NSHAY03L Human Anatomy - Muscular System PDF

NSHAY03L HUMAN ANATOMY – MUSCULAR SYSTEM BSP NATIONAL UNIVERSITY - LAGUNA | GRETCHIE C. GARA 221A The Muscular System Connective Tissue Wrappings of Skeletal Muscle Muscles are r...

NSHAY03L HUMAN ANATOMY – MUSCULAR SYSTEM BSP NATIONAL UNIVERSITY - LAGUNA | GRETCHIE C. GARA 221A The Muscular System Connective Tissue Wrappings of Skeletal Muscle Muscles are responsible for all types of body movement Three basic muscle types are found in the body - Skeletal Muscle (voluntary) - Cardiac Muscle (involuntary) Can only be found in the Heart (hardest working muscle) - Smooth Muscle (involuntary) Can be found in the hollow organs Bones and Muscles are connected through Tendons Characteristics of Muscles Endomysium – around single muscle fiber Muscle cells are elongated (muscle cell = muscle Perimysium – around a fascicle (bundle) of fiber) fibers Contraction of muscles is due to the movement of Epimysium – covers the entire skeletal microfilaments muscle Fascia – on the outside of the epimysium Microfilaments are composed of proteins: aptin & myocin (slides for the contraction Skeletal Muscle Attachments of muscles) Epimysium blends into a connective tissue attachment All muscles share some terminology Tendon – cord-like structure Prefix myo refers to muscle Aponeuroses – sheet-like structure Prefix mys refers to muscle Prefix sacro refers to flesh Tendons are stronger than aponeuroses Skeletal Muscle Characteristics Sites of Muscle Attachment - Most are attached by tendons to bones - Bones - Cells are multinucleate (meaning there are - Cartilages 2 or more nucleus in a cell) - Connective Tissue Coverings Striated – have visible banding Voluntary – subject to conscious control - Cells are surrounded and bundled by connective tissue Magnayi, Beatrice 1 NSHAY03L HUMAN ANATOMY – MUSCULAR SYSTEM BSP NATIONAL UNIVERSITY - LAGUNA | GRETCHIE C. GARA 221A Smooth Muscle Characteristics - Stabilize Joints - Generate Heat Microscopic Anatomy of Skeletal Muscle - Has no striations - Spindle-shaped cells - Cells are multinucleate - Single nucleus - Nuclei are just beneath the sarcolemma - Involuntary – no conscious control Sarcolemma – specialized plasma membrane - Found mainly in the walls of hollow organs Sarcoplasmic reticulum – specialized smooth Cardiac Muscle Characteristics endoplasmic reticulum Myofibril – bundles of myofilaments; myofibrils are aligned to give distinct bands - 1 band = light band - Has striations - A band = dark band - Usually has a single nucleus - Jointed to another muscle at an Sarcomere – contractile unit of a muscle fiber intercalated disc - Involuntary - Found only in the heart Function of Muscles - Produce Movement - Maintain Posture Magnayi, Beatrice 2 NSHAY03L HUMAN ANATOMY – MUSCULAR SYSTEM BSP NATIONAL UNIVERSITY - LAGUNA | GRETCHIE C. GARA 221A Nerve Stimulus to Muscles Organization of the Sarcomere - Thick filaments = myosin filaments - Composed of the protein myosin - Has ATPase enzyme In order for ATP to breakdown it needs an ATPase enzyme - Thin filaments = actin filaments - Composed of the protein actin Skeletal muscles must be stimulated by a nerve to contract Motor unity - One neuron - Muscle cells stimulated by that neuron Myosin filaments have heads (extensions, or cross bridges) Myosin and actin overlap somewhat At rest, there is a bare zone that lacks actin filaments Neuromuscular Junctions – association site of Sarcoplasmic reticulum (SR) – for storage of nerve and muscle calcium Synaptic Cleft – gap between nerve and muscle Properties of Skeletal Muscle Activity Irritability – ability to receive and respond to a - Nerve and muscle do not make contact stimulus but because of the synaptic cleft they are able to connect Contractability – ability to shorten when an - Area between nerve and muscle is filled adequate stimulus is received with interstitial fluid Magnayi, Beatrice 3 NSHAY03L HUMAN ANATOMY – MUSCULAR SYSTEM BSP NATIONAL UNIVERSITY - LAGUNA | GRETCHIE C. GARA 221A The result is that the muscle is shortened (contracted) Transmission of Nerve Impulse to Muscle Neurotransmitter – chemical released by nerve upon arrival of nerve impulse - The neurotransmitter for skeletal muscle is acetylcholine Neurotransmitter attaches to receptors on the sarcolemma Sarcolemma becomes permeable to sodium (Na+) Sodium rushing into the cell generates an action potential Once started, muscle contraction cannot be stopped The Sliding Filament Theory of Muscle Contraction Contraction of a Skeletal Muscle Muscle fiber contraction is “all or none” Within a skeletal muscle, not all fibers may be stimulated during the same interval Different combinations of muscle fiber contractions may give differing responses Activation by nerve causes by myosin heads (cross Graded responses – different degrees of skeletal bridges) to attach to binding sites on the thin muscle shortening filament Myosin heads then bind to the next site of the thin filament This continued action causes a sliding of the myosin along the actin Magnayi, Beatrice 4 NSHAY03L HUMAN ANATOMY – MUSCULAR SYSTEM BSP NATIONAL UNIVERSITY - LAGUNA | GRETCHIE C. GARA 221A Types of Graded Responses More fibers contracting results in greater muscle tension Muscles can continue to contract unless they run out of energy Energy for Muscle Contraction Initially, muscles used stored ATP for energy - Bonds of ATP are broken to release energy - Only 4-6 seconds worth of ATP is stored by Twitch muscles - Single, brief contraction After this initial time, other pathways must be - Not a normal muscle function utilized to produced ATP Tetanus (summing of contractions) - One contraction is immediately followed by another - The muscle does not completely return to a resting state - The effects are added Unfused (incomplete) tetanus Direct phosphorylation - Some relaxation occurs between contractions - Muscle cells contain creatine phosphate - The results are summed (CP) - CP is a high-energy molecule Fused (complete) Tetanus After ATP is depleted, ADP is left - No evidence of relaxation before the following contractions CP Transfers energy to ADP, to regenerate ATP - The result is a sustained muscle CP supplies are exhausted in about 20 seconds contraction Muscle Response to Strong Stimuli Muscle force depends upon the number of fibers stimulated Magnayi, Beatrice 5 NSHAY03L HUMAN ANATOMY – MUSCULAR SYSTEM BSP NATIONAL UNIVERSITY - LAGUNA | GRETCHIE C. GARA 221A Anaerobic Glycolysis - Reaction that breaks down glucose without oxygen - Glucose is broken down to pyruvic acid to produce some ATP - Pyruvic acid is converted to lactic acid - This reactions is not as efficient, but is fast (huge amounts of glucose are needed; lactic acid produces muscle fatigue) Muscle Fatigue and Oxygen Debt When a muscle is fatigued, it is unable to contract The common reason for muscle fatigue is oxygen debt - Oxygen must be “repaid” to tissue to remove oxygen debt Aerobic Respiration - Oxygen is required to get rid of - Series of metabolic pathways that occur in accumulated lactic acid the mitochondria Increasing acidity (from lactic acid) and lack of - Glucose is broken down to carbon dioxide ATP causes the muscle to contract less and water, releasing energy - This is a slower reaction that requires Types of Muscle Contractions continuous oxygen Isotonic Contractions - Myofilaments are able to slide past each other during contractions - The muscle shortens Isometric Contractions - Tension in the3 muscles increases - The muscle is unable to shorten Muscle Tone Some fibers are contracted even in a relaxed muscle Different fibers contract at different times to provide muscle tone The process of stimulation various fibers is under involuntary control Magnayi, Beatrice 6 NSHAY03L HUMAN ANATOMY – MUSCULAR SYSTEM BSP NATIONAL UNIVERSITY - LAGUNA | GRETCHIE C. GARA 221A Muscles and Body Movements Rotation - Movement of a body part around its longitudinal axis. - Example: Turning the head from side to side. Abduction - Movement of a limb away from the midline of the body. - Example: Raising the arms or legs laterally away from the body. Circumduction - Circular movement of a limb, combining Movement is attained due to a muscle moving an flexion, extension, abduction, and attached bone adduction. - Example: Moving the arm in a circular Muscles are attached to at least two points motion at the shoulder. - Origin – attachment to a moveable bone Body Movements - Insertion – attachment to an immovable bone Effects of Exercise on Muscle Results of increased muscle use - Increase in muscle size - Increase in muscle strength - Increase in muscle efficiency - Muscle becomes more fatigue resistant Types of Ordinary Body Movements Flexion - Decreasing the angle between two body parts. - Example: Bending the elbow or knee. Extension - Increasing the angle between two body parts, straightening a flexed part. - Example: Straightening the elbow or knee after flexion. Magnayi, Beatrice 7 NSHAY03L HUMAN ANATOMY – MUSCULAR SYSTEM BSP NATIONAL UNIVERSITY - LAGUNA | GRETCHIE C. GARA 221A Types of Muscles Prime mover – muscle with the major responsibility for a certain movement Antagonist – muscle that opposes or reverses a prime mover Synergist – muscle that aids a prime mover in a movement and helps prevent rotation Fixator – stabilizes the origin of a prime mover Naming of Skeletal Muscles Direction of Muscle Fibers - Example: rectus (straight) Relative size of the muscle - Example: maximus (largest) Location of the muscle - Example: many muscles are named for bones (e.g., temporalis) Number of origins - Example: triceps (three heads) Location of the muscle’s origin and insertion - Example: sterno (on the sternum) Shape of the muscle Special Movements - Example: deltoid (triangular) Dorsiflexion Action of the muscle Plantar flexion - Example: flexor and extensor (flexes or Inversion extends a bone) Eversion Supination Pronation Opposition Magnayi, Beatrice 8 NSHAY03L HUMAN ANATOMY – MUSCULAR SYSTEM BSP NATIONAL UNIVERSITY - LAGUNA | GRETCHIE C. GARA 221A Head and Neck Muscles Magnayi, Beatrice 9 NSHAY03L HUMAN ANATOMY – MUSCULAR SYSTEM BSP NATIONAL UNIVERSITY - LAGUNA | GRETCHIE C. GARA 221A Deep Trunk and Arm Muscles Muscles of the Pelvis, Hip, and Thigh Magnayi, Beatrice 10 NSHAY03L HUMAN ANATOMY – MUSCULAR SYSTEM BSP NATIONAL UNIVERSITY - LAGUNA | GRETCHIE C. GARA 221A Muscles of the Lower Leg Superficial Muscles: Anterior Magnayi, Beatrice 11 NSHAY03L HUMAN ANATOMY – MUSCULAR SYSTEM BSP NATIONAL UNIVERSITY - LAGUNA | GRETCHIE C. GARA 221A Superficial Muscles: Posterior Magnayi, Beatrice 12