ch. 10 11 Flashcards
produce skeletal movement maintain posture and body position support soft tissues guard entrance and exits maintain body temp store nutrients reserves
6 functions of the skeletal muscular system
how is skeletal muscle an organ
composition: skeletal muscle tissue, connective tissues, nerves, and blood vessels
skeletal muscle cells
muscle fiber
made of a bundle of muscle fibers (cells)
fascicles
surrounds entire muscle
epimysium
surrounds fascicles
perimysium
surrounds individual muscle fibers
endomysium
separates muscle from other tissues and organs
epimysium
also contains blood vessels and nerves
perimysium
contains capillaries and nerve fibers; both of which are in direct contact with each cell
endomysium
what is the epimysium also known as
fascia
continuation of collagen fibers of connective tissue coverings beyond end of muscle; cordlike
tendon
similar to tendon but is a broad sheet of CT that attaches a broad, flat muscle to another muscle or to several bones
aponeurosis
quite different than typical cells
enormous
cylindrical and is within endomysin
multinucleated
characteristics of skeletal muscle fibers
cell membrane
sarcolemma
cytoplasm
sarcoplasm
tubes- continuous w sarcolemma
transverse tubules
open to outside of muscle fiber
transverse tubules
tubular network that cover each myofibril
sarcoplasmic reticulum
lie between 2 portions of sarcoplasmic reticulum
transverse tubules
are enlarged portions near T tubules that store calcium
sarcoplasmic reticulum
contain extracelluar fluid and form passageways through the muscle fiber
transverse tubules
what ion does sarcoplasmic reticulum store
calcium
cylindrical structures inside muscle fibers; actively shorten and are responsible for muscle fiber contractions
myofibrils
2 kinds of protein filaments found in myofibrils
actin and myosin
thick filaments
myosin
thin filaments
actin
repeating functional units produced from the organized filaments in a myofibril
sarcomeres
arrangement of the filaments account for the banded appearance of myofibrils and thus muscle fibers
striations
has head and tail
myosin
contains active site that binds to myosin
actin
sliding filament theory
thin filaments slide toward center of sarcomere; alongside the thick filaments
each skeletal muscle fiber is connected to a motor neuron and will contract only when stimulated by neuron
neuromuscular junction
site where they meet
NMJ
this cytoplasm contains vessicles filled with ACh
synaptic terminal
a chemical released by a neuron to change the permeability to another cell membrane
neurotransmitter
separates synaptic terminal of neuron and sarcolemma surface of a muscle fiber
synaptic cleft
sarcolemma surface
motor end plate
steps of skeletal muscle innervation
action potential/electrical impluse arrives at synaptic terminals.
triggers exocytosis of ACh from vesicles into synaptic cleft.
ACh diffuse across cleft and binds to receptors on motor end plate.
Na+ rushing in causes action potential/electrical impulse in the sarcolemma and this enters T tubules.
ACh is broken down by AChE within cleft-intervention is stopped and ready for another action potential.
steps of the citation contraction cycle
action potential moves along T tubules
into SR triggering release of Ca2+ from the SR
into sarcoplasm around myofibrils
what role does calcium ions play in contraction
it causes active sites on actin to be exposed
what is the interaction of actin and myosin in a contraction
myosin binds with active sites of actin and forms cross bridges.
myosin head bends and pulls actin filament with it
all muscle fibers of a motor unit contract simultaneously and completely when stimulated
motor units
what determines the size of a motor unit
of how fine the control of movement can be
what has all or none contractions
motor units
what does all or none mean
the whole muscle contracts completely
smooth but steady increase in muscular tension produced by increasing the number of active motor units
recruitment
what is the relationship between motor units and an entire muscle as it contracts
motor units take turns so that one can rest while another contract- sustained contraction without fatigue and muscle is contracting slightly less than maximal tension
what causes muscle tone
some motor units are always active when entire muscle isn’t contracting; active motor unit contractions don’t cause movement but muscle is tense and firm
resting tension
muscle tone
why don’t muscles fatigue while showing muscle tone
motor units take turns to produce the muscle tone
muscle shorten when contracted
isotonic
muscle contracts but doesn’t change length
isometric
name two ways ATP energy is stored for muscle use
ATP ADP + P + ENERGY
ATP CREATINE ADP + CP
2 ways ATP is generated within muscles
aerobic metabolism
anaerobic metabolism
requires oxygen
aerobic
occurs in mitochondria
aerobic
occurs in sarcoplasm
anaerobic
end produces 36 atp
aerobic
end produces 2 atp
anaerobic
commonly found in muscle fibers and is a short term storage form of glucose
glycogen
what does glycogen do
used to produce glucose
where does atp come from in a resting muscle
oxygen is abundant for this low demand so mitochondria meet and exceed need for atp
where does atp come from in a moderate level of activity muscle
demand is met by mitochondria and oxygen increase- still using aerobic metabolism to make atp
where does atp come from in peak levels of activity
mitochondria make atp but it isn’t enough since not a lot of oxygen to sustain aerobic metabolism; rest of atp is made via glycolysis
how and when is lactic acid produced
when glycolsis its very efficient
what can accumulation of lactic acid cause
inhibit muscles to continue contracting because of ph shift in cell
what happens to lactic acid during recovery period
turns into pyruvic acid then back to aerobic metabolism and if needed glucose can be stored as glycogen
where does the lactic acid recovery period occur
liver
amount of oxygen needed to restore normal condition s
oxygen debt
significance of heat produced with muscle contractions
increase activity- more heat is released and body temp climb; heat loss at skin increase to maintain homeostasis
fast twitch fibers;
fast fibers
white muscle fibers
fast fibers
contract quickly and powerfully
fast fibers
relatively few mito and less atp so fatigue more
fast fibers
slow twitch fibers
slow fibers
red muscle fibers
slow fibers
extensive capillary network; much blood
slow fibers
more oxygen in fibers
slow fibers
made in muscle cells and combines with oxygen and stores it in muscle tissue
myoglobin
location of myoglobin
muscle tissue; (muscle blood)
stabilizes relative positions of cells so they can pull together efficiently
allow ions and small molecules to move from cell to cell- allows for a direct electrical connection between 2 muscle cells- action potential can move quickly from one cardiac muscle cell to another
function of intercalated discs
location is in the wall of hollow organs
smooth muscle
location is in the heart
cardiac muscle
typical arrangement of smooth muscle layers
2- longitudinal and circular
cells are bound together and contractions/impulses move from cell to cell in a wave
peristalsis
involuntary contractions
smooth and cardiac muscle
can undergo sustained contractions
peristalsis
con contract in response to hormones
slow to contract and slow to relax
smooth
fascicles parallel to long axis of muscle
parallel muscles
most skel muscles are this
parallel
with contraction muscle shortens and gets larger in diameter
parallel
ex of parallel
biceps branchii
fibers spread out like a fan or a broad triangle with a tendon at the apex
convergent muscle
stimulation of different portions of the muscle can change the direction of the pull
convergent
ex of convergent
pectoralis muscles
fascicles form a common angle with the tendon
pennate muscles
fibers pull at an angle
pennate muscles
ex of pennate muscle
deltoid
sphincter
circular muscles
fascicles are concentrically arranged around a opening
circular muscles
ex of circular muscles
external anal sphincter
immoveable/fixed end
origin
moveable end
insertion
prime mover; muscle responsible for most of movement
agonist
muscle who’s action opposes agonist; responsible for movement in opposite direction
antagonist
muscles that assist agonist; make agonist more efficient
synergist
location origin and insertion fascicle organization relative position structural characteristics action
how muscles are descriptive
