Presentation on theme: "Skeletal Muscle Notes. Handy Hints ________– above or upon ________ – around ______________– muscle ________ – Within ________- flesh."— Presentation transcript:
Skeletal Muscle Notes
Handy Hints ________– above or upon ________ – around ______________– muscle ________ – Within ________- flesh
Function of Muscle Tissue ____________________ – relies on integrated functions of bones, joints and skeletal muscles. Movement of substances within the body ____________________ muscle – moves blood through the heart, blood vessels ____________________ muscle – movement of blood and food through the intestinal tract Sperm and egg through the reproductive systems and urine through the urinary system.
Function of Muscle Tissue __________________________ body positions and regulating organ volume – help you stand or sit. Muscle closes off exit routes in certain organs like the stomach ___________________ production – the by- product of muscle contraction is heat. Used to generate as much as 85% of all body heat.
Structure of Skeletal Muscle Skeletal muscle is bound by connective tissue (fascia), attached to bones and is under voluntary control. Fascia (ct) ___________ (ct) periosteum (bone) This is how muscle is connected to bone ____________________ – a sheet or broad band of fibrous connective tissue under the skin or around muscles.
Structure of Skeletal Muscle Three Types of Fascia 1. _________________________– closely surrounds muscle 2. _________________________ – inward extension from the epimysium that divides muscle tissue into small compartments called fascicles (bundles of muscle fibers) 3. Endomysium – surround each muscle fiber within a fascicle
Layers of connective tissue allow: Independent movement of fibers within muscle nerves Blood vessels to pass through muscle
Muscle Cell is a skeletal muscle fiber Multinuclear – more than one nucleus ___________________ – cell membrane ___________________ – cytoplasm composed of Numerous mitochondria Parallel lying thread-like fibers called myofibrils
Myofibrils are composed of 2 types of protein filaments _________________ – thick filament containing protein myosin with projecting cross bridges _________________ – thin filaments containing protein actin
Structure of Skeletal Muscle Sarcotubular System – triad of skeletal muscle (3 parts) Sarcoplasmic reticulum (kinda like ER)– network of membrane enclosed tubules that run parallel to myofibrils. At the “A” band the S.R. enlarges to form a pair of terminals.
Structure of Skeletal Muscle ____________________– run 90 degrees to the S.R. Function: store, release and reabsorb Ca in order to help activate or release muscle contractions.
Structure of Skeletal Muscle tubules (T-tubules) – tunnel-like extensions of the sarcolemma that pass through the muscle fiber at right angles to the S.R. and between the cisternae. Function to transmit nerve impulse to all fibrils (open to outside)
Structure of Skeletal Muscle ____________________________ are filamentous protein molecules contained in muscles. In the presence of calcium ions myosin and actin will slide past each other and form cross-bridges, thereby contracting the muscle.
Structure of Skeletal Muscle
Neuromuscular junction – where the motor neuron and the muscle fiber meet. _________________________– modified sarcolemma; highly folded, many nuclei; mitochondria ________________________ knob – where the end of the motor neuron branches and terminates Synaptic vesicles - sacs in the axon terminals filled with chemicals.
Structure of Skeletal Muscle _________________________– neurotransmitter released at a neuromuscular junction. Allows sodium ions to diffuse and produces a muscle action potential (results in a muscle contraction) __________________________– found in the synaptic cleft. It inactivates acetylcholine so the muscle can get ready for the next action potential
Structure of Skeletal Muscle – 1 motor neuron and 10 or more muscle fibers.
Skeletal Muscle Contraction “ ________________ Theory or Sliding Filament Theory of Skeletal Muscle Contraction”
Origin vs. Insertion ___________________________ – muscle attaches to a movable bone ___________________________– muscle attaches to a non movable bone Muscles work in pairs
Energy Source for Contraction 1 st source – ATP, enough in muscle cell to last 6 to 8 seconds. ADP + P + energy ATP Creatine Phosphate - molecule stored in muscle cells, used to produce more ATP quickly during exercise CP creatine + P + energy 2 nd source – Glucose cellular respiration ATP O 2 needs to be present 3 rd source – carbohydrates glucose ATP Myoglobin – stores O 2 in muscle cells
Lasts 5-10 seconds ATP ADP +Energy Creatine phosphate Creatine phosphate Creatine + phosphate + energy Provides energy for prolonged muscular activity as long as nutrients and O2 last. 1 glucose 2 pyruvic acid + Energy (ATP) Pyruvic acid + O2 CO2 + H2O + Energy (ATP) Pyruvic acid + no oxygen lactic acid After ATP is used up Produce more ATP during prolonged exercise/ good for short bursts of activity 100 m dash ATP Creatine phosphate depleted Immediate source of energy Glucose (stored as glycogen)
Energy Source When used How long it lasts Formula for energy release 1 st ATP Immediat e source of energy Lasts 5-10 secondsATP ADP +Energy 2 nd Creatine phosphate After ATP is used up Produce more ATP during prolonged exercise/ good for short bursts of activity 100 m dash Creatine phosphate Creatine + phosphate + energy 3 rd Glucose (stored as glycogen) Creatine phosphat e depleted Provides energy for prolonged muscular activity as long as nutrients and O2 last. 1 glucose 2 pyruvic acid + Energy (ATP) Pyruvic acid + O2 CO2 + H2O + Energy (ATP) Pyruvic acid + no oxygen lactic acid
Muscular Responses- all or nothing principle Threshold Stimulus – minimal strength needed to elicit a muscle contraction. How do we get a “graded response”? While individual muscle fibers will contract to their fullest extent or not at all. But because there are many motor units some are contracting and some are relaxing. Thus the entire muscle can contract a “little” or “ a lot”, such as gently holding a pencil or tightly squeezing a finger.
Overworked Muscles Oxygen Debt – muscular activity is great enough, O2 cannot be supplied fast enough so ATP is produced by anaerobic respiration. Muscle Fatigue – inability of a muscle to maintain its strength of contraction. Due to lactic acid increase (Ph decrease) causing fibers less responsive to stimuli. Begins to damage the sarcolemma.
Isometric vs. Isotonic Muscle Contractions Isometric – tension increases, muscle length remains the same. Important in maintaining posture. Isotonic – tension remains the same, muscles shorten, used in movement. Both types are used in most body actions.
Fast vs. Slow Twitch Muscle Fibers White Muscle Fibers (white) – fast contracting, fewer myoglobin, hemoglobin, and mitochondria than red muscles. Have extensive SR so it can contract quickly due to ability to store and reabsorb Ca+, but fatigue quickly.
Fast vs. Slow Twitch Muscle Fibers Red Muscle Fibers(dark) – slow contracting, contain myoglobin (iron and oxygen binding protein), hemoglobin, and many mitochondria which can produce ATP to remain contracted for long periods of time without fatigue.