The biology world: Signal transmission by synapse

Signal transmission by synapse

➢ It is the junctional region between two cells which may or may not be neurons.

➢ The presynaptic cell is generally a neuron.

➢ Postsynaptic cell may be neuron, muscle cell or gland.

➢ At an electrical synapse, action potentials conduct

directly between adjacent cells through gap junctions.

➢ Each gap junction contains a hundred or so tubular

connexons, which act like tunnels to connect the

cytosol of the two cells directly.

➢ Gap junctions are common in

○ Visceral smooth muscle.

○ Cardiac muscle.

○ Developing embryo.

○ CNS.

Advantages of electrical synapse:

➢ At an electrical synapse, the action potential passes directly from the

presynaptic cell to the postsynaptic cell.

➢ The events that occur at a chemical synapse take some time and delay

communication slightly.

➢ Electrical synapses can synchronize (coordinate) the activity of a group of

neurons or muscle fibers.

➢ In other words, a large number of neurons or muscle fibers can produce action

potentials in unison if they are connected by gap junctions.

➢ The value of synchronized action potentials in the heart or in visceral smooth

muscle is coordinated contraction of these fibers to produce a heartbeat or move

food through the gastrointestinal tract.

➢ Biochemical substances which are involved in the transmission of impulse

across synapse.

➢ Some neurotransmitters bind to their receptors and act quickly to open or

close ion channels in the membrane.

➢ Others act more slowly via second-messenger systems to influence chemical

reactions inside cells.