Once again on a Saturday – thinking of changing the name – but nothing trivia-wise rhymes with Saturday. This is VERY nerdy – apologies!
This week I’m playing with THEMES. This week:
YOUR BODY IS SO COOL!
Did You Know:
(click image to enlarge)
The HOMUNCULUS is an area in your brain where your physical body, and the amount of sensory and motor/movemnt attention paid to each area by the brain, are mapped out.
In the image above, the left side represents the Somatosensory Strip (or the Sensory side) of the homunculus, and modulates signals within the post-central gyrus (specific region of the brain) coming from the thalamus (which relays sensory and motor signals to the cerebral cortex of your brain), and the size of the body parts drawn on the outside represents the amount of brain energy and physical amount of cerebral cortex tissue used to sense them. Therefore, the disproportioned body image corresponds to how much innervation that body part has in the brain, not to the area of brain used to control the body parts (density, not area – so hard to explain! sorry!).
The right side of the image above represents the Motor Strip (or the Movement side) of the homunculus, and refers to signals within the precentral gyrus (specific area of brain more towards the front of the body than the above area), coming from the premotor area of the frontal lobes, and, once again, the size of the body parts on the outside of the illustration corresponds to the amount of brain energy and physical amount of cerebral tissue (or density of nerve tissue) dedicated to that part of the body.
If you have ever taken a First Aid course done by a Kinesiologist or other Health-Sciences-background instructor, they will tell you to pinch toes, fingers, and cheeks of someone who is passed-out to try and rouse them, because, as you can see above, a lot of brain energy is used to send signals to the brain, maybe enough to wake an unconscious person.
In school, our AWESOME teacher, Michael Bard, did a demonstration of “2-point discrimination” tests to blindfolded students. A student was blindfolded, then Mr Bard used either one or two pencils (about 1/2″ apart), and touched the pencils to the students arm asking “one pencil or two”, then proceeded on hands, back, knee, cheek and fingertips. For example’s sake, let’s say Mr. Bard used two pencils the whole time, most students would only feel one point of touch on the back, knee, and outer arm (where there is less innervation), while feeling two on the hands, fingertips and cheek (because of the dense innervation). The test shows that your brain can determine fine points of touch more accurately in areas of the body with more homunculus attention! Try it yourself!
Mnemonic (sort of):
When I was in school, I really sucked at exams, I knew my stuff, but had so much anxiety I second guessed everything (with varying results). Dermatomes, and Myotomes were really hard for me. This diagram will help visualize some of what I say next:
“A dermatome is an area of the skin supplied by nerve fibers originating from a single dorsal nerve root.” Dermatomes are named according to the spinal nerve which supplies them. The dermatomes form into bands around the trunk but in the limbs their organisation is more complex as a result of the dermatomes being “pulled out” as the limb buds form and develop into the limbs during embryological development.
Each muscle in the body is supplied by a particular level or segment of the spinal cord (Cranial 1-8, Thoracic 1-12, Lumbar 1-5, Sacral 1-5) and by its corresponding spinal nerve. The muscle, and its nerve make up a myotome. This is approximately the same for every person and are as follows:
- C3,4 and 5 supply the diaphragm (the large muscle between the chest and the belly that we use to breathe).
- C5 also supplies the shoulder muscles and the muscle that we use to bend our elbow .
- C6 is for bending the wrist back.
- C7 is for straightening the elbow.
- C8 bends the fingers.
- T1 spreads the fingers.
- T1 –T12 supplies the chest wall & abdominal muscles.
- L2 bends the hip.
- L3 straightens the knee.
- L4 pulls the foot up.
- L5 wiggles the toes.
- S1 pulls the foot down.
- S3,4 and 5 supply the bladder. bowel and sex organs and the anal and other pelvic muscles.”
As you can imagine, remembering all of that was a bit hard for a frazzled mind, so it was suggested that I look up physical ways of remembering all of this and stumbled upon this project done by kids in high school – to this day it is how I remember Dermatomes and Myotomes.
This Day In History:
Sir James Young Simpson, born June 7, 1811 (died 6 May 1870) was a Scottish obstetrician, who discovered the anaesthetic properties of chloroform and successfully introduced it for general medical use. He is also responsible for the medical forceps that we know and still use today. Sir Simpson was also an early advocator of the use of midwives!
Also today, In 1967, the Haight Ashbury Free Medical Clinic opened in San Francisco. According to Wikipedia, due to the many youth descending on the city, many were in need of substance abuse treat ment, mental health services and various medical attention. The clinic was t he model for the modern form of free-clinics that we still have today. Today, the clinic focuses on medical assistance, substance abuse treatment, psychiatric services for those in the prison system, and “Rock Medicine” on-site medical services for public events/concerts.