pharm neurotransmission
Terms
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- chemical cellular communication
- neurotransmitter
- electrical cellular communication
-
1) passive conduction
2) active conduction - Boutons
- nerve terminals
- cellular charges
- due to differential ionic concentrations
- normal resting potential
- -80 mv (most cells)
- Na
- IC: 15 mM EC: 145 mM
- K
- IC: 145 mM EC: 5 mM
- Cl
- IC: 10 mM EC: 150 mM
- Ca
- IC: 0.0001 mM EC: 2 mM
- primary contribution to resting charge
-
K channels
(only channel open at rest) - dendritic conduction
- passive electrical process
- axonal conduction
-
1) active electrical process
2) involves voltage-gated Na and K channels (some Ca also)
3) Na-K ATPase to restore chemical equilibrium
4) signal initiated at axon hillock by internally ligand-gated Na channels
5) Myelinated vs Non-myelinated axons - factors leading to increased conduction rates
-
1) myelination
- decreased capacitance
- saltatory conduction
2) lower resting potential
3) increasing Na channel density
4) increasing axonal diameter - synaptic transmission
-
1) Ca channel stimulation
2) Ca released from storage in Sarcoplasm
3) increased Ca leads to biochemical change allowing fusion of vesicles with inner cell membrane
4) Ca rapidly removed back into sarcoplasm
5) fused vesicles open to synaptic space, releasing contents into synaptic cleft
6) vesicles reformed by endocytotic process, and can then be refilled - vesicles
-
contain 1 quanta of neurotransmitter
5,000-10,000 molecules neurotransmitter
other compounds also in vesicles