Muscular System Flashcards
FUNCTIONS OF THE MUSCULAR SYSTEM
Body movement
Maintenance of body posture
Respiration
Production of body heat
Communication
Heartbeat
Types of Muscles
Skeletal
Cardiac
Smooth
Location - Attached to bone
Skeletal Muscle
Location - Heart
Cardiac Muscle
Cell shape - Long, cylindrical
Skeletal Muscle
Nucleus - Multiple, peripheral
Skeletal Muscle
Striations - Yes
Skeletal Muscle
Control - Voluntary
Skeletal Muscle
Function - Move the whole body
Skeletal Muscle
Cell shape - Branched
Cardiac Muscle
Nucleus - Usually single, central
Cardiac Muscle
Striations - Yes
Cardiac Muscle
Striations - Yes
Cardiac Muscle
Control - InVoluntary
Cardiac Muscle
Function - Heart contraction to propel blood through the body
Cardiac Muscle
Location - Wall of hollow organs, blood vessels, and glands
Smooth Muscle
Cell shape - Spindle-shaped
Smooth Muscle
Nucleus - Single, central
Smooth Muscle
Striations - No
Smooth Muscle
Control - Involuntary
Smooth Muscle
Function - Compression of organs, ducts, tubes, etc.
Smooth Muscle
Characteristics of Muscles
Contractility
Excitability
Extensibility
Elasticity
Ability of the muscle to shorten reducing distance between parts of its contents
Contractility
Ability to respond to stimulus
Excitability
Ability of the muscles to be stretched
Extensibility
Ability of a muscle to return to its original length after stretching
Elasticity
Makes up 40% of body weight
• Named because attached to bones (skeleton)
• Many nuclei per cell (near periphery)
• Striated
Skeletal Muscle Characteristics
Resting Membrane Rotential - Outside cell
Na +
+ charge
Na + channels closed
Resting Membrane Rotential - Inside cell
K+
- Charge
Some K+ channels open
Why is the inside of cell negative if K+ is positive?
K+ is able to diffuse out of cell freely but other larger negative molecules cannot.
- “‘electricity”
- stimulus that causes rapid depolarization and
repolarization
~ causes muscle to contract
Action Potential
- change in charges
- inside becomes more + and outside more —
- Na + channels ope
Depolarization
Na + channels (pink) and some, but not all K+ channels (purple)] are closed. K+ diffuses down its concentration gradient through the open K+ channels, making the inside of the cell membrane negatively charged compared to the outside.
Resting membrane potential.
Na+ channels are open. Na+ diffuses down its concentration gradient through the open Na+ channels, making the inside of the cell membrane positively charged compared to the outside.
Depolarization
Na + channel is close
~ change back to resting potential
Repolarization
Na+ channels are closed, and Na+ movement into the cells stops. More K+ channels open. K+ movement out of the cell increases, making the inside of the cell membrane negatively charged compared to the outside, once again
Repolarization.
- chemicals that stimulate or inhibit a muscle fiber
- Ex. Acetylcholine
Neurotransmitter:
nerve cells that carry action potentials to muscle fibers
• Motor neuron:
where nerve cell and muscle fiber meet
• Neuromuscular junction (synapse):°
end of nerve cell (axon)
• Presynaptic terminal:
muscle fiber membrane
• Postsynaptic membrane:
space between presynpatic terminal and postsynaptic membrane
• Synaptic cleft:
- in presynaptic terminal
- store and release neurotransmitters
• Synaptic vesicle:
group of muscle fibers that motor neuron stimulates
Motor unit:
(enzyme breaks down acetylcholine)
Acetylcholinesterase
causes sarcolemma and t-tubules to increase the permeability of sarcoplasmic reticulum which releases stored calcium.
Na +
Energy is released as
ATP → ADP + P
ATP is stored in
myosin heads
• help form cross-bridge formation between myosin and actin
ATP
• must bind to myosin before cross-bridge is released
New ATP
person dies and no ATP is available to release cross-bridges
• Rigor mortis:
Energy for muscle contractions supplied by
ATP
• ATP is made in mitochondria from
aerobic or anaerobic respiration.
• During a muscle contraction, H zone and I band — but A band —-.
shorten, stays the same
• Striations of skeletal and cardiac muscle are due to
sarcomeres (actin and myosin).
Myofilaments —- length during muscle contraction.
do not change