Exam 3 Study Guide: Questions 1-14
Exam 3 Study Guide: Questions 1-14 BIOL 2312
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This 4 page Study Guide was uploaded by Anu on Friday July 15, 2016. The Study Guide belongs to BIOL 2312 at University of Texas at Dallas taught by Dr. Mehmet Candas in Summer 2016. Since its upload, it has received 46 views.
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Date Created: 07/15/16
BIOL 2312 – MODERN BIOLOGY II - EXAM 3 STUDY GUIDE CHAPTER 48: Animal Movement 1. What are the contractile filaments in skeletal muscles? How are they organized during relaxation and contraction of muscle? Ans. The contractile filaments in the skeletal muscles that make up the sarcomere include the thin (actin) and thick (myosin) filaments. The thin filaments are composed of two coiled chains of globular protein actin, while the thick filaments are composed of several strands of myosin, each with two subunits: the head and a tail. Hugh Huxley and Jean Hanson proposed the sliding filament model, which states that filaments slide past one another during a contraction, and the sarcomere can shorten with no change in lengths of the filaments themselves. One end of each thin filament is bound to a Z-disk, which forms the end of the sarcomere and anchors the filament. When the sarcomere contracts, the thin and thick filaments slide past one another; particularly the thick filament slides. Actin Myosin Interaction: Start: myosin head firmly bound to actin subunit of thin filament STEP 1: ATP binds to myosin head – head releases from the thin filament (actin), the myosin head bent STEP 2: ATP hydrolyzed – head pivots, binds to new actin subunit. Energized head is now “cocked” STEP 3: Power stroke – Pi released – neck bends back to original position, moving thin filament relative to thick filament STEP 4: ADP released – cycle is ready to repeat again As ATP binding, hydrolysis and release continue, the two ends of the sarcomere are pulled closer together. 2. What is the function of calcium ions during muscle contraction? Ans. The function of calcium ions is to bind to troponin, making the troponin-tropomyosin complex move and exposing myosin binding sites on the actin for myosin to bind to. The troponin-tropomyosin complex block sites on the actin and prevent myosin head from binding. Action potentials initiate muscle contraction: STEP 1: Action potential arrives – Ach is released from motor neuron STEP 2: ACh binds to Ach receptors – receptors on muscle cell, triggering DEPOLARIZATION that leads to action potentials STEP 3: Action potentials propagate via T-Tubules- moves across muscle cell’s plasma membrane into interior of cell via T (transverse) tubules. NOTE: there are NA+ and K+ channels located in the T-tubules that help propagate the action potential. (this was a HW question). STEP 4: Ca channels open – in SARCOPLASMIC RETICULUM in response to action potentials in T tubules 2+ STEP 5: Ca is released – from sarcoplasmic reticulum. Sarcomeres shorten when troponin and tropomyosin move in response to Ca and expose myosin binding sites in thin filaments. 3. What is motor unit in skeletal muscle? Ans. A motor unit is made up of a somatic motor neuron and the skeletal muscle fibers innervated by that motor neuron's axonal terminals. Groups of motor units work together to coordinate the contractions of a single muscle. 4. How do ATP molecules function during muscle contraction? Ans. ATP interacts with the myosin head, binding to the ATP binding site and phosphorylating to cause conformation changes in myosin. These changes on a whole cause the muscle to contract. EXTRA INFORMATION: Since the amount of ATP stored in muscles is small, metabolic pathways that generate new ATP must be activated for continued muscle contraction. These pathways are either anaerobic (in the absence of oxygen) or aerobic (in the presence of oxygen). 5. What is the role of oxygen in the muscle contraction? Ans. During muscle contraction, the muscles need continuous supply of ATP in order to contract. Oxygen is a required reactant of aerobic respiration that takes places in the mitochondria to form more ATP for the muscles. Without oxygen, the pyruvate formed from glycolysis will convert to lactic acid (an anaerobic product), which increases the acidity in muscles and causes cramps. 6. What is the "motor unit" in vertebrate skeletal muscle? Ans. Answered in number 3. 7. What is sequence of events during muscle contraction? Ans. Answered in number 2. 8. What is the role of acetylcholine in muscle contraction? Ans. Acetylcholine (Ach) is a neurotransmitter that is released from the motor neuron to the muscle cell. By binding to the receptors on the muscle cell, ACh induces an action potential and a membrane depolarization occurs. This action potential later on results in the release of Ca , which causes muscle to contract. 9. What is voluntary and involuntary muscle movement? Ans. Voluntary muscle movement can contract in response to conscious thought and are stimulated by neurons in the somatic division of the PNS. Involuntary muscle movement contracts only in response to unconscious electrical activity and are stimulated and inhibited by neurons in the autonomic division of PNS. 10. What type of muscles is used during peristalsis? Ans. Smooth muscles are used during peristalsis. This is seen in the esophagus of the digestive tract when the bolus is travelling down to the stomach. Peristalsis is the wave-like contraction of the muscle. 11. How are muscles joined to bones? Ans. Skeletal muscles are attached to two different bones by tendons, which are bands of tough, fibrous connective tissue. Ligaments are fibrous tissue that binds to bones. Therefore: MUSCLE BONE = TENDON BONE BONE = LIGAMENT 12. What is the distinction between skeletal, cardiac and smooth muscles? SMOOTH MUSCLE CARDIAC MUSCLE SKELETAL MUSCLE VOLUNTARY / Involuntary Involuntary Voluntary INVOLUNTARY Innervated by autonomic motor contracts following spontaneous Distinguished property neurons depolarizations. Stimulated by somatic motor Ach from parasympathetic at rest: Ach is released neurons (also called motor units). neruons aids in digestion by to slow down rate of Not all skeletal muscle stimulating contraction of depolarization and slow fibers have the sliding- these muscles in stomach down heart rate. filament contractile and intestines. during exercise or stress: properties Sympathetic neurons release NS norepinephrine and epinephrine Force of output depends on: norepinephrine and adrenal released to increase heart rate 1. Relative proportion of glands on kidneys release and strengthen force of different fiber types epinephrine (adrenaline) which contraction. 2. Organization of fibers inhibit contraction of muscle Fight-or-Flight response within muscle (parallel Signal from motor neuron, of sympathetic system. versus pennate). therefore, is not required 3. How muscle is used MULTINUCELATE Uninucleated 1 or 2 nuclei Multinucleated / UNINUCLEATE STRIATED / Unstriated Striated Striated UNSTRIATED BRANCHING Unbranched Branched Branched Directly connected end-to-end via specialized regions called intercalated disks. These discs are critical to flow of electrical signals from cell to cell and thus coordination of hears beat STRUCTURE Lacks internal strands of Contains sarcomeres Packed with myofibrils, each myofibrils (sarcomeres) containing thousands of Organized into thin sheets sarcomeres Tapered cells at each end LOCATION/ Lungs, blood vessels, digestive Walls of heart, responsible for Attaches to the skeleton FUNCTION system, urinary bladder and pumping blood throughout body Encircles the openings of digestive reproductive system and urinary tracts and controls swallowing, defecation and urination 13. How are the muscles categorized according to speed of contraction? Why and how do they differ in contraction speed? SLOW MUSCLE FIBERS FAST MUSCLE FIBERS INTERMEDIATE MUSCLE FIBERS COLOR Red White Pink or red MYGLOBIN High Low High CONC. ATP Via aerobic respiration Via glycolysis From glycolysis and aerobic Slow oxidative Fast glycolytic respiration Slow glycolytic MITOCHONDRIA Many Few Many FATIGUE Slow twitch Fast twitch Intermediate twitch Fatigues slowly Fatigues quickly Intermediate fatigue FUNCTION Contract slowly because myosin Contract rapidly because myosin Contractile properties vary but hydrolyze ATP at a slow rate hydrolyzes ATP at a rapid rate are intermediate between slow Fatigue slowly because they They also fatigue quickly because and fast fibers because they have many mitochondria and ATP is glycolysis rather than aerobicderive ATP from both glycolysis can generate steady quantities respiration and aerobic respiration of ATP using oxidative phosphorylation LOCATION Abundant in muscles specialized Contract and relax up to 3x faster for endurance – swimming or than slow fibers walking Well suited for bursts of activity soleus muscle in back of calf Ex. Quick escape from predators, or that keeps you upright when muscles that control your eye you stand movements NOTE: - Training does not change slow fibers to fast fibers, nor the reverse - Ration of muscle fiber types in muscles is heritable - Endurance training can increase density of blood vessels, mitochondria and myoglobin in muscle fibers, improving performance. 14. What is fatigue? What is rigor mortis? Ans. Muscle fatigue is the decline in ability of a muscle to generate force. Rigor Mortis is the stiffening of the joints and muscles of a body a few hours after death, usually lasting from one to four days.
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