36.2 – The Muscular System · The function of the muscular system is movement. ... Muscle...
Transcript of 36.2 – The Muscular System · The function of the muscular system is movement. ... Muscle...
Regents Biology
36.2 – The Muscular System
Prepared by Kim Foglia. Adapted and Modified by Nhan Pham.
Regents Biology
Muscles
The function of the muscular system is movement. More than 40% of the mass of the average human
body is muscle.
Regents Biology
Muscle
voluntary
involuntary, contract on their own
involuntary evolved first
Regents Biology
Skeletal usually attached to bones responsible for voluntary movements have many nuclei (multi-nucleated) sometimes called striated muscles
Regents Biology
Smooth are usually not under voluntary control –
can work without nervous stimulation spindle-shaped have one nucleus, not striated found in many internal organs and blood
vessels
Regents Biology
Cardiac only found in the heart striated may have one or two nuclei connected to each other by gap
junctions
Regents Biology
Muscle Contraction The fibers in skeletal
muscles are composed of smaller structures called myofibrils.
Each myofibril has smaller structures called filaments.
The thick filaments contain a protein called myosin.
The thin filaments contain a protein called actin.
Regents Biology
Regents Biology
Filaments are arranged along the muscle fiber in units called sarcomeres.
When a muscle is relaxed, there are no thin filaments in the center of a sarcomere.
During muscle contraction, the actin filaments slide over the myosin filaments, decreasing the distance between the Z lines.
Regents Biology
Muscle Contraction
Binding sites Myosin
Cross-bridge
Actin
Movement of Actin Filament
Regents Biology
Muscle Contraction When many myosin cross-bridges change shape in a
fraction of a second, the muscle fiber shortens with considerable force.
Regents Biology
Control of Muscle Contraction A neuromuscular junction – point of contact between
a motor neuron and a skeletal muscle cell Vesicles in the axon terminals of the motor neuron
release a neurotransmitter called acetylcholine. Acetylcholine produce an impulse in the cell
membrane of the muscle fiber. The impulse causes the release of calcium ions within
the fiber. The calcium ions affect regulatory proteins that allow
actin and myosin filaments to interact.
Regents Biology
Regents Biology
Regents Biology
A muscle cell remains contracted until the release of acetylcholine stops and an enzyme produced at the axon terminal destroys any remaining acetylcholine.
Then, the cell pumps calcium ions back into storage, the cross-bridges stop forming, and contraction ends.
Regents Biology
Muscles Movement Muscles do work by contracting
- skeletal muscles come in antagonistic pairs (flexor vs. extensor)
- contraction moves skeletal parts
- tendons connect bone to muscle
- ligaments connect bone to bone
Regents Biology
Regents Biology
Fast twitch & slow twitch muscles Slow-twitch muscle fibers
- contract slowly, but keep going for a long time
- more mitochondria for aerobic respiration
- long distance runner
- “dark” meat = more blood vessels
Fast-twitch muscle fibers
- contract quickly, but get tired rapidly
- sprinter
- “white” meat
Regents Biology
Muscle limits Muscle fatigue
- lack of sugar, ATP, O2
- lactic acid lowers pH which interferes with protein function
- nerve fatigue (due to loss of chemical transmitters)
Muscle cramps
- build up of lactic acid
- lack of energy (ATP)
- ion imbalance
- massage or stretching increases circulation
Regents Biology
Diseases of Muscle tissue ALS
- amyotrophic lateral sclerosis - Lou Gehrig’s disease - motor neurons degenerate
Myasthenia gravis - auto-immune - antibodies to
nerve transmitter chemical
Stephen Hawking
Regents Biology
Botox Bacteria Clostridium botulinum toxin
- blocks release of nerve transmitter - botulism can be fatal!
muscle