topic.8.muscle.muscleanatomy.contraction Flashcards
What are some general properties of muscles?
contractility: the ability of muscle to shorten with force
excitability: the ability of muscle to respond with force
extensibility: the ability of muscle to be stretched
elasticity: ability of muscle to recover from being stretched
What are the three types of muscle tissue?
skeletal muscle(striated)
cardiac muscle(branched)( striated)
smooth muscle(nonstriated)
__ are attached to bones via tendons
skeletal muscle
Skeletal muscle is responsible for what type of movement
voluntary movement
-AP from efferent neurons to muscle
What 3 features does cardiac muscle have?
-branched
-intercalated disc
-cardiac nuclei
smooth muscle found where?
Function?
Smooth muscle, found in the walls of the hollow internal organs
Function: helps with digestion and nutrient collection
T/F smooth muscle is voluntarily controlled by endocrine nervous system
False: Controlled involuntarily by endocrine and autonomic nervous
systems
Visceral smooth muscle
has numerous ___
gap junctions
skeletal muscle container muscle cells. What is another name for muscle cells?
fibers;
long, cylindrical, multinucleated
What gives rise to the striated appearance in skeletal muscle?
light and dark banding
describe the relationship between muscle fiber, fasciculi and connective tissue
Another name for muscle fiber is muscle cell. Muscle cells are grouped together into fasciculi which are then held together by connective tissue
Sarcolemma
plasma membrane of a muscle fiber (or cell)
Sarcoplasm
cytoplasm of a muscle cell
T/F one muscle fiber container one myofibrils
false: it contains several
Myofibril: contractile elements found in muscle cells (muscle fibers), made of
sarcomeres
Composed of thick and thin filaments
Sarcomere:
basic unit of contraction in a myofibril, region between two Z lines
in sarcomere, what are thick and thin filaments made up of?
thick-myosin
thin-actin and tropomyosin
Actin is attached to what in a sarcomere?
Z disk: filamentous network of protein. Serves as attachment for actin filaments
I bands:
between thick filaments
* appear lighter
I see light
A bands:
length of thick filaments
**appear darker
H zone:
region in A band where actin and myosin do not overlap
M line:
middle of H zone; delicate filaments holding myosin in place
What are the two proteins associated with actin?
Tropomyosin: an elongated protein that winds along the groove of
the actin double helix.
Troponin is found between the ends of the tropomyosin molecules
in the groove between actin strands
Thin filament composed of what three subunits
one that binds to actin, a second that binds to tropomyosin, and a third that binds to calcium ions.
The tropomyosin/troponin complex regulates the interaction between
active sites on actin and myosin.
Thick filaments made up of
Myosin II: motor protein found in skeletal muscle; generates force for muscle contraction
*several hundred myosin heads
thick filament _____ oriented pairs of actin filaments past each other
can slide oppositely
myosin II, describe head and tail
Head: binds and hydrolyzes ATP, generates force for
movement
Tail: formed from coiled-coil interaction 2 α-helices of heavy chains
Myosin has a cross bridge with what two binding sites?
1.actin binding site
2. ATP binding site
- Myosin head has ATP bound, not in contact with actin
- Myosin binding site on actin becomes available
- ATPADP+P and myosin head attaches to actin and
initiates the “power stroke”(bending of the myosin head
and movement of the actin filament) and releasing ADP - Myosin head binds a new ATP and detaches from actin
In order to have muslce contraction
myosin in thick filament must bind to actin sites on thin filament
Which band(s) will decrease when
muscle shortens?
A. A Band and I band
B. I Band and H zone
C. A Band and H zone
D. I Band only
E. A Band only
B. I Band and H zone
Muscle contraction which filament stays stationary?
thick filament
Explain the overall mechanism for muscle contraction
Thin filaments slide over thick filaments
simultaneously on each side of sarcomeres (note: the thick filament doesn’t slide)
Shortens sarcomeres and muscle fibers
Produces force that contracts the muscle
Motor neurons:
Stimulate muscle fibers to
contract
Synapse:
region where the
axon terminal of a neuron rests
on an invagination of the
sarcolemma
Neuromuscular junction(NMJ):
contact point between the axon
and muscle
1. Presynaptic terminal: axon terminal with synaptic vesicles
2. Synaptic cleft: space
3. Postsynaptic membrane (sarcolemma)
or called: motor end-plate
Synaptic vesicles contain
Neurotransmitter: substance released from a presynaptic membrane that diffuses across the synaptic cleft and stimulates (or inhibits) the production of an action potential in the postsynaptic
membrane
What is used to stimulate an AP in skeletal muscle?
Acetylcholine
Acetylcholinesterase:
A degrading enzyme in synaptic cleft. Prevents accumulation of ACh
A T-tubule (or transverse tubule)
is a deep invagination of the sarcolemma, only found in skeletal and cardiac muscle cells.
- allow depolarization
Components for Stimulation of
Skeletal Muscle Contraction
- AP travel down axon of motor neuron
- brings to receptors called ACh causes Ca2+ release from SR and bind to troponin, which exposes myosin binding site, thick can bind to actin
3.synaptic vesicles fuse - open acteycholine membrane channel
- Na rushes in , depolarization
- Spread to T-tubules, allowing quick depolarization to inner cell
how is neuron to neuron different from neuromuscular junction?
neuron to nueorn
-need lots of synpasic imput to reach threshold
-can have inhibitory imput
Neuromuscular junction:
1. one AP needed
2. no inhibitory input.
3. the action potential generated can go out in both directions to cover the entire muscle
cell.
