6.8 - 6.13 Flashcards
The membrane potential of a postsynaptic neuron is ___ at an excitatory synapse, and it is ___ at an inhibitory synapse.
depolarized; hyperpolarized or stabilized
Synapses that consist of gap junctions which allow the local currents from action potentials in one neuron to flow directly across the junction to another neuron are called ___ synapses.
electrical
Chemical synapses ___.
- have a synaptic cleft between pre- and postsynaptic cells
- may contain more than one transmitter at a time
- use neurotransmitters released by the presynaptic cell to transmit signals to the postsynaptic cell
Identify the correct sequence of information in a chemical synapse.
Presynaptic terminal, synaptic cleft, postsynaptic membrane
Postsynaptic cell neurotransmitter receptors can be divided into two types: ___, which contain an ion channel in the structure, or ___, which are linked with second-messenger systems and indirectly alter ion channels
ionotropic; metabotropic
At an ___, the membrane potential of a postsynaptic neuron is brought closer to threshold (depolarized).
excitatory synapse
Electrical synapses ___.
- transmit signals faster than chemical synapses
- conduct an action potential directly between cells via connecting gap junctions
A synapse that transmits information via the release of neurotransmitters into the synaptic cleft between cells is termed a(n) ___ synapse.
chemical
Place the events of a chemical synapse in chronological order, starting with the first at the top.
- an action potential reches the presynaptic terminal
- voltage-gated Ca2+ channels open
- Ca+ diffuses into the presynaptic terminal
- NTs are released into the synaptic cleft
- NTs bind to receptors on the postsynaptic membrane
- NTs are removed from the synaptic cleft
Neurotransmitter receptors that act indirectly on separate ion channels through a G protein and/or a second messenger are referred to as ___.
metabotropic receptors
The membrane potential of a postsynaptic neuron is either driven farther from threshold (hyperpolarized) or stabilized at its resting potential at a(n) ___ synapse.
inhibitory
Recognize a figure of an electrical synapse
x
Removal of neurotransmitters from synapses occurs by which of the following mechanisms?
- Active transport into nearby cells, such as glial cells
- Active transport back into the presynaptic terminal
- Enzymatic transformation into inactive substances
- Diffusion away from the synapse
T/F: Whether a synapse is excitatory or inhibitory is determined by what neurotransmitter is released from the presynaptic cell.
F (determined by the type of postsynaptic ion channel)
An IPSP is ___.
a graded potential in a postsynaptic cell that decreases the likelihood that the cell will reach the threshold for an action potential
T/F: Many EPSPs occurring in a short period of time are generally required to initiate an action potential in a postsynaptic neuron.
T
Excess neurotransmitters are removed from the synaptic cleft in several ways. For example, they can be actively transported back into the presynaptic axon terminal for reuse, via a process called ___. Alternatively, they can be removed into nearby ___ cells where they are degraded. They could also ___ away from the receptor site.
reuptake
glia
diffuse
A synapse could be excitatory or inhibitory depending on ___.
the type of postsynaptic ion channel influenced by the signal transduction mechanism
At some chemical synapses, the potential change in the postsynaptic neuron is either a hyperpolarization or a stabilization of the membrane potential. This type of response is known as ___ ___ ___ (IPSP).
inhibitory postsynaptic potential
When neurotransmitters such as GABA or ACh are released from neuron A and bind to receptors embedded in the membrane of the axon terminal of neuron B, causing a decrease in the amount of an excitatory neurotransmitter released by neuron B, it is called ___.
presynaptic inhibition
Receptors found in postsynaptic densities of synapses that both bind to neurotransmitters and act as ion channels are known as ___.
ionotropic receptors
A depolarization of the membrane toward threshold occurs when ___ synaptic input predominates, and either hyperpolarization or stabilization occurs when ___ input predominates.
excitatory; inhibitory
What term describes the situation in which a receptor at first responds to a neurotransmitter, but over time becomes non-responsive despite the continued presence of the neurotransmitter signal?
Receptor desensitization
Neurotransmitters do not stay bound to receptors indefinitely; instead, they ___.
- are broken down into component parts by enzymes
- diffuse away from the synapse
- are transported back into the presynaptic cell via reuptake
T/F: Whether a synapse is excitatory or inhibitory is determined by what neurotransmitter is released from the presynaptic cell.
F
A drug that is classified as an agonist ___.
binds to a receptor and produces a response similar to what occurs when the normal ligand binds
If neurotransmitter release from neuron A increases the amount of Ca2+ that enters neuron B during an action potential, ___ of the synapse between neuron B and C will occur.
presynaptic facilitation (makes it more likely that NT will be released)
A substance released by cells that alters the effectiveness of a synapse indirectly by acting at non-synaptic locations, for example by altering the presynaptic cell’s release of neurotransmitter or the postsynaptic cell’s response to the neurotransmitter, is called a(n) ___.
neuromodulator
When a receptor responds normally when first exposed to a neurotransmitter but then eventually fails to respond despite the continued presence of the neurotransmitter, this is known as ___ ___.
receptor desitization
Acetylcholine (ACh) is ___.
- a neurotransmitter
- released by neurons within the brain
- released onto skeletal muscle cells by motor neurons
Norepinephrine is ___.
a catecholamine neurotransmitter involved in sympathetic regulation of smooth and cardiac muscle
An antagonist is a ligand that ___.
inhibits the activity of receptor proteins
The most common excitatory amino acid neurotransmitter in the central nervous system is ___.
glutamate/glutamic acid
In general, neurotransmitters cause EPSPs and IPSPs. However, more complex metabolic effects in a postsynaptic cell are mediated by molecules called ___, usually via second messengers.
neuromodulators
The main neurotransmitter released onto skeletal muscle cells by motor neurons is called ___.
Acetylcholine (ACh, acetylcholine)
Which three are TRUE about dopamine?
- It is a monoamine.
- It is a catecholamine.
- It is a neurotransmitter.
Ligands that bind to and activate receptor proteins are called ___.
antagonist
The primary neurotransmitter at an estimated 50% of excitatory synapses in the CNS is ___.
glutamate
Which best describes a neuromodulator?
A compound that indirectly alters the effectiveness of a synapse by altering release of, or responsiveness to, a neurotransmitter.
Drugs that bind to and reduce the activity of receptor proteins are called ___.
antagonist
Which of the following are classified as endogenous opioids?
- Enkephalins
- Beta-endorphin
- Dynorphins
Which of the following are receptors for the neurotransmitter glutamate?
- Alpha-amino-3 hydroxy-5 methyl-4 isoxazolepropionic acid (AMPA)
- N-methyl-D-aspartate (NMDA)
What gaseous neurotransmitter is produced from L-arginine by nitric oxide synthetase?
NO
Which of the following are purines that are co-released from neurons and act as neuromodulators?
- ATP
- adenosine
Which of the following may be attributed to the effects of endogenous opioids?
- eating and drinking
- pain relief
Which of the following statements about nitric oxide (NO) are true?
- Mediates penile erection
- Causes an increase in the concentration of cyclic GMP in target cells
- Acts as a neurotransmitter
The major neurotransmitter in the peripheral nervous system at the neuromuscular junction is ___.
acetylcholine
ATP and adenosine are ___ that act mainly as ___.
purines; neuromodulators
Which of the following are classified as neuropeptide neurotransmitters/neuromodulators?
- Dynorphin
- Beta-endorphin
- Enkephalin
Which of the options are correctly identified as lipid neurotransmitters?
- Endocannabinoids
- Thromboxanes
- Leukotrienes
- Prostaglandins
At neuroeffector junctions, the receptors on the effector cell ___.
may be either ionotropic or metabotropic
Identify the true statements relating to endocannabinoids.
- Include 2-arachidonoylglycerol
- Generated in response to Ca2+ entry into some postsynaptic cells
- Receptors found in widespread locations throughout the CNS and PNS
Which is true about signaling by nitric oxide (NO)?
It diffuses into target cells and activates guanylyl cyclase.
What are the three cell types with which efferent neurons most commonly form synapses?
- muscle
- neurons
- gland
The ___ receptors are the targets of tetrahydrocannabinol (THC).
cannabinoid
T/F: The most common neurotransmitters for neuroeffector communication are acetylcholine and dopamine.
F (most common NTs for neuroeffector communication are dopamine and norepinephrine)
