Drug action in the CNS Flashcards
Briefly describe the structure of a neuron:
Dendrites, cell body, axon terminal
Describe the cell body function:
Nucleus, stores DNA and rough ER, which builds protein and mitochondria.
Describe the dendrites:
(receive information) the input region, receives input from other neurons.
Describe the axon:
Axon: main conduction unit, carries information in the form of electrical signal known as the action potential
Describe the axon terminals:
the output region, release of neurotransmitter. Conformational change, triggers release of other AP.
What are neurons?
Neurons communicate with one another at synapses
presynaptic cell –> synapse –> post synaptic cell
Is transmission electrical or chemical?
Synaptic transmission can be electrical or chemical.
Electrical synapses are very rare in the adult brain.
At the chemical synapse the pre- and postsynaptic elements are separated by a gap, called the _____ _____ .
synaptic cleft
When does an action potential occur?
An action potential occurs when a neuron sends information down an axon.
Neurons can alter their resting membrane potential to act as a signalling mechanism.
How does do action potentials initiate NT release?
At the presynaptic terminal the action potential opens Ca2+ channels and initiates neurotransmitter release.
Describe how an action potential affects ion channels:
- Neruone Resting membrane potential: -70mV
- Sodium is positive and moves in via electrochemical gradient therefore neuron becomes more positive
- Sodium reaches its threshold (+30) so closes
- K+ channel open and K+ moves out (repolarization) bringing neuron back down to negative mV
Examples of neurotransmitters:
- Acetylcholine
- Dopamine
Describe the anatomy of the synapse:
Gap between pre synaptic terminal and post synaptic terminal where NT diffuses.
How is information passed from neuron to neuron?
- Electrical signal arrives at pre synaptic terminal
- Causes an opening of voltage gated calcium channels
- Calcium enters cell and causes binding of the pre synaptic vesicles to the membrane then exocytosis occurs into the synaptic cleft
- Then diffuses across the cleft
Activate recepetos – conformational change and Enters post synaptic cleft via diffusion - Na+ moves in, = depolarization generating AP (excitatory signal)
What are the two types of signal?
Excitatory signal and inhibitory signal
What is an inhibitory signal?
= inhibiting different parts of pathway
Example: Cl- coming into cell (if chloride channels activated to open) cell goes more negative and wouldn’t get AP
GABA major inhibitory transmitter
What are the 2 dopamine receptors?
D1 excitatory, D2 inhibitory) – these receptors can be on different neurons
Describe acetycholine synthesis:
- Acetyl coenzyme A + choline (choline acetyltransferase) = Acetycholine
What is ChAT?
Choline acetyltransferase. ChAT is specific to cholinergic neurons and present in neuronal terminal in excess (i.e. enzyme is not saturated). If you have enough precursors you can continue making the transmitter.
Acetylcholine storage:
Stored in synaptic vesicles in the axonal terminal
Acetylcholine release:
Released into the synaptic cleft upon the arrival of an action potential and influx of Ca2+.
Binds to postsynaptic receptors:
Muscarinic (M1 – M5) & Nicotinic (generally excitatory)
Nicotinic receptors are composed of five types of subunits. Name the 5 types:
- Alpha (1-10)
- Beta (β2- β5)
- Delta
- Epsilon &
- Gamma
These subunits are found in different combinations in different types of nicotinic AChRs
Nicotinic Receptors are split into two types, what are the two types:
Muscle and neuronal
Location of muscle nicotinic receptors:
Neuromuscular junction
Location of neuronal nicotinic receptors:
Autonomic ganglia, CNS