Movement analysis

motor unit

a single motor neuron and the muscle fibers which it innervates

all or none law

minimum stimulus needed to illicit a response, a strong stimulus calls up many fibers/a weak stimulus calls up few fibers

neurotransmitters in stimulating muscle contraction

1. nerve impulse reaches axon terminal

2. membrane depolarizes - Ca++ channels open

3. acetylcholine migrates to presynaptic membrane

4. acetylcholine released into synapse

5. acetylcholine binds to receptor proteins on sarcolemma

6. channels open and Na+ flows into cell

7. action potential is generated, muscle impulse travels into muscle cell

8. cholinesterase breaks down acetylcholine into choline and acetic acid

Type I

slow twitch, red - more m1tochondr1a, more myoglobin, slow speed, more endurance, less power, aerobic 

Type IIa

fast twitch, less red less mitochondria, fast speed, less endurance, more power, aerobic and anaerobic

Type IIb

fast twitch, white - less mitochondria, fastest speed, tires quickly, most power, anaerobic

atrophy

loss or deterioration of muscle

hypertrophy

gain of muscle

disuse muscle atrophy

injury, desk jobs, bed-rest, astronauts - can be reversed

neurogenic atrophy

injury or disease of nerve that connects to muscle, motor neuron diseases, occurs more suddenly than disuse atrophy

ALS - amyotrophic lateral sclerosis

death of motor neurons, can no longer send messages to muscles, does not affect senses or brain function

hypertrophy

increase in size of muscle cells, chronic hypertrophy due to long term training - muscle cells increasing in size from additional myofibrils OR additional muscle cells

antagonist

muscle with opposite action of prime mover

agonist

prime muscle involved in the action

fixator muscles

fixator = stabilizer, the end of the joint that is not moving when a muscle contracts, has to be stabilized

synergist muscles

synergist = neutralizer, synergist/neutralizers contract isometrically to prevent unwanted actions of the agonists or antagonists

reciprocal inhibition reflex

when one muscle is contracted, a signal is sent via neurons that reduces contraction in opposing muscles

isotonic

“same tension” muscle contracts and shortens

isometric

“same distance” muscle contracts but are held at a fixed length

concentric

shortening of muscle while still contracting, muscle force is greater than the resistance, can overcome resistance and lift weight

eccentric

lengthening of muscle contracting, muscle force is less than the resistance, slows lowering of arm and control extension = braking

concentric

force generated: more than enough to overcome resistance, frequency: less common and eccentric, ex. usually only occurs during excercise

eccentric

force generated: not enough to overcome resistance, frequency: most common the concentric, ex. occur during everyday activities such as walking and arm swinging, used in braking or slowing of muscle action

isometric

no change in length

isotonic contraction

change in length - concentric/eccentric