Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
66 Cards in this Set
- Front
- Back
What are the four general functions of the muscle system?
|
Producing movement - locomotion, manipulation of body, movement of materials into/out of/within body
Maintaining posture - " anti-gravity" oriented up and down Stabilizing joints - esp. at shoulder and knee where not very stable Generating heat - thermogenesis; inefficient metabolism, 40% of body mass; maintain core temp |
|
Classiby the three types of muscle tissue (according to location, appearance, and type of nervous system control).
|
Skeletal - Attatched to skeleton; striated, voluntary
Smoth - in walls of hollow organs and errector pilli muscles, smooth, involuntary control Cardiac - most of the heart, striated, involuntary |
|
Name and describe the four functional characteristics of muscle.
|
Excitability - respond to stimulus (neurotransmitter, hormone, pH change); electrical current causes muscle contraction; second most excitable
Contractility - create tension b/w ends; able to do work; unique to muscle Extensibility - can be stretched by force w/o damage; muscles set in opposing pairs Elasticity - muscle fiber returns to normal length after being stretched; elastic fibers |
|
Which of the four functional characteristics of muscle is the most distinguishing or unique characteristic?
|
Contractility - capacity to procude tension b/w its ends
|
|
Which of the functional characteristics of muscle are protective?
|
Extensibility
Elasticity |
|
Name the CT sheath that surrounds individual muscle fibers. Of what type of CT is this sheath composed?
|
Endomysium
Thin layer of areolar CT Anchored to attatchment points of sarcolemma(membrane of muscle cell) to transfer contraction forces |
|
Name the CT sheath that surrounds a fasicle. Of what type of CT is this sheath composed?
|
Perimysium
Fibrous CT (dense irregular CT containing collagen and elastic fibers) protects blood vessels and nerve fibers that supply the fasicle from contractions |
|
Name the CT sheath that holds bundles of fascicles together to create a muscle. Of what type of CT is this sheath composed?
|
Epimysium
Dense irregular CT; thicker than perimysia Often blends with deep fascia which compartmentalizes regions of body and separates muscles into functional groups |
|
Series elastic elements (SEE)
|
endo, peri, and epimysium
Continuous with eachother and ends of muscle fiber Intertwine with tendons aponeruoses, fibers of periosteum |
|
What is the location of the blood vessels and nerves which suply the muscle tissue?
|
Enter and exit muscle near center, one nerve, one vein, one artery, but they branch extensively
Pass w/in CT wrappings Contained and protected by perimysium |
|
Describe the difference between indirect and direct muscle attatchment.
|
Direct - epimysium fused to periosteum of bone or perichondrium of cartilage (tibialis posterior/calf)
Indirect - attatch through tendon or aponerurosis (broad/flat); more common; CT of indirect attatchments intertwines with sharpeys fibers in the bone's periosteum |
|
Relative to muscle function, what is the significance of Sharpey's fibers?
|
- project into bones periosteum
- Intertwine with CT of indirect attatchments - very strong attatchment - Pull distributed over larger area of the bone |
|
In indirect attachments, what tissues are involved in transmitting pulling (i.e. contraction) forces from the muscle fiber to the bone?
|
Tendon - narrow and cord-like
Aponeurosis - broad and flat CT wrappings of muscle - they intertwine with sharpey's fibers in the periosteum |
|
Name and describe the four arrangements of fascicles/fibers within skeletal muscles.
|
Parallel - longitudinal axis; contracts over greatest distance (rectus abdominus, sartorius, biceps brachii
Convergent - fan shape, higher total number of fibers can attatch (pectoralis major, gluteus medius) Pennate - looks like feather; short fivers, fascicles at angle to tendon; (sememembranosis; rectus femoris, deltoid, gluteus maximus) Circular - fascicles arranged in circle around external body openings (orbicularis oris around mouth, orbicularis oculis around eyes) |
|
What is the advantage of the parallel type of fibers? of the pennate arrangement? the convergant?
|
Parallel - contract over greater distance = greatest ROM and speed
Pennate - limited contraction; favors power/strength Convergant - powerful, contracts over shorter distance |
|
Describe the chemical composition of muscle fibers.
|
75% H2O bye weight
20% protein - some contractile, some enqymes 5% salts (inorganic ones like Ca), pigments, substrates |
|
What is the function of myoglobin?
|
Pigment with high affinity for O2
O2 drawn from hemoglobin in blood, through sarcoplasm, into mitochondria |
|
What is the most prevalent chemical compound (by weight) in muscle?
|
Water - 75%
|
|
Describe how the following organelles are modified or adapted for function in skeletal muscle tissue: nucleus, mitochondria, smooth endoplasmic reticulum.
|
Nucleus - multinucleated; 100+ nuclei, just under sarcolema instead of in the center, formed by fusing mesodermal cells
Mitochondria - many, in rows near contractile proteins Smooth ER - "sarcoplasmic reticulum"; tubular network around individual myofibrils like a sleeve; Ca stored here and released when the signal occurs |
|
What gives skeletal muscle fibers a striated appearance?
|
Myofibrils = made of myofilaments = two types: thin and thick filaments
Striations occur where thin and thick filaments overlap each other (in the A band of the sarcomere) |
|
What causes each of the bands, zones and lines in a myofibril?
|
A band - dark area where thick and thin fillaments overlap
I band - light area with only thin filaments H zone - narrow light region within an A band; only thick filaments; only seen in relaxed muscle M line - divides H zone in 1/2; protein filaments connect filaments + stabilize them Z disk/line - dark line through I; edge of sarcomere; ancors thin filaments; connects w/ z lines in adjacent muscle fibers |
|
What is a sarcomere?
|
Smallest contractile unit of muscle
Makes up the myofiril Thick filament surrounded by 6 thin filaments Thin filament surrounded by 3 thick filaments; maximizes contractile ability |
|
What is the function of the Z disc?
|
Dark line through I band
Ancors thin and connects to adjacent z lines in other fibers Elastic filaments made of titin extend from a Z to M Stabilize myofilaments; enhance elasticity of fibers |
|
Identify the two primary types of myofilaments found in myofibrils.
|
Thick filaments - myosin; 2 twisted golf clubs with hinge at head;
Thin filaments - actin; G actin (with active site for myosin heads) made into F actin; anchored to Z, extend towards M |
|
Describe the structure of a myosin molecule. How are myosin molecules arranged to make up a thick filament?
|
2 golf clubs w/ handles intertwined; heads on hinge; tails towards M, heads towards Z; heads project in spiraling fashion, head oriented towards thin filament
|
|
Identify the proteins which make up thin filaments.
|
Actin - G actin polymerized into F actin
Nebulin - stabalize G-actin subunits Tropomyosin - covers active site Troponin - holds tropomyosin over active site |
|
Which of the proteins that make up thin filaments are regulatory proteins?
|
Tropomyosin
Troponin |
|
Describe the structure of an actin molecule. How are individual actin monomers arranged to make up a thin filament?
|
G actin polymerized into helical chain of F actin (a long filament)
Stabalized by Nebulin, a rod-like protein Active site covered by tropomyosin, which twists around actin filaments Troponin - 3 subunits; binds to tropomyosin, G actin, and Ca ion |
|
Which protein covers up the active sites on the actin filament in a resting muscle fiber?
|
Tropomyosin - held in place by troponin
When Ca low in sarcoplasm Ca high = it binds to troponin, changing it's shape, pulling tropomyosin and making active site open |
|
Describe the location of the sarcoplasmic reticulum (SR) with respect to the myofibrils.
|
SR forms tubular network around individual myofibrils; like a sleeve
On either side of T tubule, enlarged chambers/terminal cisternae form |
|
What is the function of the SR and terminal cisternae?
|
Reservoir for Ca2+
T tubules pass signals of voltage change to terminal cisternae to release Ca |
|
What is the significance of the Ca2+ release channels and the Ca active transport pumps in the SR?
|
Release channels - Ca goes out of SR into sarcoplasm very fast, triggers muscle contraction
Pumps - brings the Ca ions back into the SR for the next contraction signal |
|
What are the T tubules? Where are they located?
|
Tunnel-like invaginations of sarcolemma into sarcoplasm at right angles
Continuous with sarcolema; filled with extracellular fibers At A band-I band junction Composition: extracellular fluid |
|
What is the function of the T tubules?
|
All muscle fibers contract simultaneously
A way to internally conduct elecrical events |
|
Why is the triad of functional significance?
|
- T tubule and 2 terminal cisternae
- Integral proteins of T tubule = voltage sensors, pass signal - Integral proteins of terminal cis receptors and Ca release regulators Both extend into intermembrane space |
|
Describe the anatomy of a muscle, beginning with myofibrils
|
Myofibrils - repeating sarcomeres made up of thin and thick filaments, with active heads regulated by troponin and tropomyosin
Surrounded by sarcoplasmic reticulum and T tubules Many mitochondria and nuclei, wrapped in endomesium to form muscle fiber Bundles of fibers = fascicles surrounded by perimysium Whole muscle surrounded by epimysium and deep fascia, which lines body walls and wraps limbs |
|
Muscle contraction is currently best described by the sliding filament theory. Why is this name appropriate for the contraction process?
|
Thin filaments pulled past thick, creating sarcomere contraction
Proposed by Huxley and Hanson |
|
What happens to the A band, I band, Hzone, and Z disks during contraction? To sarcomere length?
|
H zone + I bands get smaller
A bands don't change, but do get closer together Maximal contraction - H band disappears Z disks/lines get closer together Sarcomere shortens |
|
Which myofibril structures or regions change length during the contraction process?
|
H zone and I bands get smaller
Sarcomere shrinks overall |
|
What is the role of Ca2+ and the regulatory proteins in the sliding filament mechanism?
|
Ca binds to troponin when it's in high conc. in the sarcoplasm
Troponin changes shape, pulling tropomyosin away from active sites on G actin Active site can interact with the myosin heads now |
|
Specifically, how do troponin and tropomyosin help regulate the contraction process?
|
Tropomyosin is a rod shaped protein; twists around actin strands, covering active sites
Troponin has 3 globular subunits; binds to G actin, Tropomyosin; Ca; can pull tropomyosin away from active binding site when Ca is bonded |
|
What is the role of ATP and the myosin crossbridge in the sliding filament mechanism?
|
ATP hydrolysis moves myosin head to high e/cocked position
When G actin active site is open, head latches on, releasing ADP + P1; this release causes shape change/power stroke towards center of sarcomere |
|
At what point in crossbridge cycling does ATP become hydrolyzed, and provide energy for activation of the myosin head?
|
Step 1 and 4
ATP has bound to myosin head, making it let go of the active site, now it hydrolyzes and cocks head back again the "reactivation of myosin head" |
|
At what point in crossbridge cycling does the power stroke occur?
|
Step 2: power stroke
Myosin attatches to active site, causing ADP +P1 to be released Release changes shape, pivoting head towards center |
|
When is the (ADP + P1) which fueled the power stroke in crossbridge cycling released?
|
At the beginning of the power stroke - it's release induces the shape change in the myosin head
|
|
What causes myosin to detach from actin after the power stroke is completed?
|
New ATP binds to head, making crossbridge detatch from active site on actin
Still in low e state but w/ATP attatched to head |
|
Describe the structure of the neuromuscular junction.
|
Functional, not physical contact
B/w axonal endings/synaptic terminals of alpha-motor neuron and muscle fiber Gated Ca ion channels in membrane; synaptic terminals = mitochon. and synaptic vesicles with acetylchoine/neurotransmitter Motor end plate/sarcolema - many invaginations w/ACH receptors associated with ligand-gated Na+ channels |
|
What specializations of the muscle fiber (at the motor end plate) enable it to resp to signals from the motor neuron?
|
Invaginatinos = surface area
ACH receptors associated with ligand/ACh-gated Na+ channels ACh binds = channels open and Na floods into sarcoplasm |
|
What is the synaptic cleft?
|
Space b/w motor end plate and synaptic terminals
Filled with acetylcholinesterase (AChE), which breaks down ACh quickly |
|
What is acetylcholine? What role does it play at the neuromuscular junction?
|
- Neurotransmitter
- Nerve impulse/action potential triggers release into synaptic cleft - Diffuses + opens ligand-gated Na+ channels; Na rushes in triggering muscle action potential, which makes Ca flood into sarcoplasm |
|
Describe the process of signal transmission at the neuromuscular junction (i.e., communication of nerve AP to the muscle fiber).
|
Nerve impulse/AP triggers ACh release into synaptic cleft
ACh opens ligand gated receptors on motor end plate Na+ rushes into muscle fiber, triggering muscle action potential MAP triggers Ca release from terminal cisternae into sarcoplasm |
|
What prevents prolonged stimulation of the muscle fiber by acetylcholine (ACh)?
|
AChE - acetylcholinesterase
In synaptic cleft Breaks down ACh quickly 1 nerve impulse = 1 contraction |
|
What two factors permit relaxation?
|
When Ca2+ levels are not elevated in sarcoplasm - ATP depemdent Ca pumps in SR re-sequester Ca
ATP runs out, so myosin head can't detatch anymore or be cocked back |
|
Describe the entire process of excitation-contraction coupling, beginning with a nerve impulse in a motor neuron.
|
Synaptic vesicles release ACh into synaptic cavity; opens Na+ channels in motor end plate
Na floods in creating muscle action potential; sweeps along sarcolema and T tubules Ca - out of terminal cisternae into sarcoplasm fast b/c of calsequestrin/high conc. Ca binds to troponin, pulls tropomyosin away from active actin site, head latches on, ADP released = shape change; ATP = let go, hydrolysis = cock again Ca conc falls as pumps re-sequester Ca; tropomyosin covers sites again; stops |
|
Identify two ways in which ATP is used to directly power muscle contraction events.
|
ATP hydrolysis cocks myosin head
Release of ADP changes shape and creates power stroke ATP attatchment makes head let go |
|
Physiologically speaking, what is the value of ATP's high energy phosphate bonds?
|
Hydrolysis - breaking bond releases energy
Used to perform cellular work, eg. crossbridge cycling |
|
Where is most of the cell's ATP produced?
|
Mitochondria - aerobic respiration
|
|
Which of the avenues of ATP production is/are anaerobic? aerobic?
|
Anaerobic - ATP from creatine phosphate; ATP from anaerobic glycolysis and lactic acid formation
Aerobic - ATP from aerobic respiration |
|
Which of the avenues of ATP production provides energy to fuel brief, high intensity activity?
|
Anaerobic glycolysis
In cytoplasm; initial series in glucose breakdown Forms pyruvic acid and if if a lot is formed, converted into lactic acid |
|
Which of the avenues of ATP production provides energy to fuel prolonged, submaximal activity?
|
Aerobic respiration
Uses fats, proteins and carbs 60-80% of energy released as heat |
|
What happens to pyruvic acid when there is not enough O2 present to completely catabolize it?
|
Converted to lactic acid
Used as fuel by liver, skeletal and cardiac muscle, kidney; converted back to glucose in liver and kidney Accumulates = acidic pH interferes w/enzyme activity |
|
What is muscle fatigue?
|
Physiological inability to contract despite continued neural stimulation
|
|
What factors contribute to onset of muscle fatigue?
|
Depletion of fuel reserves
Lactic acid accumulation Insufficient O2 supply Changes in central nervous system Decreased signal effectiveness at NMJ |
|
What is meant by the term recovery O2 uptake?
|
Higher than normal O2 consumption during recovery
"Excess postexercise oxygen consumption" - EPOC Not just attributed to metabolic events during exercise |
|
What physiologic factors are associated with recovery O2 uptake?
|
Body temp. elevation - increases body metabolic rate
Increased rate/depth of breathing, higher heart rate - support high metabolic rate Sweating - get rid of heat Replenishing muscle e. stores Tissue repair |
|
Name and describe the muscle fiber's three avenues of ATP production.
|
ATP from creatine phosphate (CP) - most rapidly available; 10 sec cont.; creates ATP and Creatine; enzyme = creatine kinase (CK); after exercise reverses
From anaerobic glycolysis + lactic acid formation - initial series of rxns in glucose breakdown; forms pyruvic acid (taken into mitochondrial respiratory chain), too much builds up = converted into lactic acid From aerobic respiration - High ATP yield; in mitochondria, releases lots of heat |