Chapter 2: Structure and Function of the Nervous System and Chapter 3: Chemical Signaling by Neurotransmitters and Hormones
_________ modulators are molecules that either increase or decrease receptor activity by binding to sites on the receptor protein separate from the agonist binding site.
Allosteric
_______ regulate the extracellular environment of the neurons, regulate CNS blood flow, and provide physical support and nutritional assistance.
Astrocytes
Synapses may occur on the dendrite (________), cell body (______), or axon (______) of the postsynaptic cell
Axodendritic, axosomatic, axoaxonic
At the peak of the action potential (+40 mV), voltage-gated Na+ channels close and cannot be opened until they reset at the resting potential, so no action potential can occur during this time (the ________).
absolute refractory period
The summation of all EPSPs and IPSPs occurring at any single moment in time occurs at the ______. If the threshold (-50 mV) is reached, voltage-gated Na+ channels open, allowing large amounts of Na+ to enter the cell to produce the massive depolarization known as the _________
axon hillock, action potential.
Neurons are surrounded by a _____ and are filled with cytoplasm and the organelles needed for optimal functioning.
cell membrane
Thousands of receptors that respond to neurotransmitters released by other neurons are found on the ______, ______, and ______ of the cell.
dendrites, dendritic spines, and soma
Future drug development will target ________ to treat psychiatric disorders that have genetic components by turning on protective genes or turning off genes associated with symptom development.
epigenetic factors
Neurotransmitters are released from nerve terminals by a Ca2+-dependent process called _______.
exocytosis
The _____ of the spinal cord constitutes cell bodies that receive sensory information and cell bodies of motor neurons that serve muscles. The ______ consists of tracts of myelinated axons that carry signals in the ascending direction, to the brain, and the descending direction, for cortical control of the spinal cord.
gray matter, white matter
Neurotransmitter receptors fall into two categories: ___________
ionotropic and metabotropic.
The cell membrane is a phospholipid bilayer that prevents most materials from passing through, unless the material is ______. Special transporters carry other essential materials, such as glucose, amino acids, and neurotransmitters into the cell. Ion channels allow ions such as ________ to move across the membrane. Other proteins associated with the membrane include receptors and enzymes.
lipid soluble Na+, K+, Cl-, Ca2+
Among the most important organelles are the ______, which provide energy for the metabolic work of the cell.
mitochondria
Most neurotransmitters make use of ____ receptor subtypes.
multiple
Oligodendroglia: -Form myelin sheath on ______ in the ________ -Inhibit regrowth of axons following neuron damage
multiple axons, CNS
Conduction of the action potential along the axon is enhanced by the insulating property of the _____ created by nearby glial cells.
myelin
At rest, neurons have an electrical charge across the membrane of -70 mV (resting potential), with the inside being more _____ than the outside.
negative
Classical neurotransmitters (amino acids, monoamines, and acetylcholine) are mainly synthesized in the ______ and then are transported into synaptic vesicles; neuropeptides are synthesized and are packaged into vesicles in the _______.
nerve terminal, cell body
In myelinated axons, regeneration of the action potential occurs only at the ________, producing a rapid, saltatory conduction that is more energy efficient because the Na+ - K+ pump needs to exchange ions only at the nodes.
nodes of Ranvier
Changes in synaptic activity increase or decrease the production of particular proteins by activating transcription factors in the ______.
nucleus
The action potential moves down the length of the axon by sequential _______ of voltage-gated Na+ channels.
opening
As the cell becomes more positive inside, voltage-gated K+ channels open and K+ exits from the cell, bringing the membrane potential back toward resting levels. The _______ by K+ causes the cell to be more polarized than normal, so it is more difficult to reach the threshold to generate another action potential (_______).
overshoot, relative refractory period
Microglia: -Perform _________ -Provide ________ function
phagocytosis, immune system
Second messengers work by activating protein kinases that _______ target proteins in the postsynaptic cell.
phosphorylate
Neurotransmitter receptors serve the purpose of signaling information from the _______. Unlike transporters, they do not carry neurotransmitter molecules across the cell membrane.
presynaptic to the postsynaptic cell
Schwann cells: -Form myelin sheath on a ______ in the ______ -Release growth factors following neuron damage -Provide a channel to guide axons to targets
single axon, PNS
Metabotropic receptors are coupled to G proteins in the cell membrane and mediate ______ transmission involving ion channel opening (e.g., inhibitory K+ channels) or second-messenger synthesis or breakdown.
slower
The nucleus of the cell is located within the _____, and protein synthesis occurs there. Transcription of the genetic code for a specific protein by mRNA occurs within the nucleus, and translation of the "recipe," carried by the mRNA, occurs on the ribosomes in the cytoplasm. Ribosomes link together appropriate amino acids to create the protein.
soma
nLocal potentials are small, short-lived changes in membrane potential found largely on the _______ after the opening of ligand-gated channels.
soma and dendrites
The principal external features of a neuron are the _____, treelike_______, and a single _____ extending from the soma that carries the electrical signal all the way to the axon terminals.
soma, dendrites, axon
Newly manufactured proteins are packaged into vesicles in the _______ and are moved by motor proteins that slide along the neuron's microtubules (part of the cytoskeleton) to the _________ (anterograde transport). Protein waste and cell debris are transported from the terminals back to the soma (retrograde transport) for recycling.
soma, terminals
The PNS is divided into the ______, which includes spinal nerves that transmit sensory and motor information for skeletal muscles, and the ________, which serves smooth muscles, glands, and visceral organs.
somatic nervous system, autonomic nervous system
nThe CNS can be divided into six regions contain- ing multiple nuclei and their associated axons, which form interconnecting neural circuits:
spinal cord, myelencephalon, metencephalon, mesen- cephalon, diencephalon, and telencephalon.
Astrocytes: -Provide ______ support -_______ ionic and chemical environment -_______ nutrients to provide energy for neurons -Perform gliosis -Regulate CNS blood flow -Coordinate reciprocal glia-neuron activity
structural, maintain, store
The axon hillock is located at the juncture of soma and axon and is responsible for ______ (or integration) of the multiple signals required to generate an action potential.
summation
The dendrites of a neuron are covered with minute spines that increase the receiving _____ of the cell. These spines are reduced in size in individuals with intellectual impairment and reduced in number in those with schizophrenia.
surface area
The autonomic nervous system has two divisions: the _____, which serves to mobilize energy for times of "fight-or-flight"; and the ______, which reduces energy usage and stores reserves.
sympathetic, parasympathetic
Axon terminals contain synaptic vesicles filled with neurotransmitter molecules that are released into the _____ between cells when the action potential arrives.
synapse
The Na+ - K+ pump also helps to maintain the negative membrane potential by exchanging ______ Na+ ions (moved out of the cell) for _____ K+ ions (taken in).
three, two
Excitatory postsynaptic potentials (EPSPs), or depolarizations, occur when ligand-gated Na+ channels open and allow Na+ to enter cell on its concentration gradient, making the cell slightly more positive and bringing the membrane potential closer to the _______ for firing. Opening Cl- channels allows Cl- to enter on its concentration gradient, making the cell more negative and farther from the threshold, causing _______ called inhibitory postsynaptic potentials (IPSPs). When ligand-gated K+ channels open, K+ exits on its concentration gradient, leaving the cell more negative inside and farther from the threshold producing an IPSP.
threshold, hyperpolarizations
Neurons commonly synthesize and release _____ or more neurotransmitters, often from different categories
two
Depending on the neurotransmitter, termination of transmitter action is accomplished by the processes of _______ (including reuptake by the pre-synaptic cell) and/or _______.
uptake, enzymatic breakdown
_____ act as phagocytes to remove cellular debris and provide immune function.
Microglia
Neurotrophic factors like _______ work by activating tyrosine kinase receptors.
NGF and BDNF
_____ are neuronal growth factors that guide the development of neurons, regulate dendritic growth and retraction, and aid in survival of neurons.
Neurotrophic factors
Four types of glial cells are found in the nervous system. _______ produce the myelin sheath on peripheral and central nervous system neurons, respectively.
Schwann cells and oligodendroglia
The resting potential results from the balance between two competing forces on K+ ions. _______ pressure moves K+ inward because it is attracted by negatively charged molecules trapped inside the cell. The ______ for K+ pushes ions out of the cell in an effort to distribute them evenly.
Electrostatic, concentration gradient
_________ is the study of how environmental demands such as diet, environmental toxins, stress, prenatal nutrition, and many others turn on or turn off the expression of specific genes. Although _______ markers do not modify DNA, they can last a lifetime and may be transmitted to future generations. Two common markers are DNA methylation and chromatin remodeling.
Epigenetics
