COMPENDIUM REVIEW #2 FOR UNIT #3

TABLE OF CONTENTS


CHAPTER 11- SKELETAL
1. Overview of the skeletal system
a. Functions
b. Anatomy of a long bone
2. Bone growth, remodeling and repair
a. Bone development and growth
b. Bone remodeling and its role in homeostasis
c. Bone repair
3. Bones of Axial Skeleton
a. Skull
b. Hyoid
c. Rib cage
4. Bones of Appendicular Skeleton
a. Pectoral girdle and upper limb
b. Pectoral girdle and lower limb
5. Articulations
a. Movements

CHAPTER 12 - MUSCULAR SYSTEM

6. Overview of Muscular System
a. Types
b. Functions
c. Skeletal
d. Names and actions
7. Skeletal Muscle and Fiber Contractions
a. Muscle fibers
b. Control of muscle fiber
8. Whole Muscle Contraction
a. Muscles have motor units
b. Energy for contraction
c. Fast twitch and slow twitch muscle fibers
d. Delayed onset soreness
9. Muscle disorders
a. Common conditions
b. Muscular diseases
10. Homeostasis
a. Protect
b. Store and release

CHAPTER 11 - SKELETAL SYSTEM


OVERVIEW OF SKELETAL SYSTEM
The skeleton supports the body, protects soft body parts, produces blood cells, stores minerals
and fat and along with muscles, permits flexible body movement.

In the anatomy of a long bone, the hyaline cartilage covers the ends of the bone. The periosteum covers the rest of the bone. Spongy bone in in the epiphyses. Yellow bone marrow is in the medullary cavity of the diaphysis and compact bone makes up the wall of the diaphysis.
See illustration.*

BONE GROWTH, REMODELING, AND REPAIR

Cells involved in growth, remodeling and repair of bone are: osteoblasts, which are bone forming cells, osteocytes, which are mature bone cells derived from osteoblasts and osteoclasts, which break down and absorb bone.

For bone growth, intramembranous ossification is when bones develop between sheets of fibrous connective tissue. For example, flat bones such as bones of the skull.

Endochondral ossification: cartilaginous models of the bones are replaced by calcified bone matrix. See illustration.*

Bone growth is affected by vitamin D, growth hormone, and sex hormones.

Bone remodeling is the renewal of bone. Osteoclasts break down bone and osteoblasts re-form bone. Some bone is recycled each year. Bone recycling allows the body to regulate blood calcium.

Repair of a fracture requires 4 steps: hematoma formation, fibrocrtilaginous callus, bony callus and remodeling.

BONES OF THE AXIAL SKELETON
The axial skeleton consists of the skull, the hyoid bone, the vetebral column and the rib cage.
The skull is formed by the cranium, which protects the brain and the facial bones. The cranium's major bones are: frontal bone, parietal bones, occipital bone, and the temporal bones.

The hyoid bone anchors the tongue and is the site of attachment of muscles involved with swallowing. The vetebral column is composed of vertebrae separated by shock-absorbing disks, which make the column flexible. It supports the head and trunk, protects the spinal cord, and is a site for muscle attachment. The rib cage is composed of the thoracic vertabrae, ribs, costal cartilages, and sternum. It protects the heart and lungs.

BONES OF THE APPENDICULAR SKELETON

The appendicular skeleton consists of the bones of the pectoral girdles, upper limbs, pelvic girdle and lower limbs.

The pectoral girdles and uppper limbs are adapted for flexibility.
The pelvic girdle and the lower limbs are adapted for supporting weight: the femur is the longest and strongest bone in the body.

Here is an illustration of all 206 bones in our bodies.*

ARTICULATIONS

Bones are joined at joints. There are 3 types of joints.

1. Fibrous joints ( such as the sutures of the cranium) are immovable.
2. Cartilaginous joints ( such as those between the ribs and sternum and the pubic symphysis) are slightly movable.

3. Synovial joints ( which have a synovial membrane) are freely movable. See illustration.*

CHAPTER 12 - MUSCULAR SYSTEM

OVERVIEW OF MUSCULAR SYSTEM

There are 3 types of muscle tissue. 1. Smooth muscle is involuntary and occurs in walls of internal organs. 2. Cardiac muscle is involuntary and occurs in walls of the heart. 3. Skeletal muscle voluntary, contains bundles of muscle fibers called fascicles, and is usually attached by tendons to the skeleton. The functions of skeletal muscles are: help maintain posture, provide movement and heat, and protect underlying organs. See illustration.*

Muscles are named for their size, shape, location, direction of fibers, number of attachments, and action. When achieving movement, some muscles are prime movers, some are synergists, and others are antagonists.

SKELETAL MUSCLE FIBER CONTRACTION

Muscle fibers contain myofibrils. Myofibrils contain actin and myosin filaments. Muscle contraction occurs when sarcomeres shorten and actin filaments slide past myosin filaments.
See illustration.*

- nerve impulses travel down motor neurons and stimulate muscle fibers at neuromuscular junctions.

- the sarcolemma of a muscle fiber forms T tubules that almost touch the sarcoplasmic reticulum, which stores CA ions.

- when CA ions are released into muscle fibers, actin filaments slide past myosin filaments.

- at a neuromuscular junction, synaptic vesicles release acetylcholine, which diffuses across the synaptic cleft.

- acetylcholine(Ach) is received by the sarcolemma, impulses begin and lead to the release of CA.

- CA ions bind to troponin, exposing myosin binding sites.

- myosin filaments break down ATP and attach to actin filaments, forming cross-bridges.

- when ADP and P are released, cross-bridges change their positions.

- this pulls actin filaments to the center of a sarcomere.

WHOLE MUSCLE CONTRATION
Muscles have motor units: several fibers under the control of a single motor axon. Motor unit contraction is described in terms of a muscle twitch, summation and tetanus. The strength of muscle contraction varies according to recruitment of motor units.

In the body, a continuous slight tension is maintained by muscle motor units that take turns contracting.
For energy, a muscle fiber has 3 ways to acquire ATP for muscle contraction.

1. Creatine phosphate transfers a phosphate to ADP, and ATP results. This CP pathway is the most rapid.

2. Fermentation also produces ATP quickly. Fermentation is associated with an oxygen debt because oxygen is needed to metabolize the lactate that accumulates.

3. Cellular respiration provides most of the muscle's ATP, but takes longer because much of the glucose and oxygen must be transported in blood to mitochondria. Cellular respiration occurs during aerobic exercise and burns fatty acids in addition to glucose.

Fast twitch muscle fibers are for sports like weight training. These rely on anaerobic means of acquiring ATP. Have few mitochondria and myoglobin, but motor units contain more muscle fibers and are known for explosive power, but fatigue quickly.

Slow twitch muscle fibers are for sports like running or swimming. These rely on aerobic respiration to acquire ATP. Have a plentiful supply of mitochondria and myoglobin, which gives them dark color. See illustration.*

MUSCULAR DISORDERS

Muscular disorders include spasms and injuries, as well as diseases such as muscular dystrophy and myasthenia gravis.

HOMEOSTATSIS

The muscles and bones produce movement and protect body parts, the bones produce red blood cells and are involved in the regulation of blood calcium levels. The muscles also produce the heat that gives us a constant body temperature. In this illustration it shows are the skeletal and muscular systems interact with other body systems.*

*http://highered.mcgraw-hill.com/classware/selfstudy.do?isbn=0072986867