EXAM 3 Flashcards
What are some additional functions of muscles? (4)
- protects organs
- forms valves
- controls pupil size
- causes “goosebumps”
What are the 3 types of muscle tissue?
- skeletal
- cardiac
- smooth
What are the 4 main muscle functions?
- moves bones
- maintains posture
- stabilizes
- heat generation (esp. skeletal muscle)
In skeletal muscle, every (1) is supplied by a (2) that (3). There is a huge (4) and (5) need. Which means there is (6).
- muscle fiber
- nerve ending
- controls activity
- nutrient
- oxygen
- much waste
Define sarcoplasm
the cytoplasm of the muscle cell
ULTRASTRUCTURE OF THIN FILAMENT
- composed chiefly of the protein [1]
- actin has kidney-shaped polypeptide subunits, called [2] aka, [3]
- has a myosin-binding site (or [4]) to which the myosin heads attach during [5]
- G actin subunits polymerize into long actin filaments called [6] (F actin)
- [7] intertwined actin filaments, resembling a twisted double strand of pearls, form the backbone of each [8]
- thin filaments also contain several regulatory proteins: [9] and [10]
- actin
- globular actin
- G actin
- active site
- contraction
- filamentous actin
- two
- thin filament
- tropmyosin
- troponin
SUFFIX
-plasmic
material making cells
SUFFIX
-filament
thread
SLIDING FILAMENT MODEL OF CONTRACTION
When the nervous system stimulates muscle fibers, the [1] on the [2] latch onto [3] on [4] in the [5], and the [6].
These cross bridge attachments [7] several times during a contraction, acting like tiny ratchets to [8] and propel the thin filaments toward [9] of the [10].
As this event occurs simultaneously in sarcomeres throughout the cell, the muscle cell [11].
- myosin heads
- thick filaments
- myosin-binding sites
- actin
- thin filaments
- sliding begins
- form and break
- generate tension
- the center
- sarcomere
- shortens
PREFIX
epi-
over
What are the functions of the skeletal muscle connective tissue sheaths? (2)
- support the cells
- reinforce and together the muscle
STEPS OF A MUSCLE CONTRACTION
- nerve impulse reaches axon terminal bulb
- voltage-gated calcium channels open
- ACh released to synaptic cleft
- ACh binds to receptor on sarcolemma
- Na+ floods into muscle fiber → depolarization
- depolarization spreads to nearby voltage-gated Na+ and K+ channels → action potential moves along sarcolemma
- action potential reached T-tubules
- voltage sensitive T-tubule proteins change shape → calcium channels open
- calcium is released to muscle fiber sarcoplasm
- calcium binds to troponin on thin filament → troponin changes shape
- altered troponin → tropomyosin shifts exposing binding sites on actin
- myosin can now form a cross-bridge with actin to allow contraction
just keep clicking 1 until you have looked at this enough
Name the two sets of intracellular tubules that help regulate muscle contraction.
- sarcoplasmic reticulum
- T-tubules
The globular heads, each associated with two light chains, are the “business end” of myosin. During contraction, they link the [1] and [2] filaments together, forming [3], and [4] around their point of attachment, acting as motors to [5]. Myosin itself [6] (acts as an ATPase) and uses the [7] to drive movement.
- thick
- thin
- cross bridges
- swivel
- generate force
- splits ATP
- released energy
Describe the epimysium. (3)
- dense irregular CT
- surrounds muscle
- sometimes blends into deep fascia
TERMS
- fascia
- fascicle
- sheet of connective tissue
- bundle of structures
What are the three modified structures in a muscle fiber?
- sarcoplasmic reticulum (stores Ca2+)
- T-tubules
- myofibrils
Muscle tissue makes up how much of body mass?
Half of all body mass
DEFINE
- origin
- insertion
- attachment to the immovable (less movable) bone
- attachment to the movable bone
What is a fascicle? (2)
- discrete bundle of muscle cells
- surrounded by perimysium
The integral proteins of the (1) form (2) through which the (3) release (4).
- sarcoplasmic reticulum
- gated channels
- terminal cisterns
- Ca2+
For skeletal muscle to contract:
- [1] (at [2])
- Nervous system stimulation required
- Must generate action potential in [3]
- [4]
- Action potential [5] along sarcolemma
- Intracellular Ca2+ levels must [6]
- activation
- neuromuscular junction
- sarcolemma
- excitation-contraction coupling
- propagated
- rise briefly
What is the sarcolemma?
plasma membrane of the muscle cell (important to signalling)
PREFIX
endo-
inner
PREFIX
peri-
around
SUFFIX
-reticulum
network
ULTRASTRUCTURE OF THICK FILAMENT
- Composed of [1] (protein): [2] + [3] polypeptide chains
- Myosin tails: [4] polypeptide chains interwoven
- Myosin heads: [5] chains: [6] during contraction
- Binding sites for
- [7]
- [8]
- each head acts as [9]
- myosin
- 2 heavy
- 4 light
- 2 heavy
- 2 smaller, light
- cross bridges
- thin filament actin
- ATP
- ATPase enzymes
Skeletal muscle: each: ? artery + ? nerve + 1/more veins
1; 1
What is a muscle fiber? (3)
- elongated, multinucleate cell
- striated appearance
- surrounded by endomysium
(1) are perfectly aligned repeating series of dark (2) and light (3) due to overlap of proteins in (4).
- striations
- A bands
- I bands
- myfilaments
Name the two storage organelles in the muscle fiber and their function.
- glycosome: stores glycogen
- myoglobin: stores oxygen
Describe the sarcoplasmic reticulum. (5)
- elaborate smooth endoplasmic reticulum
- network around each myofibril
- longitudinal along myofibril
- stores / releases Ca2+
- regulates intracellular levels of Ca2+
Describe the perimysium. (2)
- dense irregular CT
- surrounds fascicles
Describe the terminal cisternae. (2)
- perpendicular cross channels
- forms part of the triad
Describe the thick filament.
- run length of A band
- myosin
- connected at M line
Describe the endomysium. (2)
- surrounds each individual muscle fiber
- fine areolar CT
What is the resting membrane potential?
- produced by separation of oppositely charged particles across membrane in all cells
- negative = inside membrane
- positive = outside membrane
- cells = polarized
- voltage is ONLY at the membrane
- intra/extracellular surfaces
- -50 to -100 mV in different cells
- selective diffusion
Describe the T-tubules. (5)
- continuous w/ sarcolemma
- lumen continuous w/ extracellular space
- increase muscle fiber’s surface area
- penetrates interior at each A-band/I-band junction
- middle part of triad
What are the 4 characteristics of muscle tissue?
- excitability
- contractility
- extensibility
- elasticity
Define the types of attachments:
- direct
- indirect
- direct - epimysium fused to periosteum/perichondrium
- indirect - CT wrappings extend beyond muscle as tendon or aponeurosis
What is a sarcomere?
- contractile units of muscle fiber
- contains myfilaments
- region between two Z discs
(1) conduct impulses deep into the (2) and (3).
- T tubules
- muscle fiber
- sarcomere
What is a myofibril? (5)
- rodlike contractile elements
- occupies most of muscle volume
- composed of sarcomeres from end to end
- ~80% of cell volume
- modified structure
At the microscopic level, the following things occur as a muscle cell shortens:
- The [1] shorten.
- The distance between successive [2] shortens. As the [3] slide centrally, the [4] to which they attach are pulled toward the [5]
- The [6] disappear.
- The contiguous A bands move [7] together, but their length [8].
- I bands
- Z discs
- thin filaments
- Z discs
- M line
- H zones
- closer
- does not change
ROOTS
- myo
- sarco
muscle
SUFFIX
-fibril
fiber
Describe the microscopic anatomy of the muscle cell. (3)
- 10 - 100 µm diameter
- up to 30 cm long
- multiple peripheral nuclei
