functions of muscle
produce movement,
maintain posture/balance,
stabilize joints,
generate heat,
protect internal organs,
movement of internal substances
skeletal muscle (muscle fiber)
most abundant type
found attached to bones of skeleton
voluntary control
elongated cell w/ many nuclei
up to 30 cm. long
smooth muscle
Involuntary muscle found inside many internal organs of the body
cardiac muscle
Involuntary muscle tissue found only in the heart.
Agonist muscle (prime mover)
responsible for moving body parts AWAY from/out of anatomical position
antagonist muscle
return the body to anatomical position
contractibility
ability to shorten in length
Elasticity
ability of muscle cell to recoil after being stretched (back to original shape)
Extensibility
ability to be stretched when relaxed
Excitability
ability of the cell to respond to a stimulus such as a nerve signal
synergist muscles
assist the prime movers (agonists) in their actions
-or works with other muscles in groups to perform a common movement
-quadriceps muscle
Origin (anchor)
attachment at the non moving end of the muscle
-the anchor for the muscle and the point towards which the muscle contracts
insertion
attachment of the muscle at its moving end
-inserted on the body part that moves when it contracts
-biceps brachii originates on the scapula and inserts on the radial tuberosity
fascicle
bundle of muscle fibers
muscle fiber
a single muscle cell
muscle cells
muscle fibers
Tendon
Connects muscle to bone
connects muscle to periosteum of bone
Ligament
Connects bone to bone
Aponeurosis
strong sheet of tissue that acts as a tendon to attach muscles to bone
Epimysium
covers entire muscle
Perimysium
The connective tissue that surrounds fascicles.
Endomysium
Connective tissue surrounding a muscle fiber
pennate muscle
fasicles are short
attach obliquely to a central tendon
central tendon runs entire length of muscle
bipennate muscle
fascicles insert into central tendon from opposite sides
(looks like a feather)
circular muscle
fasicles arranged in a concentric ring
surrounds body openings
actions- close by contraction
sphincters
convergent muscles
broad origin
fasicles converge toward a single tendon of insertion
triangular/fan shaped
ex: pectoralis major
fusiform muscles
muscles spindle shaped with the muscle belly being wider than the origin and insertion
ex: biceps brachii
multipennate muscle
looks like many feathers side by side
ex: deltoid muscle
parallel muscles
long axes of fasicles run parallel to long axis of muscle
-strap like muscle
-long muscles which cause large movements
-not very strong but have good endurance
Myoglobin
protein found in muscle cells
-red
-acts as an extra source of oxygen
glycosomes
storage granules within muscle cells that store glycogen
-ready source of glucose needed to make ATP for contractions
glycogen
made up of repeating units of glucose
-found in skeletal muscle and liver in humans
-branched chains of glucose, found in liver and muscles
myofibrils
rod like elements found in a muscle cell
80% of muscle cells is composed of myofibrils
sarcomere
repeating contractile unit of a muscle
largest to smallest muscle
tendon
muscle
fasicle
muscle cell
myofibril
thick myofilament
thin myrofilament
thick myofilaments
myosin
thin myofilaments
actin
troponin
globular complex of 3 polypeptides
binds to -- actin, tropomyosin, calcium
tropomyosin
long polypeptide strand that spirals around actin myofilament
-helps maintain shape of thin filament
-blocks or covers binding sites in the relaxed muscle
t tubule
extension of sarcolemma, projects deep into the cell
(run transversely or side to side)
-allows nerve signal to quickly pass across the cell
sarcoplasmic reticulum (cellular organelle)
network of tubular channels that produce protein for the muscle cell and stores calcium needed for contraction
Terminal cisternae of sarcoplasmic reticulum
stores calcium until action potential (electrical signal from neuron) releases it
triad
2 terminal cisternae and 1 t-tubule in the center
sarcolemma
special name for the cell membrane of a muscle cell or muscle fiber
cross bridge cycle
myosin crossbridge
power stroke
cross bridge detachment
cocking of the myosin bridge
ATP (adenosine triphosphate)
three phosphate groups held together by covalent energy bonds
-when the bond is broken, the energy is released, resulting in ADP and one phosphate group
-transfers energy to myosin head for power stroke
motor unit
one motor neuron and all the muscle fibers it controls/supplies
slow twitch muscle fibers (red)
contract slowly with less power than fast twitch
-can swivel at rates down near 50 times per second
slow and steady
*
1/2 the speed of fast twitch
*
-called red fibers bc fibers are richly supplied with tiny capillaries to deliver oxygen
-have lots of MYO
oxidative fibers
rely on aerobic respiration using oxygen for ATP production
-need high amounts of ATP over long periods of time
-aerobic respiration will supply most efficient method
-muscle fibers resist fatigue better
fast twitch fibers (white)
contract rapidly and powerfully
-can swivel at rates near 100 times per second
twice as fast as slow pitch
-rapidly uses ATP and oxygen
-fatigue quickly, useful for sprinting and weight lifting
-athletes muscles appear bulky/large
-muscle cells have large
muscle hypertrophy
increasing muscle mass by high intensity resistance exercise (weight lifting)
-training increases muscle size by increasing fiber size, not number
muscle atrophy
decrease in the mass of muscle with corresponding decrease in strength
-can be due to lack of use(paralysis, decreased exercise) or disease process(polio, AIDS, cancer)
sarcopenia
gradual loss of muscle mass due to normal effects of aging (NORMAL)
-0.5-1% loss per year after the age of 25
-amount of connective tissue in muscle increases and muscle fibers decrease in number
muscle spasm vs. muscle cramp
both are involuntary muscle contractions
-spasm occurs very quickly without pain
-can be due to electrolyte imbalances
-dehydration, water intoxication
-muscle overuse or injury stroke
-spinal cord damage
-poor blood supply
-some medications
muscle cramp
prolonged muscle spasm that is painful
-usually occur after exercise or at night
-occurs suddenly
-sometimes feel a "lump" in the muscle
peripheral artery disease
A form of peripheral vascular disease in which there is partial or total blockage of an artery, usually one leading to a leg or arm.
-leg discomfort/pain that develops with activity, relieved with rest
-smokers, diabetics, 50+ years, high cholesterol at r
load
opposing force exerted on the muscle by the weight of the object to be moved
-load does not change with movement
muscle tension
amount of force exerted by a contracting muscle on an object
-use muscle tension, rather than contraction
-contraction implies that the muscle fibers shortened, but some muscles lengthen during a contraction and some do not change length at all
muscle tone
voluntary, skeletal muscle fibers are always slightly contracted to create muscle tone
-due to random asynchronous contractions
-control by spinal cord, cranial nerves
-maintains muscle tonicity and response time
hypotonia
floppy baby syndrome"
-abnormally low muscle tone
-often involving reduced muscle strength
-seen in many different inherited disorders
-due to infantile botulism
botox
toxin that prevents the release of acetylcholine at the neuromuscular junction, preventing muscle contraction
Infantile botulism
Often due to ingestion of honey or syrups containing the spores; sx: constipation, generalized weakness, and loss of head and limb control (rarely fatal)
-constipation, lethargy(tired), weak cry(muscle weakness) and poor feeding
hypertonia
abnormal increase in muscle tension and a reduced ability of a muscle to stretch
-caused by injury to motor pathways in the central nervous system
-increased muscle tone due to bacterial toxin
tetanus
bacterial infection that produces a toxin that leads to uncontrollable muscle contraction
-vaccine fades after 10 years
-bacteria infects tissue
isotonic contraction
muscle changes length
-once the muscle overcomes the amount of resistance, muscle will contract and peak tension will remain steady
-load does not change
2 types of isotonic contractions
1. Concentric
-bicep shortens while contracting
2. Eccentric
-bicep lengthens while contracting
eccentric contraction
to provide controlled movement of the bones when moving with resistance
-allows the muscle to actively resist gravity and stabilizes the elbow joint during extension
isometric contractions
iso = same , metric = length
muscle contracts but does not shorten
-muscle contraction without change in distance between its origin and insertion
-weight exceeds or = the muscles capability
-tension builds to that muscles peak capacity, but muscle does n
creatine phosphate
high energy molecule stored in muscle used to regenerate ATP
-each muscle fiber stores 2-3 times more CP than ATP
-provides quick source of extra ATP
graded muscle response
variations in the degree of muscle contraction
-change frequency of nerve stimulation
-change strength of the stimulus (recruitment)
recruitment
process of increasing the number of active motor units being stimulated to contract