Musculo-Skeletal System Muscles + Bones = Locomotion

Thursday Chapters # 35 and # 37 Quiz this Week!

Muscles

Why muscles? Muscle tissue is responsible for movement and locomotion in animals. Muscles rely on contractile fibers to create motion. In vertebrate animals and arthropods, muscles attach to a skeletal system to produce locomotion.

Types of muscle tissue These three types are found in vertebrates: Skeletal: striated, voluntary control Smooth: involuntary control Cardiac: involuntary control

Smooth muscle Found in the digestive tract, large blood vessels, and several organs. Have contractile fibers, but lack orderly striations of skeletal muscle.

Cardiac muscle Located only in the heart. Influenced by nerves and hormones, but has “electrical” system of its own to initiate and coordinate contractions.

Skeletal muscle Muscle tissue capable of voluntary control. Orderly striations are due to arrangement of contractile fibers. Produces locomotion.

Muscle fibers A muscle cell is a “fiber.” Fibers are multinucleated and contain myoglobin. Myofibrils contain the contractile fibers.

Slow Twitch, Fast Twitch Slow-twitch fibers: lots of myoglobin, mitochondria. Good for endurance activities. Fast-twitch: less myoglobin, but more able to use glycolysis to quickly produce ATP. Good for activities required sudden strength or speed. Different people have different ratios of these two fibers.

Myofibril The myofibril is composed of “thick” and “thin” filaments. Each of these filaments is made up of strands of protein.

Thick and thin filaments The thick filaments, made mostly of myosin, have small “heads” that move.

Thick and thin filaments The thin filaments have points to which the myosin heads temporarily attach.

Muscle fiber action

All or nothing Fibers are either “on” (contracted) or “off” (relaxed). When lifting light weights, only a few fibers may be “on.” For heavy weights, many more may be “on,” and may take turns to prevent fatigue.

Working out Exercise can build muscle mass. However, because muscle fibers (cells) are large, they rarely divide. To increase muscle power, muscles add more filaments inside of the fibers. This happens when muscles rest after exercise.

Stretching Stretching exercises add flexibility by increasing muscle length. On the molecular level, the filaments within the muscle can increase in length to accommodate stretching. However, stretching tendons can weaken joints.

Try this: Hold your pen or pencil so that it casts a shadow on your paper. Line up the tip of the shadow with a point on your paper. How still can you hold your hand? Does the point of the shadow move? Muscles generally contract by continuous “twitching” of muscle fibers. This makes it hard to hold your hand completely steady.

Skeletal Systems

Types of systems Three basic types of skeletal systems in the animal kingdom: Hydrostatic Exoskeleton Endoskeleton

Hydrostatic skeleton Earthworms and sea anemones have a hydrostatic skeleton. Circular muscles squeeze the body, forcing water to both ends, which lengthens the body. Longitudinal muscles shorten the body, making it wider.

Exoskeleton Arthropods (insects, spiders, etc) have an external skeleton made of chitin (a carbohydrate). Muscles attach to the exoskeleton, which is flexible at the joints.

Endoskeleton Vertebrates have an endoskeleton made of cartilage or bone. Bone and cartilage are living tissue (connective tissue), allowing the skeleton to grow with the organism.

Functions of the endoskeleton Support and protection for the body. Locomotion (in concert with muscles). Produce blood cells in bone marrow. Store calcium and phosphorous. Store energy in yellow marrow.

Cartilage Cartilage tissue consists of chondrocytes (cartilage cells) in a matrix of collagen protein. Cartilage is tough, flexible material that pads joints and is found in the nose and ears.

Bone tissue Bone is made up of bone cells in a matrix of collagen and minerals. Three types of bone cells: osteocytes, osteoblasts, and osteoclasts.

Bones may made up of: Compact bone tissue. Spongy bone (location of red marrow) Marrow cavity (location of yellow marrow) Bones

Healing fractures

Osteoporosis Osteoporosis is loss of bone mass, leading to brittle bones. Age, lack of calcium, sedentary lifestyle, multiple pregnancies, menopause, alcohol, and smoking contribute to osteoporosis.

Locomotion

Motion in Vertebrates Motion and locomotion are produced by muscles pulling on bones. Joints in the skeleton allow for parts of the body to flex and extend, allowing for motion. Ligaments attach bones to bones at the joints. Muscles attach to bones by tendons.

Hinge joint A hinge joint allows flexing and extending along one plane. Pairs of muscles work opposite one another to create motion.

Ball and socket joint A ball and socket arrangement allows rotational movement. Multiple pairs of muscles allow movement in a range of directions.

Gliding joints In gliding joints, bones slide past one another. Gliding joints allow twisting motion.

On your own paper... The knee is a hinge joint. Find another hinge joint in the body. What muscles move it? The hip is a ball and socket joint. Find another ball and socket joint in the body. What muscles move it? The wrist is a gliding joint. Find another gliding joint in the body. What muscles move it?

Movement Flexion: decreases angle of a joint. Extension: increases angle of a joint. Abduction: movement away from midline. Adduction: movement toward midline. Rotation: turning around an axis.

On your own paper... Give examples of joints and movements that demonstrate: Flexion Extension Abduction Adduction Rotation

Name that muscle! For each of the following slides: Name the muscle or muscle group, if you can. State what kind of movement it produces. Locate the bone (or bones) that it moves. Which muscles produce the opposite movement?