muscular system Flashcards
1
Q
myofibrils
A
contain microfilaments divided into sarcomeres
2
Q
sarcomeres
A
individual contractile units separated by a border (Z-line)
3
Q
sarcoplasmic reticulum
A
stores calcium and surrounds myofibrils
4
Q
sarcoplasm
A
same thing as cytoplasm
5
Q
sarcolemma
A
plasma membrane of muscle cells that can propogate action potentials that are invaginated by T-tubules (channels for ion flow)
6
Q
mitochondria
A
present in large amounts in myofibrils
7
Q
as submaximal stimulus increases
A
motor unit recruitment increases
8
Q
when a maximum stimulus is reached
A
all motor units are recruited
9
Q
cardiac muscle
A
- striated muscle
- one or two central nuclei
- cells separated by intercalated discs that have gap junctions
- lots of mitochondria
10
Q
smooth muscle
A
- lacks striation
- one central nucleus
- stimulated by autonomic nervous system
- does not utilize sarcomeres
11
Q
skeletal muscle
A
- striated
- multiple nuclei
12
Q
neuromuscular pathway
A
- action potential of a neuron releases ACh at a neuromuscular junction
- an action potential is generated on the sarcolemma and throughout T-tubules
- sarcoplasmic reticulum releases calcium
- calcium binds to troponin on the actin helix, allowing myosin to bind
- myosin cross-bridges form and contraction occurs
13
Q
sliding filament model (contraction)
A
- calcium exposes binding sites on actin
- myosin head attached to actin filament cross-bridge
- inorganic phosphate is released from the myosin head initiates power stroke
- new ATP attaches to myosin head –> cross bridges unbind myosin and actin unbind
- when ATP is converted to ADP+Pi, the myosin head is cocked back
14
Q
what happens if no ATP is available
A
the muscle is stuck in contraction (rigor mortis)
15
Q
think filaments
A
actin
