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A&P:I:muscle part 1

A&P:I: Muscle

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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