Topic: Nervous system, neuronal transmission
Question: Describe neuronal pathway and reflexes which maintain balance and posture of human body.
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The neuronal pathways and reflexes involved in balance and posture include:
1. Vestibular system: Detects head position and movement. Located in the inner ear. Sends signals to the brainstem and cerebellum.
2. Proprioceptors: Detect stretch and tension in muscles, joints and tendons. Send signals to the spinal cord and brain.
3. Visual system: Detects body position and movement relative to the environment. Sends signals to the brain.
4. Cerebellum: Integrates inputs from the vestibular, proprioceptive and visual systems. Modulates muscle tone and coordinates movement.
5. Brainstem: Receives inputs from above systems. Mediates posture and balance reflexes via the reticulospinal and vestibulospinal tracts.
Key reflexes:
1. Vestibulo-ocular reflex (VOR): Stimulates eye muscles to move the eyes in the opposite direction of head movement. Maintains stable vision. Controlled by vestibular nuclei in the brainstem.
2. Vestibulospinal reflex: Adjusts muscle tone and causes spine/extremities to compensate during head/body tilt. Helps maintain erect posture. Controlled by lateral/medial vestibulospinal tracts.
3. Stretch reflex: Detects changes in muscle length. Stimulates muscle to contract to maintain posture and position against perturbations. Controlled by muscle spindles, dorsal root ganglia and ventral motor neurons.
4. Righting reflexes: Generate compensatory movements in response to changes in head/body position to maintain upright posture and balance. Controlled by reticular formation and cerebellum.
In summary, balance and posture are maintained by inputs from the vestibular, visual, and proprioceptive systems which are integrated in the cerebellum and brainstem. Key reflexes like the VOR, vestibulospinal and stretch reflexes coordinate automatic movements, muscle contractions and changes in tone to stabilize the body in space and maintain an upright, balanced stance. Damage to any areas of this control system can lead to disorders of balance, dizziness or abnormal movements.
