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89 Cards in this Set
- Front
- Back
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What are the 5 characteristics of muscle tissues
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Excitability, conductivity, contractility, extensibility, and elasticity
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Excitability
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Neurotransmitters from nerves stimulate electrical changes in muscle cells' plasma membrane
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Conductivity
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Electrical impulses initiate cellular processes leading to muscle contraction
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Contractility
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Muscle cells shorten and generates a pulling force
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Extensibility
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After contraction, muscles can be stretched by contraction of an opposing muscle
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Elasticity
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After stretching, muscles can recoild to their resting length
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Skeletal muscles
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Striated, multinucleated cells, voluntary movement, maintains posture, joint stabilization via muscle tone, and heat generation
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Cardiac muscles
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Involuntary, striated, uninucleated cells separated by intercalated discs. Regulated by autonomic nervous system
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Smooth muscles and where is it found
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Involuntary, nonstriated, uninucleated, promotes peristalsis, responsible for vaso-dilation/constriction. Found in GI/Respiratory/Urogenital tracts and blood vessels
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How do muscle tissues and nerves interact with each other?
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Neurons signal muscle fibers to contract at the neuromuscular junction
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What are the three layers of CT that surround skeletal muscles
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Endomysium, perimysium, and epimysium
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Endomysium
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Surrounds individual muscle fibers (cells), binds the fibers together, and supports capillaries and nerve endings
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Perimysium
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Binds muscles fibers together into fascicles and supports the blood vessels & nerve fibers serving the fascicles
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Epimysium
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Covers the entire muscle
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How are the three layers of CT that surround the skeletal muscles related to tendons
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All three layers are continuous with the associated tendon
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What are skeletal muscles composed of?
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Many myofibrils, multinucleated, have many mitochondria, sarcoplasm, sarcolemma, transverse tubules, sarcoplasmic reticulum, terminal cisternae, and triad
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What are myofibrils composed of?
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Myofilaments of actin(thin), myosin(thick), and elastic filaments, & Sarcomeres
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Describe the microscopic structure of a skeletal muscle cell
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Whole muscle -> fasicle groups -> muscle fibers -> myofibrils -> myofilaments
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Sarcomeres and list its components
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Contractile unit in myofibrils, between Z lines. I/A bands, H zone, M line, Z discs
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I bands
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Light bands of actin only
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A bands
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Dark bands of myosin and actin
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H zone
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Central part of A band with myosin, no actin
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M line
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Center of H zone with rods that hold myosins together
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Z discs
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Protein discs where actin filaments attach. Distance between Z lines shortens during contraction
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Sarcolemma
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Plasma membrane. Surrounds each muscle cell
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Transverse (T) tubules
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Invagination of the sarcolemma. Carries electrical impulses into the cell
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Sarcoplasmic reticulumn (SR)
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Smooth ER that surrounds each myofibril within the sarcolemma. Contains Calcium ions needed for muscle contraction
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Terminal cisternae
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Sac-like portion of the SR on both sides of the T-tubules
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Traid
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Complex of a T-tubule between two terminal cisternae
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Thick filaments
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Golf club like myosin. Composed of 2 intertwining polypeptides forming the shaftlike tail & a double globular protein head projecting from the tail. Bundle of 200-500 myosin with heads outward
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Thin filaments
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Contains actin, tropomyosin, and tropnin proteins
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Fibrous (F) actin
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Two intertwined strands of protein beads called globular (g) actins
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Globular (G) actins
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Each protein bead has an active (myosin binding) site that can bind a myosin head
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Tropomyosin
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A fibrous protein that blocks the actin's myosin binding site when the muscle cell is relaxed
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Troponin
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A small calcium-binding protein attached to the tropomyosin molecule at regular intervals
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Elastic filaments
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Springy titin proteins that connect the thick filament to the Z disc and keeps the thick and thin filaments aligned to resist muscle overstretching
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Motor unit
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A neuron and all the muscle cells it stimulates
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How does the number of motor units differ in muscles that require fine muscle control vs. those involved in muscle strength
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Fine motor control (eg eye/finger muscles) have few muscle fibers per neuron (25/1). Strength involved (eg back/legs) have 1000/1
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What are the components of a neuromuscular junction
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Synaptic bulb, motor end plate, synaptic cleft, synaptic vesicles, ACh receptors, Acetylcholinesterase
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How do neurons transmit nerve impulses to muscle cells
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ACh, from the synaptic bulb, binds to receptor on muscle motor end plate which stimulates the muscle cells
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What neurotransmitter used to initiate skeletal muscle contraction
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Acetylcholine
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What enzyme degrades the neurotransmitter after it has bound to receptors in the motor end plate
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Acetylcholinesterase
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What is the sliding filament model
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Describes how thin filaments slide over thick filaments to cause muscle contraction
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Key components of sliding filament model
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ATP, cross-bridges, power stroke, recovery
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How is ATP used in the sliding filament model
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Bound to myosin head. Hydrolyzed into ADP+Pi, cocking the heads into an extended high energy position
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How are cross-bridges of the sliding filament model formed?
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Energized myosin heads bind to exposed myosin-binding sites on actin
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Describe the power stroke of the sliding filament model
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Myosin heads release the ADP+Pi and flex into a bent, low energy position, pulling the thin filaments towards the center of the sarcomere
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Describe the recovery stroke of the sliding filament model
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ATO binds to myosin heads, which causes the myosin to detach from the actin
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Muscle tones (Tonus)
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Normal state of skeletal muscle, where the muscle rests in a state of partial contraction.
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What is the purpose of muscle tones (tonus)
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Keeps muscles ready for stimulus, helps maintain posture, aids return of blood to heart
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Threshold
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Minimum voltage required to produce a muscle contraction. Lower voltages do not cause muscle contraction
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Twitch
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One cycle of muscle contraction and relaxation
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Latent period
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Brief time between the simulus and the twitch (about 2 ms)
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Refractory period
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For a few millisec after contraction, the muscles cannot contract again, regardless of the amount of stimulus received
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What are the two methods by which the contraction strength of a muscle twitch may be increased
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Recruitment (activates more motor units) and high frequency stimulation
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Treppe
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Staircase phenomenon. 10-20 stimuli/sec causes each twitch to develop more tension than the one before it
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Temporal summation
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Generating higher tension. 20-40 stimuli/sec allows twitches to piggyback on each other, produces an incomplete tentanus
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Incomplete tetanus
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Partially sustained contraction produced by 20-40 stimuli/sec
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Complete tetanus
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At 40-50 stimuli/sec, muscles do not relax between stimuli, so twitches blend into a smooth, prolonged contraction
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Example of isometric contraction
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Gripping something
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Example of isotonic contraction
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Lifting weights
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Anaerobic fermentation
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Occurs when cell metabolizes glucose without oxygen. Produces 2 ATP & Lactic acid (depletes glycogen in liver)
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Aerobic respiration
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Occurs mostly in the mitochondria in the presence of oxygen. Produces 36 ATP, CO2, & water.
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Myokinase
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Transfer Pi groups from one ADP to another forming ATP
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Creatine kinase
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Obtains Pi from creatine phosphate and donates it to ADP, forming ATP and creatine
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What is ATP needed for in muscle contraction
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Muscle relaxation. Actively transport calcium back to SR & detach myosin heads from actin after contraction
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What are the sources of glucose used in aerobic and anaerobic respiration
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Glucose from the blood and glycogen stored in muscles is used to produce ATP (anaerobically), Oxygen is then delivered to muscles for aerobic respiration
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What is oxygen debt
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Difference between the resting rate of oxygen consumption and the elevated rate following strenuous exercise
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Why is extra oxygen needed after strenuous exercise
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Replenish the body's oxygen reserves in myoglobin and hemoglobin. Oxidizes lactate to pyruvate, then to glucose, stored as glycogen in the liver
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What is the cause of muscle fatigue
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Glycogen & creatine phosphate reserves in muscles/liver & ATP synthesis declines. Lactate lowers pH inhibiting enzymes for contraction/ATP synthesis. Motor nerves deplete their ACh
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What is the cause of muscle cramps
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Lack of ATP
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Red slow twitch (slow oxidative) fibers (dark meat)
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Red due to abundant myoglobin. Many capillaries and mitochondria. Fibers contract slowly and resistant to fatigue as long as oxygen is present.
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White fast-twitch (fast glycolytic) fibers (white meat)
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Low myoglobin/mitochondra/capillaries. Twice the diameter of red fibers. More myofilaments/power(fatigues quickly). Many glycosomes (contains glycogen). Anaerobic
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Intermediate fast-twitch (fast oxidative) fibers
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Has diameter/power/fatigue resistance between red and white. Contracts quickly like white. Oxygen dependent like red so, Many myoglobin/capillaries
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Where is Red Slow, White fast, Intermediate fast twich found? What activity is each suited for
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Red (lower back, posture), white (upper limbs, lifting), intermediate (lower limbs, walking)
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Intercalated discs
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Complex junction where cardiac cells branch and join together
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How do intercalated discs allow cardiac cells to contract in unison
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Desmosomes & fascia adheran holds the cells together gap junctions which allow ions to pass from cell to cell to synchronize muscle contraction
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Components of smooth muscles
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Tropomyosin, calmodulin, dense bodies, noncontractile intermediate filaments, thin SR, no T-tubules, Ca comes from extracellular fluid through Ca channels
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What are the two types of SmM and how are they different
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Multiunit SmM and Single-unit (viseral) SmM. Multi- each unit contracts independently. Single contracts as one unit
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How are smooth muscles and skeletal muscles similar in contraction and relaxation
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Actin and mysosin interact by a sliding filament mechanism. Rise in Ca level triggers contraction. ATP energizes the sliding process
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How does smooth muscle differ to skeletal muscles in contraction and relaxation
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Ca can difusse through membrane to initiate contraction. Ca interacts with calmodulin and a kinase to activate myosin
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Hypertrophy vs. Hyperplasia, which type of muscles experience which
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HT (increase in size)(SkSmCa). HP (increase in cell number)(Sm during pregnancy & puberty).
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Muscular dystrophy
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Muscle destroying disease. Skeletal muscles degenerates and is gradually replaced by adipose and fibrous tissue
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Duchene muscular dystrophy
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Most serious. Sex-linked recessive. Rarely live past 20
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Myotonic dystrophy and symptoms
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Inherited. Can appear at any age. Symptoms: muscle spasms/weakness and abnormal heart rhythm
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Myofascial pain syndrome and symptom
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Affects 50% of all people 30-60yo. Pain due to tightened bands of muscle fibers that twich when the skin over them is touched
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Cause and Treatment for Myofascial pain syndrome
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Often associated with strained postural muscles. Treated with nonsteroidal anti-inflammatory drugs, stretching, and massage
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Fibromyalgia and symptoms
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Chronic pain syndrome of unknown cause. Symptoms: severe musculoskeletal pain, fatigue, sleep abnormalities, and headaches
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How one is diagnosed and treated for Fibromyalgia
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Pain must be present in at least 11-18 standardized points on the body. Treatment includes antidepressants, exercise, and pain killers
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