What structure in the earthworm has a similar function to the human heart?
The aortic arches function like a human heart. There are five pairs of aortic arches, which have the responsibility of pumping blood into the dorsal and ventral blood vessels. The dorsal blood vessels are responsible for carrying blood to the front of the earthworm’s body.
Whats at the most anterior end of the earthworm?
Locate the clitellum of a mature earthworm. The shorter region to one side of the clitellum is the anterior or head-end of the animal. This end of the worm is usually more pointed than the posterior end of the animal. The prostomium is the first segment at the anterior end of the animal.
Do earthworms have an anterior and a posterior explain your answer?
Find the anterior (front) end of the earthworm by locating the fleshy bump over its mouth, called the prostomium. The posterior (back) end has a small hole where solid waste is expelled, called the anus. Notice that the earthworm has a rounded dorsal (back) surface and a flatter ventral (belly) surface.
What structure does the mouth lead to earthworm?
Digestive System the worm. Find the mouth opening, the first part after the mouth is the pharynx, you will see stringy things attached to either side of the pharynx (pharyngeal muscles).
Why is MGF faster than LGF?
The instructor can discuss how axonal diameter and myelination have specific electrical effects on how the spike travels down the axon (the MGF has a larger diameter than the LGF and thus has a faster conduction velocity).
Do worms have myelin?
You may recall that the earthworm neurons are actually myelinated! Some invertebrates, such as some shrimp and some worms, actually do have myelin. Typically, as axon increases its diameter, its myelin thickness also increases.
What is a stimulus artifact?
The stimulus artifact is present whether or not the nerve is in the tube, though its form may be altered by the electrical properties of the nerve. It is called an artifact because it is a product of human intervention and is not produced by the nerve.
Are worm axons myelinated?
The median and lateral giant axons in the ventral nerve cord of the earthworm Lumbricus terrestris are ensheathed by extensive spiral glial cell wrappings which resemble vertebrate myelin. The other, smaller, axons are encompassed by attenuated glial processes, as is typical of invertebrates.
Why does myelination alter the membrane capacitance?
Membrane Capacitance Capacitance – the ability of an electrical system to store charge or the charge required to initiate an action potential/electrical impulse; the low capacitance conveyed to an axon by myelination means that a lower change in ion concentration is required to initiate an axon potential.
Does axon length affect speed?
Larger diameter axons have a higher conduction velocity, which means they are able to send signals faster. This is because there is less resistance facing the ion flow. The larger the diameter of the axon, the less likely the incoming ions will run into something that could bounce them back.
Does length of axon affect conduction velocity?
showed that conduction velocity in the minor axon branches, connecting the ipsilateral targets, is related to the axonal length from the origin neuron (Chomiak et al., 2008). Conduction velocity is decreased in shorter axons, and vice versa, to allow isochronic spiking at the target nuclei.
What increases conduction velocity?
By acting as an electrical insulator, myelin greatly speeds up action potential conduction (Figure 3.14). For example, whereas unmyelinated axon conduction velocities range from about 0.5 to 10 m/s, myelinated axons can conduct at velocities up to 150 m/s.
Which nerve Fibres has the slowest conduction velocity?
Sural nerve conduction amplitude is significantly smaller in females than males, and the latency of impulses is longer in females, thus a slower conduction velocity.
Does myelin increase resistance?
The main purpose of myelin is to increase the speed at which electrical impulses propagate along the myelinated fiber. Myelin decreases capacitance and increases electrical resistance across the axonal membrane (the axolemma).
What disease destroys the myelin sheath?
The most common type of demyelinating disease is MS. It happens when the immune system mistakenly attacks and damages myelin. The term multiple sclerosis means “many scars.” Damage to myelin in the brain and spinal cord can result in hardened scars that can appear at different times and in different places.
How long does it take for myelin sheath to repair?
We find restoration of the normal number of oligodendrocytes and robust remyelination approximately two weeks after induction of cell ablation, whereby myelinated axon number is restored to control levels. Remarkably, we find that myelin sheaths of normal length and thickness are regenerated during this time.