Chapter 7 TF
Myelin sheaths around the high number of axons in the CNS give this tissue a white color; so is called the white matter of the brain and spinal cord. a. true b. false
a. true
Of the catecholamines, dopamine acts only as a neurotransmitter molecule and not as a hormone. a. true b. false
a. true
Orthograde (forward flow) and retrograde (reverse flow) transport in neurons is characteristic of the more rapid form of molecular movement in the neuron called axonal transport. a. true b. false
a. true
Saltatory conduction of action potentials is made possible by the interruptions in the myelin sheath along axons, known as nodes of Ranvier. a. true b. false
a. true
Gaps of exposed axon between the adjacent Schwann cells for the purpose of producing nerve impulses are called nodes of Ranvier. a. true b. false
a. true
Instead of opening ionic channels directly in the postsynaptic membrane, monoamine neurotransmitters act through a second messenger molecule, such as cyclic adenosine monophosphate. a. true b. false
a. true
Interestingly, many polypeptides that function as hormones secreted by the small intestine and other endocrine glands, can also be made and serve as neurotransmitters in the brain. a. true b. false
a. true
A mixed nerve contains both sensory and motor fibers. a. true b. false
a. true
The amplitude (height) of an action potential is always the same, resulting in the "all-or-none" law of action potentials. a. true b. false
a. true
The bond between the ligand, actylcholine and its receptor protein is relatively weak bond. a. true b. false
a. true
The nervous system is composed of two principal types of cells—neurons and neuroglia. a. true b. false
a. true
The term "terminal boutons" refers to the swollen ending of the presynaptic axon terminal. a. true b. false
a. true
The tight junctions located between adjacent endothelial cells in brain capillaries that form the blood-brain barrier presents an obstacle to the use of polar drugs in the treatment of many brain diseases, such as Parkinson's disease. a. true b. false
a. true
Acetylcholine, discovered by Otto Loewi, was one of the first neurotransmitter chemicals identified and is released from nerve endings to decrease heart rate. a. true b. false
b. false
When the inside of the cell becomes more negative due to the inward flow of negative charges, the membrane will be depolarized. a. true b. false
b. false Feedback: Hyperpolarization occurs when the membrane potential becomes more negative.
A low-intensity stimulus to a collection of axons (or a nerve) will only activate those few fibers in the group with lower thresholds, whereas a high-intensity stimulus can activate many more fibers including those with higher thresholds. a. true b. false
a. true
A neuron poisoned with cyanide so that no ATP can be made will still produce action potentials for a period of time since active transport of ions is not directly involved in impulse conduction. a. true b. false
a. true
A neuron-to-muscle synapse can also be called a myoneural and neuromuscular junction. a. true b. false
a. true
Action potentials conducted along thicker, unmyelinated fibers are conducted faster than those along thin, unmyelinated fibers. a. true b. false
a. true
Although all cells have a membrane potential, only muscle fibers, neurons, and a few other cell types are able to alter their membrane potential in response to stimulation. a. true b. false
a. true
As a neurotransmitter, norepinephrine binds to a G-coupled receptor. a. true b. false
a. true
As opposed to thin, unmyelinated nerve fibers, thick myelinated fibers would be expected to mediate (to come in the middle of or to control) rapid responses of skeletal muscles. a. true b. false
a. true
Association neurons (interneurons) are located entirely within the central nervous system. a. true b. false
a. true
Astrocytes have been shown to be important in the formation of synapses in the developing nervous system. a. true b. false
a. true
At autonomic nerve endings, the effects of acetylcholine can be either excitatory or inhibitory, depending on the subtype of acetylcholine receptors present in that organ. a. true b. false
a. true
Bacterial infection of the brain would stimulate the actions of the microglial cells. a. true b. false
a. true
Chemically-regulated channels are found in the postsynaptic membrane and open in response to binding of neurotransmitter molecules (ligands) to their postsynaptic receptor proteins. a. true b. false
a. true
Depolarization of the postsynaptic membrane by specific neurotransmitter chemicals (ligands) results in an EPSP, whereas hyperpolarization of the postsynaptic membrane results in an IPSP. a. true b. false
a. true
Drugs that inhibit the action of the enzymes that breakdown catecholamines, ultimately end up promoting the effects of monoamine neurotransmitter action on the postsynaptic membrane. a. true b. false
a. true
During neuron stimulation, a fraction of a second after the Na+ gates open, they close again. Meanwhile, the resulting depolarization causes the K+ gates to open, allowing the efflux (outward flow) of K+. a. true b. false
a. true
Every patch of membrane in an unmyelinated axon contains Na+ and K+ gates that must regenerate or remake a separate, completely new action potential that will move along the axon, usually in a direction away from the cell body. a. true b. false
a. true
Exposure to nerve gas would lead to spastic paralysis. a. true b. false
a. true
Gap junctions are characteristic features of smooth and cardiac muscle cells (fibers), brain neurons, and even many embryonic tissues. a. true b. false
a. true
Schizophrenia may be caused, in part, by the mesolimbic dopaminergic pathways in the brain secreting too much dopamine or by the presence of increased numbers of D2 dopamine receptors in the forebrain. a. true b. false
a. true
Somatic motor neurons are responsible for both reflex and voluntary control of skeletal muscle. a. true b. false
a. true
Somatic motor neurons only make synapses with skeletal muscle fibers, resulting in postsynaptic depolarizations called end plate potentials. a. true b. false
a. true
Some antidepressant drugs act to block the reuptake of serotonin. a. true b. false
a. true
The absolute refractory period occurs before the relative refractory period. a. true b. false
a. true
Unlike a Schwann cell, which forms a myelin sheath around only one axon, each oligodendrocyte has extensions like the tentacles of an octopus. a. true b. false
a. true
Unlike action potentials, excitatory postsynaptic potentials (EPSPs) have no threshold potential, can be summed, and have no refractory period. a. true b. false
a. true
When neurotransmitters bind to the appropriate receptor on the postsynaptic cell the direct response is not an action potential, but rather ae graded potentials such as an EPSP or an IPSP. a. true b. false
a. true
Animals poisoned with strychnine die from asphyxiation because their glycine receptor proteins are specifically blocked and they are unable to relax the diaphragm muscle (spastic paralysis). a. true b. false
a. true Feedback: A variety of poisons cause paralysis, strychnine is one that produces spastic paralysis.
After birth, the neurons do not undergo further division by mitosis, although some neurons can regenerate severed portions or sprout new branches under some conditions. a. true b. false
a. true Feedback: After birth most nerve cells are incapable of dividing.
A negative feedback loop is created as the rate of Na+ entry increases as the rate of membrane depolarization increases in an explosive fashion. a. true b. false
b. false
All synaptic transmission is electrical rather than chemical. a. true b. false
b. false
During depolarization, that potential at which the Na+ gates open causing a sudden and very rapid change in the membrane potential as Na+ ions diffuse down their concentration gradient, is known as the threshold potential. a. true b. false
b. false
Spaces (pores) are found between the endothelial cells lining the capillary wall in the brain. These pores help form the blood-brain barrier. a. true b. false
b. false
The Nissl bodies of the cell body contain densely staining areas of active mitochondria. a. true b. false
b. false
The action potential generated at the end of the axon looks different from that formed at the beginning of the axon. a. true b. false
b. false
The central nervous system (CNS) includes the brain and the cranial nerves. a. true b. false
b. false
The greater the strength of the stimulus the greater the amplitude of action potentials; therefore the code for stimulus strength is amplitude modulated (AM), not frequency modulated (FM). a. true b. false
b. false
The high-speed conduction of neural impulses is made possible due to the cable properties of the axon. a. true b. false
b. false
The return of the membrane potential toward the resting potential is called hyperpolarization. a. true b. false
b. false
The term cable properties of neurons refers to the ability of a neuron to transmit charges through its cytoplasm; a property that is quite poor due to the cell's high internal resistance. a. true b. false
b. false
Acetylcholine is transported into the postsynaptic cell cytoplasm, where it produces its effects, such as opening ion channels. a. true b. false
b. false Feedback: Acetylcholine binds to a receptor on the surface of the postsynaptic cell.
Acetylcholinesterase is an enzyme found in the presynaptic cell that degrades acetylcholine. a. true b. false
b. false Feedback: Acetylcholinesterase degrades acetylcholine but is found on or near the postsynaptic cell.
Compared to metal wires, the axon is a very poor electrical conductor. a. true b. false
b. false Feedback: Axons are poor conductors because of the loss of charge due to the cable properties of the neuron.
Curare, a drug first used on poison darts by South American Indians, interrupts neuromuscular transmission at the synapse and thereby results in a spastic (causes muscles to spasm, or tighten) form of paralysis. a. true b. false
b. false Feedback: Curare is a competitive inhibitor of acetylcholine and will produce flaccid paralysis and stimulate muscle relaxation.
The two major subtypes of acetylcholine receptors are nicotinic and muscarinic, named after the particular toxin that bind and interact with each subtype of receptor. a. true b. false
b. false Feedback: Each of these two receptor subtypes is different and binds different toxins, which allows for the identification of the cholinergic receptor subtypes.
Epinephrine is also known as adrenalin, a hormone secreted by the adrenal cortex. a. true b. false
b. false Feedback: Epinephrine is secreted from the adrenal medulla.
GABA (gamma-amino butyric acid) and glycine are excitatory neurotransmitters in the central nervous system, depolarizing the postsynaptic membrane and forming EPSPs. a. true b. false
b. false Feedback: GABA and glycine are both inhibitory neurotransmitters.
Certain amino acids (such as glycine) act as excitatory neurotransmitters in the CNS by forming EPSPs, while others (such as glutamic acid) inhibit CNS neurons by producing IPSPs. a. true b. false
b. false Feedback: Glycine acts as an inhibitory neurotransmitter and glutamate act as an excitatory neurotransmitter.
Most inhibitory neurotransmitters act to hyperpolarize the postsynaptic membranes of their target cells, producing inhibitory postsynaptic potentials (IPSPs). a. true b. false
b. false Feedback: Hyperpolarization would take the cell further away from threshold making it more difficult to depolarize the cell.
Each Schwann cell can myelinate axons from many neurons. a. true b. false
b. false Feedback: Only oligodendrocytes can myelinate multiple axons.
Parasympathetic neurons of the peripheral nervous system use norepinephrine as the neurotransmitter at their synapses with smooth muscles, cardiac muscle, and glands. a. true b. false
b. false Feedback: Sympathetic neurons release norepinephrine and parasympathetic neurons release acetylcholine.
The longer process of a neuron that conducts impulses away from the cell body is called a dendrite. a. true b. false
b. false Feedback: The axon is the long process that conducts impulses away from the soma.