Goals for this Chapter:
1. Observe and compare the three types of muscle tissue
2. Describe the action of actin and myosin in muscle contraction and heat production
3. Identify the sources of energy for muscle contraction 4. Explain how skeletal muscles support other body systems
5. Identify conditions that impair the healthy functioning of muscle systems
6. Describe the benefits of exercise for maintaining healthy muscles
Magnificent Muscle Facts
• The human body has more than 650 muscles.
• Waste energy keeps you warm!
• No two muscles in the body have exactly the same function. When one muscle is paralyzed, either stability of the body part is impaired or some specific movement is lost.
• A muscle is pretty efficient, using about 35-50% of its potential energy.
• Muscle fibers are thinner than a human hair and can support up to 1,000 times its own weight. • Strongest muscle in the human body is: that depends on what you define as strongest.
Skeletal Muscles
Skeletal Muscles
Types of Muscles
Types of Muscles
Skeletal muscle
• Striated & tubular
• Many nuclei
• Voluntary
• Attached to bones
• Functions in circulatory system to help move blood back to the heart (contract against veins)
• Release heat
• Move bones
• Allow us to stand upright
Types of Muscles
Cardiac muscle
• Striated, tubular and branched.
• One nucleus
• Involuntary control
• Found only in walls of heart
• Functions to transport blood to the body
Types of Muscles
Smooth muscle
• Non-striated
• One nucleus
• Involuntary control
• Found in walls of internal organs
• Ex: sphincter muscles of esophagus, intestines, and urethra
• Does not fatigue easily
Action of Muscles
• During contraction, a muscle shortens when stimulated by an excitatory nerve
• During relaxation, a muscle lengthens when stimulated by an inhibitory nerve
Muscles Cooperate
• Muscles can only pull therefore they must work in pairs pulling against each other
(antagonistic)
• Eg. Biceps-triceps
– Bicep pulls to bend a joint (flexor)
– Tricep pulls to straighten a joint
(extensor)
Skeletal Muscle
• Click on the image to see an animation of the structure of skeletal muscle.
Muscles Organization
Muscle
– an organ surrounded by connective tissue and composed of several tissues,
– eg. bundles of muscle cells and nervous tissue.
Muscle fibres
–
–
–
–
muscle cells in the bundles unlike “typical”cells.
Up to 20 cm in length contain many nuclei.
Organelles within the cells (fibres)
– the cell membrane is called the sarcolemma,
– the endoplasmic reticulum is the sarcoplasmic reticulum – the cytoplasm is known as sarcoplasm.
Muscle structure
Skeletal Muscle Structure
• Muscle fibres (a specialized cell) are organized into larger bundles up to 20 cm in length
• Connective tissue wraps fibre
• Another layer of connective tissue bundles fibres
Muscle structure
• Myofibrils are composed of small subunits called sarcomeres
– Sarcomeres are the functional unit of a muscle between z disc
– Composed of actin and myosin (protein chains) – Actin is the thin filament
– Myosin is the thick filament
Actin/Myosin
Skeletal Muscle Structure
• Blood vessels and nerves run between bundles or fibres
• Cell membranes of muscle cells are called sarcolemma
• Fibres are composed of myofilaments Skeletal Muscle Structure
• Myofilaments can be thin (actin filament) or thick
(myosin filament) and overlap to give alternating light and dark bands. Muscle Contractions
Muscle Contractions
• One sarcomere is composed of both actin (thin) and myosin (thick) filaments • Z-lines divide sarcomeres • H-zone is the area where
