Histology - Muscle Flashcards
what are the steps to the contraction cycle?
- ATP binds to myosin (high E state)
- ATP hydrolyzed into ADP and P –> myosin is in “cocked” position
- Ca2+ binds to troponin, exposing active site on actin
- myosin head forms cross-bridge with actin
- during power strike, myosin head bends, ADP and P released
- new molecule of ATP attaches to myosin head –> cross-bridge detaches
- ATP hydrolyzed to ADP and P, returning myosin to “cocked” position
What causes rigor mortis?
no ATP –> unable to detach cross-bridge, so mucles lock up and don’t relax
what is the role of calcium in smooth muscle?
activates calmodulin/myosin light chain kinase (MLCK)
what is the role of calmodulin/myosin light chain kinase (MLCK) in smooth muscle?
activated by Ca2+, phosphorylation of individual myosin light chains allows binding and initiation of contraction
what is the role of calcium in cardiac and skeletal muscle?
Ca2+ binds to troponin, displacing tropomyosin and exposes many actins at once for binding to myosin
what is the sarcoplasm?
cytoplasm of muscle cells
what are myofilaments?
threadlike substructures of the sarcoplasm
what are myofilaments formed by?
actin and myosin
what provides a muscle cell with the ability to contract?
the myofilaments (actin and myosin)
what are muscle fibers?
muscle cells
how are muscle cells typically arranged relative to one another?
parallel to one another in sheets or bundles
is smooth muscle voluntary or involuntary?
involuntary
is smooth muscle striated?
no
what does the cytoplasm look like in smooth muscle?
uniform rather than striped
what is the shape of smooth muscle?
spindle-shaped (fusiform)
what does/do the nucleus/nuclei look like in smooth muscle?
single nucleus, elongated, located midway between ends of cell
is skeletal muscle voluntary or involuntary?
voluntary
is skeletal muscle striated?
yes
what forms the cross-striations of skeletal and cardiac muscle?
precise registration of sarcometric bands
what is the shape of skeletal muscle?
cylindrical, really long
what is the sarcolemma?
cell membrane of a muscle cell
what do/does the nuclei/nucleus look like in skeletal muscles?
multinucleated, located peripherally immediately below the sarcolemma
what are fascicles?
bundles of skeletal muscle cells
is cardiac muscle voluntary or involuntary?
involuntary
is cardiac muscle striated?
yes
what do/does the nuclei/nucleus look like in cardiac muscle?
one nucleus (sometimes 2) located centrally
which type of muscle cell anastomoses with one another?
cardiac muscle cells
what do intercalated discs do in cardiac muscle?
join muscle cells and increase speed of conduction of impulses
what are intercalated discs made of?
desmosomes and gap junctions
which cells are modified to function as a conducting system for heartbeats?
sinoatrial node, atrioventricular node, Purkinje fibers
in brief, describe what happens when a smooth muscle cell contracts
the intermediate filaments and dense bodies come closer together
what type of muscle is this?
smooth muscle
what type of muscle is this?
smooth muscle
what are the contractile protiens present in smooth muscle?
actin, tropomyosin, myosin II
what are the intermediate filaments of smooth muscle made of?
desmin and vimentin
what are the dense bodies of smooth muscle?
desmosomes
what is the name for the gap junctions in smooth muscle?
connexons
what are the high force-density muscles?
cardiac and skeletal muscles
what structure is this?
sarcomere
label the parts of the sarcomere
A: I band
B: A band
C: Z-line
D: H-zone
E: M-line
F: actin thin-filaments
G: myosin thick filaments
what is the I band of a sarcomere?
section near the ends of the sarcomere where there is only actin thin filaments
what is the A band in a sarcomere?
section where the actin thin filaments and the myosin thick filaments are overlapping
what is the 3D structure of a sarcomere like?
quasi-crytstalline structure
what is a syncytium?
single cell of cytoplasmic mass containing several nuclei, formed by fusion of cells or by division of nuclei
what is a myofiber?
single multinucleate skeletal muscle cell/syncytium
what are myofibrils?
bundles of actin/myosin filaments found inside skeletal or cardiac muscle cells
what is the sarcoplasmic reticulum?
found within muscle cells, stores Ca2+
what is the result of having a sarcoplasmic reticulum?
quicker signal to entirety of cell because of stored Ca2+
what are the T tubules in the sarcoplasmic reticulum?
extensions of the cell membrane
what is the terminal cisterna of the sarcoplasmic reticulum?
primary site of Ca2+ release
what is the longitudunal SR in sarcoplasmic reticulum?
location of ion channels for Ca2+ absorption
label this sarcoplasmic reticulum
A: T tubule
B: terminal cisterna
C: triad
D: longitudinal SR
what is the yellow circled structure? what type of muscle is this?
fascia adherens
cardiac muscle
what type of muscle is this?
cardiac muscle
what type of muscle is this?
cardiac muscle
what is the structure being pointed to? what type of muscle is this?
intercalated disc
cardiac muscle
true or false: the myofibers in cardiac muscle are branching
true
what part of the cardiac muscle cell anchors the cytoskeleton?
intercalated discs
true or false: cardiac muscle is not rich in mitochondria
false. it is rich in mitochondria
what type of muscle is this?
skeletal muscle
what type of muscle is this?
skeletal muscle
what type of muscle is this?
skeletal muscle
true or false: there are lots of mitochondria in skeletal muscle
true
what is the speed of Type 1 muscle? how does it get its E?
slow twitch
oxidative
what is the speed of Type 2a muscle? how does it get its E?
fast twitch
oxidative
what is the speed of Type 2b muscle? how does it get its E?
fast twich
glycolytic (anaerobic)
what is type 1 muscle used for?
long endurance
what is type 2a/2b muscle used for?
brief, explosive power
what is the diameter, capillary count, and mitochondria count of type 1 muscle?
d: smaller
cap: lots
mito: lots
what is the diameter, capillary count, and mitochondria count of type 2 muscle?
d: larger
cap: few
mito: few
what is dystrophin and where is it located?
protein located between the sarcolemma and outermost layer of myofilaments in myofiber
what is the function of dystrophin?
supports muscle fiber strength, provides a scaffold
what force does bundling provide?
flexibility
what structure is being pointed to?
perimysium coalescing to form a tendon
what makes up epi-, peri-, and endo-mysium? which structure is unique to endomysium?
vessels and nerves
satellite cells only in endomysium
what fuses to make a tendon?
collagenous fiber network
what is a golgi tendon organ stretch receptor?
a type of proprioreceptor in the collagenous fibre network
label the connective tissue elements
A: epimysium
B: perimysium
C: endomysium
what are intrafusal fibers?
modified skeletal muscle fibers that serve as sensory structures
what do intrafusal fibers sense?
proprioception, sense strength, length/position, reflex arc
what are the types of sensory and motor nerves related to intrafusal fibers?
sensory: type IA
motor: gamma
what structure is being shown here?
intrafusal muscle fiber
what type of structure is this?
intrafusal muscle fiber
what is the function of satellite cells in skeletal muscle?
stem cell responsible for muscle growth, hypertrophy, and regeneration
what structure is this?
satellite cell in skeletal muscle
what is myostatin and what is its function?
protein secreted in muscle tissues
negatively regulates muscle (demotes muscle growth)
what happens when you have a mutation in the myostatin gene?
abnormal muscle growth –> overgrowth
