2 - Introduction to neurotransmission lecutre Flashcards
describe the cell body of a neuron
nucleus, stores DNA and rough ER, which builds protein and mitochondria
describe dendrites
- the input region
- have lots of receptors
- receive input from other neurons
describe the axon
- main conduction unit
- carries info in the form of electrical signal known as the action potential (AP can vary in length)
- surrounded by myelin sheath — speeds up conduction, insulator
describe axon terminals
- the output region
- release of neurotransmitter
- aka. synaptic terminals
- electrical —> chemical signal
how do neurons communicate with each other?
synapses
at the chemical synapse the pre and postsynaptic elements are separated by a gap called the ________?
synaptic cleft
what are subcortical nuclei in the basal ganglia?
collections of cell bodies/neurons that project from one region to another
what does the AP do at the presynaptic terminal?
the AP opens Ca++ channels and initiates neurotransmitter release
what results in release of neurotransmitter?
Ca++ influx
describe the events from an AP arriving at a presynaptic terminal to the recycling of the neurotransmitter
- when an AP arrives at the presynaptic terminal it causes the opening of voltage gated Ca++ channels and Ca enters the cell
- Ca causes the vesicles to bind to the presynaptic membrane
- neurotransmitter is released into the synapse by exocytosis
- the neurotransmitter binds to receptors on the postsynaptic membrane, and the receptor determines if an excitatory or inhibitory signal is passed on
- the neurotransmitter is then broken down or directly taken back up into the presynaptic terminal by transporters where it is recycled
describe exocytosis at the synaptic cleft
- presynaptic vesicles bind to the presynaptic membrane
- transmitter is then pushed out into the synaptic cleft
- in response to the arrival of the AP
what is an agonist?
a substance which stimulates the receptors and mimics the natural ligand (eg. neurotransmitter, hormone)
what is an antagonist?
substances that block the receptor and prevents/stops the effect of the natural ligands — no activation of receptor
what is a partial agonist?
- an agonist which is unable to induce maximal activation of a receptor population, regardless of the amount of drug applied
- not as much activation of receptor as full agonist
describe inotropic receptors
- receptor is part of a ligand-gated ion channel protein and activation results in ion conductance charges
- these receptors are opening by the transmitter to allow the passage of Na+ (excitatory) or K+/Cl- ions (inhibitory) and are involved in fast transmission
- involves conformational shift
- examples : Ach, Glu, GABA
how does a conformational shift cause release of an excitatory signal?
conformational shift — Na+ rushes in — depolarisation — excitatory signal
describe metabotropic receptors
- slower
- receptor protein in membrane is coupled to effector mechanism via G-proteins
- in this signalling mechanism, agonist molecule combines with receptor proteins in the membrane
- the resulting conformational change causes activation of a membrane-associated enzymes via G-protein
- the cellular effect is usually much slower than that associated with ionotropic receptors
summarise the dopamine pathways
summarise the parasympathetic pathway
describe the direct pathway in the basal ganglia for movement
what are 4 important neurotransmitters in the basal ganglia? how do they interact to control movement?
1) GABA (throughout basal ganglia) (major inhibitory)
2) dopamine (projections from the SNc) (inhibitory or excitatory)
3) glutamate (from/to cortex and the subthalamic nucleus) (major excitatory)
4) acetylcholine (large interneurons in the neostriatum)
how does an increase in DA affect movement?
