Ch 1 structure and function of body systems Flashcards
skeletal muscles are under the control of which part of the brain?
cerebral cortex
the musculoskeletal system is comprised of…
muscle, bones, joints, tendons
muscles can only — not —
pull, not push
there are approximately —-bones in the body
206
the axiel skeleton consists of —
skull (cranium) vertebrae ribs sternum
the appendicular skeleton consists of —
shoulder girdle arms pelvic girdle legs
fibrous joints (movement)
very little/none (skull sutures)
cartilaginous joints (movement)
limited (disks)
synovial joints (movement)
very mobile
articulating bone ends are covered with —-
hyaline cartilage
types of joints that rotate about one axis
uniaxial
types of joints that rotate about two axes
biaxial
types of joints that rotate about three axes
multiaxial
number of vertebrae 1) cervical 2)thoracic 3)lumbar 4)sacrum 5)coccyx
cervical = 7 thoracic = 12 lumbar =5 sacral = 5 fused coccyx = 3-5 fused
each skeletal muscle is an organ that contains —–
muscle tissue connective tissue nerves blood
Epimysium covers (1) and is continuous with (2)
1) muscles 2) tendons
tendons attach to the bone
periosteum
what are fasciculi?
bundles of muscle fibers
endomysium in continuous with —
the sarcolema
epimysium, perimysium, and endomysium are continuous with —-
the tendon
the junctions between a motor neuron and the fibers it innervates
motor end plate/ neuromuscular junction
each muscle cell has only one
neuromuscular junction
a motor neuron and the fibers it innervates
motor unit
sarcoplasm is the —-
cytoplasm of a muscle fiber
sarcoplasm contains —-
contractile proteins (actin/myosin) other proteins stored glycogen and fat particles sarcoplasmic reticulum mitochondria enzymes
draw a muscle
draw a motor unit
Thick contractile filaments
Myosin
thin contractile filaments
actin
myosin
a pair of myosin filaments form a —–which interacts with —–
crossbridge which interacts with actin
actin and myosin are orginized longitudinally in the smallest contractile unit of skeletal muscle, the —
sarcomere
M-bridge
where adjacent myosin filaments anchor to eachother
Z-line
where actin filaments are anchored
how many actin filaments surround one myosin filament?
6
how many myosin filaments surround each actin filament?
3
A-band
corresponds with the alignment of the myosin filaments
I-band
corresponds with areas in two adjacent sarcomeres that contain only actin filaments
Z-line
the middle of the I-band
H-Zone
area in the center of the sarcomere where only myosin is present
the H-zone —- during muscle contraction
decreases
the I-band —- during muscular contraction
decreases
sarcoplasmic reticulum: where, what does it store?
system of tubules which terminate around the Z-line, store calcium
the regulation of —- controls muscle contraction
calcium
T-tubules
transverse tubules: run perpendicular to the SR (sarcoplasmic reticulum)
calcium is released to all surface depths of a muscle….producing a ….
at the same time, producing a coordinated contraction
draw the sliding filament theory
the sliding filament theory states:
actin filaments at each end of the sarcomere slide toward the center of the sarcomere, pulling the Z-lines towards the center of the sarcomere, shortening the muscle fiber
only a small displacement of the actin filament occurs with each flexion of the myosin crossbridge, so….
very rapid, repeated flexions must occur in many crossbridges throughout the entire muscle for measurable movement to occur.
troponin
a protein that sits on the actin filament
for muscle contraction to occur, calcium must bind with
the troponin that sits on the actin filament
troponin and calcium binding activates
tropomyosin
tropomyosin allows for
a strong bond between actin and myosin
the amount of force produced by a muscle at any given time is directly related to
the number of myosin crossbridges bound to actin filaments cross-sectionally at that instant in time.
power stroke def.
the energy for pulling action during muscle contraction
hydrolysis def.
breakdown of ATP (adenosine triphosphate) to ADP (adenosine diphosphate)
hydrolysis is catalyzed by the enzyme…
myosin adenosine triphosphatase (ATPase)
Contraction phase of muscle contraction
when hydrolysis happens and ATP is converted to ADP through the enzyme ATPase
Recharge phase of muscle contraction
the process of contraction phase plus another ATP molecule replacing the ADP on the myosin crossbridge to allow temporary relaxation for another contraction
relaxation phase of muscle contraction
stimulation of nerve stops, calcium is pumped back in to the SR which prevents the link between actin and myosin filaments.
type of signal that comes from motor neurons
electrochemical signals from spinal cord to muscle
action potential def
when a motor neuron fires an impulse
muscles that must function with great precision have motor units that innervate….
as few as one muscle fiber
Muscles that produce large, gross movements have motor neurons that innervate….
many (several hundred) fibers
action potential def
electric current that flows along a motor neuron
an action potential is not capable of….
directly exciting muscle fibers. The motor neuron excites the muscle fiber(s) that it innervates by chemical transmission.
arrival of the action potential at the nerve terminal causes release of…
acetylcholine, which diffuses across the neuromuscular junction, cuasing excitation of the sarcolemma.
the all or none principle of muscle
if there is a motor neuron stimulus, all innervated fibers will contract; a stronger action potential cannot create a stronger contraction.
twitch
a brief muscle contraction
if multiple action potentials cause multiple muscle twitches…
the force of the twitches summates and the resulting force is greater than that produced by a single twitch
tetanus
when twitches happen so rapidly that they merge and completely fuse; this is the maximal amount of force the motor unit can develop.
classification of muscle fibers by twitch time
slow twitch and fast twitch
fast twitch muscle/ motor unit
develops force and also relaxis rapidly
slow twitch muscle/motor units
develop force and relax slowly, long twitch time
type 1 fibers
slow twitch
type IIa fibers
fast twitch
type IIx fibers
fast twitch
type I fiber characteristics
high capacity for aerobic activity
withstand fatigue
limited force development (low myosin ATPase activity
type II fiber characteristics
inneficient, fatigue quickly
rapid force development
high anaerobic output
high myosin and ATPase activity
Difference between type IIa and type IIx fibers
type IIa have greater capacity for aerobic metabolism, more capillaries surrounding them, greater resistance to fatigue
motor unit recruitment patterns are graded from less to more force…
in two ways:
1) variation in twitches
2) increasing the number of motor units that are activated