ANATOMY OF SKELETAL MUSCLE

___________________________

________

Extrafusal muscle fiber

Myofibril

_____________

__________________

_________

________

CONTROL OF MOVEMENT: STRIATED MUSCLESSKELETAL (STRIATED) MUSCLE:

- each muscle = ____________________________________- each muscle cell = _______________________________________- Myosin: ___________________________________________- Actin: _________________________________________________

Filamentous protein with ross bridgesFilamentous protein where cross bridges of myosin bind

___________

MUSCLE CONTRACTION

Myosincrossbridges

Actinfilaments

Myosinfilament

Actinfilament

Movement ofactin filament

Myosincrossbridge

Movement ofmyosin filament

Heads of cross bridges:1. Attach to active sites on actin filaments2. “Ratchet” forward3. Release4. Repeat- Only occurs in the presence of ________How is calcium released? ___________________________

________From activity at neuromuscularjunction

Watch muscle contraction movie

NEUROMUSCULAR JUNCTIONSynapse between terminal of _________________and a ___________ is called a neuromuscularjunction;

Terminals of alpha motor neurons synapse on_____________- grooves along the surface ofmuscle fibers;

When motor neuron fires, _____________ isliberated from terminals at the endplate anddepolarizes muscle fibers - ________________;

Depolarization of muscle fiber opens _________________________________, producing a largecalcium 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 tofire = contraction or “twitch” of fiber.

MOTOR UNITS

- weak muscular contraction = _______________________- strong contraction = _______________________- discrete/fine movements = __________________________

____________- crude/gross movements = __________________________

____________

Alpha motor neurons

Muscle fibers

Motor unit: __________________________________________________________________________

Motor pool: All motor neurons that innervate fibers of a single muscle.

Axons

Localization and distribution of motor neurons in the spinal cord

Somatosensory (mechano) and nociceptive (pain) receptors

Glabrous skin: _________________________________Hairy skin: __________________________________

There are 3 groups of somatosensory receptors:

1. ______________ 2. ______________ 3. ______________

skin that covers the rest of the body

Somatosensory pathway from receptors to somatosensory (primary) cortex:

How pain reaches the somatosensory cortex

How is the phenomenon of “referred pain” produced?

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

MONOSYNAPTIC STRETCH REFLEXInvolves:- _________________- _________________________________- __________________________________________________________________

- ______________________________- ____________________________________

Watch stretch reflex movie

How muscle spindles work!- Gamma motor neurons provide the ________

________________________________- without gamma motor neurons, the spindles

would become _________________________________________

- gamma motor neurons function _________________________________ to an appropriatedegree of tension

Muscle spindles

Gamma motor neurons

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

Extrafusal muscle

“slack” and unresponsiveto stretch.

to adjust the length of intrafusal muscles

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 worktogether to withdraw limb from pain.

CROSSED EXTENSOR REFLEX

Think of this reflex as being ____________ withprevious polysynaptic withdrawal reflex

For example, if flexion reflex triggered in oneleg, ___________________________________

All this happens _________________________;the brain has nothing to do with it.

This serves to:- ______________________________________________________________

- ____________________________________________________________

An example of a complex sensorimotor reflex is________.- spinal cat, when placed on a treadmill can

____________________________________________________________________________

“connected”

help remove or push entire body away from painful stimulus;

help restore balance when flexed leg is withdrawn.

initiate normal walking when provided with somatosensory feedback of treadmill on feet.

GOLGI TENDON REFLEXor how not to shred your muscles and bones!

Golgi Tendon Organ: ___________________________________________________________________________________________

- only contacts ________________________- if maximally activated, ___________________

________________________________- helps prevent tearing of muscles and tendonsfrom bone

receptor organ sensitive to stretch and located at the junction of the tendon and muscle.

___________________

_____________________________

______________________

_________________________

Golgi tendonorgan

Pseudounipolarneuron

inhibitory interneuron

alpha motor neuron