EMG Chewing Lab

Today, we are going to explore a lab that was conducted in class this week. The goal of this lab was to monitor the electrical activity of the masseter muscle as different foods were eaten, and discover which foods require the most electrical activity. To accomplish this, a group member attached monitors to their cheek and forearm, and ate four different foods. For a constant variable, we also tracked the electrical activity of the jaw when it was at rest and when it was clenched. 

As the monitor collected data, it recorded it in a chart where wavelengths were visible and could be measured. These charts can be seen below.

Penut Butter and Jelly Sandwich Chart

 Cookie Chart

Ruffles Potato Chips Chart 

Oreo Ball Chart

 Compiled mV Data 

Relaxed Jaw/Clenched Jaw Chart

 To find the delta mV, we measured the Maximum mV of a given wave and subtracted the Minimum mV from it. The resulting number was then graphed. We repeated this process for the constant variables and the other foods.

The graph below illustrates the compiled data from the experiment.

As you can see from the graph, the peanut butter and jelly sandwich required the most electrical muscle activity, 0.538 mV, while the chips required the least amount of electrical activity, 0.38 mV.  I believe this was the case as a result of the textures of the foods. The Oreo ball and PB&J were much "gooey-er" than the other foods, which were light and crunchy. More effort was required to break down the softer, stickier substances than the cookie and chips, resulting in more electrical use.

The results from this lab were very different than my hypothesis- the complete opposite, in fact. I thought that the chips would require more electrical activity, as the initial bite is more difficult than the initial bite of the PB&J. I did not take into account, however, the following bites. The chip became easier to chew the longer it was in the subject's mouth, while the PB&J only varied slightly. It is also more difficult to complete the bite through a sticky substance than it is to take a quick, sharp bite from a chip, which I had not thought about, either. It would be very interesting to repeat this lab with different, more diverse foods, such as steak and raw carrots. This would show more varying results than those reflected in the original experiment.

Thanks for joining in the exploration of electrical muscle activity!

Muscle Anatomy and Physiology Model Building

Hello everyone! Today we are going to discuss muscle anatomy as well as the anatomy and physiology of the neuromuscular junction. 

First up is the skeletal muscle anatomy, as can be seen in the illustrations below. The first picture shows the muscle in its entirety while the second depicts a zoomed-in view of the myofibril. 

As you can see, each part of the muscle anatomy is composed of bundles of fibers that work together. This is a very general description, however, it can be broken down to the parts labeled above.

Next is the anatomy and physiology of the neuromuscular junction. In basic understanding, the neuromuscular junction is where a motor neuron can transmit a signal to the muscle fiber, which then causes the muscle to contract. Just like in the muscle, there are multiple components to this junction. 

To begin with, calcium enters the neuron through the voltage-gated calcium channel. This begins a process that results in the secretion of a neurotransmitter, acetylcholine, from the axon terminal. The acetylcholine travels across the synapse until it is intercepted by the acetylcholine receptors within the muscle cell membrane. The acetylcholine causes sodium ions to passe through the neurotransmitter-gated channel in the acetylcholine receptors, and into the muscle cell. Once it has done its job, the acetylcholine is broken down by an enzyme called acetylcholinesterase. This prevents the muscle from overcontracting. As the sodium ion passes through the neurotransmitter-gated channel, it depolarizes and excites the muscle cell membrane upon entrance. The muscle then contracts due to this impulse, and the neuromuscular junction has served its purpose, for the time being.

To make this model, I used styrofoam, a funnel, and "I Love Lucy"'s Vitameatavegamin candies.

Check out a video of the neuromuscular junction model here: http://youtu.be/Vt8lekZoBUI.

Thanks for joining me in this lesson about muscle anatomy and physiology!

Bone Growth, Development, and Remodeling

Bones are very interesting in both their growth and function, as well as their recovery after damage has occurred. We are going to explore this further, beginning with bone growth and development.

Bone Growth and Development Overview
When babies are born, their skeletal system contains 300 components. These components are actually pieces of cartilage, which undergo a process called ossification, that allows them to become bone. The bony skeletal structure begins to develop at 8 weeks, endochondral ossification begins at the second month, and bone growth continues even after birth.

Bony skeleton development: 

http://images.agoramedia.com/wte3.0/gcms/fetal-development-skeletal-system-article.jpg

Cartilage contains no blood vessels or nerves, and are surrounded by perichondrium, which prevents outward growth. Some of the cartilage remains, however, such as that found in the nose and ear. Cartilage can be classified as hyaline, elastic, or fibrocartilage. Matrix is secreted both inside and against the outside of the bone, through appositional and interstitial processes. This calcifies, or hardens the bone. Cartilage calcifies during normal bone growth, as well as during old age, which causes arthritis.

The pieces that do ossify often fuse together, creating a skeletal system of 206 bones by the end of development. Bones can be classified into two categories: axial skeleton and appendicular skeleton. The axial skeleton contains the bones of the skull, vertebral column, and rib cage. The appendicular skeleton contains the bones of the upper and lower limbs, as well as the shoulders and hips. Bones can also be classified as long bones, short bones, flat bones, and irregular bones. Long bone growth generally stops around the end of puberty, which prevents you from getting taller.

Fetal skull before fusion:

http://bio.sunyorange.edu/updated2/embry.html/2.The%20Skeletal%20System_files/45%20FRONTAL.jpg

Skull after fusion:

https://shortnotesinplasticsurgery.files.wordpress.com/2012/04/1289-and-1290.jpg

The Ossification Process 

There are two types of ossification: intramembranous ossification, which replaces the thin connective tissue membrane with bone, and endochondral ossification, which replaces fetal cartilage with bone. Both types, however, rely on the thyroid hormone calcitonin for the regulation of calcium metabolism.

In bone production, there are three really important cells to consider: osteoblasts, osteoclasts, and osteocytes. Since your bones are always either growing or adapting to support your body, there are cells that will actually destroy bone, and others that will repair the bone to support its new requirements. Osteoclasts originate in bone marrow, and move to the bone surface where they will eat away old bone or protuberances that are out of place. Osteoblasts also come from the marrow and make their way to the surface to fill in cavities and restore bone. After their job is done, they flatten and line the surface of the bone. They then work to regulate calcium, as well as activate osteoclasts through the production of special proteins. Osteocytes come from osteoblasts and can be found inside the bone. As the osteoblasts build the bone, some surround themselves with new material while extending "arms", called dendrites, to other osteocytes. Osteocytes sense pressures and cracks, and help direct osteoclasts to where the bone needs to be dissolved.

The process of ossification:

http://skeletalsystemdev.weebly.com/uploads/7/0/4/3/7043675/5513674_orig.jpg?467

Diagram of osteoclasts, osteoblasts, and osteocytes in action:

http://www.nature.com/bonekey/knowledgeenvironment/2012/120229/bonekey201236/images_article/bonekey201236-f1.jpg

Diagram depicting bone growth and remodeling:

http://classes.midlandstech.edu/carterp/Courses/bio210/chap06/Slide17.JPG

And there you have it: the background of bone growth, development, and remodeling!