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Flashcards in Chemical Neurotransmitters Deck (80)
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Define synapse

A specialised junction between the axon terminal and post synaptic cell


What are the two types of synapses?

Electrical synapse
Chemical synapse


Why is synaptic transmission important?

Synaptic transmission is important to understand how the nervous system operates the following:
- cognition, learning & memory
- actions of psychoactive drugs
- causes of psychiatric and neurological disorders


What is a gap junction composed of?

6 connexins (gap junction protein) which make a connexon.
The pore size is 2nm


What is an electrical synapse? Expand on its transmission and where it is found. (7 points)

- It allows the direct transfer of ionic current from one cell to the next.
- Gap junctions are composed of 6 connexins; that make up 1 connexon. The pore size is 2nm.
- Ions can flow bidirectionally.
- The cells are said to be electrically coupled.
- The conduction speed is very fast (0.3milliseconds) unlike the delay seen in chemical transmission.
- It is found in neuronal pathways that are associated with escape reflexes (fight or flight --> amygdala) or in neurones that need to be synchronised (cardiomyocytes that make up the heart muscle - you want the propagation of the action potential to proceed smoothly and uninterrupted from one cell to another to provide a uniform contraction of the heart)
- they are common in non-neuronal cells (glial cells - maintain homeostasis, form myelin)


Explain the information flow through neurones

Dendrites collect electrical signals.
Cell body integrates incoming signals and generates an outgoing signal to axon (through axon hillock)
Axon passes electrical signals to dendrites of another cell or to an effector cell


Define neuropharmacology

The study of the drugs on the nervous system


How are neurological and psychiatric disorders often caused by?

An imbalance of chemical transmitters in the brain


How can chemical synaptic transmission be modulated?

Drugs and Toxins


What do receptor agonists do?

They mimic the action of a neurotransmitter e.g. Morphine activates u-opioid receptors in the brain and spinal cord


What do receptor antagonists do?

They inhibit the normal action of a neurotransmitter e.g. ketamine blocks the action of glutamate at the NMDA receptor


Excitatory receptor + agonist = ____ signal



Inhibitory receptor + antagonist = ____ signal



Excitatory receptor + antagonist = ____ signal



Inhibitory receptor + agonist = ____ signal



What is an axon hillock?

The part of the neurone where the cell body meets the axon


What is the resting membrane potential and what is this due to?

-70mV - this is due to the concentration of ions (+vely or -vely charged particles) inside and outside the cell


What is on the outside of the cell?

High concentration of +vely charged Na ions and some -vely charged Cl ions


What is on the inside of the cell?

Low concentration of +vely charged K ions and high concentration of -vely charged protein ions


If enough +vely charged ions enter the cell, thereby resulting in more excitatory post synaptic potentials. Then the membrane potential reaches a threshold of excitation at the axon hillock. This will trigger an action potential. What is an action potential?

A brief increase in the permeability of the membrane to Na+ (in), immediately followed by a brief increase in the permeability of the membrane to K+ (out). Once an action potential is generated, it propagates all the way down to axon to the terminal buttons. While EPSP's are small, local and contained graded changes in the membrane potential from more -ve to more +ve, an AP is a brief but larger reversal in the membrane polarity. Once the AP reaches the terminal buttons this change in membrane polarity causes Ca channels which are normally held closed to open, and let Ca into the cell. Ca acts as a signal to release the neurotransmitter substance which is docked at the presynaptic membrane via exocytosis. The neurotransmitter then binds to the post-synaptic receptor and the cycle begins again.


Neurotransmitters are released in _____



Summarise synaptic signal integration

Neurotransmitters are released in quanta. Each neurone can receive thousands of inputs in the form of ion channel and G protein-coupled receptor activation.


EPSP Summation:

Neurones perform sophisticated computation by adding together EPSPs to produce a significant post synaptic depolarisation.
Types of Summation: Spatial and Temporal summation
These complex inputs give rise to discrete outputs in the form of action potentials a.k.a neural computation.


What are the two types of EPSP summation?



Name two excitatory neurotransmitters (Na+ enters):



What will a single presynaptic action potential give rise to?

a small EPSP in a post synaptic neuron


What is and what will SPATIAL summation of EPSPs give rise to?

When two or more presynaptic inputs are active at the same time, their individual EPSPs are added together. It is better than TEMPORAL because it is quicker in generating an AP


What is and what will TEMPORAL summation of EPSPs give rise to?

When the same presynaptic input fibre fired APs in quick succession, the individual EPSPs add together. Not as good as SPATIAL because it takes longer to generate an AP.


Name two inhibitory neurotransmitters (Cl- enters):



What glial cells are present in the CNS to myelinate the axons there?