Describe the types of central inhibition and the mechanism by which postsynaptic inhibition is generated

Types: According to the different mechanisms of central inhibition, inhibition can be divided into two categories: postsynaptic inhibition and presynaptic inhibition.

Post-synaptic inhibition mechanism: Inhibitory postsynaptic potentials of the anterior horn of the spinal cord motor neurons either innervate the extensor muscles or the flexor muscles. The afferent nerve impulses from the extensor muscle spindle can excite the extensor motor neurons, and can also inhibit the flexor motor neurons through the inhibitory interneurons at the same time. If a microelectrode is inserted into the cell body of a flexor motor neuron and the afferent nerve from the extensor muscle shuttle is stimulated to cause inhibition of the flexor motor neuron, a hyperpolarization of the postsynaptic membrane of the cell body is seen. At this time, the value of the membrane potential approaches the -80mV level. This hyperpolarized membrane potential change is called inhibitory postsynaptic potential (IPSP). Changes in inhibitory postsynaptic potential are very similar to those in excitatory postsynaptic potential in terms of time course, but the former is hyperpolarized and the latter is depolarized, and the direction of change is exactly the opposite (Figure 10-16). It is conceivable that the postsynaptic membrane is in a hyperpolarized state. An inward current will appear at the site of the axon initiating segment, resulting in an action potential that is not easily burst at that site, which is also manifested as inhibition. Since this inhibition is caused by the appearance of inhibitory postsynaptic potentials in the postsynaptic membrane, it is called postsynaptic inhibition. Inhibitory postsynaptic potentials are formed as a result of increased CI-permeability of the postsynaptic membrane.