Welcome to another Spinal Column. Last time we were investigating cardiac muscle, which means that this subject will conclude today with a quick look at smooth muscle.

Smooth muscle contains the same elements as striated muscle. However, due to a different arrangement of the contractile proteins, this muscle lacks the striations typically found in skeletal muscle.

Smooth muscle is found in arteries and veins, the urinary bladder, and the gastrointestinal tract. In many cases, smooth muscle exhibits spontaneous activity that is modified by neural and hormonal factors.

Smooth muscle cells are usually arranged in sheets that are either arranged longitudinally or circularly.

A combination of both orientations is needed to generate the peristalsis and segmental movements within the gastrointestinal tract.

As with cardiac cells, some of the smooth muscle cells are triggered to contract by action potentials from adjacent cells, which exhibit an intrinsic pattern of depolarisation called pacemaker activity.

This creates slow regular waves of contractions within the tract that vary in length from three to 20 seconds. The neural control of the bowel is co-ordinated by the central and autonomic nervous system.

This allows co-ordination of the muscles and glands so that the appropriate amount of blood is directed to the stomach and intestines for the uptake of nutrients when digestion and absorption occur.

Due to the neural control of the bowel, adjustments made with manipulation to the lumbar spine and pelvis can have a positive influence on a sluggish bowel.

It is not uncommon for people who attend for chiropractic treatment of a low back problem to experience an improvement in the frequency of bowel movements.

Manipulation of the low back and pelvis in children also improves the occasionally distressing problem for constipated youngsters.

Some patients report a decrease in the frequency of painful spasms from Irritable Bowel Syndrome commonly known as IBS. Ensuring optimal function of the joints of the pelvis and lumbar spine allows the nerve supply to the bowels to pass from the spinal cord unhindered, thus facilitating bowel motility.

The urinary bladder is a sac of smooth muscle lined with epithelial cells that stretches as it fills with urine. The junction of the bladder and the urethra forms the internal sphincter that also consists of smooth muscle.

Another site of smooth muscle is the eye. The iris is a pigmented ring of smooth muscle that controls the amount of light entering the pupil before it hits the lens and is refracted onto the retina.

The smooth muscle allows the aperture formed by the pupil to be changed by six fold, resulting in a thirty fold difference in light entering the eye. I hope this short overview has highlighted the different characteristics and locations of the various muscle types.

In response to requests from readers, forthcoming columns will provide information regarding specific subjects and will include a case history relating to the particular subject where possible.

Some of the forthcoming subjects will be types of arthritis such as rheumatoid, osteoarthritis and ankylosing spondylitis. I have also been asked to cover subjects including asthma, osteoporosis, spinal fusion, discectomy and laminectomy. If you have any comments or suggestions, please contact Ilkley Chiropractic Clinic on 605060.