Synapatic Transmission Flashcards
Two different types of receptors
Metabotrophic, ionotrophic
Gap junctions consist of
Hexagonal array of proteins (connexion) forming clusters of channels. Each is about 1-2nm in diameter. Open or closed regulated by ionic concentrations. Very fast.
Organs that contain electrical synpases
Pancreas, heart muscle, smooth muscle
Chemical synapse cleft nm
20-50 nm wide
Presynaptic synapse contains
Synaptic vesicles, secretory granules, mitcohondria and active zone
Postsynaptic synapse contains
Receptors which conner the intercellular signal to an intracellular signal
Neurotransmitter criteria
Must be made in the nerve (enzymatic components or precursors present)
Stimulation results in a postsynaptic response
Can be mimicked by exogenous application of neurotransmitter
Mechanism to terminate actions
Ca2+ role in synapse
Ca2+ must bind with synaptic vesicles and direct them to the terminal so they can fuse and release their chemical into the synapse
Purpose of dendritic cells
Communicating with other neurons
3 types of glia in CNS
- Microglia- white blood cells
- Astrocyte- Star shaped cell that helps form the blood-brain barrier, recycles transmitters, communicates with the ventricles (AKA helps move ions, o2 or Co2 away or to neurons)
- Oligodendrocytes- produce myeline sheathes
- Ependymal cells- Creates barriers between compartments
Difference between schwann cells and oligodendrocytes
1 schwann cell at a time wraps around the axon
Oligodendrocytes wraps around a lot axons (communicating with a lot of different neurons. More efficient)
Synthesis of neurotransmitters
Primarily in the nerve terminal.
Stored in vesicles involves ATP.
Quantal release
Dendritic spines
All different sizes of spines that cover the dendritic arms. They are composed of microfilaments.
Dynamic- can come and go based on use of portions of the brain.
Different shapes of dendritic spine
Can indicate the health of the brain or diseases of the brain. ex: down syndrome, Fragile X syndrome
2 examples in the autistic spectrum
Anglemans syndrome and fragile X syndrome
Activity in the brain determines the type of ____ and what they look like
Dendritic spines
Immature spine shape
Thin, stringy. Brain hasn’t matured appropriately
Mature spine shape
Wider, mushroom. Brain has matured.
Release of neurotransmitter
Ca2+ binds to synaptotagmin
Snare
Molecules on the synaptic vesicle that hold the vesicle down to the pre synaptic area and binds it so it can’t move
Synaptobrevin II, SNAP 25 and Syntaxin
Cause the vesicle to be pulled down to the terminal. Allows fusion and a pore opens.
The release of a neurotransmitter
ATP-ADP causes the pore to close and separation of the vesicle from the AZ ??
Actions depend on the receptor and strength of the signal
Recycling of the vesicle
Cytoskeleton grabs the vesicle after it released it’s contents and pulls it back into the axon terminal.
How to remove neurotransmitter from the synpase
- Diffusion causes neurotransmitter to move down concentration gradient and away from synapse.
- Enzymatic degradation by acetylcholinesterase.
- Uptake by neurons or glia cells, which are neurotransmitter transporters.
Prozac
Serotonin reuptake inhibitor
PNS glial cells (2)
Schwann cells produce myelin sheathes
Satellite cells support cell bodies
Retina Glia
- astrocytes, but only in the inner retina around the larger blood vessels.
- Main glia- muller cells. Important in retinal development
- Microglia
Summation types
Adding of the graded potentials
Temporal- Summation of effect of neurotransmitters released from 2 or more firings of the same end bulb in rapid succession onto a second neuron.
Spacial- Summation of effects of neurotransmitters released from several end bulbs onto one neuron.
The more neurotransmitter released the greater the change in ___
Potential o the postsynaptic cell
Neuronal circuits
Diverging - single cell activates a lot of cells
Converging - One cell is stimulated by many others
Reverberating- Impulses from later cells repeatedly stimulate early cells in the circuit.
Parallel after discharge- single cell stimulates a group of cells that all stimulate a common postsynaptic cell
Myasthenia gravis
Autoimmune disease that results in the decline of muscle strength. Body produces antibodies against the acetylcholine receptor, which is (N-ionotropic/nicotine) neostigmine.
Optometrists may be the first to notice the disease due to pt complaining of double vision (diplopia)- one muscle may be weaker than the other. (ptosis)
MS
Autoimmune disease results in loss of transmission. Body produces antibodies against MBP found in myelinated neurons.
Attacks Myelin basic protein, typically seen in a peripheral nerve first.
How do drugs modify synaptic transmission?
They can interfere or stimulate normal processes in the neuron involved in neurotransmitter synthesis, storage, and release and in receptor activation.
How does the tetanus toxin affect synaptic mechanisms?
Prevents vesicle fusion with the membrane, inhibiting neurotransmitter release and causes increased muscle contraction.
How does the bacilli toxin (botulism) affect synaptic mechanisms?
Interferes with actions of SNARE proteins at excitatory synapses that activate muscles. Characterized by muscle paralysis.
Low doses are used for botox injections. Used to rent wrinkles, severe sweating, and more.
EPSP
A depolarizing postsynaptic potential. Results from the opening of ligand-gated Na+ channels. The postsynaptic cell is more likely to reach threshold.
ISPS
Inhibitory postsynaptic potential. Results from the opening of a ligand gated Cl- or K+ channels. It causes the post synaptic ell to become more negative or hyper polarized. The postsynaptic cell is less likely to reach threshold.
