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