Muscles Flashcards
Muscles
Three types:
Smooth (internal organs),
Cardiac (heart, endogenous activity)
and Striate (Skeletal, Facial)
Striate
Band of parallel fibers, each fiber made of many cells but acts as unit; Attached by tendons to bones;
- Come in Antagonistic Pairs:
Striae Antagonistic Pairs
Flexor and Extensor
Flexor
moves bone toward body
Extensor
move same bone away from body
Neuro-Muscular Junction
(primarily involving Striate Muscles);
- Motor Neurons (“Alpha Motor Neurons”) exit Ventral Root of Spine»_space; Striate muscles
- Neuron synapses directly onto muscle, releasing Acetylcholine (ACh), always sufficient to trigger response
- Usually 1 axon branches to multiple muscle fibers; the fewer fibers per axon the more precise the control
- Like in a neuron, Muscle fiber response is all/nothing depolarization
usually 1 axon branches to…
…multiple muscle fibers
the fewer fibers per axon…
….the more precise the control
muscle fiber response
Like in a neuron, is all/nothing depolarization => Na+ and then K+ gates open/close
- Ca++ enters muscle cells => triggers energy-requiring process that causes muscle contraction
- Afterward, Ca++ is actively pumped out, and a Na+/K+ Pump repolarizes fiber for next contraction
Contractile Mechanism
- Within each fiber is a string of Sarcomeres
Sacromeres
(the contractile units) each consisting of….
Myosin and
Actin
Myosin
thick protein filament with knobby bead-like clusters (“Cross Bridges”) along it,
Actin
thin protein filament, a coiled double-strand braid, anchored to muscle
Contraction
Myosin Cross Bridges hook into (grab) coiled Actin, bend to tighten coil, release, repeat
the only active muscle response is…
…Contraction!!
all stretch is
PASSIVE
