Muscles Flashcards
Muscle
Contractile
Morphology - smooth, striated
Activity - voluntary, involuntary
Prefix - sarco (flesh) or myo-
Muscle definitions
- ) a tissue type
2. ) a specific mass of muscle tissue with an origin, insertion, and action
Myofiber
Individual muscle cell
Myofibril
Contractile elements within a myofiber
Muscle Morphology
- can be flattened or cylindrical
- arrangement of myofibers determines mobility/dexterity
- epimysium, perimysium,
endomysium
Epimysium
Upon, outermost layer
- connective tissue layer (fascia) around individual muscle
Perimysium
Connective tissue bundles that run between muscle fascicle
-groups of many myofibers
Endomysium
Surrounds each individual myofiber (individual cell)
- will not be able to see grossly, difficult to make out histologically
Myofiber morphology
- elongated
- frequently multi-nucleated
- filaments or fibrils (contractile elements)
- -> actin, thin
- -> myosin, thick (stains darker on electron micrograph)
Smooth muscle
Found on viscera
–> intestines, blood vessels, bronchi
Striated muscle
Found in heart and skeletal muscle
Voluntary
Skeletal muscle
Involuntary
Cardiac and visceral muscle
Skeletal muscle is ____ and ____
Voluntary, striated
Viscera is ____ and ____
Involuntary, non-striated
Cardiac is ____ and _____
Involuntary, striated
Skeletal muscle
- Multi-nucleated, peripheral
- Acts as syncytium
- Red, white, intermediate (gross)
- Twitch or contractile speed (fast or slow)
Skeletal muscles can regenerate because they _____
Have multiple nuclei located in the periphery
Type 1 muscle fiber
- –> Slow, oxidative
- Many mitochondria
- Large amount of myoglobin and cytochrome
- Slow twitch = fatigue resistant
Where are type 1 muscle fibers found?
Mammal limbs, migratory bird breast, marathon runners
Type 2a muscle fiber
- -> Fast, oxidative glycolytic
- Many mitochondria, much myoglobin
- Abundant glycogen
- Capable of anaerobic function (glycolysis)
- Fast twitch = fatigue resistant
Type 2b muscle fiber
- -> Fast, glycolytic fibers
- Large fibers, “pink”
- Less myoglobin and mitochondria than types 1 and 2a
- Much glycogen
- Fast twitch fatigue prone motor units
- High lactic acid production
Type 2a fibers are found in _____ and type 2b fibers are found in ____
Gazelles, cheetas
Myofibrils
Bundles of myofilaments (actin, myosin)
- Provide striations
- Sarcomere: Z line to Z line
Sarcomere components
- A band: dark, mostly myosin, center of sarcomere
- I band: light, mostly actin
- M line: center of A band, point of myosin attachment
- Z line: actin filaments attach between adjacent sarcomeres
- H band: between actin filaments
Muscle contraction (sarcomere component)
Myofilaments remain the same length
- Increase interdigiation
- H and I zones get smaller, A band remains
Muscle contraction regulation
Controlled by calcium!
- Sarcoplasmic reticulum (cisterna, holds calcium)
- Transverse tubular system
- Tropomyosin, troponin, etc
Transverse tubules
Invagination of the plasma membrane that causes calcium release upon depolarization
Neuromuscular junction
- Axon and myofiber
- -> motor endplate (synapse)
- neuron + myofiber = motor unit
- Acetyl choline = neurotransmitter
Cardiac muscle
- Striated, involuntary
- Central nuclei
- Intercalated disks
- Spontaneous rhythmic contraction
- Permanent cells (scar tissue formation upon death)
Intercalated disks
Where cardiac cells join
- tightly adhered
- NOT found in skeletal muscle!
Smooth muscle
- Elliptical, fusiform cells
- No cross-striations
- Actin/myosin contractile elements
- No T tubular system
- Involuntary
What are the intermediate filaments of actin/myosin
Desmin and vimentin
Can smooth muscle contract rapidly?
No, lacks T tubular system
Leiomyo
Prefix for smooth muscle
Involuntary components of smooth muscle
- Autonomic control (epi, NE, Ach)
- Calcium –> calmodulin –> myosin
- Stretch
What type of contraction does smooth muscle perform?
Sustained contraction
- aka latch state
- slow, prolonged
Where is smooth muscle located?
GI, bronchioles, vessels, repro
Skeletal summary
- Striated
- Voluntary
- Peripheral nuclei
- 1, 2a, 2b
- AcH
Cardiac summary
- Striated
- Involuntary
- Central nuclei
- Intercalated disks
- AcH - slows the heart
- NE - increases heart rate and contractility
Smooth summary
- No striations
- Involuntary
- ANS
- Sustain
