Compendium Review: Unit 3 Chapters 11&12

Movement: Muscle and Bone Table of Contents: I. Introduction II. Muscle A. Overview of Muscular System B. Muscle cell structure 1. parts of muscle cells 2. calcium release in muscle C. Sliding Filament Model 1. whole muscle contraction 2. muscle contraction requires energy III. Bones A. Overview of skeletal system B. Structure of Bone 1. fetal bone formation 2. growth plate 3. medullary cavity C. Calcium Regulation and Bone D. Osteoporosis IV. Joints A. Movement Across Joints B. Technical Vocabulary 1. flexion and extension 2. adduction and abduction 3. rotation and circumduction C. Total Movement Picture V. Conclusion I am always in motion. Whatever it is that I’m doing, my body never seems to stop moving. And, there are times when I am not even conscious to particular movements that my body is creating. What causes the possibility for these bodily actions? Due to the structure of the human body, movement is caused by muscle, bone, and joints. And each part contains particular structures and processes that aid in the body’s motor output.

Movement occurs from the muscles in the body. And, “…all muscles, regardless of their particular type, can contract…and when muscles contract…the body…moves” (Mader 228). There are three types of muscle such as, smooth, cardiac, and skeletal, that has different structures, is located throughout different regions of the body, and has contrasting functions that are either involuntary or voluntary. Skeletal muscles, in particular, have several different functions such as, body support, and movement of bones, uphold body temperature, aid in the movement of cardiovascular veins and lymphatic vessels, and the protection of internal organs. The appearance of skeletal muscle has striated fibers that are attached to the body’s skeleton, allowing for voluntary movement. Skeletal muscles also operate in opposite pairs (bicep and tricep) to allow for the pulling of muscle contraction. The skeletal muscles, along with the other types of muscles, are made up of cells.
These cells are called muscle fibers that contain several components. And, “each muscle fiber…is innervated by a motor neuron that controls the contraction of the fiber” (entochem.tamu.edu/VertInvertContractswf/index.html). Each muscle cell has a plasma membrane called the sarcolemma. As in all cells throughout the body, the sarcolemma is a polarized membrane that allows for particles to pass in and out. The muscle cell also has cytoplasm called sacroplasm and an endoplasmic reticulum called the sacroplasmic reticulum. The sacroplasm contains all the organelles in the cell and the sacroplasmic reticulum is the, “…smooth ER of a muscle fiber that stores Ca2+” (Mader 232). But, the muscle fibers also have some special features. For example, the sarcolemma in the muscle fiber contains T-tubules that run the length of the cell and communicates
Figure 1: Structure of muscle cell
nerve impulses that create the release of calcium ions from the sacroplasmic reticulum. The release of calcium from the sacroplasmic reticulum occurs in several steps. First, motor neuron’s messages arrive at the ends of the neuron’s axon. Then, the process of the neuro-muscular junction synapse (small gap where the axon terminal is separated from the sarcolemma, causing the release of acetylcholine and the binding of this discharge with ACh receptors) precedes the motor neuron’s plan to the muscle fibers. Next, the process of action potential (the depolarization and repolarization of the sarcolemma by the opening and closing of sodium and potassium gates, causing voltage change) takes place in the sarcolemma. This voltage change from action potential causes the calcium ions to release from the sacroplasmic reticulum, which in turn causes the muscle to contract from the shortening of protein units. The shortening of the protein units, which are called actin and myosin units (or sacromeres) from the release of calcium can be applied to the sliding filament model.
The sliding filament model consists of the movement of the actin and myosin units. The actin units slide past the myosin units, creating an advance towards one another. This creates the shortening of the actin units by moving inward and the myosin units to almost fade away. This also occurs from the use of the energy, ATP, which is broken down by the myosin units in order for the myosin cross-bridges to connect to the actin units and pull them forward. Muscle filaments can also produce and use energy in other means. Figure 2: Sliding filament model where sarcomere shortens due to actin-myosin units pulling inward.
The use of energy can be produced and used by the CP pathway, which is anaerobic, fermentation, which is also anaerobic, and cellular respiration, which is aerobic. The CP pathway is, “the simplest and most rapid way for muscle to produce ATP…because it only consists of one reaction” (Mader 237). This reaction allows for creatine phosphate (ADP) to immediately change into creatine (ATP). This process is used when the muscles are used during short-term, intense exercise that lasts less than ten seconds. The process of fermentation, “…produces two ATP from the breakdown of glucose to lactate…” (Mader 237). This is also a rapid use of production of energy, but creates the buildup of lactate, which cannot be metabolized quick enough by the cells to maintain homeostasis. And, cellular respiration allows for the use of energy, but at a slower release, from stored energy in the muscles called glycogen. Along with movement occurring by the way of the muscles, it also happens with the aid of the bones.

The bones are a part of the body’s skeletal system. Bones have several functions that allow for survival. They help support the body such as, the legs and the pelvis, protect vital parts of the body such as, the brain, heart and lungs, and nerves in the spinal chord, produces blood cells, stores minerals such as, calcium and phosphate salts, and fat, and allows for flexible body movement. The bones within the body also have particular structures.
The structure of bones begins as early as fetal development and follows a process of fetal bone formation and remodeling that continues throughout a lifetime. And the process of bones growth can occur by several different cells such as, osteoblasts, osteocytes, and osteoclasts. It first begins with a bone model made of mostly cartilage. Then, bone-forming cells called osteoblasts, cover the main portion of the newly forming bone, which is called the diaphysis, with organic secretions and deposition of calcium. Next, blood vessels located within the bone, cause the osteoblasts to form spongy bone, which has thin plates that are separated by uneven spaces. After that occurs, the medullary cavity is formed, which is located in the diaphysis that will eventually composed of compact bone. Also, the second phase of ossification begins to appear on the epiphyses of the developing bone, which is the expanded area on the end of bones where red blood cells are created. Then, growth of the bones continues throughout adolescence, due to the cartilage within the medullary cavity. And lastly, the epiphysis growth plate, which is a grouping of cartilage below the epiphysis of the bones, allows for the body to keep increasing in length as long as the growth plates consist within the bones. But when the growth plates close off bone growth, the bone stops increasing length. Along with the growth of bones, the regulation of bone also occurs from calcium.
Inside bones, the mineral, calcium, is stored. The osteoclasts cells, which are, “…bone-absorbing cells…” (Mader 210) break down bone, which is then renewed by the osteoblasts. This process helps keeps bones at their strongest point and allows for the regulation of calcium into the bloodstream. It occurs with a negative feedback mechanism by keeping blood calcium levels at a constant state. But, there are results that can occur from the use of calcium that creates a contrary perspective of the role of bone.
The negative result of osteoporosis can occur. Osteoporosis is, “…a disease of bone in which the bone mineral density (BMD) is reduced, bone micro architecture is disrupted, and the amount and variety of non-collagenous proteins in bone is altered” (en.wikipedia.org/wiki/Osteoporosis). It occurs when calcium need within the body exceeds the role of bone support, causing bone resorption to take place more rapidly than calcium deposition from the
Figure 3: Osteoporosis in the bones.
osteoblasts and osteoclasts. Unfortunately, it can lead to many more incidences of bone fracture and effects more groups of elderly women. Osteoporosis can be prevented from healthy lifestyle choices such as, intake of calcium in diet and weight bearing activates. Along with the occurrence of movement from muscles and bones, joints also have a significant role.

Joints are the central area where bones are connected and muscles attach to or extend over. And there are specific kinds of joints. One type is called synovial joints. A synovial joint is, “…a joint having a cavity filled with synovial fluid, a lubricant for the joint” (Mader 222). This type of joint allows for a one way movement of the limbs, because they are structured like a pivot. As the body moves, the contraction of the muscles cause the bones to shift in relevance to another bone and is aided by the joints. There are also specifics that describe these movements permitted by synovial joints.
Figure 4: Structure of synovial joint.

The first is the action of flexion and extension. Flexion is the type of joint movement that decreases the angle of the joint and extension allows for the angle of the joint to increase. The second type of action is adduction and abduction. Adduction allows synovial joints to move body parts toward the center of the body and abduction allows the movement of body parts away from the center of the body. The third type is rotation and circumdution. Rotation is the synovial joint’s movement of it moving around its specific axis and circumfusion makes the bodily movement of a cone-shape. And lastly, the movement of inversion and eversion, allows for the foot to turn inward or outward. Overall, the process of the total movement picture possesses three major points.
The first point of the total movement picture is the process of neurons. Stimuli that are provided by the external or internal environments, triggers muscle to contract. Then, in order for muscles to contract, the actin and myosin units slide towards each other in the sliding filament model. And lastly, the muscles cause the drawing of bones that causes the movement across joints.

I am always in motion. And it is due to the structure of the human body of muscles, bones, and joints, that I am able to perform movement. Muscles consist of muscle fibers that allow for organelles to perform specific processes such as, calcium release, the sliding of actin-myosin units, and the use of energy. Bones help support the body, produce blood cells, store mineral salts, protect vital areas of the body, and allow for flexibility. And joints are the area where bones and muscles connect and are able to work together in unison by permitted movements. This provides total movement by response to stimuli by the nervous system.

Sources:
Works:
Human Biology 10e. Mader, Sylvia S.
en.wikipedia.org/wiki/Osteoporosis
entochem.tamu.edu/VertInvertContractswf/index.html
Pictures:

www.mhhe.com/.../s5/assets/images/anm5s5_1.jpg

www.ucl.ac.uk/news/ucl-views/images/osteo.jpg
trc.ucdavis.edu/.../week10/slidingfilament.gifwww.visit-islay.com/.../body_files/image002.gif