If heavy metals are injurious to the central nervous system why are eating utensils made of metal and do they have any deleterious affect?

I don't think stainless steel is a heavy metal.

You kind of answered your own question by referring to both 'heavy metals' and 'metal.' They are not the same thing. While 'heavy metals' are metal, not all metals are 'heavy metals.'

'Heavy metals' refer to metallic chemical elements that have relatively high density and are poisonous at low concentrations. Examples of heavy metals would be mercury, cadmium, chromium, thallium, and lead.

And from the US department for Labor:

"Toxic metals, including 'heavy metals,' are individual metals and metal compounds that negatively affect people's health. Some toxic, semi-metallic elements, including arsenic and selenium, are discussed in this page. In very small amounts, many of these metals are necessary to support life. However, in larger amounts, they become toxic. They may build up in biological systems and become a significant health hazard."

The metals that we use in our everyday lives, such as in spoons, do not contain enough poisonous metals to accumulate in our body enough to do harm. And the main metals in our utensils are not at all harmful.

Note: whilst cast iron and stainless steel are actually beneficial to health, some people are concerned about the use of aluminium in pans. It's not a heavy metal, nor are deleterious effects in the small quantities caused by cookware proven, but some people only use coated aluminium as a precaution. More dangerous are copper pans which should always have an inert lining.