| Synapse meaning | - Point where 1 neuron communities with another or with an effector
- Important in linking different neurons together therefore coordinating activities
- Transmits info, not impulses |
| Structure of synapse | - Transmits info from 1 neuron to another through neurotransmitters
- Neurons separated by small gap, synaptic cleft
- Neuron that releases neurotrans. called presynaptic neuron
- Axon of this neuron ends in swollen portion, synaotic knob
- This possesses many mitochondria + large amounts of endoplasmic reticulum
- These required in manufacture of neurotrans., takes place at axon
- Neurotrans. stored in synaptic vesicles
- Once NT released from vesicles, diffuses to postsynaptic neuron, possesses specific receptor proteins on its membrane to receive it |
| Features of synpases | - Unidirectionality
- Summation |
| Unidirectionality | - Syanpases can only pass info in 1 direction
- From presynaptic neuron to postsynaptic neuron
- In this way, act as valves |
| Summation | - Low-frequency AP often lead to release of insufficient concs. of NT to trigger a new AP in postsynaptic neuron
- But can do so in process called summation |
| Two types of summation | - Spatial summation
- Temporal summation |
| Spatial summation | - 2 impulses from 2 or more different nuerones arrive at the same time will summate to produce a threshold potential |
| Temporal summation | - 2 sub-threshold stimuli arrive from the same presynaptic neurone in a short period of time
- These summate to produce a threshold potential |
| Inhibition | - Synapses that prevent production of and AP on postsynaptic neuron
- By opening chloride ion protein channels on the postsynaptic neuron
- This causes K gated ion channels to open, K ions are able to diffuse out |
| Drugs can increase transmission of impulses at a synapse by: | - Causing more NT to be produced in the synaptic knob
- Causing more NT to be released at the presynaptic membrane
- Preventing the breakdown of NTs by enzymes |
| Drugs can decrease transmission of impulses at a synapse by | - Preventing production of NT in the presynaptic knob
- Preventing the release of NT at the presynaptic membrane
- The NT that leaks out of the cell is destroyed by enzymes |
| MDMA | - MDMA inhibits the reuptake of serotonin into the presynaptic neurone by binding to the specific proteins that enable serotonin reuptake, located on the presynaptic membrane; this increases the amount of serotonin present in the brain
- Serotonin is usually reabsorbed into the presynaptic neurone to be recycled for future action potentials
- MDMA also triggers the release of further serotonin from presynaptic neurones, further adding to the increase |
