The Neuron, Synaptic Transmission, and Neurotransmitters (J3)



The Neuron, Synaptic Transmission, and Neurotransmitters
1. The CNS (Central Nervous System):
> 90,000,000,000 neurons; basic component of CNS.
> All thought, action, memory, & behavior results from CNS (biochemical) interactions between neurons.
> Psychoactive drugs alter neuronal processes.

2. Neurons:
> Soma = cell body
> The DNA (genetic material) of the cell is in the nucleus.
> Dendrites (typically a cell has 100s) receive input from other neurons via receptors, generating an electrical current that travels to the soma; then down the axon (there is only one) to another cell (neuron, muscle, organ, gland).
> A given neuron in the brain may receive several thousand synaptic connections from other neurons. The brain has many trillions of synapses. The number of possible different connections in a human brain is larger than the total number of atomic particles in the known universe.
> A synapse is the point of contact between an axon terminal and another cell. It consists of the synaptic cleft (a minute space) between the presynaptic membrane (@ the axon terminal) of one neuron and the postsynaptic membrane of the receiving cell.

3. Neurotransmitter (NT)
> The presynaptic terminal contains small synaptic vesicles, each containing 1000s of molecules of a chemical neurotransmitter, which are released into the synaptic cleft.
> The neurotransmitter diffuses across the synaptic cleft and attaches to protein receptors on the postsynaptic membrane.
> Thus, information is transmitted chemically (and quickly) from a neuron to another cell.
> Neurotransmitter (NT) removal occurs via: An enzyme in the synaptic cleft breaks down the NT. The presynaptic cell most often reabsorbs the NT via a reuptake transporter receptor present @ the presynaptic membrane.
> Specific Neurotransmitters
~ Acetycholine (ACh) effects memory, behavioral arousal, attention, mood. Terminated via achetylcholine estrase (AChE); enhanced via AChE inhibitors.
~ Catecholamine NT: Dopamine (DA), Norepinephrine (NE), Epinephrine (adrenalin). In CNS commonly is DA, and its metabolite NE.
~ Serotonin
~ Amino Acids can act as NTs.
~ Glutamate,
~ GABA
~ Peptite transmitters