Aug 2015 01

Dead meat

By: Dave Wheeler

Unless you're a vegetarian, then you're used to eating muscle:

  • Chicken breast is the muscle that a chicken would use to beat it's wings to fly
  • Leg of lamb is the thigh muscle
  • Beef tenderloin (which is in two sections which we know as sirloin and rump) runs along the backbone of the cow. Incidentally, in humans, the tenderloin is known as the psoas and runs from the lower spine, through the pelvis to the upper leg.

So far, so good - but what makes some meat (muscle) lean and other tough?

Lean meat, like beef tenderloin or chicken breast, is muscle that hasn't been used very much (think "lean muscle"). Tougher meat comes from muscles that have  been worked hard - for example the dark meat on chicken.

The difference between the dead meat that we eat and our own muscles is that they're brought into action by electrical impulses


Muscle stimulation

The process of stimulating a muscle - that is getting it to contract - is called innervation.

Notice the middle part of the word and how closely related it is to the word nerve.

That's because it's nerves that stimulate the muscle into action.

If you make a decision to flex your arm at the elbow to show off your bicep, then the nerve that runs from the spine down the arm (called the median nerve) sends an electrical impulse to the relevant muscles to innervate them, causing them to contract - effectively pulling your lower arm closer to your upper one.

Some nerves are like motorway lanes - open to one way traffic (that is, electrical signals). The nerves that carry signals from the central nervous system to the target muscles are called motor (or efferent) nerves.

Other nerves are mixed and can carry 2 way traffic - signals from the central nervous system to the muscles, and signals to the central nervous system (e.g. about the temperature of the skin).

Without the electrical impulses from nerves, our muscles would literally be dead meat.


A network of nerve endings

The fact that nerves are numbered suggests that there are only a limited number. This is true of the main "superhighways" of nerve pathways, but in fact, nerves branch out into sub branches, which then branch out into sub-sub branches, which then branch out into sub-sub-sub branches, which then... well, you get the idea.

In fact, there's a whole web of nerve connections woven into the entire fabric of all human tissue. It's not just muscle - skin and our organs too  have nerve endings which send and/or receive information.

It's this "world wide web" of nerve endings that allows us to have such fine control over our muscles, a facet of movement known as proprioception.


When things go wrong

Certain medical conditions like Parkinson's Disease, Motor Neuron Disease and Multiple Sclerosis all affect the nervous system and therefore interfere with the electrical impulses going to muslces. 

But more common conditions can also cause disruption to the nerve impulses destined for muscles. If a nerve gets trapped or compressed, it can cause innervation of the muscles along the route of the nerve.

Take for example sciatica, where the sciatic nerve which runs from the base of the spine all the way down the back of the leg becomes compressed. People with sciatica will experience pins & needles, muscle ache,  or pain in the muscles of the upper and lower leg.

In some cases, an overworked muscle can compress the nerve - so whilst around 90% of cases of sciatica are due to disc compression at the root of the sciatic nerve at the spine, most of the remainder of cases of sciatica  are due to the overworking of a muscle called the piriformis (at the side of the buttock) which can grow too big for the space it's in and compress the nerve.

Most of the time, if you're getting repeated pins & needles, pain like electric shocks, or muscles contracting involuntarily, then it's going to be something to do with your nerves.

If you've been to the doc, and it turns out that it's a compressed nerve due to an overworked muscle, or repetitive strain, then give me a call & I'll help.