Unit 3 Part 2 Flashcards
What makes up 40 percent of an individual’s body weight?
Muscle
Muscle, tissue or organ contraction is usually a response to a
Stimulus
Muscle size depends upon___
Use
How many muscles are there in the human body
656
How many antagonistic pairs of muscles
327
2 unpaired muscles
– Orbicularis oris
– Diaphragm
Usual number of contractions around eyes
100,000x/day
how long can individual muscle cells be
12 inches (30cm) long
number & diameter of muscle fibers begins to decrease at what age
40
___ muscle mass may be lost at what age
50%; 80
release a neurotransmitter that causes a chemical reaction and the muscles contract.
motor neurons
____ happens when the brain sends electronic signals to the _____ on the muscles,
Movement; motor neurons
stabilizes joints and help maintain body positions, such as standing or sitting.
Skeletal muscle contractions
__ continuously contracts when you are awake.
Postural muscles
what contraction of neck muscles hold your head
upright
sustained contractions
muscles in our _____ keep us upright by maintaining constant tension.
torso
accomplished by sustained contractions of sphincters
Storage
ringlike bands of smooth muscle, which prevent outflow of the contents of a hollow organ.
sphincters
closes off the outlets of stomach or urinary bladder that causes storage
smooth muscle sphincters
pumps blood through the blood vessels of the body.
Cardiac muscle contractions
Adjust blood vessel diameter
Move food and substances
Push gametes (sperm and oocytes)
Propel urine
Smooth muscle contractions
promote the flow of lymph and aid the return of blood in veins to the heart.
Skeletal muscle contractions
% of body heat is
produced by muscle
85
Body movement
produce ___ that helps regulate body temperature
heat
carried by the blood to the surface of the skin and turn into sweat (sweat evaporation)
Excess heat
-Multinucleated
-Striated
-Voluntary control
-thick
-long
-unbranched
-cylindrical
skeletal muscle
-Striated and uni-nucleated
-Branching cells
-Intercalated discs separate cells
- Rhythmicity
-Only found in wall of heart
- Self-exciting tissue
- Large transverse tubules
cardiac muscle
-Uninucleated
-No striations
-Involuntary control
-small
-spindle shaped
smooth muscle
Contraction of muscles is due to
the movement of
microfilaments
prefixes of muscle
myo, mys, sacro
shape of muscle cells/muscle fiber
elongated
The ability to receive and respond to a stimulus
ELECTRICAL EXCITABILITY
skeletal muscle stimulus
neurotransmitter (chemical signal) release by a neuron (nerve cell).
smooth muscle stimulus
neurotransmitter, hormone, stretch, change in pH, change in Pco2 or change in Po2
cardiac muscle stimulus
neurotransmitter, hormone, or stretch.
types of stimulus
-autorhythmic electrical signals
-chemical stimuli
___ is the generation of an electrical impulse or ____ that travels along the plasma membrane of the muscle cell.
RESPONSE; MUSCLE ACTION POTENTIALS
– ability to shorten forcibly
–defining property
CONTRACTILITY
–ability to be stretched within limits, without
being damaged
– Smooth muscle is subject to the greatest amount of
stretching (stomach filled with food); Cardiac muscle
stretched when heart is filled with blood
EXTENSIBILITY
ability to recoil and resume original length
after being stretched.
ELASTICITY
– More than a local effect
– Electrical charge spreads along the muscle fiber
CONDUCTIVITY
Each skeletal muscle is a separate organ
composed of hundreds to thousands of cells
called
fibers
surround muscle fibers and whole muscles
Connective tissues
penetrate into muscles
Blood vessels and nerves
-sheet or broad band of fibrous connective tissue
-deep in the skin and surrounds muscles and other organs of the body.
Fascia
separates muscle from skin
Superficial fascia
-dense irregular connective tissue
-lines the body wall and limbs and holds muscles together.
Deep fascia
around single muscle fiber
Endomysium
around a fascicle (bundle) of fibers
Perimysium
covers the entire skeletal muscle
Epimysium
on the outside of the epimysium
Fascia
Endomysium, perimysium, and epimysium come together:
AT?
TO?
example?
– at ends of muscles
– to form connective tissue attachment to bone matrix
– i.e., tendon or aponeurosis
Skeletal muscles are _________ muscles, controlled by ____ of the central nervous system
voluntary; nerves
Neurons that stimulate skeletal muscle are
somatic motor neurons
Form a neuromuscular junction (= myoneural junction)
somatic motor neurons
Sites of muscle attachment
– Bones
– Cartilages
– Connective tissue coverings
-bring in oxygen and nutrients (glucose, fatty acids) and remove heat and waste
-plentiful in the muscle tissue
Capillaries
Skeletal Muscle Organization
(Largest to Smallest)
Skeletal Muscle
Muscle Fascicles
Muscle Fibers
Myofibrils
Sarcomere
Myofilaments
-The cell membrane of a muscle cell
- Surrounds the sarcoplasm
-A change in transmembrane potential begins contractions
-All regions of the cell must contract simultaneously
Sarcolemma
– Tiny invaginations of the sarcolemma
– Penetrate the sarcolemma
– Bring extracellular materials into close proximity of the deeper parts of the muscle fiber
– Open to the outside of the fiber, filled with interstitial fluid
– Muscle action potentials travel along
– Closely associated with SR
Transverse tubules (T-tubules)
- Contains various organelles specifically designed to meet the needs of the contractile skeletal muscle fiber
-multi-nucleated - located in the periphery of the muscle cell
Sarcoplasm
- High demand for energy (ATP)
- Lots of glycogen granules
- Myoglobin
- Myofibrils
Sarcoplasm
provide glucose for energy needs
glycogen granules
Protein with a high affinity for oxygen; Transfers oxygen from the blood to the mitochondria of the muscle cell
Myoglobin
create the biggest part of the cytoplasm, oriented longitudinally with long axis of muscle fiber
Myofibrils
– Saclike membranous network of tubules
– Surrounds each myofibril
– Contains terminal cisternae
Sarcoplasmic reticulum (SR)
Dilated end sacs
terminal cisternae
- Located where the SR ends
-Store high concentrations of calcium
-Concentrate Ca2+ (via ion pumps) - Release Ca2+ into sarcomeres to begin muscle
contraction
terminal cisternae
– Release of Calcium
– Activate skeletal muscle contraction
– Transmit nerve impulses
– store high concentrations of calcium
SR and T-tubules Function
Each T-tubule will be flanked by a terminal cisterna. This forms ______ consisting of 2 terminal cisternae and one T-tubule branch.
triad
- rod-like structures that extend the length of the cell.
- long bundles of protein structures called myofilaments (thick and thin).
- Sarcomere are the basic unit
- built from three kinds of proteins
Myofibrils
3 Muscle Proteins
Contractile
Regulatory
Structural
Contractile muscle proteins
Myosin
Actin
Regulatory muscle proteins
Troponin
Tropomyosin
Structural muscle proteins
Titin
Nebulin
Alpha-actin
Myomesin
Dystrophin
Workhorses – generate force during contraction
Contractile Proteins
-forms backbone of thin filament; contains sites where myosin heads bind during muscle contraction
22%
Actin
-form shaft of thick filaments; binds to binding site on
actin during muscle contraction.
-Functions as motor protein
-44%
Myosin
the basic component of each actin myofilament
G-actin (globular actin)
two strands of G-action molecules are twisted together with two regulatory proteins:
–tropomyosin
–troponin
– Rod-shaped protein that occupies the groove between the twisted strand of actin molecules
– Blocks the myosin binding sites on the G-actin
molecules when muscle is relaxed
-5%
Tropomyosin
-A complex of three globular proteins.
* One is attached to the actin molecule
* One is attached to tropomyosin (holds in position)
* One contains a binding site for calcium\
- 5%
Troponin
Thin Myofilaments in a RELAXED muscle
* ___ is blocked from binding to actin
* Strands of _____ cover the myosin binding sites
* _____ binding to ____ moves tropomyosin away from myosin-binding sites
* Allows muscle contraction to begin as myosin binds to ___
Myosin
tropomyosin
Calcium ion; troponin
actin
Thick myofilaments are made the protein __
myosin
- Composed of a rod-like tail and two globular heads
- Interact with actin during contraction.
- Form CROSS-BRIDGES
- Contain binding sites for both actin and ATP
Myosin
-each myosin can interact with___actin filaments
-each actin can interact with __ myosin filaments.
6
3
- Align the thick and thin filaments properly
- Provide elasticity and extensibility
- Link the myofibrils to the sarcolemma
Structural Proteins
(9%)
-extends from Z disc to M line and attaches to myosin.
Titin
-forms the M line; helps stabilize position of thick filaments
Myomesin
(3%)
-attaches into Z disc and lies alongside thin filaments; internal support and attachment for actin
Nebulin
-links thin filaments to integral membrane proteins of sarcolemma.
Dystrophin
- bind to actin molecules of the thin filament and to titin
a-actinin
- Repeating individual units in each myofibril
– Smallest contractile unit of the muscle fiber
– Arrangement of Myofilaments
Sarcomere
-borders of the sarcomere
– Perpendicular to long axis of the muscle fiber
– Anchor thin myofilaments (actin)
Z-lines
Anchors the filaments and interacts with cytoskeletal framework
Z disc
– Perpendicular to long axis of the muscle fiber
– Anchor thick myofilaments (myosin)
M-lines
- Anisotropic
- Area where actin and myosin overlap
- Equal to the length of the thick myofilaments (myosin)
- Contains the H-Zone
A-Bands
dark under the microscope
Anisotropic
– Lighter area within the A-Band that contains only myosin
– The M-Line is located with the H-zone
H-Zone
- Isotropic
- Light area composed of actin only
- Contains the Z line, which is the boarder of the sarcomere
I-Bands
Thin filaments slide past the thick filaments, and the
sarcomere and muscle fiber shortens
Walk Along Theory or the Ratchet Theory.
Thin filaments move towards the center of
the sarcomere from both ends
Sliding Filament Theory
Sarcomere Partially Contracted
I Band – shorter
H Band - shorter
A Band – same length
Z line - closer
Sarcomere Completely Contracted
I Band – almost disappeared
H Band – almost disappeared
A Band – same length
Z line - closer
accomplished by the thin filaments from opposite sides of each sarcomere sliding closer together or
overlapping the thick filaments further.
Contraction
becomes smaller as the thin filaments approach each
other.
H-zone
becomes smaller as the thin filaments further overlap the thick filaments.
I band
width of the _____ remains unchanged as it depends on the thick filaments and the thick filaments do not change length.
A band
