What is a Saltatory stimulus?

What is a Saltatory stimulus?

Saltatory conduction (from the Latin saltare, to hop or leap) is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.

What causes Saltatory conduction?

Electrical signals travel faster in axons that are insulated with myelin. Action potentials traveling down the axon “jump” from node to node. This is called saltatory conduction which means “to leap.” Saltatory conduction is a faster way to travel down an axon than traveling in an axon without myelin.

Why does a stronger stimulus cause more action potentials?

The trick that the nervous system uses is that the strength of the stimulus is coded into the frequency of the action potentials that are generated. Thus, the stronger the stimulus, the higher the frequency at which action potentials are generated (see Figs. 1 and 2 below).

What happens if there is a weak stimulus at the initial segment and threshold is not reached?

Weak stimuli that do not reach threshold do not produce an action potential. Thus we say that the action potential is an all-or-none event. Action potentials always have the same amplitude and the same duration. At -55 millivolts the membrane is depolarized to threshold, and an action potential is generated.

What is the best analogy of saltatory conduction?

Unmyelinated gaps between adjacent ensheathed regions of the axon are called Nodes of Ranvier, and are critical to fast transmission of action potentials, in what is termed “saltatory conduction.” A useful analogy is that if the axon itself is like an electrical wire, myelin is like insulation that surrounds it.

How do nodes of Ranvier speed up conduction?

By acting as an electrical insulator, myelin greatly speeds up action potential conduction (Figure 3.14). As it happens, an action potential generated at one node of Ranvier elicits current that flows passively within the myelinated segment until the next node is reached.

What is the difference between depolarization and repolarization?

Depolarization is caused when positively charged sodium ions rush into a neuron with the opening of voltage-gated sodium channels. Repolarization is caused by the closing of sodium ion channels and the opening of potassium ion channels.

Why is Saltatory conduction faster than continuous conduction?

Saltatory conduction occurs in myelinated axons from one node of Ranvier to the next node. Therefore, the action potential is only generated at the neurofibrils in myelinated axons. Hence, it is faster than continuous conduction. Continuous conduction occurs along the entire length of unmyelinated axons.

What is the best analogy of Saltatory conduction?