ch.10 Flashcards
three types of muscles?
skeletal, cardiac and smooth muscle
what is the basic function of muscles? (6)
- muscle tension
- create movement
- maintain posture
- stabilize joints
- generate heat
- regulate flow of materials through hollow organs
which muscles have visible striations?
skeletal and cardiac
how are muscle cells arranged to one another?
parallel
why are skeletal muscles known as fibers?
due to their length and appearance
striated muscle tissue are found attached by __ to the skeleton.
connective tissue
how are cardiac muscle cells structured?
shirt and highly branched.
Intercalated disc
join adjacent cells
intercalated disc contain what?
gap junctions and desmosomes(modified tight junctions) that unite the cells and permit them to coordinate contract
which muscles do not have striations?
smooth muscles
how are smooth muscle cells structured?
long and flat with “spindle shaped) pointed ends and a single centrally located nucleus
where can smooth muscles be found?
In most hollow organs in the eye, skin, and some glandular ducts.
how are many smooth muscles linked?
by gap junctions to allow synchronized contractions
what are the properties of muscles cells? (3)
- contractility
- Excitability
- Conductivity
Contractility
the ability to contract where proteins in the cell draw closer together
Excitability
the ability of a cell to respond to a stimulus
conductivity
the ability of a cell to conduct electrical changes across the entire plasma membrane
Extensibility
the ability of cell that allows it to be stretch without rupturing. ( up to 3 times their resting length)
elasticity
the ability of a cell that allows it to return to its original length after it has been stretched
myocytes, or muscle cells, are described using special terminology such as (3)
- Sarcoplasm
- Sarcolemma
- Sarcoplasmic reticulum
Sarcoplasm
the myocyte’s cytoplasm
sarcolemma
the myocytes plasma membrane
Sarcoplasmic reticulum
is a modified endoplasmic recticulm that forms a weblike network surrounding the myofibrils
transverse tubules
are deep inward extensions that surround each myofibril
t-tubules are filled with?
extracellular fluid
each myofibril is made of hundred to thousands of myofilaments, which consist of one or more of the following types of proteins… (3)
- contractile proteins (generate tension)
- Regulatory proteins ( that dictate when a fiber may contract)
- Structural proteins (maintain alignment and fiber stability.
what are the three types of myofilaments
- Thick filaments
- Thin filaments
- elastic filaments
thick filaments
composed of the contractile protein myosin
thin filaments
composed of the protein actin tropomyosin, and troponin
elastic filaments
composed of single spring like protein called titin that stabilizes and resists excessive stretching force
each myosin has ___ at each end linked by __ tails
globular heads
interwining
how are myosin head connected to the tails
by a hinge like neck
Thin filament: multiple actin
subunits string together like beads in the thin filament
Think filament: tropmyosin
long, rope like regulatory protein that twist around actin, covering up its active sites
thin filaments: troponin
is a small globular regulatory protein that holds tropomyosin in place and assists with turning contractions on and off
DMD
Degenerative muscular disease occurring almost exclusively in boys
how is DMD (Duchenne Muscular Dystrophy) caused
by a defective gene for the protein dystrophin, coded on the X chromosome.
protein Dystrophin
is a structural protein found in striated muscle fibers that anchors the sarcolemma to the surrounding connective tissue and to the myofibrils
What happens in the absence of normal dystrophin
the sarcolemma breaks down and the muscle fiber is destroyed and replaced with fatter and fibrous connective tissue
What are the symptoms of DMD
from btwn the age of 2 and 12..
weakness of the proximal limb muscles and a waddling gait
generally wheelchaired by 12 and dead from respiratory cardiac failure by age 20
multiple muscle fibers form a ..?
fasicle
each fasicicle is surrounded by a layer of connective tissue called
perimysium
what makes up a skeletal muscle?
bundles of fascicles which is surrounded by the epimysium, a connective tissue layer
The perimysium and epimysium comes together at the end of the muscle to form a ___?
a tendon, that binds the muscle to its attaching structure (usually bone)
what muscles are enclosed in a thick layer of connective tissue called fascia?
skeletal muscles
what does fascia do?
anchors them to the surrounding tissues and holds groups of muscles together
striations appear microscopically as alternating …? (2)
light bands, where only think filaments are found
dark bands, where both thin and thick filaments are found.
Dark and light areas of striations include the following specific regions
The I band (in light, mnemonic)which is composed only of thin filaments
That a band (in dark mnemonic) contains the zone of overlap, the region where we find both thick and thin filaments and where tension is generated during contraction
The Z disc is found in the middle of the Iband and is composed of structural proteins.. (3)
- Anchor the thin filaments in place and to one another
- serve as attachment points for elastic filaments
- Attached myofibrils to one another across the entire diameter of the muscle fiber
Where is the H zone in the dark and light areas of striations specific regions
In the middle of the a band where only thick filaments exist
Where is the M line located in the dark and light areas of striations specific regions
That M line is a dark line in the middle of the a band made up of structural proteins that hold the thick filaments in place and serve as an anchoring points for elastic vitamins
Membrane potentials
Are due to an unequal distribution of ions near the plasma membrane resulting in a polarized resting state
A thin layer of negatively charged ions exist where
In the cytosol on the inside of the cell while a thin layer of positively charged ions exist on the outside of the cell
Go back to slides 39 42n43
..
The membrane potential of a cell is the___that exist across the plasma membrane
Electrical potential
Voltage
A difference in charge (potential) between two points
Because the potential across the sarcolemma is small it is measured in a unit called
Millivolt
Resting membrane potential’s
Change only when the barrier to ion movement is removed from the plasma membrane
Sodium and potassium ions can then move through the sarcolemma using protein channels and carriers
They will only move by the fusion if a gradient exist between two regions
How does the concentration gradient maintained by the sodium/phosphate pump
The pump moves three sodium ions outs and two phosphate ions into the cell, per ATP hydrolyzed
ATP Hydrolysis is necessary because this pump moves the ions against a concentration gradient
This creates a high concentration of sodium in the extracellular fluid while the concentration in the cytosol remains lower
This creates a high concentration of phosphate in the cytosol why the concentration in the extracellular fluid remains lower
Why are the sodium/phosphate ATP Ase pumps critical
Because they provide much of the driving force for the passive diffusion of sodium and potassium ions to membrane channels
Action potentials
brief changes in the membrane potential of a cell from a resting negative value to a positive value then back to its resting negative value
These changes can be used to electrically communicate with and sometimes stimulate a response from other cells
Gated channels
Contain gates that are normally closed and open only in response to some sort of stimulus
Action potentials are generated by opening two types of gated ion channels in the plasma membrane such as
Ligand – gated channels (chemically gated) open response to the presence of a chemical or ligand
Voltage – gated channels opens and closes in response to changes in the membrane potential of the plasma membrane
