The document discusses physiology related to human balance and equilibrium. It defines static and dynamic equilibrium and describes the key systems and structures involved in maintaining balance, including the vestibular system, cerebellum, and their interconnections. The cerebellum coordinates movement and balance through three main sections. The vestibular system detects head movement through five receptor organs in each inner ear and sends signals to the brainstem and cerebellum through the vestibular nerve and nuclei.

1. Physiology of Body Equilibrium & Balance SYED TOUSIF AHMED

2. Centre of gravity To balance the centre of gravity must be above the support point.

3. Physiology Of Body Balance

4. Physiology Of Body Balance

7. BALANCE Anticipatory Mechanisms (internal) Proactive Mechanisms (external) Reactive Mechanisms Sensory Systems Body Schema Neuro-muscular Synergies Musculo-skeletal Components

8. Balance and Orientation Pathways

12. Figure 12.17b (b) Medulla oblongata Flocculonodular lobe Choroid plexus of fourth ventricle Posterior lobe Arbor vitae Cerebellar cortex Anterior lobe Cerebellar peduncles • Superior • Middle • Inferior

13. Cerebellum Cortico cerebellum Vestibulo cerebellum Spinocerebellum

18. Granule cell axons ascend to the molecular layer, bifurcate and form parallel fibers that run parallel to folia forming excitatory synapses on Purkinje cell dendrites. Cerebellar cortex also has several types of inhibitory interneurons: basket cells, Golgi cells, and stellate cells. Purkinje cell axon is only output of cerebellar cortex, is inhibitory and projects to the deep nuclei and vestibular nuclei. Deep nuclei axons are the most common outputs of the cerebellum (excitatory).

19. Cerebellar Cortical Circuits

21. Cerebellar Output Pathways Lesions of lateral cerebellum affect distal limb coordination. Medial lesions affect mainly trunk control, posture, balance, and gait. Cerebellar deficits occur ipsilateral to the lesion because cerebellar outputs go to the contralateral side and then motor pathways decussate back to the original side (“double cross-over”). Vermis lesions do not cause unilateral deficits because medial muscle groups typically receive bilateral UMN inputs.

22. Static Equilibrium 1) keep the body in a desired position , Static equilibrium – The equilibrium is maintained in a FIXED POSITION , usually while stood on one foot. maintenance of body posture relative to gravity while the body is still.

23. Dynamic Equilibrium 2) move the body in a controlled way . Dynamic equilibrium The equilibrium must be maintained while performing a task which involves MOVEMENT e.g. Walking the beam. – maintenance of the body posture (mainly the head) in response to sudden movements. Tracking a moving object.

25. The vestibular labyrinth

29. Vestibular receptors

30. Static Equilibrium Inside the vestibule are two chambers : utricle and saccule . Regions of hair cells and supporting cells called maculae . Otoliths – “ear rocks”

32. Maculae

34. the vestibular labyrinth Anterior Lateral Posterior

35. Otolithic membrane Hair cell Anatomy: Maculae of Utricle or Saccule Physiology: Linear acceleration of head

40. Vestibular pathways

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