Musculoskeletal System Flashcards
responsible for all voluntary movements such as running as well as some involuntary movements such as breathing
skeletal muscle
responsible for the beating action of the heart
cardiac muscle
creates the movement in many hollow internal organs such as the gut and is under the control of the autonomic (involuntary) nervous system
smooth muscle
All three muscle types use the same – mechanism
sliding filament contractile
skeletal muscle cells called – are large and have many nuclei
muscle fibers
muscle fibers form through the fusion of many individual embryonic muscle cells called
myoblasts
a specific muscle such as the biceps is composed of 100s or 1000s of muscle fibers bundled together by –
connective tissue
Muscle contraction is due to the interact between contractile proteins – and –
actin and myosin
thin filaments
actin filaments
thick filaments
myosin filaments
true or false the actin and myosin filaments lie parallel to each other
true
Each muscle fiber is packed with – which are bundles of thin actin and thick myosin filaments arranged in an orderly fashion
myofibrils
each thick myosin filament is surrounded by
6 thin actin filaments
each thin actin filament sits within a triangle of
3 thick myosin filaments
the myofibril consists of repeating units of contraction called –
sarcomeres
where there are only actin filaments the myofibril appears –
light
where there are both actin and myosin filaments the myofibril appears
dark
bundles of myosin filaments are held in a centered position within the sarcomere by a protein called
titin
between the ends of the myosin bundles and Z lines, titin molecules are very
stretchable
In a relaxed skeletal muscle, resistance to stretch is mostly due to the – of titin molecules
elasticity
As the muscle contracrs, the sarcomeres – and the band pattern changes
shorten
H zone and the I band become narrower and the Z lines move toward the A band when the muscle
contracts
consists of 2 long polypeptide chains coiled together, each ending in a large myosin globular head
myosin molecule
a myosin filament is made up of many myosin molecules arranged in parallel, with their heads projecting – at each end of the filament
sideways
consists of actin monomers polymerized into a long molecule that looks like two stands of pearls twisted together
actin filament
the myosin heads can bind to specific sites on actin forming – between the myosin and actin filaments
cross-bridges
the myosin heads also have – activity, when they are bound to actin they can bind and hydrolyze ATP
ATPase
the stiffening of muscles soon after death
rigor mortis
ATP is needed to break the – so when ATP production ceases with death, the muscles stiffens
actin-myosin bonds
Each myosin filaments has – head(s) at both ends
many
muscle cells are – because their plasma membranes can generate and conduct action potentials
excitable
in skeletal muscle fibers, AP are initiated by motor neurons arriving at a
neuromuscular junction
the axon terminals of motor neurons are generally – and form synapses with hundreds of muscle fibers
highly branched
A motor neuron and al of the fibers with which it forms synapses constitute a –
motor unit
The fibers contract – when its motor neuron fires
simultaneously
Increase a muscle’s strength of contraction by
increasing the firing rate of an individual motor neuron or recruit more motor neurons
The muscle fiber’s plasma membrane is continuous with a system of T tubules that descend into its cytoplasm or
sarcoplasm
T tubules come very close to the ER of the muscle cell which is also called the
sarcoplasmic reticulum
When the muscle fiber is at rest, there is a – concentration of Ca2+ in the sarcoplasmic reticulum and a lower concentration in the –
higher; sarcoplasm
spanning the space between the membranes of the T tubes and the membranes of the sarcoplasmic reticulum are –
two proteins
located in the T tubules membrane; it is voltage-sensitive and changes it conformation when an AP reaches it
dihydropyridine (DHP) receptor
located in the sarcoplasmic reticulum membrane; it is a Ca2+ channel
ryanodine receptor
has three subunits that binds: actin, tropomyosin, and Ca2+
troponin
When the muscle is at rest, the – strands are positioned so that they block the sites on the actin filament where myosin heads can bind
tropomyosin
difference between cardiac and skeletal muscle
cardiac muscle cells are much smaller and only have on nucleus
cardiac muscle cells branch and the branches of adjoining cells interdigitate into a meshwork that is resistant to –
tearing
adding to the strength of cardiac muscles are – that provide strong mechanical adhesions between adjacent cells
intercalated disc
protein structures that allow cytoplasmic continuity between cells in intercalated discs offer low-resistance pathways for ionic currents to flow between cells
gap junctions
AP initiated at one point in the heart spreads – through a large mass of cardiac muscle
rapidly
– and – have low density of actin and myosin filaments but they initiate and coordinate the rhythmic contractions of the heart
pacemaker and conducting cells
pacemaker cells make the vertebrate heartbeat – meaning it it generated by the heart itself
myogenic
A heart removed from a vertebrate can continue to beat with no input from the nervous system; although input from the ANS modifies the – of the pacemaker cells it is not essential for their continued rhythmic function
rate
In cardiac muscle cells, the T-tubues are larger and the voltage-sensitive DHP proteins in the T tubules are– and are not physically connected with the ryanodine receptors in the sarcoplasmic reticulum
Ca2+ channels
structurally the most simple muscle cells
smooth muscle cells
smooth muscle cells are smaller than skeletal muscle cells and are usually – and have 1 nucleus
long and spindle-shaped
Some smooth muscle tissue such as the wall of the digestive tract have cells that are arranged in sheets and individual cells in a sheet are in – contact with one another through gap junctions as they are in cardiac muscle
electrical
plasma membrane of smooth muscle cells are sensitive to
stretch
Smooth muscle contracts after being stretched, and the harder it is stretched, the – it contracts
harder
changes in vascular smooth muscle– are responsible for controlling the distribution of blood in the body
tone
The neurotransmitters of the sympathetic and parasympathetic postganglionic cels alter the – of smooth muscle cells
membrane potential
minimum unit of contraction
twitch
the level of tension an entire muscle generates depends on the number of – and the frequency at which –
number of motor units activated and the frequency at which the motor units fire
in muscles responsible for fine movements (fingers), a motor neuron may innervate - muscle fibers
one or a few
in muscles that produces large forces (biceps) a motor neuron innervates – muscle fibers
many
At the level of a muscle fiber, a single AP stimulates a – twitch
single
If APs reaching the muscle fiber are adequately separated in time, each twitch is discrete,
all-or-none phenomenon
Twitches sum at high levels of stimulation because the calcium pumps in the sarcoplasmic reticulum are not able to – the Ca2+ ions from the sarcoplasm between AP
clear
eventually a stimulation frequency can be reached that results in continuous presence of Ca2+ in the sarcoplasm at high enough levels to cause continuous activation of the contractile machinery a condition called
tetanus
The lack of ATP causes – since the action of ATP is to break actin-myosin bonds
fatigue
energy released from the hydrolysis of ATP “re-cocks” the – allowing them to cycle through another power stroke
myosin heads
Many muscles of the body maintain a low level of – even when the body is at rest
tension
comes from the activity of a small but chaining number of motor units in a muscle
muscle tone
have high ATPase activity that can recycle their actin-myosin cross-bridges rapidly
fast-twitch fibers
have lower ATPase activity that develop tension more slowly but can maintain it longer
slow-twitch fibers
oxidative or red muscle because they contain myoglobin, have many mitochondria and well supplied with blood vessels
slow-twitch fiers
slow-twitch fibers have substantial reserves of – so they can maintain steady prolonged production of ATP as long as oxygen is available
fuel (glycogen and fat)
glycolytic or white muscle have few mitochondria, little or no myoglobin, and fewer blood vessels
fast-twitch fibers
good for short-term work that require maximum strength
fast-twitch fibers
there are fast-twitch fibers that are somewhat oxidative and therefore – in their properties between slow-twitch and fast glycolytic fibers
intermediate
intermediate fibers can become more oxidative with – training and more glycolytic with strength training
endurance
The most important determinant of you muscle fiber types is your
genetic heritage
When a muscle is stretched and the sarcomeres are lengthened, there is less overlap between the actin and myosin filaments; therefore fewer – can form and less – produced
fewer cross-bridges; less force
if the – are stretched too much, actin and myosin do not overlap and no force can be produced
sarcomeres
anaerobic activities increase
strength
aerobic activities increase
endurance
– is a function of the cross-sectional area of muscles: the more actin and myosin filaments in a muscle fiber, the more muscle fibers in a muscles, the more tension it can produce
strength
stress on a muscles does minor – (soreness) but it also induces the formation of new actin and myosin filaments in existing muscle fibers
tissue damage
after serious muscle damage, new muscle fibers can also be produced from stem cells called – in muscle
satellite cells
In general, the major effect of strength truing is to produced – rather than more muscle fibers
bigger
aerobic exercise enhances muscles’ – involving greater number of mitochondria, increases in enzymes in energy use, and increases in density of capillaries that deliver oxygen to muscles
oxidative capacity
oxygen-bind protein that has a higher affinity for oxygen that hemoglobin
myoglobin
uses preformed ATP and creatine phosphate that are rapidly exhausted
immediate system = 10 kilocalories
metabolizes carbohydrates to lactate and pyruvate within a few seconds but lacks sustained efficient
glycolytic system
metabolizes carbohydrates or fats all the way to water and carbon dioxide producing sustained efficiency but kicks in after about 1 minute
oxidative system
True or False: ATP is present in muscles in very small amounts
true
muscle fibers contain a storage compound called – that stores energy in a phosphate bond which it can transfer to ADP
creatine phosphate (CP)
the rate at which oxidative metabolism can make ATP available to do work is – than the the rate at which the other two systems can supply ATP
slower
the rate at which muscle glycogen is replenished depends on –
diet
high muscle glycogen replenishing
high-carbohydrate diet
low muscle glycogen replenishing
high-fat diet
intermediate muscle glycogen replenishing
mixed
Carbo-loading: for 3 to 5 days, athletes exercise at a level that – muscle glycogen; then 2 or 3 days before the even they taper down their level of truing and eat a diet rich in complex carbs which results in – in which the restoration of muscle glycogen stores “overshoots” and reaches above-normal levels
depletes; glycogen supercompensations
– muscle has the greatest rate of cycling
insect
vertebrate (and most invertebrate) striated muscle is called – because the cycling of the contractile mechanism is linked to the firing of the motor neurons
synchronous
the contractile cycling and the resulting frequency are not tied to the firing rate of the – motor neurons
flight
rigid supports against which muscles pull to create directed movement
skeletal muscles
cnidarians, annelids, and other soft-bodied invertebrates have – consisting of a volume of fluid enclosed in a body cavity surrounded by muscle
hydrostatic skeletons
constriction of circular muscles – and – the segments, pushing them forward
narrows and elongates
constriction of longitudinal segments – the segments, pulling the trailing segments forward
shortens and bulges outward
bulging, shortened segments serves as – as long, narrow segments project forward
anchors
– help the widest part of the body to hold firm against substratum preventing backward sliding
bristles
hardened, rigid outer surface to which muscles can be attached
exoskeleton
the simplest example of the exoskeleton is the – of a mollusk
shell
some marine mollusks (clams) have shells composed of protein strengthened by crystals of –
calcium carbonate (rock-hard material)
shells of – mollusks like snails generally lack the hard mineral component and are much lighter
land
the most complex exoskeletons are found among –
arthropods
an exoskeleton or – covers all the outer surfaces of the arthropod’s body and all its appendages
cuticle
the cuticle contains stiffening materials everywhere except at – where flexibility must be retained
joints
a drawback of the rigid arthropod exoskeleton is that it cannot
expand
If an arthropod becomes too larger it must – or shed its exoskeleton forming a new, larger one
molt
a molting animals is – because the new exoskeleton takes time to harden
vulnerable
the vertebrate endoskeleton consist of – and –
cartilage and bone
an advantage of endoskeletons over exoskeletons of arthropods is that – in the body can grow without the animal shedding its skeleton
bones
the human skeleton consists of – bones
206
axial skeleton
skull, vertebral column, sternum, and ribs
appendicular skeleton
pectoral and pelvic girdle, arms, legs, had, feet
produce an extracellular matrix that is tough, rubbery mixture of polysaccharides and proteins (mainly fibrous collagen)
cartilage cels
collagen fibers run in all directions like reinforcing cords through the gel-like matrix and give it the well-known – and – or “gristle”
strength and resiliency
found in parts of the endoskeleton where both stiffness and resiliency are required (joints)
cartilage
supportive tissue in stiff but flexible structures like larynx, nose, and ear pinnae
cartilage
sharks and rays are called – because their skeletons are composed entirely of cartilage
cartilaginous fishes
contains collagen fibers but gets its rigidity and hardness from an extracellular matrix of insoluble calcium phosphate crystals
bone
lay day down new matrix material on bone surfaces in layers; in long bones these layers form concentric tubes parallel to the long axis of the bone
osteoblasts
osteoblasts gradually become enclosed within bone at which point they cease laying down matrix but continue to exist within small lacunae
osteocytes
despite the vast amounts of matrix between them, osteocytes communicate about – through long cellular extensions that run through tiny channels in the bone
controlling activities of cells that are laying down or removing bone
cells that remove bone; derived from the same cell linear that produces white blood cells
osteoclasts
because of the positive effects of physical stress on bone deposition, weight-bearing exercise is effecting in preventing an treating the loss o bone density and strength
osteoporosis
includes eating disorders, cessation of menstrual cycling, and osteoporosis
female athlete triad
forms on a scaffold of connective tissue membrane
membranous bone
forms first as a cartilaginous structure resembling the future mature bone then gradually ossifies to bone
cartilage bone
outer bones of skull are – bone
membranous
bones of the limbs are
cartilage bones
the long bones of legs and arms ossify first at the – and later at the –
first at the center (shaft) and later at each end
growth can continue until the areas of – join
ossification
the soft spot on the top of a baby’s head is the point at which the skull bone have not yet joined
fontanelle
solid and hard bond
compact
having numerous internal cavities that make it appear spongy although it is rigid
cancellous
the shafts of the long bones of limbs are cylinders of – surrounding central cavities that contain the bone marrow
compact bone
where the cellular elements of the blood are made
bone marrow
the ends of long bones are – bone
cancellous
most of the compact bone in mammals is called –
Haversian bone
each Haversian system is a set of thin, concentric bony – between which are the osteocytes in their lacunae
cylinders
A narrow canal containing – runs through the center of each Haversian system
blood vessels and nerves
adjacent Haversian systems are separated by boundaries called –
glue lines
Haversian bone is resistant to fracturing because cracks tend to – at glue line
stop
– are sites of elongation between the ossified regions
epiphyseal plates
muscles and bones work together around – where two or more bones come together
joints
true or false: muscles can exert force in only one direction
true
muscles create movements around joints by working in – when one muscle contrast the other relaxes
antagonistic pairs
when both muscles contract the joint becomes – (posture)
rigid
muscle that bends or flexes the joint
flexor
the muscles that straightens or extends the joint
extensor
A lever has an – arm and a – arm that work around a fulcrum (pivot)
effort arm and load arm
2 Load arm: 1 effort arm generate – over a small distance
much force
5 Load arm: 1 effort arm moves low weights long distances with –
speed
an example of a lever system designed for applying maximum force is (effort arm is long relative to the load arm)
human jaw
an example of a lever system designed of speed is the (effort arm is short relative to the load arm)
human leg
