4.3 Control of Posture & Gait Flashcards
What information does vision give?
Position, speed, direction, motion of other objects
What information does proprioception give?
Force, pressure
What information does otoliths give?
Gravity (tilt), linear acceleration
What information does semicircular canals give?
Rotational (angular) velocity and acceleration
Sensory loss may occur in all the systems stated above due to various factors, but control is adaptive with some degree of redundancy/reserve:
• People lacking information from one sense can still perform well if the motor task is not too difficult → generally 2 out of the 3 systems above are required for balance
• Various forms of sensory loss leading to altered posture and gait will be discussed using various clinical case studies below
- Illness: Meniere’s disease (affects the __________), cataracts (affects __________), neuropathy (affects ___________)
- Injury: Physical injury, poisoning, drug toxicity
- Ageing: Visual, proprioceptive, vestibular performance declines
inner ear; visual acuity; proprioception;
Proprioception is the sense which provides information about the ______________
• Compensation involves constant monitoring and cognitive control of all actions
o Gestures may appear normal, but actions are not spontaneous and conscious effort is constantly required
orientation of the body in space and where each part is in relation to each other
what are stance compensations for propioception?
- Wide base of stance from front to back, side to side to increase stability
- Hyperextension of knee locks the joint for passive stability
what are gait compensations for propioception?
Limited trunk, arm movement to reduce need to control moving masses
• Hyperextension of knee locks the joint for passive stability
what are fine movement compensations for propioception?
Generally slow and deliberate (e.g. closing box of eggs)
• Careful application of pressure at fingertips (e.g. picking up eggs)
VESTIBULAR LOSS
The vestibular system is primarily involved in the sense of _____________ and the coordination of ________________
• A patient suffered from complete vestibular function loss due to damage of the vestibular system by gentamicin (used to treat life-threatening infection)
• Compensation is also possible, allowing the patient to carry out ADLs regularly
Without normal vestibular function, the patient cannot walk properly (___________ and unsteady when turning) with eyes closed, and affects the free standing position:
• Free standing position can be tested using the ________________ position (putting one foot in front of the other) → swaying is a positive sign of impaired function
The performance of the patient tends to deteriorate as the _______________
balance and spatial orientation,
movement with balance;
veers to one side;
tandem Romberg;
balancing task becomes more difficult and when the visual sensory information is lost:
Information from all senses are used to deduce position and motion, and all these information are usually congruent (giving same interpretation):
• If different senses disagree with another, ______________ (e.g. illusion of self-motion in a stationary train; circularvection)
• Prolonged or severe sensory conflict causes ______________
one of the senses is given more weight over another;
motion sickness (e.g. seasickness, airsickness, space sickness)
Rotation of a decerebrated pigeon produces characteristic head movement (nystagmus):
• Nystagmus is a specific eye movement which enables a stable image to be maintained on the retina in humans → whole head moves in pigeons as they cannot move eyes
• Visual stimulus generates a ____________ as the brain attempts to keep the image on the retina for as long as possible:
o Eye drifts in ___________ (slow phase) → quick reset when it ______________ (fast phase)
Without visual input, the vestibular system generates the nystagmus by trying to compensate for the movements of the head:
• However, it only senses _____________→ generates nystagmus for a short while but decays when the bird reaches constant velocity
• _________________ results when the rotation is ceased, producing deceleration which is detected by the vestibular system
continuous nystagmus;
direction of motion;
reaches the extent of the orbit
acceleration;
Opposite (post-rotational) nystagmus
AUTOMATIC REACTIONS
Automatic reactions are triggered by particular combinations of sensory stimuli appropriate for particular situations:
• If the reactions are inappropriate, voluntary compensation may be required
• Conscious anticipation produces a _______________________
postural set (tendency to respond in a specific way which is appropriate to an expected perturbation)
