Chemical Neural Signalling Flashcards
What is the cause of the maximum for the firing rate of a neuron?
Duration of the refractory period
Ion associate with hyperpolarization at the dendrite (IPSP)
Cl- and K+ (also a way of polarizing a cell)
What is an example of endogenous ligand?
Acetyl choline
Is acetyl choline an excitatory or inhibitory neurotransmitter?
Depends on the receiver
Characteristics of electrical synapses
- Flows between cells (an action potential will continue)
- Faster than chemical one (no delay) -> electrical speed (instant)
- Used for synchronisation
- Bi-directional -> 2 direction of flow
Characteristics of chemical synapses
- Active (new potential is created)
- One direction -> from a cell to the other
- Slow (1 ms delay)
- Used for integration and computation
Which element flow into the cell at the end of the axon?
Ca 2+ (calcium) flow into the cells (because outside concentration is bigger) and release the content of vesicles, neurotransmitters.
Different types of neurotransmitters
- Serotonin
- Glutamate
- Gaba
- Acetyl choline
- Dopamine
Postsynaptic receptors
channel that open when a particular neurotransmitter binds the receptor -> Na+ can enter the cell and, if sodium enter the cell, we add positivity and the cell get depolarised. This channels are located in the postsynaptic membrane.
2 type of receptors
- metabotropic receptor
- ionotropic receptor
Metabotropic receptor
somewhere else in the cells an axion channel opens up (g protein-coupled receptors). They are slower and used slow process that larger one
Ionotropic receptor
ligand-gated ion channel. They are faster (change immediately).
Type of channels
1) Non gated -> always open (resting potential of the cell)
2) Voltage-gated -> they can open
3) Mechanosensitive -> sensitive to movement
EPSP (excitatory postsynaptic potential)
increase likelihood of action potential. It pushes the postsynaptic cell a little closer to the threshold for an action potential.
IPSP (inhibitory postsynaptic potential)
decrease the likelihood of action potential. It results from the opening of channels that permit chloride ions (Cl-) to enter the cell. These ions are much more concentrated outside the cell than inside -> they make the cell more negative.
Spatial summation
sums input from different synapses that overlaps in time. Sums the inputs from different places at the same time
Temporal summation
sums input from one synapse that overlaps in time. In this case post-synaptic potential is being sum -> they last longer and they can create action potential (too fast)
The prompt cessation of transmitter effects is achieved in one of two ways
- Degradation: transmitter can be rapidly broken down and thus inactivated by a special enzyme, a process known as degradation
- Reuptake: transmitter molecules may be rapidly cleared from the synaptic cleft by being taken up into the presynaptic terminal. In this case special receptors for the transmitter called transporters are located on the presynaptic axon terminal and bring the transmitter back inside.
Convergence
information flow from a lot of sources come to one cell -> different sources of information together
Divergence
information flow into different outputs
