Chp 3.2: Synaptic Transmission Flashcards
How do neurons communicate? (2)
- Communicate with chemicals
- The firing (presynaptic) neuron releases chemicals called neurotransmitters into the synaptic cleft
Where is the synaptic cleft located between 2 neurons?
between the axon terminal of one neuron and the dendrite of the next neuron
Synapse
-a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron (or its target)
Neurotransmitters (4)
-Chemicals produced by neurons
-Synthesized (made) inside neurons
-
-Stored in synaptic vesicles
-Released by presynaptic neuron
- Bind to receptor sites in postsynaptic neuron, where they produce a chemical reaction that is either excitatory or inhibitory
- Neurotransmitters bind only to specific sites
Synaptic Vesicles
Chambers that molecules are stored in within the axon terminal
Receptor Sites
protein molecules on neurons’ dendrites or soma that are specially shaped to accommodate a specific neurotransmitter molecule
What are the five steps of chemical communication?
synthesis, storage, release, binding, and deactivation
Where are neurotransmitters stored?
Synaptic vesicles
Describe how neurotransmitters are communicated between neurons? (3)
- neurotransmitters are released by presynaptic neuron
- bind to receptor sites in postsynaptic neuron
- neurotransmitters bind only to specific sites
What are the 2 types of neurotransmitters?
- Excitation
- Inhibition
Describe the five steps of chemical communication.
1) Synthesis - The chemical molecules are formed inside the neuron.
2) Storage - Then get stored in the synaptic vesicles within the axon terminals.
3) Release - When action potential comes down the axon, the vesicles move to the surface of the axon terminal and release the chemical neurotransmitter into the fluid-filled space between the axon of the sending (presynaptic) neuron and the membrane of the receiving (postsynaptic) neuron.
4) Binding - The molecules of neurotransmitter cross the synaptic space and bind to receptor sites (the receptor sites each have a specially shaped surface that fits a specific transmitter molecule). Once the neurotransmitter has bound to a receptor site, it can have an effect.
5) Deactivation - Deactivation through reuptake or breakdown.
Excitatory neurotransmitters (3)
- depolarises neurons
- stimulate flow of Na+
- Increase likelihood of action potential
Inhibitory neurotransmitters (3)
- hyperpolarizes neuron
- Stimulates K+ to flow out
- Decrease likelihood of action potential
Does a successful binding of a neurotransmitter to postsynaptic neuron cause an action potential?
It does not necessarily trigger an action potential.
What are the 2 methods of deactivation?
Breakdown
Reuptake
Define breakdown (deactivation)
Other chemicals in the synapse break down neurotransmitters into their chemical components
Define reuptake (deactivation)
Neurotransmitters are taken back into presynaptic axon terminal
Glutamate (glutamic acid)
Excitatory; found throughout the brain; involved in the control of all behaviours, especially important in learning and memory
GABA (gamma-aminobutyric acid)
Destruction of GABA-producing neurons in Huntington’s disease produces tremors and loss of motor control, as well as personality changes
Acetylcholine (ACh)
Memory loss in Alzheimer’s disease (undersupply)
Muscle contractions, convulsions (oversupply)
Norepinephrine
Depression (undersupply)
Stress and panic disorders (oversupply)
Serotonin
Depression, sleeping, and eating disorders
Dopamine
Parkinson’s disease and depression (undersupply)
Schizophrenia (oversupply)
Endorphins
Insensitivity to pain (oversupply)
Pain hypersensitivity, immune problems (undersupply)
neuromodulators
neurotransmitter substances that are released by neurons and circulate within the nervous system to affect the sensitivity of many neurons to their natural transmitter substances
