muscular system Flashcards
Name 2 root words for muscle.
myo and sarco
the study of muscles
myology
a skeletal muscle cell
myofiber or muscle fiber
under conscious control
voluntary
not under conscious control
involuntary
striped or banded in appearance
striated
long, striated, multinucleate, voluntary cylinders
skeletal muscle
short, branched, striated, uni-nucleate and involuntary muscle
cardiac muscle
fusiform, uni-nucleate, non-striated, and involuntary
smooth muscle
4 characteristics of muscle tissue
- excitability - can react to stimuli
- elasticity - snaps back to shape
- extensibility - can stretch
- contractility - can shorten
5 functions of muscle
- cause movement
- produce body heat
- protect internal organs
- guard entrances and exits to the body
- give posture and body position and stabilize joints
Why do muscles need a good nerve and blood supply?
nerves tell it to contract
blood brings in food and oxygen and carries away waste
outer CT covering, over the entire muscle
epimysium
covering over muscle fascicles
perimysium
covering over individual muscle fibers
endomysium
What do the epimysium, perimysium and endomysium form at the ends of a muscle?
tendon or aponeurosis
What is the difference between a tendon and an aponeurosis?
tendon - cord - Achilles (calcaneal)
aponeurosis - sheet - lumbar, galea
What travels throughout the perimysium?
blood supply and nerves
where a muscle starts, usually on the less movable bone
origin
where a muscle ends, usually on the more movable bone
insertion
what a muscle does
action
the nerve supply to a muscle
innervation
when the epimysium is fused to the periosteum
direct attachment
Which is more common, an indirect or a direct attachment? Why?
indirect - Most muscles have a tendon or aponeurosis because there is less bulk, and it can pass over joints more easily.
muscle cell membrane
sarcolemma
muscle cell cytoplasm
sarcolemma
muscle ER
SR - sarcoplasmic reticulum
contractile organelle in a muscle - cylinders of thick and thin myofilaments
myofibril
contractile unit of a myofibril - from z line to z line
sarcomere
the stored glycogen granules in a muscle
glycosomes
pigment in muscle that stores oxygen
myoglobin
How many myofibrils are in a single muscle fiber?
hundreds to thousands - 80% of fiber volume
the lighter region of the striations - made of thin fibers
I band
the darker region of striations - made of the length of the thick fibers
A band
holds actin threads together and forms a sarcomere
z lines
holds thick fibers together at middle of sarcomere
m line
the region where there are both thick and thin fibers
zone of overlap
the regulatory proteins on the actin
troponin and tropomyosin
the protein thick fibers are made up of
myosin
the protein that most of the thin filament is made up of
actin
the myosin heads form this when they connect to the actin
cross bridges
the place on the actin where the myosin head attaches
active site (binding site)
the lighter region in the middle of the A band, where there is no overlap
H zone
ATPase is what - Where is it found in muscle?
enzyme that breaks down ATP - found on the myosin head
the elastic protein filament that extends from the thick filament to the Z line and helps it spring back to place
titin
the end sacs of the SR that hold calcium
terminal cisternae (cistern)
the protrusions of the sarcolemma into the interior of the muscle fiber
t-tubules
2 terminal cisternae and 1 t-tubule
triad
What does the triad correspond to on the sarcomere? Why is this location important?
zone of overlap - so calcium is released to the correct location
a structural protein that links the thin filaments to the sarcolemma
dystrophin
the model of muscle contraction
sliding filament theory
do the actin or myosin molecules shorten when a muscle contracts? Explain.
No, they slide past one another as the myosin heads grab and pull on the actin threads. The actin slides toward the M line.
a nerve impulse
action potential
a place where a nerve and muscle meet
neuromuscular or myoneural junction
neurons that stimulate muscles
motor neurons
neurons that take information to the CNS
sensory neurons
the gap between a neuron and a muscle or another neuron
synaptic cleft
the sacs of chemicals in a synaptic knob
synaptic vesicles
the chemicals that send nerve messages across the synapse
neurotransmitters
the neurotransmitter in a neuromuscular junction
ACh - acetylcholine
what are the folds in the motor end plate, and what is their purpose
junctional folds - increase SA - more receptors
the cell membrane before the synapse
presynaptic membrane
the cell membrane after the synapse
postsynaptic
the sarcolemma of a muscle at the point of the synapse
motor end plate
the enzyme that breaks down ACh
AChE - acetylcholinesterase
What is the importance of AChE?
allow the message to stop
food poisoning that prevents the release of ACh causing paralysis
botulism
an autoimmune disease that attacks the ACh receptors causing paralysis
MG - myasthenia gravis
the electrical condition of the motor end plate before it receives the message
polarized - having 2 opposite charges on different sides of the membrane
What happens to the sarcolemma’s polarity as it sends the message?
depolarized - loses its charge difference
What has to happen to the sarcolemma’s charge before it can send another message?
repolarized - get the opposite charges again
How is the membrane repolarized?
sodium-potassium pump
local depolarization
end plate potential
the period of time during which the membrane cannot respond to another stimulus because it isn’t completely repolarized
refractory period
What are the two types of refractory period, and how are they different?
- absolute refractory period - absolutely no response no matter how strong the stimulus
- relative refractory period - will respond if stimulus is strong enough
Why does cardiac muscle need a longer refractory period?
We want the heart to fill with blood before contracting again.
stiffness after death
rigor mortis
What causes rigor mortis?
no ATP or energy so cross bridges don’t release
When does rigor mortis finally stop?
after myofilaments start to decay
When does rigor mortis start? When is its peak time? When does it typically cease?
starts - 3 to 4 hours after death
peak - 12 hours after death
stops 48 to 60 hours after death
Other than time, what affects rigor mortis?
environmental conditions like temperature
the force exerted by a contracting muscle
muscle tension
the opposing force to muscle contraction
load
when the load is not moved but the tension increases
isometric
when the load is moved
isotonic
one motor neuron and all its fibers
motor unit
How do muscles generate more power?
more motor units are recruited
Compare motor units in the eye and leg.
eye - small and precise
leg - large and powerful
a graph of a single contraction/relaxation sequence in a muscle - a muscle twitch
myogram
the period at the beginning of the myogram where there is not a response yet
latent period
the upward tracing as tension increases
contraction phase
the downward tracing as tension decreases
relaxation
as the stimuli come a little faster and the next twitch is higher
wave summation
when the muscle reaches maximum tension with some relaxation
incomplete tetanus
when the stimuli come so fast that no relaxation is seen in the graph
complete tetanus
All actual muscle activity is what kind of myogram?
complete tetanus
when our muscles can respond to different needs like lifting something light or something heavy
graded muscle response
How can we get a graded muscle response? 2 ways
- stronger stimulus
2. higher frequency stimulus
the minimum stimulus necessary to cause a response - 2 terms
- threshold
2. liminal
a stimulus below that necessary to cause a response - 2 terms
- subthreshold
2. subliminal
getting more motor units involved - 2 terms
- recruitment
2. multiple motor unit summation
the strongest stimulus that can increase contractile force
maximal stimulus
How does recruitment progress?
smallest motor units first - largest and least reactive last
usually not all motor units are working at the same time so others can rest and take over when needed
asynchronous
when some muscle fibers are contracted at any given time
muscle tone
What are the 2 biggest advantages of having muscle tone?
- higher metabolism - burn food more
2. more stability for joints - muscles are ready to contract if needed
What are the two parts of an isotonic contraction, and how are they different?
- concentric - shortening
2. eccentric - lengthening - stronger
usable cellular energy
ATP - adenosine triphosphate
Where is the energy stored in ATP, and how does the cell get the energy?
phosphate bonds - break bonds
a chemical that can store phosphate to phosphorylate ADP and make ATP
CP - creatine phosphate
How long can stored energy in muscles last?
14-16 seconds
What does the body have to do after the muscles use all their stored energy?
make more by respiration
What are the 2 kinds of respiration, and how do they compare?
- aerobic - more efficient (with oxygen) - makes more energy and less waste
- anaerobic - less efficient (without oxygen) - makes less energy and more waste
What are the end products of aerobic respiration, and what happens to them?
CO2 and H2O - exhale them
What are the end products of anaerobic respiration, and what happens to them?
lactic acid - circulates in blood until it can be removed - makes muscles tired and sore
another name for anaerobic respiration
glycolysis
What does glycolysis literally mean, and how much energy is produced?
breakdown of glucose into 2 pyruvic acids - 4 ATP - 2 are invested so a net of 2ATP per glucose
What are the advantages of anaerobic respiration?
starts quickly and can progress faster - also when there is no oxygen present
How long can anaerobic exercises last?
a minute
What organelle does aerobic respiration? How much ATP is generated?
mitochondrion - 32 ATP per glucose
the length of time a muscle can use aerobic respiration
aerobic endurance - anaerobic threshold
the main muscle that causes a movement - 2 terms
- agonist
2. prime mover
the muscle that works opposite the agonist
antagonist
a muscle that helps with a motion but is not the main muscle
synergist
a muscle that stabilizes a joint to allow another to work
fixator
Give 2 examples of antagonistic muscle pairs
- biceps and triceps
2. quadriceps and hamstrings
Give 7 ways muscles are named.
- location
- shape
- relative size
- direction of fibers
- number of origins
- location of attachment
- action
the inability to contract with sufficient neural stimulation
fatigue
What has to happen for a muscle to recover from activity?
- release heat
- pay back oxygen debt by breathing heavily
- replace energy reserves - ATP, glycogen, CP
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when a muscle loses mass due to inactivity
atrophy
when a muscle gains mass due to use
hypertrophy
force generated by cross bridges
internal tension
force transferred from cross bridges to load
external tension
how much overlap determines the strength of a contraction - ideal is 80-100% of resting length
- can’t contract with too much or too little overlap
length-tension relationship
immature muscle cells
myoblasts
what happens to myoblasts
fuse to make a myotube
what do we call myoblasts that don’t fuse, and for what are they used
satellite cells - repair of damaged muscle
What happens to satellite over time - so how is muscle repaired?
are used up - get fibrosis instead of regeneration
In what direction does muscle develop?
head to toe
proximal to distal
Who has more muscle mass, men or women and why?
men - due to testosterone which stimulates muscle development
synthetic male sex hormones
anabolic steroids
world’s most common genetic disorder, affects muscle - muscle first enlarges due to fat and then atrophies
muscular dystrophy
the most common form of MD - what causes it
Duchenne muscular dystrophy - lack of the protein dystrophin
What is the most common cause of death in muscular dystrophy?
respiratory failure
gradual loss of muscle mass with age
sarcopenia
a condition that limits blood flow to the muscles of the appendages (particularly the legs) causing pain during walking
intermittent claudidication
What should be done first for minor muscle injuries?
RICE - rest, ice, compression, elevation
a sudden, involuntary muscle twitch
spasm
a pulled muscle with excessive stretching and some torn fibers due to overuse
strain
inflammation of muscle
myositis
muscle pain
myalgia
disease of muscle
myopathy
How are muscle fibers classified? 2 ways
- speed of contraction - size of fiber (fast and slow twitch)
- how they make energy (glycolytic and oxidative)
How do glycolytic fibers get energy?
glycolysis - anaerobic
How do oxidative fibers get their energy?
aerobic respiration - with oxygen
fast twitch fiber scientific name
slow oxidative
slow twitch fiber scientific name
fast glycolytic
intermediate fiber scientific name
fast oxidative
What are fast twitch fibers best at?
endurance
What are slow twitch fibers best at?
power - sprints and jumps
What is the advantage of intermediate fibers?
can be trained to get better at both power and endurance
which fibers are thin because they don’t have a lot of stored energy or many myofibrils but with many mitochondria and good blood supply
slow oxidative - slow twitch
which fibers are thick with lots of stored energy and myofibrils but without a good blood supply and without many mitochondria
fast glycolytic - fast twitch
Which fiber type would be called red meat? Why
slow - good blood supply
Which fiber type would be called white meat? Why?
fast - poor blood supply
Where do the characteristics of the fast oxidative fibers fit in with the other two?
intermediate - pink, medium amounts of most everything
What determines the predominate fiber type?
genetics - interspersed throughout the muscle
- but within a motor unit, they are all the same
How does load affect contraction speed?
greater load slows contraction speed
a disease of chronic inflammation of muscles, its CT and tendons
fibromyalgia or fibromyositis
protrusion of an organ through a body cavity wall
hernia
a non-sex linked type of MD, less common than Duchenne MD
myotonic dystrophy
a disease of sustained, powerful muscular contractions caused by a toxin released from bacteria
tetanus
Why are people more likely to get tetanus from a puncture wound?
doesn’t bleed and flush out the wound
What is another name for the disease tetanus and why?
lockjaw - jaw muscles are often affected first
What does aerobic exercise do to promote endurance?
more capillaries, more mitochondria, more myoglobin
What kind of muscle activity promotes hypertrophy?
resistance exercises like weightlifting
What happens to a muscle to make a muscle hypertrophy?
larger fibers rather than more fibers - more CT, splitting of fibers
What are 5 differences between skeletal and smooth muscle?
- less CT
- different neuromuscular junction - has varicosities and diffuse junctions or swellings instead of the classic bulb…
- less developed sarcoplasmic reticulum
- no striations - no sarcomeres
- have a third kind of myofilament called an intermediate filament which attaches to the sarcolemma at regular intervals by something called a dense body
What are the two layers of smooth muscle?
- longitudinal layer - makes lumen shorter
2. circular layer - constricts lumen
the wavelike contractions of smooth muscle that move food through the digestive tract - alternating longitudinal and circular contraction
peristalsis
What is different about the thick filaments of smooth muscle?
fewer and with heads along the entire length
What is different about the regulation and calcium binding site of smooth muscle?
has a chemical called calmodulin instead of troponin
What is the major difference in the arrangement of thick and thin fibers in smooth muscle?
diagonal so they twist when they contract
Why are smooth muscle fibers synchronized?
gap junctions allow transmission from fiber to fiber
What is the purpose of pacemaker cells?
self-excitatory cells that set the rhythm but can be affected by neural stimulation or hormones
a circular muscle that opens or closes a hole
sphincter
examples of sphincters
orbicularis oris and orbicularis oculi
muscles with a broad origin and a tendon insertion
convergent
example of convergent muscles
pectoralis major
muscles whose fibers run side by side - what is the advantage?
parallel - most movement
example of parallel muscles
sartorius
muscles whose fibers come in on an oblique angle to the tendon - like a feather
pennate
pennate on 1 side, 2 sides, many sides - what is the advantage?
unipennate, bipennate, multipennate - most power - especially multipennate
muscles with a big belly and a torpedo shape
fusiform
what provides leverage for muscles?
bones
what is the fulcrum for the muscles?
joints
What are the 3 types of lever systems? Give an example for each.
1st - seasaws and scissors
2nd - wheelbarrow
3rd - tweezers
most muscles in the body are what type of lever?
3rd class lever
