Neurotransmission and neurotransmitters Flashcards
Name the types of glial cells and what do they do?
- glial cells - provide support for the neurons
* astrocytes-hold the neurons in place * oligodendrocytes - provide myelin * microglia - clean up from dead tissue and important link with the immune system
what is an ion?
an atom with different protons (+) and electrons (-). e.g. can be positive or negative
What are some of the ion qualities?
electorstatic gradient - attraction/repulsion
osmotic balance of diffusion gradient - ions ten to spread around uniformly
Why do the extracellular and intercellular environments have different charges?
difference in the charge is due to different concentration of sodium (Na+), potassium (K+), Chloride (Cl-) and organic aminos (A-)
What are gated channels?
sodium-potassium pump, forcing our sodium (Na+)
What are non-gated channels?
membrane permeability allowing ions to move more easily
What does it mean that AP is all or none?
if stimulation is strong enough it produces an action potential - rapid depolarisation and repolarisation of membrane
Describe the process of neurotransmission
the action potential opens calcium channels located at the presynaptic membrane, which binds with the protein embedded in the membrane of the synaptic vesicles. The pores widen and the neurotransmitter is released into the synaptic cleft. the neurotransmitter binds with the post synaptic receptor and then it is quickly deactivated
How are neurotransmitters deactivated?
- reactivating pumps that send back the neurotransmitter into the presynaptic membrane
- broken down or de-activation by enzymes
- by diffusion of the neurotransmitter away from the region of synapse
What does the type of neurotransmitter release, by a neuron depends on?
the rate of stimulation or sometimes on the postsynaptic neuron
What are the major types of excitatory neurotransmitters
- acetylcholine
- catecolamine (dopamine, norepinephrine, epinephrine, noradrenaline)
- glutamate
- histamine
- serotonine, etc
What are the major types of inhibitory neurotransmitters
GABA
Clycine
what is an antagonist drug?
reduce the ability of neurotransmitter to bind to the receptor sites
what is an agonist drug?
prevents there-uptake of the neurotransmitter
What causes the neurotransmitter release?
In neurotransmission when the signal reaches the buttons, it is the action potential that causes a rush of calcium into the synaptic cleft, binding to the receptors inside. That leads to a change in little vesicles (containing neurotransmitters)
What are the qualities of active conduction?
Active conduction (action potential) i.e.,
- no Inhibitory or Excitatory
- no graded
- no degradation
- grey and white matter
What are the qualities of passive conduction?
Inhibitory or Excitatory
- Graded
- Degradation
- grey matter
Describe electrical synapses
ions move from one neuron to the next via direct physical connection.
- passive current flow. - no delay, - bidirectional, synchronisation role of large population of neurons
What does LTP stand for?
Long term potentiation o the lasting increase in synaptic strength
What does LTD stand for?
Long term depression. Lasting decrease in synaptic strenght
What is an ATP
adenosine triphosphate is an extracellular signaling molecule, which acts as a neurotransmitter in CNS and PNS.
It is energy storing
What does ATO do?
Used for fuel to operate small transmembrane pumps that release the enzymes that move potassium and sodium. Each ATP has enough energy to move two potassium ions in the cell for every 3 sodium ions out of the cell
What is LTP triggered by?
by the NMDA receptors
What is LTP maintained by?
The AMPA receptors
What is the NMDA receptor?
the NMDA is blocked by magnesium, which is only released when postsynaptic cells are sufficiently depolarised, it then becomes permeable to calcium, sodium and potassium
What happens if a stimulus is strong enough to cause an LTP?
If the stimulus is strong enough, the post synaptic neuron is depolarised following sustained activation of AMPA. Once the threshold is reaches the magnesium in NMDA withdraws and lets calcium into the cell. The increase calcium contraiton makes the synapse ore efficient. Both glutamate and depolarisation are needed to occur at the same time, to activate NMDA and without it an LTP cannot occur
What happens in AMPA when glutamate is released?
When glutamate binds to AMPA the channels open to let sodium in the post synaptic dendrite to start depolarisation. If it reaches the threshold an action potential is triggered and the impulse is transmitted to the next neuron. Then the NMDA receptor admits calcium into the post-synaptic cell. When it is at rest the calcium channel is blocked by magnesium, so even if glutamate binds the calcium cannot enter the cell. Only if depolarisation is reached the magnesium will withdraw to let calcium into the cell
