3/22/99

Physiology II

 

Unit XI—Motor Control

Reflex

·        Brain stem—relay station, involuntary functions, doesn't learn

·        Cortex—center of learning, sends out signals to control, Corticofugal

·        Spinal cord—innate process, doesn't learn, acts by reflex

 

Organization of the cord

·        Gray matter—integrated, w/draw reflex

·        Fig 54.1

·        Anterior neurons, interneurons,

·        Interneurons—highly excitable, take up cord area, things junction, referral of pain, shared junctions—a cell w/a lot of dendrites

·        Anterior motor neurons—innervate skeletal muscle—efferent

·        Gamma motor neurons—1/3, muscle spindles and golgi organs

·        Reflex arc

·        Reciprocal circuits—function of output to pull away after the sensory information has come in

·        Dampen input renshaw cells w/in interneurons, inhibitory—create lateral inhibition, focus a signal, focus output of cord

·        Receptors—muscle spindle and golgi tendon

·        Muscle spindle

·        Extrafusal—muscle fibers

·        Intrafusal—excitatory information, feedback information back to the

·        Throughout the belly of the muscle

·        Length and the rate at which the length is changing

·        Rate receptors

·        Dynamic response—while the change is occurring, measures acceleration

·        Static response—while it is just sitting there

·        Golgi tendon organ

·        Located in the tendon of the muscle

·        Monitors tension in the muscle and tendon

·        Muscle contraction and pull on golgi tendon

·        Fibers bound together

·        Rate of change of tension on the muscle

·        Muscle controls itself at a subconscious level

 

Muscle Spindle

·        Made of 3-12 Intrafusal fibers

·        Pointed ends—have some actin and myosin like regular muscle fibers

·        Attached by glycocalyx matrix to Extrafusal fibers

·        Central portion doesn't have the capacity as much to contract

·        When stretched, diminished contact w/sensory fibers—altered contact

·        Lengthen muscle and excite the sensory fibers

·        When relaxed, full contact w/sensory fibers

·        1° and 2° sensory endings

·        annular fibers—wrap around muscle spindle

·        2° endings—small sensory endings; type II fibers; innervated by receptors on each side of the 1° receptor

·        process of looking at stretch

·        2 types of receptors—dynamic and static

·        nuclear bags—fibers that have large grouping of nuclear material; 1-3 per

·        nuclear chains—3-9, not as large--static