A&P:I: Muscle
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| What are the three muscle types | cardiac
skeletal
smooth
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| What do skeletal muscles do/attached to? | Skeletal system
allows us to move
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| 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
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| What are the functions of the skeletal muscles? | Produce skeletal movement
Maintain body position
Support soft tissues
Guard body openings
Maintain body temperature
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| Where are cardiac tissue found? | Cardiac muscle is striated, found only in the heart
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| 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
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| Where is smooth muscle | Forms around other tissues
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| 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
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| 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
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| Epimysium | Exterior collagen layer
Connected to deep fascia
Separates muscle from surrounding tissues
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| Perimysium | Surrounds muscle fiber bundles (fascicles)
Contains blood vessel and nerve supply to fascicles
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| Endomysium | Surrounds individual muscle cells (muscle fibers)
Contains capillaries and nerve fibers contacting muscle cells
Contains satellite cells (stem cells) that repair damage
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| What makes up a tendon (bundle) or aponeurosis (sheet) | Endomysium, perimysium, and epimysium
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| What forms a connective tissue attachment to bone matrix and ends of muscles? | Endomysium, perimysium, and epimysium
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| Skeletal muscle cells are also called what? | fibers
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| 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
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| Sarcolemma | The cell membrane of a muscle cell
Surrounds the sarcoplasm (cytoplasm of muscle fiber)
A change in transmembrane potential begins contractions
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| Transverse tubules | Transmit action potential through cell
Allow entire muscle fiber to contract simultaneously
Have same properties as sarcolemma
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| Myofibrils | Lengthwise subdivisions within muscle fiber
Made up of bundles of protein filaments (myofilaments)
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| What are myofilaments responsible for? | for muscle contraction
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| What are structural units of myofibrils? | Sarcomeres-
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| Sarcomeres look like what? | striped or striated pattern within myofibrils.
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| What do A bands stand for? | Thick filaments
myosin
has an m line in the center
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| What are I bands? | thin filaments
actin
there are z lines at the centers of I bands at the end of the sarcomere.
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| What are zones of overlap? | densest, darkest area on a light micrograph
Where thick and thin filaments overlap
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| ___ are the most prevalent organic compound | proteins
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| Why is there hundreds of nuclei in the skeletal muscle cells? | protein synthesis
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| What are areas of the sarcomere? | z line
m line
zones of overlap
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| What make up the sarcomere? | myosin=blue=thick
actin=red=thin
titan=green=stringy line
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| True or false. One of the functions of the skeleton is movement? | false needs muscle for the skeleton to move.
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| 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
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| Triad | formed by 1 T tubule & 2 terminal cisternae
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| Cisternae | Concentrate Ca2+ (via ion pumps)
Release Ca2+ into sarcomeres to begin muscle contraction
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| How are muscle contractions made? | Is caused by interactions of thick and thin filaments
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| What determines interactions of the muscle contraction? | structures of the protein molecules
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| What triggers a contraction? | Free Ca2+ in the sarcoplasm triggers contraction
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| 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
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| 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
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| What is needed for a contraction? | calcium
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| Thick filaments | Contain twisted myosin subunits
Contain titin strands that recoil after stretching
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| Myosin molecule | Tail:binds to other myosin molecules
Head:made of 2 globular protein subunits & reaches the nearest thin filament
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| What happens to myosin heads during contraction? | interact with actin filaments,
forming cross-bridges
pivot, producing motion
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| In a sarcomere does the myosin move true or false. | false only partially the head moves.
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| What gets smaller/bigger in a sarcomere when there is a contraction? | Sarcomere=smaller
actin/zones of overlap=bigger
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| What happens in a muscle contraction (skeletal) | Z lines move closer together
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| Step 1) Neural Control of Skeletal Muscle Contraction | Neural stimulation of sarcolemma:
@ neuromuscular junction NMJ
causes excitation–contraction coupling
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| 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
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| Step 3) Neural Control of Skeletal Muscle Contraction | Action potential (electrical signal):
travels along nerve axon
ends at synaptic terminal
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| 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)
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| 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)
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| 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
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| 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
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| Contraction Cycle step 1 | Exposure of active sites of F actin of thin filament
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| Contraction Cycle step 2 | Formation of cross-bridges due to interaction of actin filaments w/ myosin heads forming cross-bridges that pivot, producing motion
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| Contraction Cycle step 3 | Pivoting of myosin heads
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| Contraction Cycle step 4 | detachment of cross bridges
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| Contraction Cycle step 5 | reactivation of myosin
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| What depends of the contraction duration? | duration of neural stimulus
number of free calcium ions in sarcoplasm
availability of ATP
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| What happens in the relaxation of the contraction? | Ca2+ concentrations fall
Ca2+ detaches from troponin
Active sites are recovered by tropomyosin
Sarcomeres remain contracted
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| ___ is an active process? | contraction
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| What is passive process? | relaxation and return to resting length
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| Rigor Mortis | A fixed muscular contraction after death
Caused when ion pumps cease to function
calci builds up in the sarcoplasm
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| isotonic contraction | Skeletal muscle changes length resulting in motion
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| Isotonic:Concentric contraction | If muscle tension > resistance: muscle shortens
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| Isotonic:eccentric contraction | If muscle tension < resistance: muscle shortens
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| Isometric Contraction | Skeletal muscle develops tension, but is prevented from changing length
Note: Iso = same, metric = measure
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| What are inversely related? | Resistance and Speed of Contraction
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| The heavier the resistance on a muscle: | the longer it takes for shortening to begin
and the less the muscle will shorten
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| How does a muscle fiber return to its resting length? | Elastic forces
Gravity
Opposing muscle contractions
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| Muscle relaxation: Elastic forces | The pull of elastic elements (tendons and ligaments)
Expands the sarcomeres to resting length
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| Muscle relaxation: Gravity | Can take the place of opposing muscle contraction to return a muscle to its resting state
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| Muscle relaxation: Opposing muscle contractions | Reverse the direction of the original motion
Are the work of opposing skeletal muscle pair
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| what does a sustained muscle contraction use alot of? | ATP energy
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| Muscles store enough energy to start ___ | contraction
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| What must muscle fibers manufacture more if there is a need? | ATP
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| Adenosine triphosphate (ATP) | the active energy molecule
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| Creatine phosphate (CP) | the storage molecule for excess ATP energy in resting muscle
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| How do the cell produce atp? | -aerobic metabolism of fatty acids in mitochondria
-anaerobic glycolysis in the cytoplasm
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| Aerobic Metabolism | Is the primary energy source of resting muscles
Breaks down fatty acids
Produces 34 ATP molecules per glucose molecule
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| 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
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| 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
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| Muscle Fatigue | Depletion of metabolic reserves
Damage to sarcolemma and sarcoplasmic reticulum
Low pH (lactic acid)
Muscle exhaustion and pain
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| 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
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| 3 Types of Skeletal Muscle Fibers | Fast fibers
slow fibers
intermediate fibers
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| 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)
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| 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)
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| 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
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| 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
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| Aerobic Endurance | Aerobic activities (prolonged activity):
supported by mitochondria
require oxygen and nutrients
Improved by:
repetitive training (neural responses)
cardiovascular training
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| Where is the intercalated discs found at? | -specialized contact points between cardiocytes
Join cell membranes of adjacent cardiocytes (gap junctions, desmosomes)
Discs
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| Function of intercalated discs | Functions
Maintain structure
Enhance molecular and electrical connections
Conduct action potentials
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| 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
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| 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
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| Whats the difference b/w smooth and striated muscle? | -Different internal organization of actin & myosin
-Different functional characteristics
-nonstriated
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| 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
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| 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
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| What are the characteristics of smooth muscle?? | Excitation–Contraction Coupling
Length–Tension Relationships
control of contractions
smooth muscle tone
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| 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
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| 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)
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| 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
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| Characteristics of smooth muscle: smooth muscle tone | Maintains normal levels of activity
Modified by neural, hormonal, or chemical factors
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