The Human Neck:



The Human Neck: A Simplified Method of Teaching Anatomy

Jim Holman

Ridgefield High School

Ridgefield, WA 98642

Mentor:

Anita Vasavada, Ph.D.

School of Chemical Engineering and Bioengineering

Washington State University

Pullman, WA 99164

A project supported by the National Science Foundation Grant #EE-0338868

Project Summary

The human body is an amazing jungle of complicated structures. Perhaps one of the more complicated areas is the neck. Because there are so many small parts to it, this module will take a holistic approach to teaching the anatomy of the neck.

The module will first cover the physiology of the neck, followed by images of neck anatomy enhanced by a physical model to help demonstrate the components of the neck. Finally, the module will cover the use of software that is intended to allow students to manipulate the neck joints and view the muscles in simulated action, as well as plot muscle properties (such as length or force) vs. joint angle (head position).

Introduction

Science and Engineering are often referred to as the same processes. Although they are closely related, there are notable differences between them. Some of these differences include the facts that science is deductive and qualitative, while engineering is conductive and quantitative. In general terms, scientists ask themselves the question, “Why does that happen?”, while engineers as themselves, “how can I use that to make something else happen.” The goal of the SWEET (Summer at WSU-Engineering Experiences for Teachers) Program is to expose science teachers to engineering in hopes that the teachers will in turn expose their students to engineeringthereby increasing student interest in the field.

This module will focus on simplifying the neck to more effectively teach the anatomy to high school biology students. The anatomy of the human neck is very detailed and complex, much more so then the average biology class will undertake. Therefore, by simplifying the entire region into general pieces, and using physical and computer models to simplify and focus on the most important parts of the neck, the overall effect of the neck anatomy can be taught at a manageable level. In keeping with the theme of learning the neck in a holistic approach, the function and general anatomy of the neck will be stressed, rather than memorization of each and every portion. The main instructional tool of this module will be lecture, but it will include many chances for students to get hands-on experience with the physical models and SIMM program.

The module will begin with a lecture on the process of muscle contraction. Covered in this section will be the process of how a muscle contracts, how a contraction is triggered, and how a muscle gets energy to contract. This review will contain diagrams and explanations to help maintain the knowledge of the process. Next, an introduction to anatomy terms will be included to ensure that students are proficient with the terms and their meanings.

The module will then cover the anatomy of the neck. The anatomy of the neck will be subdivided into covering the muscles and bone features in the neck. Both will be discussed in conjunction with a physical model and computer simulation of the head/neck region.

Finally, the module will conclude with an in-depth examination of the computer simulation software, called SIMM. The module will contain direction in using the program as well as how to go about obtaining it. As was mentioned previously, the physical model and computer program models were designed to be used simultaneously.

Goals and Objectives

The goal of this module is to provide a useful unit on the anatomy of the human neck. Upon completion of this module, students will be able to:

1. Describe the structure of a skeletal muscle

2. Explain the role of myosin and actin containing myofilaments

3. Describe the events of a muscle cell contraction

4. Explain how ATP is generated during muscle contraction

5. Describe the events that lead to a muscle contraction

6. List the eight muscles covered in this module, as well as their insertions, origins and function

7. State the location of the eight muscles on the physical model and SIMM model

8. List and locate the bones of the neck

9. Operate and manipulate the SIMM models

10. Explain in their own words what happens to a human during whiplash.

11. Apply correct anatomical terminology when discussing the orientation of body

parts (anatomical terms).

Muscle Contraction

Please refer to the following website for a diagram of the key players in muscle contraction:



The thick and thin filaments do the actual work of a muscle. Thick filaments are made of a protein called myosin. At the molecular level, a thick filament is a shaft of myosin molecules arranged in a cylinder. Thin filaments are made of another protein called actin. The thin filaments look like two strands of pearls twisted around each other.

[pic]

During contraction, the myosin thick filaments grab on to the actin thin filaments by forming crossbridges. The thick filaments pull the thin filaments past them, making the sarcomere shorter. In a muscle fiber, the signal for contraction is synchronized over the entire fiber so that all of the myofibrils that make up the sarcomere shorten simultaneously.

[pic]

There are two structures in the grooves of each thin filament that enable the thin filaments to slide along the thick ones: a long, rod-like protein called tropomyosin and a shorter, bead-like protein complex called troponin. Troponin and tropomyosin are the molecular switches that control the interaction of actin and myosin during contraction.

While the sliding of filaments explains how the muscle shortens, it does not explain how the muscle creates the force required for shortening. To understand how this force is created, let's think about how you pull something up with a rope:

1. Grab the rope with both hands, arms extended.

2. Loosen your grip with one hand, let's say the left hand, and maintain your grip with the right.

3. With your right hand holding the rope, change your right arm's shape to shorten its reach and pull the rope toward you.

4. Grab the rope with your extended left hand and release your right hand's grip.

5. Change your left arm's shape to shorten it and pull the rope, returning your right arm to its original extended position so it can grab the rope.

6. Repeat steps 2 through 5, alternating arms, until you finish.

Please refer to the following website for an illustration of this concept:



To understand how muscle creates force, let's apply the rope example.

Myosin molecules are golf-club shaped. For our example, the myosin clubhead (along with the crossbridge it forms) is your arm, and the actin filament is the rope:

During contraction, the myosin molecule forms a chemical bond with an actin molecule on the thin filament (gripping the rope). This chemical bond is the crossbridge. For clarity, only one cross-bridge is shown in the figure above (focusing on one arm).

Initially, the crossbridge is extended (your arm extending) with adenosine diphosphate (ADP) and inorganic phosphate (Pi) attached to the myosin.

As soon as the crossbridge is formed, the myosin head bends (your arm shortening), thereby creating force and sliding the actin filament past the myosin (pulling the rope). This process is called the power stroke. During the power stroke, myosin releases the ADP and Pi.

Once ADP and Pi are released, a molecule of adenosine triphosphate (ATP) binds to the myosin. When the ATP binds, the myosin releases the actin molecule (letting go of the rope).

When the actin is released, the ATP molecule gets split into ADP and Pi by the myosin. The energy from the ATP resets the myosin head to its original position (re-extending your arm).

The process is repeated. The actions of the myosin molecules are not synchronized -- at any given moment, some myosins are attaching to the actin filament (gripping the rope), others are creating force (pulling the rope) and others are releasing the actin filament (releasing the rope).

[pic]

Please refer to the following website for demonstrations of how muscles contract:



Triggering the Contraction

Let’s examine what occurs within a skeletal muscle, from excitation to contraction to relaxation:

1. An electrical signal (action potential) travels down a nerve cell, causing it to release a chemical message (neurotransmitter) into a small gap between the nerve cell and muscle cell. This gap is called the synapse.

2. The neurotransmitter crosses the gap, binds to a protein (receptor) on the muscle-cell membrane and causes an action potential in the muscle cell.

3. The action potential rapidly spreads along the muscle cell and enters the cell through the T-tubule.

4. The action potential opens gates in the muscle's calcium store (sarcoplasmic reticulum).

5. Calcium ions flow into the cytoplasm, which is where the actin and myosin filaments are.

6. Calcium ions bind to troponin-tropomyosin molecules located in the grooves of the actin filaments. Normally, the rod-like tropomyosin molecule covers the sites on actin where myosin can form crossbridges.

7. Upon binding calcium ions, troponin changes shape and slides tropomyosin out of the groove, exposing the actin-myosin binding sites.

8. Myosin interacts with actin by cycling crossbridges, as described previously. The muscle thereby creates force, and shortens.

9. After the action potential has passed, the calcium gates close, and calcium pumps located on the sarcoplasmic reticulum remove calcium from the cytoplasm.

10. As the calcium gets pumped back into the sarcoplasmic reticulum, calcium ions come off the troponin.

11. The troponin returns to its normal shape and allows tropomyosin to cover the actin-myosin binding sites on the actin filament.

12. Because no binding sites are available now, no crossbridges can form, and the muscle relaxes.

As you can see, muscle contraction is regulated by the level of calcium ions in the cytoplasm. In skeletal muscle, calcium ions work at the level of actin (actin-regulated contraction). They move the troponin-tropomyosin complex off the binding sites, allowing actin and myosin to interact.

Please refer to the following website for a demonstration on triggering a contraction and binding sites:





Energy for Contraction

Muscles use energy in the form of ATP. The energy from ATP is used to reset the myosin crossbridge head and release the actin filament. The three ways that muscles can produce ATP are:

1. Break down creatine phosphate, adding the phosphate to ADP to create ATP

2. Carry out anaerobic respiration, by which glucose is broken down to lactic acid and ATP is formed

3. Carry out aerobic respiration, by which glucose, glycogen, fats and amino acids are broken down in the presence of oxygen to produce ATP

Muscles have a mixture of two basic types of fibers: fast twitch and slow twitch. Fast- twitch fibers are capable of developing greater forces, contracting faster and have greater anaerobic capacity. In contrast, slow-twitch fibers develop force slowly, can maintain contractions longer and have higher aerobic capacity.

Teaching Point: (ask students the following to check for understanding)

- When would you use different types of muscles?

- What do you think the fiber type of neck muscles?

Anatomical Terms

Directional Terms

Superior or cranial- toward the head end of the body; upper (example, the hand is part of the superior extremity).

Inferior or caudal- away from the head; lower (example, the foot is part of the inferior extremity).

Anterior or ventral- front (example, the kneecap is located on the anterior side of the leg).

Posterior or dorsal- back (example, the shoulder blades are located on the posterior side of the body).

Medial- toward the midline of the body (example, the middle toe is located at the medial side of the foot).

Lateral- away from the midline of the body (example, the little toe is located at the lateral side of the foot).

Proximal- toward or nearest the trunk or the point of origin of a part (example, the proximal end of the femur joins with the pelvic bone).

Distal- away from or farthest from the trunk or the point of origin of a part (example, the hand is located at the distal end of the forearm).

Planes of the Body

Coronal Plane (Frontal Plane)- a verticle plane running from side to side; divides the body or any of its parts into anterior and posterior portions.

Sagittal Plane (Lateral Plane)- a verticle plane running from front to back; divides the body or any of its parts into right and left sides.

Median plane- sagittal plane through the midline of the body; divides the body or any of its parts exactly into right and left halve

Axial Plane (Transverse Plane)- a horizontal plane; divides the body or any of its parts into upper and lower parts.

[pic]

Neck Anatomy

Muscles:

|Muscle |Color |Origin |Insertion |Functions |

|Sternocleidomastoid |Red |Skull |Sternum |Flex, Tilts head |

|Upper Trapezius |Blue |Skull |Clavicle |Turn/tilt head |

|Lower Trapezius |Blue |C7 |Scapula |Turn/tilt head |

|Splenius cervicis |Green |C7 |C3 |Rotate/tilt head/extend |

|Iliocostalis capitis |Brown |3rd Rib |C5 |Extend/bend spine |

|Longissimus capitis |Purple |C6 |Skull |Extend/bend spine |

|Scalenus |Orange |C5 |2nd Rib |Flexes neck |

|Semspinalis capitis |Yellow |C5 |Skull |Extend/rotate head |

**Color refers to the color of the corresponding muscles on the physical and SIMM models.

Bone

The normal anatomy of the spine is usually described by dividing up the spine into 3 major sections: the cervical, or neck, the thoracic, or trunk/ribcage, and the lumbar spine, or lower back. Each section is made up of individual bones called vertebrae. There are 7 cervical vertebrae and these make up the bones of the neck.

Please refer to the following website to see a diagram of the vertebral column:



An individual vertebra is made up of several parts. The body of the vertebra is the primary area of weight bearing and provides a resting place for the fibrous discs which separate each of the vertebrae. The lamina covers the spinal canal, the large hole in the center of the vertebra through which the spinal nerves pass. The spinous process is the bone you can feel when running your hands down your back. The paired transverse processes are oriented 90 degrees to the spinous process and provide attachment for back muscles.

[pic]

There are four facet joints associated with each vertebra. A pair that face upward and another pair that face downward. These interlock with the adjacent vertebrae and provide stability to the spine, as well as allow movement between vertebrae.

The vertebrae are separated by intervertebral discs which act as cushions between the bones. Each disc is made up of two parts. The hard, tough outer layer called the annulus, or fibrous, surrounds a mushy, moist, gel-like center termed the nucleus.

The general functions of the spine are to:

1. Bear the weight of the head and other objects above

2. Allow movement of the back, neck, and head.

3. Protect the spinal cord.

As you can see, the spine needs to be strong yet flexible!

Please refer to the following website to view diagrams of two vertebrae and their components:

SIMM

Using This Simulation

Please refer to the MusculoGraphics website at the following address in order to view products and demonstrations or to apply to download the SIMM Tryout Version that is necessary to successfully complete this module:

** When requesting the download information, please refer to the SWEET Program at Washington State University and Dr. Anita Vasavada.

Produced by MusculoGraphics, Inc., SIMM (Software for Interactive Musculoskeletal Modeling) is a graphics-based software package that enables the customer to quickly develop and analyze musculoskeletal models. In SIMM, a musculoskeletal model consists of representations of bones, muscles, ligaments, and other structures. Muscles span the joints and develop force, thus generating moments about the joints. SIMM enables an analysis of a musculoskeletal model by calculating the joint moments that each muscle can generate at any body position. By manipulating a model using the graphical interface, the customer can quickly explore the effects of changing musculoskeletal geometry and other model parameters on the muscle forces and joint moments.

Basic Operation Instructions

SIMM is an extremely complex program and many commands are necessary to successfully manipulate the models. The initial step for students to complete is to work through the tutorial portion of the program. Although the tutorial is designed using the leg model, the same basic operations will be the same with the neck model.

To Do In SIMM

After completing the tutorial, the students will open the Sample Neck Model under the Help Menu. After also opening the Model Viewer window, the students are now free to experiment with the neck model. The following are required of the students; however, they may feel free to experiment further with the program after completion of the required material.

1. Locate the eight muscles listed previously in the module on both the neck model and the physical model.

2. Describe which muscles are contracting with each of the three motions located in the Model Viewer.

3. Using the Plot Maker, make one plot of muscle length vs. force for one muscle in each of the three motions.

4. View the whiplash simulation and describe what happens to a human neck during this trauma.

** Each step MUST be observed by the teacher before advancing to the next step.

Biology and Engineering

After looking at the neck in Biology class, it is important to address the fact that Biology and Engineering work side by side in a lot of cases. Some of these cases are the use of models to analyze clinical calculations (like whiplash). It is important that engineers understand how the head moves, because they want to prevent the extreme movements experienced in whiplash. This takes not only an understanding of the neck, but also of math and physics. Other areas that Biology and Engineering work together are in accident reconstructions, and in the process of easing neck and lower back pain.

Teaching Point: What are some possible solutions to minimizing whiplash?

References

Some of the URL’s listed below have already been cited. The remainder may be of use to expand other concepts. Several of these Websites were employed as sources of information for this module.





















................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download