In the last blog post I went through how the nervous system is organised and gave a brief overview of what the different components actually do for us. For the next two or three post I’d like to delve a little deeper into these components, starting with the sensory (afferent) nerves. The sensory nerves do exactly what it says on the tin, they relay information from the body back to the CNS from thousands of receptors that sense what is going on around them. This way the CNS has a constant flow of updated information on the status of the body and its surrounding area so that it can then react in the right way. The information a particular sensory nerve carries depends on the type of receptor it is attached to. These receptors either provide information about the external environment (exteroceptors), internal environment (interoceptors) or about body, joint and muscles position (proprioceptors).
The exteroceptor, interoceptor and proprioceptor groups are, in turn, composed of specific receptors that are named after the jobs they do. Mechanoreceptors detect mechanical pressure and provide the sensations of touch, pressure, vibration, positional sense, hearing and equilibrium. Thermoreceptors detect changes in temperature while nociceptors are stimulated by physical and chemical damage to tissues (i.e. pain). Photoreceptors detect light in the retina of the eyes, while chemoreceptors detect chemicals in the mouth (taste), nose (smell) and bodily fluids. Finally, osmoreceptors sense the osmotic pressures in the body’s fluids. Not all sensory nerves, however, have specific receptors attached to them, with many having free nerve endings that are stimulated by pain, heat, tickling and itching.
The majority of the sensory information is passed along the sensory nerves to the spinal cord and then up to the brain to be interpreted and acted upon. However, some of the information (mechanoreceptor information about overstretched muscles for example) gets interpreted at the spinal cord for speed of reaction and is called a reflex.
Due to the fact that the sensory nerves pass through the spine to get to the spinal cord, a chiropractor must test them in order to find out whether spinal damage is compromising the flow of information. This is done by conducting a sharp/soft touch test and by testing a person’s reflexes. The detection of a change in the reflexes or sensation not only indicates that a mechanical problem is compromising nervous system, but the location of the altered reflex of sensation also indicates the spinal level the is under stress. This is because the body can be segmented (dermatomes) like a patchwork doll in terms of the specific areas innervated by the sensory nerves. For example, the middle finger is innervated by the sensory nerve that exits the spine between the sixth and seventh cervical vertebrae.
Next time I want to take a closer look at the motor nerves (both the somatic and autonomic divisions. As always, if you have any comments of recommendations on how to improve this blog, please leave them below.
Ever wondered how important your nervous system is? I want to spend the next couple of posts going through what the nervous system does for us and why, in my opinion, it is the most important system in the body. If you think about it we live our lives through our nervous system and without it we won’t even know where we were in space! We can see where we are, hear what’s around us, smell what’s around us, touch what’s around us and taste what’s around us thanks to the flow of information going up and down our nerves and being processed by our brain and spinal cord. Add to that the fact that the central nervous system (the brain and spinal cord) co-ordinates the workings of the internal goings on in the body, like the conductor of an orchestra, and you have the most impressive computer system in the world!! Even nature knows how important it is by protecting its core components (the brain and spinal cord) by encasing them in bone (the skull and the spine).
At its simplest level, the nervous system can be divided into two parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The PNS consists of all the nerves that provide a link between the body and the CNS and can be sub-divided into the sensory (afferent) nerves and the motor (efferent) nerves. The sensory nerves pass information from all the sensory organs of the body back to the CNS to be processed, while the motor nerves pass instructions from the CNS to all the muscles, organs and tissues of the body. The motor nerves can be further divided into the somatic nervous system (communicating with the voluntary skeletal muscles) and the autonomic nervous system (itself being sub-divided into the sympathetic and parasympathetic systems) allow the CNS to control the organs of the body and all the sub-conscious bodily processes e.g. breathing and movement within the digestive tract. I’m going to look at the somatic and autonomic nervous systems in a little more detail over the next two posts in order to give you a deeper understanding of what they do for us.
Finally in this post I want to explain why a chiropractor is looking at the nervous system, after all, we’re just bone doctors right? Wrong! A chiropractor is a neuromusculoskeletal doctor i.e. neuro (nerves), musculo (muscles), skeletal (bones). Because the spinal cord runs through the spine, and because the peripheral nerves emerge from the spine through small gaps in close proximity to the spinal joints, freeing up the spinal joints help free up the nerves and therefore helps free up the communication pathways from the CNS to the body.
Next post I will be looking at the sensory nerves and what effect they have on the body. As always, I welcome any comments you may have and, until next time, I hope you keep healthy.
So I’d like to start this post by letting you know how grateful I am for the comments that everyone has left about my last two posts. For a start, it’s great to know that someone is actually read them and it gives me a fantastic incentive to continue writing knowing that people are finding the subject matter interesting and informative. I promise to do my best to keep them coming and making them worth checking out!
In this post I’m going to go through muscles, and in particular the core stabilising muscles that everyone keeps on going on about. Muscles can be classified in a number of different ways, and one of the simplest ways of grouping the skeletal muscles (those that attached to and influence the movement of the skeleton) is into those that stabilise joints and those that mobilise joints. Every joint needs help to fine tune its movement and this is where the core stabilising muscles come into their own. We are not talking about the big bulk muscles here that you see body builders work at in the gym but the tiny muscles that lie deep in the body right next to the joints they help. The major difference between the stabilising muscles and the mobilising muscles is the number of joints that the muscle crosses between its attachment points. Core stabilising muscles only cross one joint (mono-articular muscle) and are therefore perfectly placed to fine tune the movement within that joint e.g. multifidus in the spine, vastus medialis in the knee or the rotator cuff muscles in the shoulder. Mobilising muscles, however, cross two or more joints (bi- and multi-articular muscles) and are therefore better suited to bigger more powerful movements e.g. the biceps and triceps in the arm or the hamstrings and quads of the leg.
Damage or weakening (atrophy) of the core stabilising muscles leads to a reduction in stability of the joint it influences and therefore an increased risk of damage. If we take multifidus in the spine as an example, injury or atrophy leads to overplay within the joint movement and greatly increases the potential that an ordinary movement, such as forward bending or twisting, can lead to irritation of the joint, an inflammatory response by the body and the resultant muscle spasm (your typical acute lower back pain episode). Diagram 3 shows how, while the mobilising muscles provide the ‘guy ropes’ for the spine, it’s damage to the core muscles that ultimately lead to severe stabilising problems.
Hopefully this explains why exercising the core stabilising muscles is so important and why we hear so much about them from gyms and in the media. If you are in to going to classes at the gym then Pilates, Tai-Chi or Callanetics are fantastic to promote core toning. If you are more of a DIY exerciser then all you need is an exercise ball and you can do a full core routine in the comfort of your living room in front of the TV! It doesn’t need to take much time and effort out of your day but please look at fitting it into your daily routine in order to take charge of your own joint health.
OK, so the subject for this fortnight’s blog is the centre piece of the skeleton…the pelvis. You may wonder why I’m dedicating a whole blog post just on the pelvis, but that becomes clear when I tell you that the pelvis not only provides attachment points for the lower limbs and all the muscles of the upper legs, buttocks and lower back, but also provides the foundations for the spine to sit on! Because of its central position in the 3D jigsaw of the skeleton, any contortion or malfunction of the pelvis will have knock on effects on the orientation of the spine and lower limbs, and can therefore be one of the major aggravating factors of spinal problems.
The pelvis is essentially a ring made up of two pelvic bones (comprising of the fusing of the ilium, ischium and pubis bones) and the sacrum (located at the back with the spine sitting on top and the coccyx attached below). The pelvic bones attach to the sacrum at the sacroiliac (SI) joints and attach to each other at the front (anterior) at the symphysis pubis. There are a huge amount of ligaments attached around the pelvic joints in order to stabilise the structure resulting in none of the joints having a great deal of movement. The little movement that is found in these joints is essential to dissipate the huge amount of stress and strain put on the area. Any laxity in these joints however, during the latter stages of pregnancy for example, could lead to an increased potential of damage or irritation in these joints.The movement pattern works in a gyroscopic fashion with the left side of the pelvis moving forward when the right side moves back and visa versa. Taking this movement pattern into account, if one of the SI joints is damaged then it immediately has a knock-on effect on the other one. If that damage leaves the pelvic ring in a contorted position then the spine, which sits on top of the pelvic, will be forced out to the side putting the joints, discs and nervous system under increases stress and increasing the potential to damage.
As mentioned above, the pelvis provides an attachment to a lot of muscles (some of which can be seen in the diagram). These muscles help to strengthen and stabilise the area, but when you look at the power of some of these muscle groups (the quads, the hamstrings, the gluts, the adductors etc.) it’s easy to understand that muscle tightness, imbalance and injury can have a detrimental effect on the mechanics of the area. The pelvis can be tilted forwards, backward or even twisted as a result of tight muscles, adding stress and potential irritation to the joints in the spine, hips, knees and ankles. This is one of the reasons why stretching following exercise is essential to a healthy fully functioning body.
So that’s it for another posting, but next time I’m going to go through the muscles that attach and affect the spine. If you have any feedback on the two posts to date or how the blog can be improved, please feel free to complete the comments section below.
So I’m going to start with the framework to the body and look at the skeleton, particularly the spine. The skeleton is just a series of bones that are joined together at a series of joints in order to provide a moving framework that gives protection to organs and attachment points to muscles, tendons and ligaments. The fact that all the bones joint to the ones next to them means that the skeleton is a massively complicated 3D jigsaw puzzle that forms a chain just like the kids song – “ the foot bone’s connected to the ankle bone, the ankle bone’s connected to the shin bone etc. As a result, damage to one area of the skeleton will have a knock on effect on the areas connected. So an ankle problem could influence the knee, which could influence the hip, which could influence the pelvis, which could influence the spine etc.
The central component of the skeleton is the spine and pelvis and, while a chiropractor can manipulate most of the joints in the body, it is the spine and pelvis that we tend to concentrate on because of its close proximity to the nervous system. The spine is made up of a series of spinal bones (vertebrae) stacked one on top of another and can be split into 3 sections: the Cervical spine (the neck) with 7 vertebrae; the Thoracic spine (the mid back) with 12 vertebrae; and the Lumbar spine (the lower back) with 5 vertebrae. The vertebrae are numbered from top to bottom in each section so C1 is at the top of the neck and L5 is at the bottom of the lower back. As you can see from the diagram above, the spine should be straight when looked at from the front or back but has some natural curves when you look at it from the side. The cervical and lumbar spine curve towards the front (termed lordosis) and the thoracic spine curves backwards (termed kyphosis). If these curves are increased for any reason (e.g. poor posture) then it increases the stress and strain on the joints, discs and nerves.
The joints between the vertebrae (termed facet joints) are at the back of the spine (one each side) and can be seen in the diagram above by the arrows. Between the main body of the vertebrae is also a disc made up of a tough fibrous outer part (shaped like a ring donut) and a softer inner part (with a toothpaste consistency). The gaps to the right of the facet joints provide space for the nerves to exit the spine from the spinal cord. As these gaps (Inter-Vertebral Foramen or IVD’s) are so close to the disc and joint, damage to either structure could have an adverse influence on the nerve….and therefore what ever tissue or organ that that nerve goes to.
OK, that’s it for this post but please feel free to give me any feedback you may have at firstname.lastname@example.org or comment below. Next time I’m going to go through the pelvis and it’s knock on effect on the spine.