na+ leakage channels,
(3) differences in both ion concentrations and electrical gradients,
(4) the fact that there are numerous large, nondiffusible anions in the cytosol,
(5) sodium–potassium pumps that help to maintain the proper distribution of sodium and potassium.
3, 4, and 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 (or varicosity),
(3) either depolarization or hyperpolarization 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 membrane,
(7) binding of neurotransmitters to receptors in the postsynaptic neuron’s plasma membrane
2, 4, 5, 1, 7, 6, 3
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
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 hyperpolarizes, 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 and 3
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 chemicals.
(5) A graded potential is useful for communication over long distances.
2, 3 and 4
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 and 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.
1, 4 and 5
Neurons with just one process extending from the cell body; are always sensory neurons.
Unipolar neurons
Small phagocytic neuroglia
Microglia
Help maintain an appropriate chemical environment for generation of action potentials by neurons; part of the blood-brain barrier
Astrocytes
Provide myelin sheath for CNS
Oligodendrocytes
Contains neuronal cell bodies, dendrites, axon terminals, unmyelinated axons, and neuroglia
Gray matter
A cluster of cell bodies within the CNS
Nucleus
Form CSF and assist in its circulation; form blood-cerebrospinal barrier
Ependymal cells
Neurons having several dendrites and one axon; most common neuronal type
Multipolar neurons
neurons with one main dendrite and one axon; found in the retina of the eye
Bipolar neurons
provide myelin sheath for PNS axons
Schwann cells
support neurons in PNS ganglia
Satellite cells
a cluster of neuronal cell bodies located outside the brain and spinal cord
Ganglion
composed primarily of myelinated axons
White matter
bundles of axons and associated connective tissue and blood vessels in the PNS
Nerves
extensive neuronal networks that help regulate the digestive system
enteric plexuses
a sequence of rapidly occurring events that decreases and eventually reverses the membrane
potential and then restores it to the resting state; a nerve impulse
action potential
a small deviation from the resting membrane potential that makes the membrane either more
or less polarized
graded potential
period of time when a second action potential can be initiated with a very strong stimulus
relative refractory period
the minimum level of depolarization required for a nerve impulse to be generated
threshold
the recovery of the resting membrane potential
repolarization
a neurotransmitter-caused depolarization of the postsynaptic membrane
excitatory postsynaptic potential
a neurotransmitter-caused hyperpolarization of the postsynaptic membrane
inhibitory postsynaptic potential
time during which a neuron cannot produce an action potential even with a very strong stimulus
absolute refractory period
polarization that is less negative than the resting level
depolarizing graded potential
results from the buildup of neurotransmitter released simultaneously by several presynaptic
end bulbs
spatial summation
the hyperpolarization that occurs after the repolarizing phase of an action potential
after-hyperpolarizing phase
polarization that is more negative than the resting level
hyperpolarizing graded potential
results from the buildup of neurotransmitter from the rapid, successive release by a single
presynaptic end bulb
temporal summation
the part of the neuron that contains the nucleus and organelles
cell body
rough endoplasmic reticulum in neurons; site of protein synthesis
nissl bodies
store neurotransmitter
synaptic vesicles
the process that propagates nerve impulses toward another neuron, muscle fiber, or gland cell
axon
the highly branched receiving or input portions of a neuron
dendrites
a multilayered lipid and protein covering for axons produced by neuroglia
myelin sheath
the outer nucleated cytoplasmic layer of the Schwann cell
neurolemma
first portion of the axon, closest to the axon hillock
initial segment
site of communication between two neurons or between a neuron and an effector cell
synapse
form the cytoskeleton of a neuron
neurofibrils
gaps in the myelin sheath of an axon
nodes of Ranvier
general term for any neuronal process
nerve fiber
area where the axon joins the cell body
axon hillock
area where nerve impulses arise
trigger zone
the numerous fine processes at the ends of an axon and its collaterals
axon terminals
interstitial fluid-filled space separating two neurons
synaptic cleft
