In these types of sensory cells, opening or closing of specific ion channels in the membrane, results in alteration of action potential frequency Other sensory receptors are not neurons, but are closely associated with neurons. These types of sensory receptors typically release neurotransmitters in response to the stimulus. Thus, what matters is the destination in the brain of the axons carrying sensory impulses, not the actual external stimulus. An important property of sensory receptors is integration , begins at the level of the sensory neuron which sums graded receptor potentials. The underlying mechanism of action for effectors of motion depends on either microtubules or microfilaments.
Skeletons also function in support and protection.
Stimulatory neurotransmitter substances released by the neuronal axon cause a depolarization of the muscle membrane. If the depolarization is above threshold, an action potential is triggered over the surface of the fiber. The action potential is due to the same combination of voltage-gated ion channels that cause action potentials in nerve cells. Muscle contraction involves a ratchet-like mechanism in which actin and myosin microfilaments slide past one another. ATP provides the energy this movement.