Synapses Flashcards
Synapse
junction between two cells where they communicate with each other
Presynaptic cell
The cell that transmits a signal toward the synapse
Postsynaptic cells
The cell that receives the signal from the synapse
Types of synapses (2)
Electrical
Chemical
Electrical synapses
Occur between gap junctions, where local currents flow directly form one cell to a neighboring cell
Important in cardiac muscle cells and many types of smooth muscle
Connexons
Structures that separate adjacent cell membranes in gap junctions.
They are 6 tubular proteins
Chemical synapses
Occurs where a neurotransmitter (chemical messenger) communicates a message to an effector
3 components of a chemical synapse
Presynaptic terminal - end of an axon
Synaptic cleft - space between the end of the axon and the cell with which is synapses
Postsynaptic membrane - membrane of the postsynaptic cell
What causes the neurotransmitter release?
Action potentials in the presynaptic terminal
Synaptic vesicles
an organelle in the cytoplasm that contains neurotransmitters
Neuromodulators
Substances released from neurons that influence the likelihood of an action potential being produced in the post-synaptic cell
Excitatory postsynaptic potentials (EPSP)
the graded potential that results from the depolarization of the postsynaptic cell.
Might produce an action potential
Occurs because the membrane becomes more permeable to Na+
How do local anesthetics work?
The block voltage-gated Na+ channels, which prevent action potentials from propagating along sensory neurons, which means neurotransmitters are not released and EPSPs can’t be produced.
Inhibitory postsynaptic potential IPSP
when neurotransmitter and receptor results in hyperpolarization of the postsynaptic membrane
Move the membrane further from threshold, decreasing the likelihood of an action potential
Acetylocholine // effect and clinical examples
Effect: excitatory in CNS; inhibitory or excitatory in ANS
Myasthenia Gravis - weakness & even paralysis
