The Nervous system cells, synapses, and drugs - Exam 3 Flashcards
Who discovered the synapse? How?
Charles Scott Sherrington discovered the synapse by pinching puppies paws and timing how quickly they reacted
Define synaptic transmission
The process of neurotransmitters being sent from one neuron to another
What types of synapses are primarily associated with synaptic transmission?
Axon-dendrite synapses
Where are neurotransmitters released?
From the presynaptic membrane of the sending neuron
What surrounds the sending neuron?
The presynaptic membrane
Where are neurotransmitters received?
On the postsynaptic membrane of the dendrite of the receiving neuron
What surrounds the receiving neuron?
The postsynaptic membrane
How are the neurotransmitters stored and protected?
The neurotransmitters themselves are inside synaptic vesicles, and the vesicles are kept in storage granules
What makes and stores neurotransmitters?
The presynaptic neuron
The place where synaptic vesicles release the neurotransmitters is called what?
The release zone
Where is the release zone?
The region in the terminal button of the sending neuron where synaptic vesicles attach to the presynaptic membrane and release their neurotransmitter into the synaptic cleft
The last step of synaptic transmission is what?
For the neurotransmitter to travel across the synaptic cleft to attach to a postsynaptic receptor on the membrane of a dendrite of the receiving neuron
Neurons with more dendritic spines have more what?
More postsynaptic receptors
The structure that holds individual molecules of neurotransmitter is called _____
synaptic vesicles
The structure that surrounds the dendrite and keeps the inside separate from the outside is called ____
postsynaptic membrane
The structure that surrounds the terminal button and keeps the inside separate from the outside is called ____
presynaptic membrane
What is the structure that holds collections of neurotransmitters?
Storage granules
What are the two ways messages are sent between cells?
Electrically and chemically
When are messages sent electrically?
When messages are sent within the cell (down the axon)
When are messages sent chemically?
When messages are sent between cells (across the synapse)
Action potentials are triggered by what?
The axon hillock
What are the four steps of the release zone of the synapse?
Synthesis/storage, release, activation, and inactivation:
1) The neurotransmitter itself must be created and stored at the end of the axon
2) The neurotransmitter must be transported to the presynaptic membrane and released in response to an action potential
3) The neurotransmitter must be able to activate the receptors on the receiving cell’s postsynaptic membrane
4) The receptor lets go of the neurotransmitter, which has to go somewhere. It must be removed or inactivated from the synapse so that the process can be terminated.
If a neurotransmitter is a large molecule, where is it made and stored in the presynaptic neuron?
(step 1 of the release zone)
The neurotransmitter is synthesized in the cell body (soma) and then transported down the axon when it is needed
If a neurotransmitter is a small molecule, where is it made and stored in the presynaptic neuron?
(step 1 of the release zone)
The chemical is stored at all times in the terminal buttons (sometimes it’s even synthesized there)
How do neurotransmitters enter the synaptic cleft?
(step 2 of the release zone)
When an action potential reaches the terminal button, it triggers the opening of gates for calcium ions (Ca2+) and Ca2+ ions enter the neuron. The Ca2+ ions connect to the synaptic vesicles that contain the neurotransmitter.
Ca2+ ions then usher the vesicles to the presynaptic membrane, the vesicles fuse with the membrane, and then the vesicles open up and dump their contents into the synaptic gap (exocytosis). This is only possible because the electricity from the action potentials causes calcium to enter the neuron.
What are postsynaptic receptors?
step 3 of the release zone
They’re uniquely shaped proteins that neurotransmitters attach to in order to achieve message transmission
What are the two classifications of receptors?
step 3 of the release zone
Receptors are classified as either ionotropic or metabotropic based on how they become activated by a neurotransmitter
How do neurotransmitters become removed or inactivated from the synapse?
(step 4 of the release zone)
The inactivation process is different depending on the neurotransmitter; some just diffuse away, some go through reuptake, and some experience enzymatic deactivation.
But after a neurotransmitter attaches to a receptor for a very brief period of time and has its effect it detaches. Many neurotransmitters experience a process of reuptake, but those who don’t will either diffuse away or experience enzymatic deactivation
What is reuptake?
step 4 of the release zone
When a neurotransmitter is sucked back up into the presynaptic neuron through transporter proteins to be recycled for later use
Give an example of enzymatic deactivation and describe the process
(step 4 of the release zone)
Acetylcholine is a neurotransmitter that experiences enzymatic deactivation. Basically an enzyme comes alone and busts acetylcholine into its individual components of acetyl and choline, which renders it ineffective for additional effects on other receptors
How are Ca2+ channels opened?
step 3 of the release zone
They’re voltage gates channels
What are the 4 types of ion channels?
(step 3 of the release zone)
Ligand-gated, mechanically-gated, voltage-gated, and always open
What are ionotropic receptors also called?
(step 3 of the release zone)
Ligand-gated
How do ligand-gated/ ionotropic receptors work?
(step 3 of the release zone)
They contain a specialized binding site for specific neurotransmitter and n ion channel that directly opens when a molecule of the neurotransmitter attaches
How do metabotropic receptors work?
(step 3 of the release zone)
They contain a binding site for a neurotransmitter but don’t have an ion channel; instead, they achieve their effect through a series of metabolic chain reactions that involve G-proteins and second messengers that eventually open an ion channel
When are metabotropic receptors useful?
(step 3 of the release zone)
For taste, arousal, attention, pleasure, and emotion because it creates slower and longer lasting effects.
Most neurotransmitters discussed in this class utilize what type of receptors? (step 3 of the release zone)
Metabotropic receptors
How long does transmission of a neurotransmitter typically take?
0.01 microseconds
Most individual neurons release how many kinds of neurotransmitters?
At least 2 or more
Each individual receptor can allow how many types of neurotransmitter to attach to it?
Only one
When neurotransmitters attach to the receptor what two types of responses can they create?
Excitation or inhibition
Define excitation
When a neurotransmitter attaches to the receptor and increases the likelihood of the receiving neuron reaching its threshold of excitation and generating its own action potential
Define inhibition
When a neurotransmitter attaches to the receptor and decreases the likelihood of the receiving neuron reaching its threshold of excitation so an action potential is less likely
Describe how excitatory neurotransmitters work
They cause a brief movement of ions that make the cell a bit more positively charged. In doing this, they depolarize the neuron, which brings the membrane potential closer to the threshold of excitation
Describe how inhibitory neurotransmitters work
They cause a brief movement of ions that make the cell a bit more negatively charged. In doing this, they hyperpolarize the neuron, which brings the membrane potential further from the threshold of excitation
Describe excitatory postsynaptic potentials (EPSPs)
There’s a brief depolarization of a neuron membrane in response to stimulation (which happens when a neurotransmitter attaches to a postsynaptic receptor). This means that a neuron is more likely to produce an action potential
Describe inhibitory postsynaptic potentials (PPSPs)
There’s a brief hyperpolarization of a neuron membrane in response to stimulation (which happens when a neurotransmitter attaches to a postsynaptic receptor). This means that a neuron is less likely to produce an action potential
Where do ESPS and ISPS occur? Where do their depolar/hyperpolarizations go?
They occur at the receiving location of a postsynaptic neuron, and resulting depolarizations (ESPSs) and hyperpolarizations (ISPSs) move down into the cell body where there’s a structure called the axon hillock
Where’s the axon hillock?
Where the cell body and axon meet
What is neural integration?
When the axon hillock sums/integrates the incoming ESPSs and ISPSs; should the amount of depolarization reach the threshold of excitation, an action potential is triggered
What are the two types of neural integration at the axon hillock?
Temporal summation and spatial summation
What is temporal summation?
It involves summing potentials that occur from the same place on a dendrite over time (temporal = multiple times, same place)
What is spatial summation?
It involves summing potentials that occur at different places on a neuron’s different dendrites at the exact same time (spatial = one time, multiple places)
The impact a drug has depends on what two things?
Its affinity and efficacy
Define affinity
The tendency of a drug to bind to a receptor
Define efficacy
The tendency of a drug to actually activate a receptor
What are the two classifications of drugs?
Agonists and antagonists
What are some examples of agonistic and antagonistic effects?
Increase or decrease NT production, affect vesicles and transport, impact release zone, enhance or prevent binding to receptors, or accelerate or block reuptake so the neurotransmitter is active in the synapse for shorter or longer
What do addictive substances affect?
Dopamine and norepinephrine synapses in the nucleus accumbens
Why do people abuse drugs?
Part of the mesolimbic pathway (the pathway for liking/wanting things) projects from the NAc, which allows associations between a drug and its effect to be learned. Sexual excitement, gambling, and video games also affect dopamine in that area of the brain. Some evidence indicates that individuals with major depression have underdeveloped responses in the nucleus accumbens
What type of drug are opiods?
Analgesics
Give examples of CNS stimulants and what they do
Nicotine, caffeine, amphetamine, cocaine create general activation and arousal
Give examples of CNS depressants and what they do
Alcohol, barbiturates, benzos create general suppression and relaxation
Give examples of analgesics/ opioids and what they do
Opium, morphine, codeine, heroin, suboxone, methadone, oxys create pain relief and altered experience
Give examples of hallucinogens and what they do
LSD and psilocybin create altered perceptual experience
Give examples of diverse CNS effects and what they do
Weed creates pain, nausea, and mild hallucinations
Give examples of psychotherapeutics and what they do
They are a form of therapy for mental health
What do stimulants do (physically and chemically)?
They excite neural activity and arouse body functions, which is why they’re used to stay awake, lose weight, boost mood/ athletic performance. Chemically they stimulate dopamine release and inhibit dopamine reuptake
What do amphetamine and methamphetamine do as stimulants (physically and chemically)?
They create up to 8 hours of heightened energy and euphoria. Chemically they inhibit the dopamine transporter (slowing reuptake) and stimulate dopamine synapses by increasing the release of dopamine from the presynaptic terminal
What does ritalin do as a stimulant?
Ritalin (methylphenidate) blocks the reuptake of dopamine but in a more gradual and controlled rate
What does nicotine do as a stimulant?
It stimulates the one type of acetylcholine receptor called the nicotinic receptor; nicotinic receptors are abundant in the nucleus accumbens and facilitate dopamine release. Repeated exposure to nicotine makes the drug more rewarding but every other stimuli less rewarding. About 3 cigarettes can activate almost all nicotinic cholinergic receptors in the CNS and PNS
What do opiates do (physically and chemically)?
They decrease sensitivity to pain and increase relaxation by attaching to natural endorphin receptors in the brain. They cause constricted pupils, slowed breathing, lethargy, and pleasure.
Why are opiates so addictive?
With repetitive use the brain stops producing its own endorphins and the body’s need for the drug increases. Endorphin synapses may contribute to certain kinds of reinforcement by inhibiting the release of GABA (the calm neurotransmitter) indirectly. Inhibiting GABA indirectly releases dopamine, which can cause feelings of euphoria.
What does alcohol do as a depressant (physically and chemically)?
It slows neural activity and body functions. This causes disinhibition, slowed neural processing, memory disruption, and reduced self awareness. It has many physiological effects including enhanced GABA response and the blockage of glutamate receptors. There is a genetic component to alcohol use disorder.
Signals are carried across the synapse between most neurons by:
A) direct electrical connections between the two cells.
B) carrier molecules.
C) the release of neurotransmitter molecules into the synapse.
D) the sodium-potassium pump.
C) the release of neurotransmitter molecules into the synapse.
Communication of neural signals/information from one neuron to another (across the synapse) involves:
A) vesicles that suck up neurotransmitter molecules into the terminal buttons
B) the opening of voltage-gated channels in the axon
C)direct electrical contact of the pre- and post-synaptic neuron membranes.
D) the binding of neurotransmitters at postsynaptic receptors that trigger changes in the membrane potential.
D) the binding of neurotransmitters at postsynaptic receptors that trigger changes in the membrane potential.
Calcium enters the cell when an action potential is generated. Electrostatic pressures push calcium into the cell. Therefore, calcium channels are: A) chemically-gated and voltage-gated. B) passive. C) chemically-gated. D) voltage-gated.
D) voltage-gated.
If the channels for calcium were blocked:
A) neurotransmitters could not be released from the cell.
B) passive channels would close.
C) Na+ would be stuck inside of the cell.
D) voltage-gated ion channels would remain closed.
A) neurotransmitters could not be released from the cell.
In order to produce depolarization (EPSP) or hyperpolarization (IPSP), neurotransmitters:
A) are released into the synapse from the axon hillock.
B) alter ion channel activity for many minutes at a time.
C) open ion channels called receptors in the postsynaptic membrane.
D) act through ionotropic receptors to activate a second-messenger.
C) open ion channels called receptors in the postsynaptic membrane.
Which researcher pinched dogs to determine their reflex arc? A) Skinner B) Pavlov C) Cajal D) Sherrington
D) Sherrington
The speed of conduction through the reflex arc is never more than \_\_\_\_\_\_\_ m/s. A) 11 B) 20 C) 10 D) 15
D) 15
Which is an accurate analogy for spatial summation?
A) None of these answers
B) Pinching both the index finger and thumb at the same time.
C) Pinching the index finger and then a minute later pinching the thumb.
D) Pinching the index finger once then again about a second later.
B) Pinching both the index finger and thumb at the same time.
Which increases the frequency of a neuron's action potentials? A) ESPNs B) IPSPs C) ISPNs D) EPSPs
D) EPSPs
What is inhibition of a neuron? A) Zero excitation. B) Increase in spontaneous firing rate. C) Increase in excitation. D) Suppression of excitation.
D) Suppression of excitation.
