10/19/2009

CONTROL OF MOVEMENT: STRIATED MUSCLES SKELETAL (STRIATED) MUSCLE: - each muscle = ______lots of muscle cells (muscle ) - each muscle =packed ______with and filament -Myosin: Filamentous______protein with cross bridges -Actin: ______Filamentous where cross bridges of myosin bind

ANATOMY OF

Axon______of alpha motor______neuron Endplate______

Extrafusal muscle ______Muscle

Tendon______Myofibril

Actin______filament

______Myosin filament ______Z discs (bands)

MUSCLE CONTRACTION

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Myosin Myosin cross bridges filament

Actin filaments

Actin MtfMovement of filament actin filament

Myosin cross bridge

Movement of myosin filament Heads of cross bridges: 1. Attach to active sites on actin filaments 2. “Ratchet” forward 3. Release 4. Repeat -Onlyoccurs in the presence of How is calcium released? From______activity at neuromuscular ______junction

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NEUROMUSCULAR JUNCTION between terminal of alpha______motor and a muscle______fiber is called a ;

Terminals of alpha motor synapse on motor______enplates - grooves along the surface of muscle fibers;

When fires, ______acetylcholine is liberated from terminals at the endplate and depolarizes muscle fibers - endplate______; potentials

Depolarization of muscle fiber opens ______voltage- dependent______calcium channels , producing a large ______calcium influx into the fiber;

Calcium triggers the actin-myosin “rowing” action leading to the contraction______of muscle fibers;

Calcium is extruded from fiber by “pump”;

Endplate potential ______always cause muscle fiber to fire = contraction or “twitch” of fiber.

MOTOR UNITS : ______One + its + all the ______muscle fibers it innervates (contacts) Motor pool: All______motor neurons that innervate fibers of ______a single muscle

Muscle fibers Alpha motor neurons

Axons

- weak muscular contraction = ______few motor units activated _ - strong contraction = lots______of motor units activated - discrete/fine movements = ______small motor units – few fibers ______activated - crude/gross movements = big______motor units – lots of units ______activated

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Localization and distribution of motor neurons in the

Somatosensory (mechano) and nociceptive () receptors

Glabrous : skin______that does not have follicles (hairless) Hairy skin: skin______that covers the rest of the body There are 3 groups of somatosensory receptors: 1. ______Nociception 2. ______Hapsis 3. ______Proprioception

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Somatosensory pathway from receptors to somatosensory (primary) cortex:

How pain reaches the somatosensory cortex

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How is the phenomenon of “referred pain” produced?

Arm and pain “referred” from pain receptors during heart attack.

MONOSYNAPTIC STRETCH Involves: - ______intrafusal muscle - ______muscle spindle (signals stretch) - ______spindle afferent neuron (pseudounipolar ______sensory neuron) - ______intrafusal (gamma) motor neuron - ______extrafusal muscle and motor neuron

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5 10/19/2009

How muscle spindles ! - Gamma motor neurons provide the ______overall ______sensitivity of the muscle spindles - without gamma motor neurons, the spindles would become ______“slack” and unresponsive to______stretch. - gamma motor neurons function to______adjust the length______of intrafusal muscles titto an appropriate degree of tension Gamma motor neurons

Muscle spindles

Extrafusal muscle

Spindle “slack” - insensitive to strech Spindle “tight” - ready to respond to strech

POLYSYNAPTIC : EXAMPLE OF WITHDRAWAL FROM PAIN - reflexes requiring interneurons______in the spinal cord - concept of ______antagonistic muscles (flexor vs. ______extensor muscles) - ex., vs. of - reciprocal innervation (excitatory vs. inhibitory) -excitatory ______and inhibitory work ______together to withdraw limb from pain.

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CROSSED EXTENSOR REFLEX Think of this reflex as being ______“connected” with previous polysynaptic

For example, if flexion reflex triggered in one , extensor______reflex is triggered in other leg

All thi s h appens ______;attht the level of fth the spi nal cord the has nothing to do with it.

This serves to: - ______help remove or push entire body away from ______painful ; - ______help restore balance when flexed leg is ______withdrawn.

An example of a complex sensorimotor reflex is ______. - spinal cat when placed on a treadmill can ______initiate normal walking when provided with ______somatosensory feedback of treadmill.

GOLGI REFLEX or how not to shred your muscles and ! Golgi Tendon : ______receptor organ sensitive ______to stretch and located at the junction of the ______tendon and muscle. - only contacts ______inhibitory interneurons. - if maximally activated, completely______inhibits ______alppyha motor neuron activity. - helps prevent tearing of muscles and from

Golgi______tendon organ______Pseudounipolar ______neuron

alpha______motor neuron inhibitory______interneuron

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