Neuro Chapter 6
Studying Neurotransmitter Systems
Terms in this set (44)
Method for locating potential neurotransmitters
What is the general term given to the type of neurotransmitter receptor that conducts ions through a pore?
What is the general term given to the type of neurotransmitter receptor that does not directly conduct ions through a pore. This type of receptor is coupled to intracellular signalling mechanisms, usually through G-proteins.
True or False. Neurones only make one neurotransmitter.
This theory, called Dales principle, is largely discredited. Many neurones make one small molecule neurotransmitter and one peptide neurotransmitter.
However, in practical terms it is often useful to consider neurones as only making one neurotransmitter. For example, serotinergic neurones make serotonin.
Main excitatory neurotransmitter
The neurotransmitter whose abundance is increased by fluoxetine
(Select all that apply)
-Clear "excess" neurotransmitter from the synaptic cleft
-Are also used to pack neurotransmitter into synaptic vesicles
-Are a site of action for many clinically important drugs
Which of the following statements can be applied to "excitatory" neurotransmitters?
Increase the likelihood that an action potential will be fired
The only thing that defines a neurotransmitter as excitatory is if its actions result in an increased likelihood of neurotransmitter firing. Glutamate is the archetypal excitatory neurotransmitter, tho many others can be.
Within the CNS, is made principally by the raphe nuclei.
Major anatomical site(s) which give(s) rise to dopaminergic projections
Ventral Tegmental Area
Receptors whose function is potentiated by benzodiazepines such as lorazepam
Neurotransmitter whose receptors are blocked by the antipsychotic haloperidol
Neurotransmitter whose receptors are stimulated by the Parkinsons disease treatment Ropinirole
Inhibitory neurotransmitter of the spinal cord that appears to have only ionotropic (no metabotropic) receptors
Neuropeptide whose actions are mimicked by morphine
Is/are broken down by Monoamine Oxidase A
Neurotransmitter whose actions at ionotropic receptors will result in an EPSP
EPSP stands for Excitatory Postsynaptic Potential. This term refers to the local depolarization that occurs when glutamate binds to ligand-gated sodium channels. If enough EPSPs are generated in a sufficient timeframe, an action potential will fire
What is the interval called during which a neuron is dormant after an action potential has been completed?
Absolute refractory period
Why does the resting potential occur?
The inside of a neuron has a higher concentration of negative ions than the outside
Which of the following is a function of the myelin sheath?
Increases the speed at which nerve impulses travel along an axon
The sensations we experience when we think we'll hit another car on the freeway are due to activation of which system?
Central Nervous System
Which type of sensory information does not pass through the thalamus?
In which lobe of the brain is Wernicke's area, the part of the brain involved in understanding language?
The left temporal lobe
Glial cells, which make up the support structure of the nervous system, perform four functions:
Provide structural support to the neurons
Remove waste products
Cell body: the central area of the neuron. It contains the nucleus and other structures common to all cells in the body, such as mitochondria.
The highly branched fibers that reach out from the neuron are called dendritic trees. Each branch is called a dendrite. Dendrites receive information from other neurons or from sense organs.
The single long fiber that extends from the neuron is called an axon. Axons send information to other neurons, to muscle cells, or to gland cells. What we call nerves are bundles of axons coming from many neurons.
Some of these axons have a coating called the myelin sheath. Glial cells produce myelin, which is a fatty substance that protects the nerves. When an axon has a myelin sheath, nerve impulses travel faster down the axon. Nerve transmission can be impaired when myelin sheaths disintegrate
At the end of each axon lie bumps called terminal buttons. Terminal buttons release neurotransmitters, which are chemicals that can cross over to neighboring neurons and activate them. The junction between an axon of one neuron and the cell body or dendrite of a neighboring neuron is called a synapse.
An inactive neuron is in the resting state. In the resting state, the inside of a neuron has a slightly higher concentration of negatively charged ions than the outside does
This situation creates a slight negative charge inside the neuron, which acts as a store of potential energy called the resting potential. The resting potential of a neuron is about -70 millivolts.
When something stimulates a neuron, gates, or channels, in the cell membrane open up, letting in positively charged sodium ions. For a limited time, there are more positively charged ions inside than in the resting state. This creates an action potential, which is a short-lived change in electric charge inside the neuron.
Absolute refractory period
Channels in the membrane close, and no more sodium ions can enter. After they open and close, the channels remain closed for a while. During the period when the channels remain closed, the neuron can't send impulses. This short period of time is called the absolute refractory period, and it lasts about 1-2 milliseconds. The absolute refractory period is the period during which a neuron lies dormant after an action potential has been completed.
All or none law
Neural impulses conform to the all-or-none law, which means that a neuron either fires and generates an action potential, or it doesn't. Neural impulses are always the same strength—weak stimuli don't produce weak impulses. If stimulation reaches a certain threshold, or minimum level, the neuron fires and sends an impulse. If stimulation doesn't reach that threshold, the neuron simply doesn't fire. Stronger stimuli do not send stronger impulses, but they do send impulses at a faster rate.
Neural impulses are always the same strength. Stronger stimuli do not send stronger impulses, but they do send impulses at a faster rate.
The gap between two cells at a synapse is called the synaptic cleft. The signal-sending cell is called the presynaptic neuron, and the signal-receiving cell is called the postsynaptic neuron.
Neurotransmitters are the chemicals that allow neurons to communicate with each other.
Neurotransmitters are kept in synaptic vesicles, which are small sacs inside the terminal buttons. When an action potential reaches the terminal buttons, which are at the ends of axons, neurotransmitter-filled synaptic vesicles fuse with the presynaptic cell membrane. As a result, neurotransmitter molecules pour into the synaptic cleft. When they reach the postsynaptic cell, neurotransmitter molecules attach to matching receptor sites. Neurotransmitters work in much the same way as keys. They attach only to specific receptors, just as certain keys fit only certain locks.
Post synaptic potential
When a neurotransmitter molecule links up with a receptor molecule, there's a voltage change, called a postsynaptic potential (PSP), at the receptor site.
PSP: EPSP or IPSP
Receptor sites on the postsynaptic cell can be excitatory or inhibitory
The binding of a neurotransmitter to an excitatory receptor site results in a positive change in voltage, called an excitatory postsynaptic potential or excitatory PSP. This increases the chances that an action potential will be generated in the postsynaptic cell.
Conversely, the binding of a neurotransmitter to an inhibitory receptor site results in an inhibitory PSP, or a negative change in voltage. In this case, it's less likely that an action potential will be generated in the postsynaptic cell.
Action in PSP
Unlike an action potential, a PSP doesn't conform to the all-or-none law. At any one time, a single neuron can receive a huge number of excitatory PSPs and inhibitory PSPs because its dendrites are influenced by axons from many other neurons. Whether or not an action potential is generated in the neuron depends on the balance of excitation and inhibition. If, on balance, the voltage changes enough to reach the threshold level, the neuron will fire.
Neurotransmitter molecules soon detach from receptors and are usually returned to the presynaptic cell for reuse in a process called reuptake.