neuron motor unit is one motor neuron and all muscle fibers its branches innervate. delicate control...
TRANSCRIPT
Neuron
Motor Unit
• Is one motor neuron and all muscle fibers its branches innervate.
• Delicate control - a few muscle fibers per motor unit. Stimulates 6 to ___ fibers.Eye
• Gross movement have over ______ muscle fibers per unit.
• All fibers in a motor unit contract when stimulated with a threshold stimulus.
NEUROMUSCULAR JUNCTION
____ -the junction between a motor neuron ending and a muscle fiber.
Composed of a motor neuron, and muscle fiber.
Has a motor end plate.Motor end plate is the junction between the
muscle fiber and the axon terminals.
Nerve Action
• 1. Action potential moves down the axon• 2. Increase in _____causes acetylecholine
to be released.• 3.Acetylecholine moves synaptic gap• 4.Acetylecholine reaches motor end plate• 5.Acetylecholine _______ with receptors
Nerve Action
• 6. Repolarized
• 7. Acetylecholine to _______
• 8. Acetylecholine is broken down to A_____ and C______.
• 9. Ready again to receive an impulse.
Single Muscle Contraction
• 3 phases Latent period Contraction period Relaxation period Followed by recovery(refractory period)
ISOTONICISOTONIC
• Equal + tension
• Force used to produce work and work is ______.
• Object moves and muscle shortens
Isometric• Muscle produces heat but
_______work is done• Muscle does not shortens• Examples
Standing Holding a door
Oxygen Debt
• A_____ of extra oxygen needed to metabolize the accumulated lactic acid and restore normal ______ levels.
Fatigue• Lactic acid builds up and makes
the muscle to feel _________.• Body needs oxygen to change
lactic acid into carbon dioxide and water.
Aerobic
•With ________
•Pyruvic acid + oxygen = CO2 + H2O + _________.
Anaerobic
•Without oxygen•Pyruvic Acid is changed to lactic acid.
Contraction speed
• Classified:Fast-twitch (type II fiber)Slow-twitch (type I fibers)
Fast-twitch
• Relaxation cycle is about 30msc
• More mitochondrea than slow-twitch
• Pale in color - _______ muscle
• Fast quick movement
• Example Eye - Hand Sprinter
Slow-twitch
• Relaxation cycle is about 3000msc
• Fewer mitochondrea than fast-twitch
• _______ Muscle
• Prolonged, steady contractions
• Example Back muscle Long distance runners
Smooth Muscle
• Appear smooth
• Involuntary muscles
• Contract and relation periods are slower than skeletal muscle
• Action is ____________
• Contraction may last ____ sec or longer
• Examples - stomach, intestine, bladder, uterus during child birth.
Smooth Muscle
• Poorly organized sarcoplasmic reticulum
• NO Z line or T tubules• Types
Single unit - sphincters, pacemaker cells
Multiunit - iris of eye, goose bumps
Cardiac Muscle
• Found only in the __________!
• Huge #’s of mitochondrea
• Well developed sarcoplasmic reticulum and T tubules
• Intercalated disk
• Refractory period is ______msc, almost as long as the contraction
Cardiac Muscle
• Never stops beating in a life time
• ____________beats a day
• At 70 years old your heat would have pumped 2.5 billion times.
• If oxygen is deprived _____ sec, cardiac muscle cells may stop contracting, resulting in heart failure.
When things Go WRONG! Muscle injuries
• Skeletal muscle - satellite cells under the endomysium cause cell division.
• Smooth muscle - causes the proliferation of cells. Pregnancy enlarging of uterus.
• Cardiac muscle - childhood can regenerate but in adults is replaced by connective tissue.