Chapter 4: MOTOR PHYSIOLOGY Flashcards
Anterior to the central cortical sulcus
Brodmann Area 4 and 6
Primarily involved with discrete voluntary movements
More than ½ is concerned with controlling muscles of the hands and speech
Primary Motor Cortex (Area 4)
Nerve signals generated cause much more complex patterns of movement
Premotor Area (Area 6)
Most important output pathway from the motor cortex
CORTICOSPINAL (PYRAMID) TRACT
giant pyramidal cells that are only found in the motor cortex.
BETZ CELLS
Cross at the lower brain stem and follows a course adjacent to the corticospinal tract
RUBROSPINAL TRACT
Serves as an accessory route for transmission of relatively discrete signals from the motor cortex to the spinal cord
RUBROSPINAL TRACT
communicates closely with the motor cortex through the corticorubral tract
Located: mesencephalon
RED NUCLEUS
it has 2 types: Pontine reticulospinal tract & Medullary reticulospinal tract
RETICULOSPINAL TRACT
excites the anti-gravity muscles of the body
PONTINE RETICULOSPINAL TRACT
inhibits the anti-gravity muscles of the body
MEDULLARY RETICULOSPINAL TRACT
Selectively control the excitatory signals to the different anti-gravity muscles to maintain equilibrium
VESTIBULOSPINAL TRACT
Give rise to the nerve fibers that leave the cord by way of the anterior roots, and directly innervate the skeletal muscle fibers.
ANTERIOR MOTOR NEURONS
It gives rise to large A alpha motor fibers.
It goes directly to the extrafusal muscle fibers
ALPHA MOTOR NEURONS
It gives rise to A gamma motor fibers
It go directly to the intrafusal muscle fibers
GAMMA MOTOR NEURONS
Signals from spinal nerves terminate first to the interneurons where they are processed and combine with the other signals from other tracts or nerves and converge in the anterior motor neurons
INTERNEURONS
muscle is stretched suddenly, excitation of the spindles causes?
sudden muscle streched = ?
REFLEX CONTRACTION
sudden muscle streched = REFLEX CONTRACTION
Lengthening the whole muscle stretches the mid portion of the spindle and, therefore, excites the receptor.
MUSCLE SPINDLE
Even if the length of the entire muscle does not change, contraction of the end portions of the spindle’s in trafusal fibers stretches the midportion of the spindle and therefore excites the receptor.
MUSCLE SPINDLE
helps control muscle tension. Specifically:
- It provides a negative feedback mechanism that prevents the development of too much tension on the muscle.
- Lengthening reaction: sudden reaction in the spinal cord that causes instantaneous relaxation of the entire muscle.
- Equalize contractile forces of the separate muscle fibers.
GTO (GOLGI TENDON ORGANS)
When a stretch reflex excites one muscle, it often simultaneously inhibits the antagonist muscles
RECIPROCAL INHIBITION
Neuronal circuit that causes this reciprocal relation
RECIPROCAL INNERVENTION
Simplest manifestation of muscle spindle function.
MUSCLE STRETCH REFLEX
Any type of sensory stimulus from a limb is likely to cause the flexor muscles of the limb to contract, thereby withdrawing the limb from the object
Flexor Withdrawal Reflex
Painful stimulus is applied to the hand; as a result, the flexor muscles of the upper arm become excited
Flexor Withdrawal Reflex
Painful stimulus applied –> flexor muscle excites –> flexor withdrawal
Signals from sensory nerves cross to the opposite side of the cord to excite extensor muscles
Crossed Extensor Reflex
After a stimulus elicits a flexor reflex in one limb, the opposite limb begins to extend
Crossed Extensor Reflex
Tract that excites and inhibits the anti-gravity muscles of the body
RETICULOSPINAL TRACT
Pressure on the foot pad causes the limb to extend against the pressure applied to the foot
Positive Supporting Reaction
When laid on one side, it will make uncoordinated movements to try to raise itself to standing position
Cord “Righting” Reflexes
Rhythmical stepping movements of one limb → flexion followed by extension
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Reciprocal stepping of opposite limb → forward movement of one limb causes the other to move backwards
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Diagonal stepping (mark time reflex
Stepping Reflexes
Position sense → allows one to find the exact point of irritation
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To-and fro scratching movement
Scratch Reflex
