Integrative Neuroscience- Sensory systems-Touch

• paleocortex and archicortex

  3 layers-Pyriform cortex

  4 layers- Hippocampus
• Neocortex consists of?


  Motor/visual cortex and is 6 layers
• Based on the somatopic maps and homuclus what is the most sensitive?

  HANDS/FINGERS

  UPPER/LOWER LIPS
• secondary somatosensory area


  Throat, tongue, teeth, jaws and gums
• Somatopic maps


  1. chin, upper and lower lip, face and nose

  2.leg, foot, genitalia, and toes

  3a. Trunk, neck, head, shoulders, arm, elbow, forearm, hands, digits

  3b. thumbs and eyes

  
  

  ALL GOES TO S1 OR PRIMARY SOMATOSENSORY CORTEX
• Thalamus for face?

  Ventral Posterior Medial(VPM)
• Thalamus for body?

  Ventral posterior Lateral (VPL)
• Proprioceptive pathway differs compared to the other pathway because


  It always goes ipsilateral and heads straight to the cerebellum with no need of thalamus
• Proprioceptive pathway

  In general, proprioceptive information ascends as part of the DCML pathway.

  
  

  Some proprioceptive information enters the spinal cord through the dorsal roots and synapses at neurons in both the dorsal and ventral horn (stretch reflexes).

  
  

  Some first order neurons from the lower body that enter the spinal cord between the mid lumbar and thoracic levels synapse in Clarke's nucleus in the lumbar region, and then gors up to the thoracic region then goes up via dorsal spinocerebellar tract to the cervical spinal cord and then directly into the cerebellum and dorsal column nuclei.
• trigeminothalamic pathway structure?

  Trigeminal ganglion goes directly to the pons where it crosses over immediately and then goes up called the medial lemniscus(First order), then to the midbrain called the trigeminal lemniscus after that the VPM(Ventral posterior medial thalamus)(Second order), then the somatosensory cortex(Third order)
• trigeminothalamic pathway


  carries impulses for most somatic sensations from the face, nasal cavity, oral cavity, and teeth
• dorsal column-medial lemniscal system for body structure for the upper body?

  Mechanoreceptors starting from the upper body goes to the cervical spinal cord. Where it goes up ipsilateral to the caudal medulla called the cutaneous tract(First order neuron). In the caudal medulla it synapses in the cutaneous nuclei, and then crosses over. In which it goes to the rostral medulla, up to the pons called the medial lemniscus and the from the pons it synapses with the VPL(Ventral posterior lateral thalamus)(second order neuron), and then goes to the somatosensory cortex(Third order neuron)
• dorsal column-medial lemniscal system for body structure for the lower body?

  Mechanoreceptors starting from the lower body goes to the lumbar spinal cord, then goes ipsilateral to the caudal medulla called the gracile tract and then synapses in the medulla containing the gracile nucleus(First order neuron), then goes to the other side and goes to the rostral medulla and up to the pons(medial lemniscus) then to the VPL(ventral posterior lateral thalamus)(Second order neuron), where it then goes to the somatosensory cortex(Third order neuron)
• First, second and third order of neurons in the dorsal column-medial lemsiscal system for body?


  First order of neurons- Through dorsal column

  
  

  Second order of neurons- Medulla(nucleus gracilis and cuneatus) to thalamus via medial lemiscus

  
  

  Third order of neurons- Thalamus to somatosensory cortex
• How to differentiate between the dorsal column and the ventral column?

  In the dorsal column there are less amount of gray matter and it consists of 4 bumps along the edges.

  On the ventral column lies a deeper fissure and more gray matter
• Cross section of the spinal cord?

  Fasciculus gracilis and fasciculus cuneatus is locted in the dorsal column of the spine
• Dorsal column-medial lemiscal system

  Muscle fiber/touch to DRG, then to dorsal column. It goes up ipsilateral towards the medulla, where it crosses to the other side, and then goes to the thalamus and then the cortex.
• What is the name of the touch pathway?

  Dorsal column-medial lemiscal system
• How many neurons do sensory pathways have?

  3
• How is the golgi tendon formed?

  Branched of group Ib afferents
• What does golgi tendon organs do?

  Detect muscle tension
• What does having many or few spindles do?

  Many spindles requires precise control-

  While few spindles require coarse control,
• Extraocular muscles such as the eyes, and muscles in the neck and hand have?

  Many spindles
• Large muscles for coarse movements have?

  Few spindles
• Tension on intrafusal fibers are controlled by? and where is it located?

  Y motor neurons from the ventral horn
• What is group II?

  Myelinated fibers; slowly adapting- STRETCH
• What is group la?

  Large myelinated fibers that are rapidly adapting- STRETCH
• What type of afferent fibers are activated when stretching?

  Group la and Group II
• What do the muscle spindles do?

  monitor skeletal muscle length and trigger stretch reflexes- basically signal stretch
• What do proprioceptors do?

  detect stretch or tension
• What helps in proprioception?

  Golgi tendons organ, muscle spindles and joint receptors
• What is propriception?

  When our bodies are in space, msucle feedback to the CNS
• What is trigeminal ganglia?

  Sensory receptors for the face
• What is the dorsal root ganglia?

  cell bodies of sensory neurons of the body
• What are dermatome used for?

  It can determine the level of lesion of the spinal cord
• dermatome are?

  Area of skin supplied by a single spinal nerve
• What does deformation cause?

  It lowers the threshold
• What do rapidly adapting afferents show?

  Convey changes in ongoing stimulation
• What do slowly adapting afferents show?

  Convey spatial attributes such as size and shape
• Pacinian is fast or slow adapting

  Fast adapting