Factors that increase conduction speed:

* Myelination: Myelin is a fatty substance that insulates axons. This insulation prevents the electrical signal from dissipating and allows the signal to jump from one node of Ranvier to the next (saltatory conduction), significantly increasing conduction speed.

* Axon diameter: Larger diameter axons have less resistance to the flow of ions, leading to faster conduction.

* Temperature: Higher temperatures generally lead to faster conduction, as the ions move more quickly. However, extremely high temperatures can damage neurons and slow conduction.

* Stimulus strength: A stronger stimulus creates a larger depolarization, which can lead to faster conduction.

* Type of neuron: Different types of neurons have varying conduction speeds. For example, motor neurons, which control muscle movement, tend to have faster conduction speeds than sensory neurons, which transmit information from the senses.

Factors that decrease conduction speed:

* Lack of myelination: Neurons without myelin sheaths conduct impulses much slower, as the signal dissipates along the axon.

* Smaller axon diameter: Smaller diameter axons have more resistance to the flow of ions, leading to slower conduction.

* Lower temperature: Lower temperatures slow down the movement of ions, leading to slower conduction.

* Drugs and toxins: Certain drugs and toxins can interfere with the function of neurons and slow conduction. For example, alcohol and certain medications can affect the activity of neurotransmitters, slowing down communication between neurons.

* Diseases: Certain diseases, such as multiple sclerosis, damage the myelin sheath, leading to slower conduction and a variety of neurological symptoms.

It's important to understand that these factors often work in conjunction with each other. For example, the presence of myelin significantly increases conduction speed, even in smaller diameter axons.