Exam #3 Flashcards
What are two methods used to classify joints? What are the subclasses and descriptions?
Structural Classifications:
Fibrous = fibrous connective tissue Cartilaginous = cartilage Synovial = not joined directly
Functional Classifications:
Synarthrosis = immovable Amphianthrosis = slightly movable Diarthrosis = freely movable
What is the function of synovial fluid?
Synovial fluid is held in the cartilage, mechanically squeezed out, and lubricates the surface to reduce friction
What are the types of synovial joints? Axial? How do they move? Where are they found?
Plane joint = non-axial, slipping/gliding movement only (intracarpal joint)
Hinge joint = uniaxial, convex cylinder in one bone articulates with that of another (elbow joint)
Pivot joint = uniaxial, rotation on a single axis (proximal radiolnar joint)
Condyloid joint = biaxial, ovoid articulation (metacarpophangeal joint)
Saddle joint = biaxial, opposing surfaces are reciprocally concave-convex (carpometacarpal joint of thumb)
Ball & socket joint = multiaxial, one rounded bone fits into the cup-like depression of another bone (shoulder joint)
Muscle functions?
Movement of bones/blood
Maintaining posture and body position
Control of body openings and passages (vasodilation & vasoconstriction)
Heat generations (esp. in skeletal muscle) (vasoconstriction)
Glycemic control (reg. blood sugar levels)
What are the characteristics of muscle tissue?
Excitability (responsiveness or irritability): ability to receive and respond to stimuli
Contractility: ability to shorten when stimulated
Extensibility: ability to be stretched
Elasticity: ability to recoil to resting length
Organization of skeletal muscle?
Muscle tissue (cells / fibers)
Connective tissues
Nerves
Blood Vessels
Organization of connective tissue?
epimysium
perimysium
endomysium
What’s the role of the sarcomere?
… the functional unit of muscle contraction, separated by a dense material called Z lines.
What is the Z-line?
A dark thin protein band to which actin filaments are attached in myofibrils
What is the M-line?
runs through the exact center of the sarcomere
provide elasticity to the muscle
What are the binding sites on a myosin head? What do they do?
Binding site for actin to convert chemical energy, in the form of ATP, to mechanical energy.
Binding site for ATP (ATP hydrolysis, performs a power stroke associated with release of hydrolysis products, and detaches from actin upon binding with new ATP. )
What are the requirements for skeletal muscle contraction?
Activation: neural stimulation at a neuromuscular joint (NMJ)
Excitation-contraction coupling:
• Generation and propagation of an action potential along the sarcolemma
• Final trigger: a brief rise in intracellular Ca2+ levels
What are the steps of muscle relaxation?
- Ach is broken down by AChE
- SR recaptures Ca2+
- Active sites covered, no cross-bridge formation
- Contraction ends
- Relaxation occurs, passive return to resting length
What are the steps in initiating muscle contraction?
- Ach released, binding to receptors
- Action potential reaches T-tubule
- SR releases Ca2+
- Active site exposure, cross-bridge formation
- Contraction begins
Describe the sliding filament theory
- In the relaxed state, thin and thick filaments overlap only slightly
- During contraction, myosin heads bind to actin, detach, and bind again, to propel the thin filaments toward the M line
- As H zones shorten and disappear, sarcomeres shorten, muscle cells shorten, and the whole muscle shortens
Define motor unit (diff. between small and large motor units)
- Motor unit = a motor neuron and ALL (four to several hundred) muscle fibers it supplies
- Small motor units in muscles that control fine movements (fingers, eyes) 1 neuron : 4-6 fibers
- Large motor units in large weight-bearing muscles (thighs, hips) 1 neuron : 1000s fibers
Define muscle twitch. What are the phases?
… response of a fiber to a single stimulus
- latent period = delay between activation of nerve and activation of muscle
- contraction phase = cross-bridge formation, creates tension
- relaxation phase = reabsorption of Ca into SR
What’s the difference between fused and unfused tetanus?
fused tetanus = force of contraction is smooth and constant because of very frequent APs (until fatigued)
unfused tetanus = force of contraction varies
Define tetanus
contraction of a muscle caused by stimuli (AP)
Define muscle tension
force of a muscle contraction
What is length-tension relationship?
amount of overlap between actin and myosin
too much overlap = not much force/tension
too little overlap = decreased froce/tension
How does the length of a sarcomere differ in the heart?
sarcomere length is shorter in the heart than in skeletal muscle, allowing heart to pump blood
What is motor unit recruitment?
same muscle to lift different masses (small mass = 5 fibers // large mass = 12 fibers)
What are the many differences between slow and fast twitch muscle fibers?
large red slow twitch = (2 low glyco, 4 highs) • low glycogen content • low glycolytic capacity • high fatigue resistance • high capillary supply • high mitochondria • high myoglobin (carries oxygen) • aerobic • steady power
small white fast twitch = (2 high glyco, 4 lows) • high glycogen content • high glycolytic capacity • low fatigue resistance • low capillary supply • low mitochondria • low myoglobin (carries oxygen) • anaerobic • explosive power
Most human muscles are mixed fibers, pink
Know the types of muscle contractions
Isotonic:
• concentric = muscle contracts, muscle opposes load (lifts)
• eccentric = muscle elongates, muscle holds load
Isometric = muscle contracts, cannot oppose load (cannot lift)
What is Myostatin?
inhibits muscle differential, muscles stay are normal size
Myostatin deficiency, muscles get super toned without any regulation by Myostatin
What is muscle metabolism for?
What are the types?
Sources of energy?
Time?
muscle metabolism is for the energy used in muscle contraction
- Direct phosphorylation = coupled reaction of creatine phosphate and ADP. Anaerobic. 15s
- Anaerobic respiration = glycolysis and lactic acid formation. Anaerobic (no O2 needed). 30-60s
- Aerobic respitation = glucose, pyruvic acid, fatty acid. Aerobic (O2 required). Hours
Describe muscle fatigue
Physiological inability to contact
Occurs when:
• Ionic imbalances (K, Ca, Pi) interfere with E-C coupling
• Prolonged exercise damages the SR and interferes with Ca regulation and release
• Total lack of ATP occurs, during states of continuous contraction
Describe oxygen deficit/debt
Extra oxygen needed after exercise for:
• oxygen reserves
• glycogen stores
• ATP and CP reserves
Conversion of lactic acid to pyruvate acid, glucose, and glycolygen
Describe heat production
~40% of the energy released in muscle activity is useful as work
remaining 60% given off as heat
dangerous heat levels prevented by radiation of heat from skin and sweating
What does muscle performance depend on?
the distribution of muscle fibers
ID the structure that coordinates skeletal movement
golgi tendon organ = prevents overstretching and tearing of tendon
muscle spindles (in muscle itself)
un-stretched muscle: APs are generated at a constant rate
stretched muscle: APs are generated at a high rate
What are the two types of muscle pathology?
Neurogenic diseases
• Muscular Sclerosis = degeneration of myelin sheath
• Spinal muscular atrophy = degeneration of spinal muscle
Myopathic diseases:
• Muscular dystrophy
• Mitochondrea Myopathy
What is eburnation?
the rubbing/friction of bone-on-bone
What is atrophy?
shrinkage of muscle due to lack of use
What is hypertrophy?
enlargement of muscle due to overuse
What is Rigor Mortis?
no ATP to release myosin heads, muscles stay contracted as the cross-bridge formation remains
What’s the difference between smooth and skeletal muscle contraction?
smooth = muscle contraction regulated by MLCK complex
skeletal = muscle contraction regulated by TTC complex
Describe how mature muscle fiber becomes multinucleated
muscle fibers develop through the fusion of mesodermal cells called myoblasts
What forms the triad?
T-tubule & 2x terminal cisternae
What is transmembrane potential?
difference in electrical potential (voltage) across the membrane of a lining cell
What is action potential (AP)?
nerve impulses that allow for muscle contraction
Where are neurotransmitters found?
in vesicles in the motor neuron axon
What is a threshold stimulus?
minimum strength (mV) to initiate a contraction
What does “all-or-none response” mean?
the muscle fibers either contract or do not, there is no partial contraction
What does a partial but sustained contraction describe?
muscle tone
What attributes to the striated appearance of skeletal muscles?
repeating sarcomere units
What transmits muscle impulses into the cell interior?
T-tubules
What regulates Ca2+ levels? What is it called with Ca gates are opened/closed?
SR & T-tubules
open Ca gate = depolarization
closed Ca gate = repolarization
What happens to muscle when there is no Ca present? … and with Ca present?
Without Ca, the muscle is relaxed because myosin heads cannot form cross-bridge
With Ca, the binding of Ca to troponin causes a shift in the TTC allowing cross-bridge formation
What are the 7 steps of the NMJ?
- ) AP travels the length of the axon of a motor neuron to the axon terminal
- ) voltage gates Ca channels open, and Ca ions diffuse into the terminal
- ) Ca entry causes synaptic vesicles to release ACh via exocytosis
- ) ACh diffuses across synaptic cleft and binds to ACh receptors on ligand-gated cation channels
- ) ligand-gated cation channels open
- ) Na ions enter muscle fiber, K+ ions exit, causing AP to become less negative
- ) once the membrane potential reaches threshold value, an AP propagates along sarcolemma
What are the 4 steps of the cross bridge cycle?
- ) cross-bridge formation = ATP hydrolysis to ADP, cocks myosin head
- ) cross bridge formation = myosin head attaches to actin in presence of Ca
- ) power stroke = shortening of sarcomere, pulling actin towards center (M-line)
- ) cross bridge detachment = ATP releases myosin from actin (Ca is then reabsorbed into SR)
- ) reactivation of myosin head =
What is bronchoconstriction?
constriction of the airways in the lungs due to the tightening of surrounding smooth muscle
What is bronchodilation?
expansion of bronchial air passages
Describe smooth muscle contraction
slow, sustained contractions
non-voluntary
contain actin and myosin filaments
no striations, no sarcomeres
What are the 4 steps in excitation-contraction coupling?
- ) Ca comes in from the ECF & SR
- ) Ca binds to calmodulin, making it active
- ) Calmodulin activates MLCK, giving it energy
- ) MLCK phosphorylates and cocks myosin head
Describe the force of muscle contraction
force is affected by the relative size of the fibers (fiber diameter)
cell hypertrophy: increase of size and force of contraction)
cell hyperplasia (more cells)
What are the 4 common muscle disorders?
Tetanus - permanent contraction
Botulism - no AP
Myasthenia gravis - low nerve stimulation
Lou Gehrig’s - ALS, degeneration of motor neurons
What are the 5 ligaments in the shoulder joint?
coracoacromial
coracoclavicular
coracohumeral
glenohumeral
acromioclavicular
What are the 5 ligaments in the knee joint?
fibular collateral
tibial collateral
posterior cruciate
anterior cruciate
patellar ligament
What are the three different layers of connective tissue in a muscle?
perimysium
epimysium
endomysium
