Neuro

• dorsal roots contain sensory (afferent ) fibres, ventral roots contain motor (efferent ) fibres
• autonomic LMNs innervate smooth muscle
• somatic LMNs have cell bodies in the CNS. Their axons travel in the PNS
• The meninges are the coverings of the brain. Working brain out:

  • cerebral cortex
  • pia mater
  • arachnoid
  • dura mater
• in the forebrain, grey matter is superficial as the cortex but is also deep to form the basal nuclei
• the cerebrum is formed of two cerebral hemispheres. Its neurones are in the external surface of gyri and also deep to the surface in basal nuclei.
• the cerebral cortex's lobes and their functions are:

  • frontal lobe: motor cortex and association
  • Parietal lobe: somatosensory
  • Temporal lobe: audition, learning and memory
  • Occipital lobe: vision
  • Rhinencephalon: olfaction, learning and memory
• the subcortical structures of the cerebrum are the limbic system (e.g. hippocampus - behaviour and emotion ) and the basal nuclei (extrapyramidal motor system)
• the long, deep line separating the the two hemispheres of the cerebrum is the dorsal longitudinal fissure
• the left and right hemispheres of the cerebrum are connected by the corpus callosum.
• the forebrain controls and receives information from the opposite side of the body. Tracts to and from the body decussate (mostly in the caudal midbrain )
• the basal nuclei modify cortical initiations (signals from the forebrain) of voluntary movement
• the thalamus processes all sensory information except olfaction through thalamic nuclei prior to them reaching the cerebral cortex
• the lateral geniculate nucleus of the thalamus is the synapse point for visual information before it reaches the cerebral cortex
• the ascending reticular activating system of the brainstem determines arousal (consciousness/ awareness) and regulates sleep
• the brainstem consists of the midbrain, pons and medulla oblongata
• the principle functions of the brainstem are:

  • motor and sensory innervation of the face and neck via cranial nerves
  • ascending afferent (sensory) and descending efferent (motor) tracts
  • regulation of cardiac and respiratory function
  • consciousness and sleep cycles
• the rostral and caudal colliculi of the midbrain serve different functions

  • rostral = visual reflexes
  • caudal = auditory reflexes
• the midbrain contains the cranial nerves for eye movement ( CN 3 - oculomotor (which also controls pupillary contraction) and CN 4 - trochlear )
• the pons contains the motor nucleus of the trigeminal nerve ( CN 5) for the muscles of mastication
• the pons connects the cerebrum and cerebellum via its transverse fibres
• the cerebellum is a sensory structure however the signals it recieves are not consciously perceived. They are used to modify and coordinate muscle action
• the cerebellum compares motor commands from the cerebrum with information coming from proprioceptors. this ensures coordination, precision and accurate timing of movement
• the cerebellum is attached to the brainstem by three bundles of fibres called the peduncles at the level of the pons
• in the cerebellum there are differing functional areas:

  • hemispheres = regulation of fine movement
  • vermis = truncal and limb movements
  • flocculonodular node = equilibrium and posture
• the spinocerebellar tracts consist of 2 neuron pathways which are mostly ipsilateral
• the cervical intumescence is at the level of c6 to t2
• the lumbar intumescence is at the level of L4 to S3
• in the spinal cord, ascending tracts to the forebrain are found in the dorsal funiculus
• in the spinal cord, ascending tracts to the cerebellum are found in the lateral funiculus
• in the spinal cord, descending tracts are found in the ventral funiculus
• the spinal formula of the dog is 81373 and the spinal cord terminates at L6 or 7
• the spinal formula of the cat is 81373 and the spinal cord terminates variably
• the spinal formula of the ox is 81365 and the spinal cord terminates at L6 or S1
• the spinal formula of the hors is 81865 and the spinal cord terminates at S1 or 2
• is dogs, CSF should be collected at L5. in the horse this is L7
• the functions of CSF are:

  1. protection and buoyancy for mechanical protection
  2. excretion of waste products such as metabolites and drugs
  3. nutrition, transporting metabolites, nutrients and neurotransmitters
  4. chemical buffer to maintain ionic balance
• CSF is formed in the choroid plexus and ventricular blood vessels and is absorbed via the arachnoid villi into cerebral venous sinuses and perineural lymphatics
• the choroid plexus is a highly vascularised structure which attaches to the ependymal cells lining all four cerebral ventricles
• CSF is produced through ultrafiltration of plasma through the choroid plexus and modified by secretions from the epithelial secretory cells.