BIOS 1710: Biological Sciences II, Week 3 Notes
BIOS 1710: Biological Sciences II, Week 3 Notes BIOS1710
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This 6 page Class Notes was uploaded by Sydney Jones on Monday September 12, 2016. The Class Notes belongs to BIOS1710 at Ohio University taught by Scott Moody in Fall 2017. Since its upload, it has received 28 views. For similar materials see Biological Sciences II: Ecology, Evolution, Animal Body Systems in Biology at Ohio University.
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Date Created: 09/12/16
Ch 37 Muscles -Muscles must generate force to pull against a resistance to move bones ▯ they do this by changing length - Heart ‘movement’ only requires contractions Types of muscles Types of Mucels Striated Unstriated Skeletal Cardiac Smooth Mucels Muscel Muscel • Skeletal Muscles o Striated o Connect Bones o Multinucleate o Long and unbranched (29cm) o Voluntary • Cardiac o Striated o Heart o 1-2 nuclei o Intercalated discs o Branches Interdigited- so information can move to different cells o Involuntary • Smooth o Not striated o Artery wall, digestive/respiratory system o 1 nucleus o Unbranched o Sheets around organs o Involuntary Muscle Organization Muscle Tissue- bundles of muscles fibers Fibers- one cell, contain myofibrils can be up to 20 cm long Myofibrils- contain sarcomeres The Sarcomere Sarcomere- section between two Z discs, shorten when the muscle contracts (shortens) and relaxes (lengthen) Actin- thin filament Myosin- thick filament; has myosin heads Tropomysosin- protein that runs in the grooves of the actin Z Discs- action and myosin are attached here; regularly spaced along the myofibril Titin- links the myosin filaments to the z discs at he end of the sarcomere Muscle Contraction Sliding Filament Model- muscles produce force and change length by the sliding of actin relative to myosin ▯ only the sarcomere shortens Cross-Bridges- sites where actin and myosin bind Cross-bridge Cycle 1. Myosin head binds ATP to detach 2. Myosin head hydrolyzes ATP ▯ ADP and phosphate (P); head is cocked back 3. Myosin then binds to action (froing cross-bridge) 4. Myosin release ADP and P 5. Release created the power stroke 6. Myosin head pivots forward pulling acting toward the midline Start at 2 min for cross-bridge cycle: https://www.youtube.com/watch?v=hr1M4SaF1D4 **Rigor Mortise- There is no ATP to unbind Myosin and Actin Skeletal Muscle Contraction 1. Action potential travels down the neuron acetylcholine is released 2. Acetylcholine binds with the motor endplate (receptors) 3. This opens the Na channels causing depolarization 4. Depolarization moves down through the T-tubules and into the sarcoplasmic reticulum (SR) 5. When at the SR Ca is released 6. Ca binds to troponin uncovering the myosin binding sites Excitation-contraction Coupling- when calcium is released and binds to troponin 7. Contraction stops when calcium is broken down or pumped back into the SR Smooth Muscle Contraction - Activated by autonomic nervous system, stretching of the muscle, hormones, etc.… - Theses will activated the release of Ca - Lack tropomyosin but has calmodulin: 2 • Calmodulin binds with Ca • This activates myosin kinase, causing them to bind with actin • A second enzyme stops the process - Relaxation is slower in smooth muscle Contractile Properties - More fibers means more force - The more overlap in the cross-bridge cycle the more force: intermediate length muscle fibers have the greatest force Force vs. Velocity -Larger forces need a slower velocity to have time for creating more binding sites Isometric Force- when the muscle must generate force but does not shorten (shorten velocity is 0), carrying a heavy bucket of water Lengthening Contraction- when the external load against which they contract exceeds their force output (up to 75% more force) Antagonist Pairs - Muscles can only pull; not push Flexion- bone segments rotate closer together Extension- bone segments move apart Agonist- groups of muscles that produce similar motions; increase strength and control of motions Motor Unit *a motor neuron and the muscle fibers that it is connected to -Small motor units have fine movements and vice versa - More motor units means greater force *Twitch -Force depends on the frequency of the stimulation *a single action potential Force Summation- if a second action potential happens before muscle relaxation more force is made Tetanus- sustained force at a high stimulation Slow and Fast Twitch Fibers Two different types of fibers: Fast-Twitch Slow-Twitch Red muscle ▯ many mitochondria and White muscle▯ few mitochondria & myoglobin myoglobin with well supplied blood vessels Anaerobic glycolysis for ATP Aerobic respiration Cross-bridges happen quickly Cross-bridges happen slowly Fatigue quickly Highly resistant to fatigue Cannot replenish ATP fast enough Can maintain prolonged ATP production is oxygen is available Weight lifters & sprinters Long-distance runners & swimmers Strength- cross-section of muscle; more myosin means more strength; repetitive movement despite fatigue creates more actin and myosin Endurance- capacity to use oxygen to ATP; need for more oxygen creates mitochondria Skeletons 3 types: 1. Hydrostatic- uses pressure of internal body fluids to support the body 2. Exoskeleton- hard hollow structures outside the body 3. Endoskeleton- hard structures inside the body made of cartilage and bone Hydrostatic - Fluid surrounded by muscle - Alternate contractions of longitudinal and circular muscles Exoskeletons - Muscles attach internally - Hard to repair - During growth they molt and become vulnerable Mollusks: mineralized calcium carbonate and proteins Insects: cuticle composed of chitin Clams: do not molt but instead just add rings Endoskeleton - Inside the body - Humans have 206 bones Two parts: Axial- ribcage, backbone, and skull Appendicular- everything else Tendon - Can grow in the body Tendons- made of collagen; attach muscle to Ligament bone Ligament- attach bone to bone Bone- made by osteoblasts *bones meet at joints Cartilage- made of of cells scattered in a gelatinous matrix; provides padding between bones Types of Joints: - Ball and socket ▯ Shoulder and hip o Has a broad range of motion o Has 3 sets of antagonistic muscles o Not very stable - Hinge ▯ Elbow and knee o Has one axis of motion Formation of Bones -Axial Skeleton: has precursor cells that become osteoblast; slow process - Other bones: becomes cartilage first (Endochondral Ossification) - Chondroblasts grow the cartilage model - Cartilage expands for grows - Blood vessels and osteoblasts invade and create a bone Parts of the Bone Compact Bones- forms the dense walls of the bone’s shaft Spongy Bones- porous and found on the inner surface at the end of limbs Bone Marrow- fatty tissue with in the central cavity Growth Plate- between the compact and spongy bone; where new cartilage is added for growth
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