Muscle Physiology PDF

💪🏾 Muscle Created @October 28, 2024 12:05 PM Class Physiology 1A Lecture 1_ muscle intro - 1 slide PP.pdf Lecture 2_molecular Course mechanisms-1 slides PP.pdf Lecture 3_ regulation of contraction...

💪🏾 Muscle Created @October 28, 2024 12:05 PM Class Physiology 1A Lecture 1_ muscle intro - 1 slide PP.pdf Lecture 2_molecular Course mechanisms-1 slides PP.pdf Lecture 3_ regulation of contraction 1 Materials slide PP.pdf Lecture 4_muscle comparison 1 slide PP.pdf Muscle contractions Mechanism of animal movement Amoeboid movement(in which cells change shape to move forward) I.e eosinophils in immune cells Ciliary and flagellar bending Muscle 1  Muscle Lever Systems Work at a Mechanical Disadvantage Skeletal Cardiac Smooth Skeleton Heart Hollow organs Striated Striated Non striated Voluntary Involuntary Involuntary Movement ,heat , production Pump blood Movement, control organ size Increased manoeuvrability Muscle fibre are wrapped in connective tissue Epimysium Muscle 2 Muscle 3  myofibril - long thread like structures which contain myosin and actin and are organised into units called sarcomeres which is why the muscle is striated T-tubules - extensions of the cell membrane which allow action potential to reach muscle fibre cause release of calcium ions from sarcoplasmic reticulum There is a terminal cisterna of the sarcoplasmic reticulum on either side of a t- tubule. All together they are called a triad. This is important for excitation- contraction coupling sarcoplasmic reticulum - stores calcium ions Muscle 4  Structure of myofibril sarcomere- contractile unit containing myosin and actin I-BAND (isotropic) - Appears light, because only actin filaments are present A-BAND(anisotropic)- Appears dark because there is overlapping of both filament z line - Located in the centre of each I-band. Distance between adjacent Z-lines is a sarcomere H-ZONE - At the centre of the A-band. Only myosin filaments here. Z zwischen sheibe M mittel H heller During contraction the I and h band contract as actin and myosin move towards each other and overlap. A band STAYS THE SAME ANS THE ACTIN AND MYOSIN JUST SLIDE PAST Muscle 5 Muscle 6 Muscle 7 Muscle 8  structure of actin filaments Long chains of globular proteins, which are coiled around one another in a helix Troponin - site where calcium ions bind Tropomyosin - long thin thread wound around the actin (covers the myosin- binding site) structure of myosin filaments Heads protrude (globular proteins)Tails wrap around one another to form filaments (fibrous proteins) Muscle 9 Muscle 10  optimal range 2.0-2.2 which allows overlap of actin and myosin and muscle can generate maximum force efficiently. too short-too much overlap prevent cross bridge cycling as the actin filaments can start overlapping leaving no available binding sites for myosin heads. Also cause z line to be too close to actin filaments. reduce sensitivity to calcium ions too long - insufficient overlap Muscle 11  Role of ATP in the Cross-Bridge Cycle ATP has two distinct roles in the cross-bridge cycle: Energy source: ATP hydrolysis provides the energy for cross-bridge movement. Allosteric regulator: Binding of ATP to myosin breaks the link between actin and myosin. This allows the cycle to be repeated Muscle 12  Role of ATP in the Cross-Bridge Cycle ATP has two distinct roles in the cross-bridge cycle: Energy source: ATP hydrolysis provides the energy for cross-bridge movement. - Allosteric regulator: Binding of ATP to myosin breaks the link between actin and myosin. This allows the cycle to be repeated Reabsorption of calcium ions from the sarcoplasm into the sarcoplasmic reticulum (via active transportglx)k Muscle 13  TROPONIN COMPLEX MADE UP OF 3 SUBUNITS TnT TnC TnL resting state-constant inhibition > tropomyosin blocks myosin binding sites on actin, preventing contraction when a muscle cell is stimulated ca2+ are released to bind to TnC subunit of troponin The binding of the calcium causes a conformational change in the troponin complex. This changes moves tropomyosin deeper into the groove of actin as tropomyosin moves, it exposes myosin binding sites on actin. 4 calcium binding sites on troponin(TnC SUBUNIT) 2 high affinity binding sites and 2 low affinity binding sites Muscle 14 Muscle 15  Prescence of ATP and calcium for muscle contraction to occur Twitch: A twitch is a single, brief contraction of a muscle fiber in response to a single action potential. Tetanus: Tetanus occurs when a muscle fiber is stimulated repeatedly at a high frequency, resulting in a sustained contraction. Tetanus can be either unfused (incomplete) or fused (complete). The latent period is the time delay (around 10 milliseconds) between the arrival of the action potential at the muscle fiber and the onset of muscle contraction.(the twitch) Muscle 16  EXCITATION - CONTRACTION COUPLING 1. The arrival of an action potential at the neuromuscular junction, which triggers the release of the neurotransmitter acetylcholine. 2. Acetylcholine binds to receptors on the muscle fiber membrane (sarcolemma), causing depolarization and the generation of a muscle action potential. Muscle 17  3. The action potential travels down the T-tubules, invaginations of the sarcolemma that penetrate deep into the muscle fiber. 4. Depolarization of the T-tubules activates voltage-gated calcium channels (DHP receptors), which are mechanically coupled to ryanodine receptors on the sarcoplasmic reticulum. 5. Activation of the ryanodine receptors causes a massive release of calcium ions from the sarcoplasmic reticulum into the cytoplasm. 6. Calcium ions bind to troponin, initiating the cross-bridge cycle and muscle contraction. Muscle 18  ISOMETRIC CONTRACTION# Muscle 19  muscle develops tension without changing length measure of tension generated ISOTONIC CONTRACTION muscle shortens, while load remains constant measure rate of shortening ESSENTRIC CONTRACTION# load exceeds muscle tension load pulls muscle to a longer length Muscle 20  characteristic skeletal cardiac smooth banding pattern Yes Yes No thick and thin filament Yes Yes Yes t tubles Yes Yes No SR Developed Developed Little multi nucleated cells Yes Yes only a few No gap junctions No Yes Yes unitary or no multunit ca2+ sensor Troponin Troponin Calmodulin Muscle 21 Muscle 22 Muscle 23 Muscle 24 Muscle 25 Muscle 26