VPB 121: Veterinary Physiology - II (2+1)

REGIONS OF CEREBRAL HEMISPHERE

• Frontal lobe: Voluntary motor activity, vocal ability and higher mental functions.
• Parietal lobe: Associated with movement, orientation, recognition, and perception of stimuli.
• Occipital lobe: Involved in visual processing
• Temproal lobe: Involved with perception and recognition of auditory stimuli.

Topographical organisation of cerebral cortex

• Visual cortex
• Auditory cortex
• Somatosensory cortex
• Motor cortex

Frontal lobe

Motor areas

• Primary motor cortex which is the exact motor cortex
  • Primary motor cortex is formed by precentral gyrus and has small narrow zone which posses BETZ cells. Primary motor cortex is a centre for voluntary movement, and initiates voluntary movement this is origin of corticospinal tract and project fibres to pons, corpus striatum red nucleus and subthalamus. Most of the skeletal movement are under the control of motor cortex.Stimulation of excitomotor cortex causes quick and phasic movement.
• Supplementary motor area
  • Present in the medial surface of the hemisphere,has greater threshold stimulation of this part causes show movement which causes some change in posture for brief period of time.There are other areas in primary motor cortex which includes secondary motor cortex which compensates loss function of primary motor cortex. Adjacent to this area is that, the one which control mainly postural and stretch reflex which on stimulation causes inhibition of reflex induced movement of cortically induced movement.It exerts such inhibitory influence.It has connection with caudate nucleus and reticular formation.
• Premotor cortex
  • Fibres of pyramidal and extra pyramidal tracts original from here, this area is concerned with
    • Excitatory effects
    • Complex coordinated movement of contra lateral side of the body.
      • Rotation of head and trunk to the opposite side simultaneous movement of flexion and extension of contra lateral limbs.
      • Adjacent to the premotor cortex is the area concerned with movement of eyes, pupillary dilation and secretion of lachrymal glands.

Prefrontal areas

• This area is concerned with socializing in animals. Stimulation of this area causes low frequency of autonomical, respiratory, circulatory renal and gastrointestinal responses.
• This area is principally connected to thalamus. Hypothalamus sub cortical and other cortical region.

Parietal lobe

• Parietal lobe have areas concerned with sensory function

Somesthetic area or primary sensory cortex

• All somesthetic sensation is perceived here except pain and crude temperature with are perceived at the thalamus.
• This is the area which helps in discriminating the qualities of external objects like size, shape, texture, weight and position of limbs in relation to space.
• Judging of the particular sensation and nature is done by this areas
• Its function includes
  • Discrimination and localisation of touch
  • Recognition and discrimination of different stimuli at different intensities
  • Spatial recognition –to relate the movement and position of limbs
  • Recognise the stimulation and dissimilarities [size, shape, weight]
  • Taste sensation –different taste in relation with different taste receptors. This area is adjacent to the motor cortex governing the masticatory muscles.