Microstructure of Muscle Flashcards
skeletal muscle is responsible for the movement of the _____, _____ and ______
skeleton, eyes, tongue
muscle is classified into three types which include the _____, _____ and _______ muscle
cardiac, skeletal, smooth
the cardiac muscle is responsible for the rhythmic beating of the _______
heart
smooth muscle is responsible for the construction and dilation of the ________ and ______ and changing the shape of ________
blood vessels, airways, internal organs
skeletal muscle is considered ________ control
voluntary
smooth and cardiac muscle is considered _______ control
involuntary
most muscle cells are derived from the ________
mesoderm
Around the time of gastrulation, the developing nervous system folds into a _______
tube (neural tube)
Somites are blocks of mesoderm on either side of the neural tube that give rise to ________ and _______
sclerotomes, dermomyotomes
sclerotomes form the _______ and _______
vertebra, ribs
dermomyotomes contain the dermatome cells that form the layer of the skin called the _______ and the myotome cells (myoblasts) that form _______
dermis, skeletal muscles
myoblasts migrate and fuse to form mature skeletal muscle cells which are long, cylindrical, ______ cells
multinucleated
mature myoblasts are called _______, _______ or _______ fibers
myotubes, myofibers, extrafusal
Satellite cells are progenitor cells responsible for _______ and limited muscle cell _______
growth, repair
Skeletal muscle is rigorously organized by
sheaths of _______
connective tissue
Individual myofibers are surrounded by ________
endomysium
Groups of myofibers are bundled together into _______, surrounded by ______
fascicles, perimysium
All fascicles together are surrounded by _______ that is continuous with _______ that bind muscle to bone
epimysium, tendons
Myofibrils span the length of the cell and are composed of repeating ________
sarcomeres
Sarcomeres consist of proteins called _________, organized in an overlapping fashion
myofilaments
sarcomeres are the _______ unit of skeletal muscle
contractile
sarcomeres are composed of two main types of filaments which are ________ filaments and _______ filaments
myosin (thick), actin (thin)
the I bands of the sarcomere are the light bands that consists of the portions of _______ that do _______ overlap with myosin
actin filaments, not
in the middle of the I band is the Z disc that consists of proteins that anchor ________ in place and one sarcomere extends from Z disc to Z disc
thin filaments
the A bands are the dark bands that contain both _______
actin and myosin
myosin is considered the thicker chains of proteins with _______
“heads”
actin are considered the thin chains of proteins inserted into the ______
z disc
During contraction in skeletal muscle:
1) Myosin heads bind to actin filaments, forming ________
2) Myosin changes formation and pulls actin towards the _______ of the sarcomere, causing thick and thin filaments to slide past one another
** the I band appears ______, as more actin and myosin filaments overlap
“cross-bridges”, center, smaller
Neurons in your spinal cord have long processes called ______ that synapse with muscle fibers at the _______ and when a nerve impulse is triggered, a chemical is released that crosses the _______
axons, neuromuscular junction, synapse
synapse is the space between the end of an ______ and another _____ that allows for electrochemical communication
axon, cell
Skeletal Muscle Contraction;
1) nerve impulse triggers release of ________ at the neuromuscular junction, stimulating receptors in the sarcolemma
2) impulse spreads from sarcolemma to T tubules and _____ is released from terminal cisternae
3) Ca2+ binds _____, it changes shape causing tropomyosin to slide away, exposing the binding sites on actin filaments where ______ heads can bind
4) myosin heads pivot moving filament forward towards the center of the sarcomere, ______ binds to the myosin head which detaches it from _____ and myosin returns to its normal position
5) when nerve impulses stop, _____ is transported back into the SR, tropomyosin covers actin binding sites and filaments slide back into a relaxed state
acetylcholine, Ca2+, troponin, myosin, ATP, actin, Ca2+
the sarcoplasmic reticulum is a reservoir for _____
Ca2+
transverse tubules are the infoldings of the ______ found in between the cisterna of the ______
sarcolemma, sarcoplasmic reticulum
stimulation of the transverse tubule membrane by ________ triggers a muscle contraction
nerve impulses
a traid is a t-tubule surrounded by two terminal ______ of the SR on either side located at the _______ junction
cisternae, A-I
During muscle relaxation, actin binding sites
are ______, and myosin _______
covered, can’t bind
the tropomyosin on actin filaments _______ the binding sites in relaxed state
covers
the troponin on actin filaments ______ the binding sites by knocking tropomyosin off when Ca2+ in bound due to troponin changing _______
uncovers, conformation
Maintaining posture requires small, steady _______ for long periods of time
contractions
Jumping requires quick, forceful ______ for short periods of time
contractions
type 1 skeletal muscle fibers are ________, have a _____ rate of contraction, ______ force, use ______ respiration, have a ______ rate of fatigue and are used for ______ and _______
slow oxidative, slow, low, aerobic, slow, posture, distance running
type IIa skeletal muscle fibers are ________, have a _____ rate of contraction, ______ force, use ______ or _____ respiration, have a ______ rate of fatigue and are used for ______
fast oxidative-glycolytic, fast, medium, aerobic, anaerobic, medium, jogging moderate distances
type IIb skeletal muscle fibers are ________, have a _____ rate of contraction, ______ force, use _______ respiration, have a ______ rate of fatigue and are used for ______, ______, and ______
fast glycolytic, fast, powerful, anaerobic, fast, sprinting, jumping, powerlifting
To move in a coordinated manner without hurting yourself, your brain needs to understand two things:
1) Where your muscles are in _____ (proprioception)
2) How much ______ is being placed on your muscles
space, force
______ and _______ have sensory receptors that contribute to proprioception
Muscles, tendons
Muscle spindles detect muscle ______
length
Golgi tendon organs detect ______ on muscle
tension
Muscle spindles are encapsulated organs located within a muscle among _______, where the fibers within the capsule are termed _______ fibers and all other muscle fibers in a muscle are called _______ fibers
myofibers, intrafusal, extrafusal
Intrafusal muscle fibers have _______ that wrap around them and when the muscle is stretched, intrafusal fibers are passively stretched and enwrapped nerves are
stimulated which sends a signal to the brain of
where the _______ is in space and its
state of ______
nerve fibers, muscle, contraction
Cardiomyocytes are muscle cells found
in the ________ of the heart wall
myocardium
______ muscle is responsible for rhythmic contractions of the heart that pump blood through the body
cardiac
Rhythmic contraction of heart muscle occurs
_______ direct stimulus from the nervous system
without
contraction stimulus in the heart is initiated locally in specialized cardiac conducting cells located in the _______ where the stimulus is then transmitted through structures
called the _______
sinoatrial (SA) node, heart conduction system
Purkinje fibers are specialized cells adjacent to the _______ that transmit contractile impulses to some ________ and ______ junctions between cardiomyocytes allow propagation
of the signal
myocardium, cardiomyocytes, gap
cardiac muscle cells only contain ___ to ____ nuclei
1, 2
cardiac muscles are similar to skeletal muscle organization where the _______ is around individual muscle cells, the _______ around fascicles and ______ around the whole heart muscle
endomysium, perimysium, epimysium
cardiac muscles have the same _______ apparatus as skeletal muscle
contractile
Intercalated discs are junctions between ________ that mechanically link cells and allow for _________
cardiac myocytes, electrochemical communication
Intercalated discs consist of three main junctions that include ______, ________ and ________
desmosomes, fascia adherens, gap Junctions
Desmosomes mechanically ______ cells and helps cells resist ______ during regular contractions, ensuring they don’t pull apart
link, strain
Fascia adherens hold cells together at their ends, helps form a larger functional _______ and provides ______ point for thin filaments of the sarcomere
muscle fiber, insertion
gap junctions electrochemically ______ cells
and permits _____ and ________ to pass from one cell to another, allowing many cells to contract simultaneously
couple, ions, small molecules
an organization difference between cardiac and skeletal muscle is that the SR and T tubules form diads at the ______
Z disc
smooth muscle is responsible for changing the shape and diameter of ______ and _____
internal organs, tubes
smooth muscle is found in ______, ______ and _______ or organs such as the ______ and ______
and the walls of certain organs or vessels contain smooth muscle in different ______
blood vessels, airways, intestines, stomach, uterus, orientations
in the small intestine one layer of smooth muscle oriented longitudinally and one oriented circularly, this helps ______
down the digestive tract where the circular layer ______ and ______ tube while longitudinal layer ______ and ______ tube
propel food, constricts, dialates, shortens, lengthens
smooth muscle does not contain ______ or ______, has only ____ and lacks ______
perimysium, epimysium, one nucleus, striations
smooth muscle has actin and myosin filaments, but they are arranged differently than skeletal muscle, and do not form
_______ arranged in repeating _____
myofibrils, sarcomeres
Smooth muscles contain structures called ________, structures which, attach to the _______, serve as insertion sites for _________ (similar to Z-disc), serve as insertion site for _______ of the cytoskeleton and contain junctions such as ______ and ________
dense bodies, plasma membrane, actin filaments , intermediate filaments, desmosomes, gap junctions
Smooth muscle does not have _______ so when a muscle contracts a stimulation occurs and infoldings of the ______– (caveolae) concentrate Ca2+
T tubules, plasma membrane
in smooth muscle Ca2+ bind to ______ causes uncovering of binding sites on actin by displacement of ______, myosin heads bind, change conformation and cause filaments to _______ each other, this pulls on dense bodies, which then pulls the _______ and cytoskeleton, causing the whole cell to contract and twist
calponin, caldesmon, slide past, plasma membrane
Depending on need, smooth muscle contraction can occur as an entire sheet of cells at once _______ or as multiple individual cells by themselves _______
(single-unit), (multi-unit)
in a single unit smooth muscle contraction many cells are activated by only
_______ nerve fibers:
- Instead of a neuromuscular junction, SM has wider synapses called ______ where neurotransmitter diffuses across the
space, stimulating several cells at a time
- _________ allow propagation of signal
- Useful for hollow organs like ______
one or two, varicosities, Gap junctions, stomach
in a multi-unit smooth muscle contraction muscle cells are innervated ________:
- contain fewer ______
- Useful for small, individual muscles, e.g. erector pili muscle in ______
individually, gap junctions, skin
_________ is the replacement of damaged cells by mitosis to regenerate muscle
Hyperplasia
_______ is the increase in size by increasing protein synthesis or adding organelles to regenerate muscle
Hypertrophy
Cells that can undergo ______ are better at regeneration and repair
hyperplasia
Smooth muscle cells can undergo _______
hyperplasia
Skeletal muscle can only undergo _______ because myofibers cannot undergo ________ and ________ cells can fuse with damaged myofibers and assist in repair
hypertrophy, mitosis, satellite
Cardiomyocytes cannot undergo _______ and there is limited evidence of a stem cell population and damaged cardiomyocytes can
undergo _______ or may be replaced fibroblasts and connective tissue
mitosis, hypertrophy
