Test 3 - Lecture 3 ( Posture, Balance, Vol Movement ) Flashcards
Relative orientation of the head, trunk, & limbs
Posture
Capability to maintain a stable posture
Balance
The resistance of a muscle to stretch by external loads, reflecting the overall stiffness of the muscle arising from active force generation
Muscle tone
A point that represents the average position of the body’s total mass; the net effect of gravity upon the body is through …
Center of mass
The ground, or platform upon which we make contact to which the gravitational force, acting through the body’s center of mass, is applied…
Base of support
Pulling forces, established through muscle activation, to counteract external forces that would otherwise pushy the body off balance
Force vectors
Loss of balance may occur whenever postural ______ is lost
Equilibrium
Displacement of the center of mass away from its center of balance relative to the current stance
Sway
(Forward - anteriorly)
(Backward - posteriorly)
To counter act, the muscles closest to the origin of displacement are activated …
First
Compensatory muscle activation continues progressively moving away from the origin of displacement to…
Stabilize & brace
An active compensatory response triggered by a disturbance to postural equilibrium
Reflex
Counteracting forces no longer off-set displacement forces, causing loss of balance if not quickly restored
Disturbances to equilibrium
Particular motor reflexes originate from neural networks where
Brainstem & spinal cord
Learned preparatory state that may be executed in advance of a stimulus
Postural set
Feed forward signaling is …
Anticipatory (awareness of current body position & of intended movement generates adjustments in muscle tone in advance of voluntary movement)
Feed back signaling is …
Compensatory (to maintain posture during movements & when external forces are varying)
Feed - _____ responses are stereotyped & can be improved through learning & practice
Feed back responses
Report changes in orientation and balance via changes in the length & tension of specific muscles
Proprioceptors
Twice as fast as vestibular & visual responses
Report head motion
Vestibular receptors
Report motion relative to external objects in the visual field
Visual input
Respond to changes in length & tension along muscles & tendons
Proprioceptors
Changes in orientation within the gravitational field
Vestibular
Respond to movement of an image across the retina
Photoreceptors
Postural adjustments there require the integration of more than one sensory inputs called…
Sensorimotor transformations
Integration of visual & vestibular sensory input is largely _______ involving nuclei within the brainstem & cerebellum
Sub-cortical
