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.