Unit 2 Muscles Study Guide PDF

Unit 2: Muscles Study Guide Muscles: Skeletal, Cardiac and Smooth Introduction to Skeletal Muscle Functions of Skeletal Muscle Explain all the general functions of skeletal muscles: Movement - skeletal muscles attach to the skeleton and moves the body by moving bones Maintena...

Unit 2: Muscles Study Guide Muscles: Skeletal, Cardiac and Smooth Introduction to Skeletal Muscle Functions of Skeletal Muscle Explain all the general functions of skeletal muscles: Movement - skeletal muscles attach to the skeleton and moves the body by moving bones Maintenance of posture - certain skeletal muscles contract continuously to maintain posture, enabling the body to remain standing or seated Joint stabilization Heat generation - muscle contractions produce heat that plays a vital role in maintaining normal body temperature Characteristics of Skeletal Muscle Tissue Describe all the characteristics of skeletal muscle tissue: Contractility - Muscle contracts forcefully. Muscle cells shorten and generate a strong pulling force as they contract Excitability - Nerve signals or other factors excite muscle cells, causing electrical impulses to travel along the cells’ plasma membrane. These impulses then stimulate the cells to contract Extensibility - Muscle tissue can be stretch by the contraction of an opposing muscle Elasticity - after being stretched, muscle tissue can recoil passively and resume its resting length Anatomy of Skeletal Muscle Gross Anatomy of Skeletal Muscle Identify and describe the three connective tissue layers associated with a muscle: Epimysium ○ An “overcoat” of dense, irregular connective tissue surrounding the whole skeletal muscle ○ Means “outside of the muscle” ○ Sometimes the epimysium blends with the deep fascia that lies between neighboring muscles Perimysium  ○ Within each skeletal muscle, the muscle fibers are separated into groups. Each group, which resembles a bundle of sticks tied together, is called a fascicle. Surrounding each fascicle is a layer of fibrous connective tissue called the perimysium (“around the muscle”). Endomysium ○ Within a fascicle, each muscle fiber is surrounded by a fine sheath of connective tissue consisting mostly of reticular fibers. This layer is the endomysium (“within the muscle”). Describe the structure and function of a tendon and an aponeurosis: A tendon is composed of dense, regular connective tissue primarily made up of parallel collagen fibers bundled together in a hierarchical structure(like the skeletal muscles), with smaller bundles (primary fiber bundles) grouping into large bundles (secondary and tertiary fiber bundles) all surrounded by a connective tissue sheath called the epitenon It acts like a rope with tightly packed collagen fibers running along its length, allowing for efficient transfer of muscle force to bone. An aponeurosis is a flat, sheet-like structure composed of dense fibrous connective, mostly made up for tightly packed, parallel bundles of collagen fibers, which allows it to withstand a lot of tension in one direction while acting as a broad attachment point for muscles to bones or fascia. ○ Similar to a tendon, except for its shape. It contains fibroblasts and very few blood vessels or nerves. Explain the function of blood vessels and nerves serving a muscle: The primary function of blood vessels and nerves is to supply the muscle with oxygen, nutrients and the ability to contract, via nerve impulses. Microscopic Anatomy of Skeletal Muscle Describe the sarcolemma, T-tubules and sarcoplasmic reticulum of a skeletal muscle fiber: Sarcolemma is a specialized plasma membrane of a skeletal muscle cell. Sarcoplasmic reticulum is a fancy smooth endoplasmic reticulum which interconnected tubules that surround each myofibril like a sleeve T-tubules are continuous with the sarcolemma, penetrating the cell’s interior at each A- band and I-band junction. Nerve generated impulses are further conducted by the t- tubules that run between each myofibril Distinguish between thick and thin filaments: There are two types of myofilaments, composed of contractile proteins: ○ Thin - contain actin molecules (plus other proteins) ○ Thick - contain bundled myosin molecules These filaments contain ATPase enzymes that split ATP to release the energy required for muscle contraction Both sides of the thick filament are studded with knobs called myosin heads The sliding of the thin and thick filaments produces muscle shortening (contraction) Explain the organization of myofibrils, myofilaments and sarcomeres: Myofibrils are organelles of the muscle cell that contain myofilaments. A segment of the myofibril is called the sarcomere. These layers are organized much like the fascicles and bundles of the epimysium, perimysium and endomysium. Know the H zone, I band, A band, Z disc, sarcomere, M line, etc: The boundaries at the end of each sarcomere are called Z discs. Thin (actin) filaments attach to each Z disc extending toward the center of the sarcomere In the center of the sarcomere, overlapping the thin (actin) filaments are the thick (myosin) filaments. The sarcomere structure explains the pattern of striations in skeletal muscle fibers. The dark bands are created by the full length of thick filaments, along with the inner ends of the thin filaments. This central region of the sarcomere is called the A band. The center of the A band, where no thin filaments reach, is called the H zone. The M line is in this H zone center where tiny rods hold the thick filaments together perpendicular to the filaments. The two ends of the A band, where there are no thick filaments, this region is called the I band. Skeletal Muscle Fiber Types Criteria for Classification of Muscle Fiber Types Explain and know all the fascia criteria used to classify skeletal muscle fiber types. Give examples of each: We have two types of fibers: thin and thick (actin or myosin). Depending on the presence of either or both a light (I band) or dark (A band will appear on the muscle). The area between two consecutive light bands is called a sarcomere (the smallest contractile unit of the muscle). Criteria for Classification of Muscle – Fascicle arrangement Skeletal muscles consist of fascicles in various arrangements with different structures and functional properties. Circular – when fascicles are arranged in concentric rings typically found surrounding external body openings which they close by contracting A general term for them is sphincters (“squeezers”). Examples: orbicularis oris and orbicularis oculi Convergent – fascicles converge towards a single insertion tendon. Usually triangular or fan shaped. Ex: pectoralis major Parallel – the length of the fascicles run parallel to the long axis of the muscle. These muscles are strap-like. Ex: sartorius Fusiform – a modification of the parallel arrangement resulting in a spindle-shaped muscle with and expanded belly (midsection). Ex: biceps brachii Pennate – “feather-like” pattern where short fascicles attach obliquely to a central tendon. Can be in three forms: o Unipennate: fascicles insert into only one side of the tendon. Ex: Extensor digitorum longus o Bipennate: fascicles insert into opposite sides of the tendon. Ex: rectus femoris o Multipennate: fascicles insert into tendon from several different sides. Ex: deltoid A muscle’s fascicle arrangement determines its range of motion and power. The longer and more nearly parallel the fascicles are to a muscle’s long axis, the more the muscles can shorten, but such muscles are not as powerful. Muscle power depends more on the total number of muscles cells in the muscle. The stocky bipennate and multipennate muscles shorten very little but because they have the most fibers, are most powerful. Classification of Muscles Know criteria used to name muscles: Location - bone or body region associated with the muscle Shape - deltoid = triangle Size ○ maximus - largest ○ minimus - smallest ○ longus - long Direction of fibers ○ Rectus - fibers run parallel to imaginary line like midline or bone (straight) ○ Transversus – runs perpendicular to midline ○ Oblique - fibers run at angles (at a slant) to an imaginary defined axis Number of origins ○ Biceps - two origins ○ Triceps - three origins Location of attachments - named according to origin or insertion Ex: Temporalis Action - flexor, extensor, and adductor; named for muscle action Skeletal, Cardiac and Smooth Muscle Tissue List and describe the similarities and differences between skeletal, cardiac and smooth muscles: Similarities: ○ Skeletal and smooth muscle cells are elongated and are called muscle fibers ○ Muscle contraction depends on two kinds of myofilaments: Actin Myosin ○ Muscle terminology is similar Sarcolemma - muscle plasma membrane Sarcoplasm - cytoplasm of a muscle cell Prefixes - myo, mys, and sarco refer to muscles