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A&P:I:muscle part 1
A&P:I: Muscle
| Question | Answer |
|---|---|
| What are the three muscle types | cardiac skeletal smooth |
| What do skeletal muscles do/attached to? | Skeletal system allows us to move |
| What are the structures of the skeletal muscles? | Muscle tissue (muscle cells or fibers) Connective tissues (1-3 following) Nerves – voluntary muscles, controlled by nerves of CNS Blood vessels - supply large amounts of oxygen & nutrients & carry away wastes |
| What are the functions of the skeletal muscles? | Produce skeletal movement Maintain body position Support soft tissues Guard body openings Maintain body temperature |
| Where are cardiac tissue found? | Cardiac muscle is striated, found only in the heart |
| What are the 7 characteristics of cardiocytes | are small have a single nucleus have short, wide T tubules have no triads have SR with no terminal cisternae are aerobic (high in myoglobin, mitochondria) have intercalated discs |
| Where is smooth muscle | Forms around other tissues |
| What does the smooth muscle do in blood vessels and Reproductive /glandular systems? | In blood vessels: regulates blood pressure and flow In reproductive and glandular systems: produces movements |
| What does the smooth muscle do indigestive and integumentary system? | In digestive and urinary systems: forms sphincters produces contractions In integumentary system: arrector pili muscles cause goose bumps |
| Epimysium | Exterior collagen layer Connected to deep fascia Separates muscle from surrounding tissues |
| Perimysium | Surrounds muscle fiber bundles (fascicles) Contains blood vessel and nerve supply to fascicles |
| Endomysium | Surrounds individual muscle cells (muscle fibers) Contains capillaries and nerve fibers contacting muscle cells Contains satellite cells (stem cells) that repair damage |
| What makes up a tendon (bundle) or aponeurosis (sheet) | Endomysium, perimysium, and epimysium |
| What forms a connective tissue attachment to bone matrix and ends of muscles? | Endomysium, perimysium, and epimysium |
| Skeletal muscle cells are also called what? | fibers |
| What do skeletal muscle fibers look like and how are they made? | Are very long Develop through fusion of mesodermal cells (myoblasts) Become very large Contain hundreds of nuclei |
| Sarcolemma | The cell membrane of a muscle cell Surrounds the sarcoplasm (cytoplasm of muscle fiber) A change in transmembrane potential begins contractions |
| Transverse tubules | Transmit action potential through cell Allow entire muscle fiber to contract simultaneously Have same properties as sarcolemma |
| Myofibrils | Lengthwise subdivisions within muscle fiber Made up of bundles of protein filaments (myofilaments) |
| What are myofilaments responsible for? | for muscle contraction |
| What are structural units of myofibrils? | Sarcomeres- |
| Sarcomeres look like what? | striped or striated pattern within myofibrils. |
| What do A bands stand for? | Thick filaments myosin has an m line in the center |
| What are I bands? | thin filaments actin there are z lines at the centers of I bands at the end of the sarcomere. |
| What are zones of overlap? | densest, darkest area on a light micrograph Where thick and thin filaments overlap |
| ___ are the most prevalent organic compound | proteins |
| Why is there hundreds of nuclei in the skeletal muscle cells? | protein synthesis |
| What are areas of the sarcomere? | z line m line zones of overlap |
| What make up the sarcomere? | myosin=blue=thick actin=red=thin titan=green=stringy line |
| True or false. One of the functions of the skeleton is movement? | false needs muscle for the skeleton to move. |
| Sarcoplasmic reticulum | membranous structure surrounding each myofibril Helps transmit action potential to myofibril Similar structure to SER Forms chambers (terminal cisternae) attached to T tubules |
| Triad | formed by 1 T tubule & 2 terminal cisternae |
| Cisternae | Concentrate Ca2+ (via ion pumps) Release Ca2+ into sarcomeres to begin muscle contraction |
| How are muscle contractions made? | Is caused by interactions of thick and thin filaments |
| What determines interactions of the muscle contraction? | structures of the protein molecules |
| What triggers a contraction? | Free Ca2+ in the sarcoplasm triggers contraction |
| What are in thin filament? | -Nebulin - holds F actin strands together -Troponin - a globular protein that binds tropomyosin to G actin and is controlled by Ca2+ -Tropomyosin - is a double strand prevents actin–myosin interaction |
| How are contractions initiated? | Ca2+ binds to receptor on troponin molecule Troponin–tropomyosin complex changes (the shape=change funtion) Exposes active site of F actin |
| What is needed for a contraction? | calcium |
| Thick filaments | Contain twisted myosin subunits Contain titin strands that recoil after stretching |
| Myosin molecule | Tail:binds to other myosin molecules Head:made of 2 globular protein subunits & reaches the nearest thin filament |
| What happens to myosin heads during contraction? | interact with actin filaments, forming cross-bridges pivot, producing motion |
| In a sarcomere does the myosin move true or false. | false only partially the head moves. |
| What gets smaller/bigger in a sarcomere when there is a contraction? | Sarcomere=smaller actin/zones of overlap=bigger |
| What happens in a muscle contraction (skeletal) | Z lines move closer together |
| Step 1) Neural Control of Skeletal Muscle Contraction | Neural stimulation of sarcolemma: @ neuromuscular junction NMJ causes excitation–contraction coupling |
| Step 2) Neural Control of Skeletal Muscle Contraction | Cisternae of SR release Ca2+: which triggers interaction of thick and thin filaments consuming ATP and producing tension |
| Step 3) Neural Control of Skeletal Muscle Contraction | Action potential (electrical signal): travels along nerve axon ends at synaptic terminal |
| Step 4) Neural Control of Skeletal Muscle Contraction | Synaptic Terminal Releases neurotransmitter (acetylcholine or ACh) into the synaptic cleft (gap between synaptic terminal and motor end plate) |
| Step 5) Neural Control of Skeletal Muscle Contraction | Acetylcholine or ACh: travels across the synaptic cleft, binds to membrane receptors on sarcolemma, causes sodium–ion rush into sarcoplasm, is quickly broken down by enzyme (acetylcholinesterase or AChE) |
| Step 6) Neural Control of Skeletal Muscle Contraction | Action Potential Generated by increase in sodium ions in sarcolemma, travels along the T tubules, & leads to excitation–contraction coupling |
| Step 7) Neural Control of Skeletal Muscle Contraction | Excitation–Contraction Coupling Action potential reaches a triad: releasing Ca2+ & triggering contraction Requires myosin heads to be in “cocked” position - loaded by ATP energy |
| Contraction Cycle step 1 | Exposure of active sites of F actin of thin filament |
| Contraction Cycle step 2 | Formation of cross-bridges due to interaction of actin filaments w/ myosin heads forming cross-bridges that pivot, producing motion |
| Contraction Cycle step 3 | Pivoting of myosin heads |
| Contraction Cycle step 4 | detachment of cross bridges |
| Contraction Cycle step 5 | reactivation of myosin |
| What depends of the contraction duration? | duration of neural stimulus number of free calcium ions in sarcoplasm availability of ATP |
| What happens in the relaxation of the contraction? | Ca2+ concentrations fall Ca2+ detaches from troponin Active sites are recovered by tropomyosin Sarcomeres remain contracted |
| ___ is an active process? | contraction |
| What is passive process? | relaxation and return to resting length |
| Rigor Mortis | A fixed muscular contraction after death Caused when ion pumps cease to function calci builds up in the sarcoplasm |
| isotonic contraction | Skeletal muscle changes length resulting in motion |
| Isotonic:Concentric contraction | If muscle tension > resistance: muscle shortens |
| Isotonic:eccentric contraction | If muscle tension < resistance: muscle shortens |
| Isometric Contraction | Skeletal muscle develops tension, but is prevented from changing length Note: Iso = same, metric = measure |
| What are inversely related? | Resistance and Speed of Contraction |
| The heavier the resistance on a muscle: | the longer it takes for shortening to begin and the less the muscle will shorten |
| How does a muscle fiber return to its resting length? | Elastic forces Gravity Opposing muscle contractions |
| Muscle relaxation: Elastic forces | The pull of elastic elements (tendons and ligaments) Expands the sarcomeres to resting length |
| Muscle relaxation: Gravity | Can take the place of opposing muscle contraction to return a muscle to its resting state |
| Muscle relaxation: Opposing muscle contractions | Reverse the direction of the original motion Are the work of opposing skeletal muscle pair |
| what does a sustained muscle contraction use alot of? | ATP energy |
| Muscles store enough energy to start ___ | contraction |
| What must muscle fibers manufacture more if there is a need? | ATP |
| Adenosine triphosphate (ATP) | the active energy molecule |
| Creatine phosphate (CP) | the storage molecule for excess ATP energy in resting muscle |
| How do the cell produce atp? | -aerobic metabolism of fatty acids in mitochondria -anaerobic glycolysis in the cytoplasm |
| Aerobic Metabolism | Is the primary energy source of resting muscles Breaks down fatty acids Produces 34 ATP molecules per glucose molecule |
| Anaerobic Glycolysis | Is the primary energy source for peak muscular activity Produces 2 ATP molecules per molecule of glucose Breaks down glucose from glycogen stored in skeletal muscles |
| Energy Use and Muscle Activity: At peak exertion? | At peak exertion: muscles lack oxygen to support mitochondria muscles rely on glycolysis for ATP pyruvic acid builds up, is converted to lactic acid |
| Muscle Fatigue | Depletion of metabolic reserves Damage to sarcolemma and sarcoplasmic reticulum Low pH (lactic acid) Muscle exhaustion and pain |
| The Cori Cycle | The removal and recycling of lactic acid by the liver Liver converts lactic acid to pyruvic acid Glucose is released to recharge muscle glycogen reserves |
| 3 Types of Skeletal Muscle Fibers | Fast fibers slow fibers intermediate fibers |
| Skeletal muscle fibers: fast fibers | Contract very quickly Have large diameter, large glycogen reserves, few mitochondria Have strong contractions, fatigue quickly -White muscle:mostly fast fibers, pale (e.g., chicken breast) |
| Skeletal muscle fibers: slow fibers | Are slow to contract, slow to fatigue Have small diameter, more mitochondria Have high oxygen supply Contain myoglobin (red pigment, binds oxygen) -Red muscle:mostly slow fibers, dark (e.g., chicken legs) |
| Skeletal muscle fibers: Intermediate fibers | Are mid-sized Have low myoglobin Have more capillaries than fast fiber, slower to fatigue -Most human muscles: mixed fibers, pink |
| Anaerobic Endurance: | Anaerobic activities (e.g., 50-meter dash, weightlifting): use fast fibers, fatigue quickly with strenuous activity Improved by: frequent, brief, intensive workouts, hypertrophy |
| Aerobic Endurance | Aerobic activities (prolonged activity): supported by mitochondria require oxygen and nutrients Improved by: repetitive training (neural responses) cardiovascular training |
| Where is the intercalated discs found at? | -specialized contact points between cardiocytes Join cell membranes of adjacent cardiocytes (gap junctions, desmosomes) Discs |
| Function of intercalated discs | Functions Maintain structure Enhance molecular and electrical connections Conduct action potentials |
| What do the intercalated discs do for the heart? | Because intercalated discs link heart cells mechanically, chemically, and electrically, the heart functions like a single, fused mass of cells |
| functions of cardiac tissues | 1)Automaticity: contraction without neural stimulation controlled by pacemaker cells 2)Variable contraction tension: controlled by nervous system 3)Extended contraction time 4)Preventionof wave summation and tetanic contractions by cell membranes |
| Whats the difference b/w smooth and striated muscle? | -Different internal organization of actin & myosin -Different functional characteristics -nonstriated |
| 8 characteristics of smooth muscle cells | Have scattered myosin fibers Myosin fibers have more heads per thick filament Have thin filaments attached to dense bodies Dense bodies transmit contractions from cell to cell |
| continued 8 characteristics of smooth muscle cells | Long, slender, and spindle shaped Have a single, central nucleus Have no T tubules, myofibrils, or sarcomeres Have no tendons or aponeuroses |
| What are the characteristics of smooth muscle?? | Excitation–Contraction Coupling Length–Tension Relationships control of contractions smooth muscle tone |
| Characteristics of smooth muscle: excitation-contraction coupling | Free Ca2+ in cytoplasm triggers contraction Ca2+ binds with calmodulin: -in the sarcoplasm -activates myosin light chain kinase Enzyme breaks down ATP, initiates contraction |
| Characteristics of smooth muscle: Length-tension relationship | =Thick and thin filaments are scattered =Resting length not related to tension development =Functions over a wide range of lengths (plasticity) |
| Characteristics of smooth muscle: control of contractions | Subdivisions: -multiunit smooth muscle cells: =connected to motor neurons -visceral smooth muscle cells: =not connected to motor neurons rhythmic cycles of activity controlled by pacesetter cells |
| Characteristics of smooth muscle: smooth muscle tone | Maintains normal levels of activity Modified by neural, hormonal, or chemical factors |
Created by:
talennna
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