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Home , Extrafusal muscle fiber, Myofibril

10/19/2009

CONTROL OF MOVEMENT: STRIATED MUSCLES SKELETAL (STRIATED) MUSCLE: - each muscle = ______- each muscle = ______-: Filamentous______protein with cross bridges -: ______Filamentous protein where cross bridges of myosin bind

ANATOMY OF

______

Extrafusal muscle fiber ______

______Myofibril

______

______

MUSCLE CONTRACTION

Watch movie

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

1 10/19/2009

NEUROMUSCULAR JUNCTION Synapse between terminal of ______and a ______is called a ;

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

When fires, ______is liberated from terminals at the endplate and depolarizes muscle fibers - ______;

Depolarization of muscle fiber opens ______, producing a large calcium influx into the fiber;

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

Calcium is extruded from fiber by “pump”;

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

MOTOR UNITS : ______Motor pool: All motor neurons that innervate fibers of a single muscle. Muscle fibers Alpha motor neurons

Axons

- weak muscular contraction = ______- strong contraction = ______- discrete/fine movements = ______- crude/gross movements = ______

2 10/19/2009

Localization and distribution of motor neurons in the spinal cord

Somatosensory (mechano) and nociceptive (pain) receptors

Glabrous skin: ______Hairy skin: skin______that covers the rest of the body There are 3 groups of somatosensory receptors: 1. ______2. ______3. ______

3 10/19/2009

Somatosensory pathway from receptors to somatosensory (primary) cortex:

How pain reaches the somatosensory cortex

4 10/19/2009

How is the phenomenon of “referred pain” produced?

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

MONOSYNAPTIC STRETCH REFLEX Involves: - ______- ______- ______- ______- ______

Watch stretch reflex movie

5 10/19/2009

How muscle spindles work! - Gamma motor neurons provide the ______- 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 REFLEXES: EXAMPLE OF WITHDRAWAL FROM PAIN - reflexes requiring ______- concept of ______- ex., biceps vs. triceps of arms - reciprocal innervation (excitatory vs. inhibitory) -excitatory ______and inhibitory interneurons work ______together to withdraw limb from pain.

6 10/19/2009

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

For example, if flexion reflex triggered in one leg, ______

All thi s h appens ______; the brain has nothing to do with it.

This serves to: - ______help remove or push entire body away from ______painful stimulus; - ______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 on feet.

GOLGI REFLEX or how not to shred your muscles and bones! : ______receptor organ sensitive ______to stretch and located at the junction of the ______tendon and muscle. - only contacts ______- if maximally activated, ______- helps prevent tearing of muscles and from bone

Golgi______tendon organ______Pseudounipolar ______neuron

alpha______motor neuron inhibitory______interneuron

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