Neurochemistry Flashcards
Neurochemistry
Basic chemical composition and processes of the nervous system
Neuropharmacology
Study of compounds that selectively affect the nervous system
The majority of synapses in mammalian nervous systems are (chemical/ electrical)?
Chemical
Electrical synapse (Gap Junction)
Fused presynaptic and postsynaptic membrane that allows an action potential to pass directly from one neuron to the next
Which synapse is faster, electrical or chemical?
Electrical
Which synapse allows for more flexibility in neuron to neuron communication, electrical or chemical?
Chemical
Endogenous ligands
neurotransmitters and hormones
4 stages of neurotransmission
- Synthesis and stored in the axon terminal
- Transported to presynaptic membrane and released in response to an action potential
- Able to activate the receptors on the target-cell membrane located on the postsynaptic membrane
- Inactivation to prevent indefinite activation
Synthesis and storage
-neurotransmitters can be synthesized in the axon terminal: building blocks from food are pumped into the cell via transporters (this is how most highly studied neurotransmitters are synthesized)
-neurotransmitters can be synthesized in the cell body: according to instructions contained in the DNA and transported on microtubules to axon terminal
Neurotransmitter release
-the action potential opens voltage-sensitive calcium channels
-calcium enters the terminal and binds to the protein calmodulin forming a complex
-complex causes some vesicles to empty their contents into the synapse and others get ready to empty their contents
Exocytosis is mediated by:
specialized proteins called SNARES
- v SNARES attach to vesicles
-t SNARES attach to presynaptic membrane
Receptor-site activation
after being released, the neurotransmitter diffuses across the synapse and activates receptors on the postsynaptic membrane
Transmitter-activated receptors
protein embedded in the membrane of a cell that has a binding site for a specific neurotransmitter
3 outcomes of neurotransmitters binding to a transmitter-activated receptor?
- depolarization of the postsynaptic membrane causing excitatory action on the postsynaptic neuron
- hyperpolarization of the postsynaptic membrane causing inhibitory action
- Initiate other chemical reactions that modulate inhibitory or excitatory action
Autoreceptors
receptors that neurotransmitters that do not cross the cleft bind to
Ionotropic receptors
-embedded in membrane
-ligand gated ion channels
-opens and closes directly to allow neurotransmitters in
Metabotropic receptor
-embedded membrane protein with a binding site for a neurotransmitter, but no pore
-linked to a G protein that can affect other receptor or act with second messengers to affect other cellular processes
-G protein coupled receptor
Deactivation of the neurotransmitter
- diffusion away from synaptic cleft
- degradation by enzymes in the synaptic cleft
- Reuptake into the presynaptic neuron for reuse
- Taken up by neighboring glial cells
T/F methods of deactivation are mutually exclusive
false
Axo-dendritic synapse
axon terminal synapses on a dendrite
Axo-somatic
axon terminal synapses on the cell body
Axo-axonic
synapse between two axons
Type II synapses
-inhibitory