Synapse Flashcards
What is a synapse
refers to the points of contact between neurons where information is passed from one neuron to the next. Synapses most often form between axons and dendrites, and consist of
1. presynaptic neuron 2. synaptic cleft
3. postsynaptic neuron
There are two main kinds of synpases (chemical and electrical synapse). What are the major differences?
ES are more direct and faster but less efficient and have less plasticity
ES do not require Neurotransmitters
CS are the most common type of synapse in human nervous system
They allow cells to communicate by releasing NT that bind to receptors on post-synaptic cell (can either excite or inhibit post synaptic cell)
CS can be modified through processes such as LTP and LTD, which allow for changes in strength over time
What influences whether a synapse excites or inhibits postsynaptic cell?
It depends on type of NT and receptors involved
What are the steps in a chemical synapse?
- Action potential:
An action potential, or nerve impulse, travels down the axon of the presynaptic neuron - Voltage-gated calcium channels:
The action potential causes voltage-gated calcium channels to open, allowing calcium ions to enter the axon terminal of the presynaptic neuron. - Neurotransmitter release:
The influx of calcium ions triggers the release of neurotransmitter molecules from vesicles within the axon terminal. The neurotransmitter is released into the synapse, or the small gap between the presynaptic and postsynaptic cells. - Neurotransmitter binding:
The neurotransmitter molecules bind to receptors on the postsynaptic cell, either excitatory or inhibitory. - Postsynaptic response:
The binding of the neurotransmitter to the receptors on the postsynaptic cell elicits a response, either excitation or inhibition, depending on the type of neurotransmitter and receptor involved. - Neurotransmitter reuptake:
After the neurotransmitter has been released and has elicited a response in the postsynaptic cell, it may be taken back up into the presynaptic neuron through a process called reuptake. This helps to terminate the signaling process and prepare for the next action potential. - Enzyme degradation:
Some neurotransmitters may also be broken down by enzymes in the synapse, further terminating the signaling process.
What are neurotransmitter?
- chemicals that are produced and released by neurons in the brain and central nervous system. They are involved in transmitting signals from one neuron to another, and are essential for the proper functioning of the nervous system.
- many different types of neurotransmitters, and each has a specific role in the body e.g.,
Acetylcholine - involved in muscle control, memory, and learning.
Dopamine - involved in pleasure, reward, and motivation
Serotonin - involved in mood, sleep, and appetite
Norepinephrine - involved in arousal, attention, and the fight-or-flight response.
How are NT stored in body?
Neurotransmitters are synthesized and stored in vesicles within the neuron
What happens to NT when an action potential reaches the end of a neuron?
When an action potential (an electrical signal) reaches the end of a neuron, the vesicles release their contents into the synapse (the small gap between two neurons).
The neurotransmitter then diffuses across the synapse and binds to receptors on the postsynaptic neuron, transmitting the signal across the synapse.
What is a consequence of abnormalities in NT?
Abnormalities in neurotransmitter function can lead to various neurological and psychiatric disorders, such as depression, anxiety, and Parkinson’s disease. Many medications used to treat these conditions work by altering the levels or activity of specific neurotransmitters in the brain.
What is the role of receptors?
= proteins that are located on the surface of cells, including neurons (nerve cells).
They are responsible for receiving chemical signals from other cells and converting them into a form that the cell can understand.
In the context of a synapse, receptors are found on the postsynaptic cell, which is the cell that receives the chemical signal from the presynaptic cell.
- allow the communication between neurons to be precise and specific.
- Different types of receptors are activated by different neurotransmitters, and this allows the activity of the postsynaptic cell to be finely tuned in response to the activity of the presynaptic cell
What are ionotropic receptors?
- Fast and more direct response
- Second messenger independent (directly linked to an ion channel)
When a chemical signal, such as a neurotransmitter, binds to the receptor, it causes the ion channel to open or close, allowing ions (such as sodium, potassium, or calcium ions) to flow into or out of the cell.
This change in ion concentration can alter the electrical activity of the cell, resulting in a change in the cell’s behavior.
What are the effects of ionotropic receptors?
direct effect
* Neurotransmitter attaches to receptors and immediately opens ion channel
- Occur quickly and are short lasting
What are metabotropic receptors?
lead to a slow and more complex response, which lasts longer
they are not directly linked to ion channels
Instead, they are coupled to intracellular signaling pathways that involve the activation of enzymes and the production of second messengers.
-> When a chemical signal binds to a metabotropic receptor, it activates a signaling pathway that leads to the production of second messengers, which then go on to activate other enzymes or ion channels.
What are the effects of metabotropic receptors?
indirect effect that leads to changes in activity of ion channels
- effects can include changes in the activity of ion channels, changes in the synthesis or degradation of signaling molecules, or changes in the expression of genes.
Metabotropic effects are typically slower to occur than ionotropic effects, as they involve the activation of intracellular signaling pathways.
What happens when an excitatory signal is received?
When an excitatory stimulus is received, the membrane potential of the neuron becomes more positive, and if it reaches a certain threshold, an action potential is generated
And what happens during and after an action potential?
-> During an action potential, the membrane potential of the neuron becomes more positive for a brief period of time and then returns to its resting state. This rapid change in the membrane potential is caused by the opening and closing of ion channels in the cell membrane.
