Somatosensory 3 Flashcards
Trigeminal nerve innervation
CN V most of the head
Facial nerve innervation
Facial nerve Cn VII : part of the ear
Glossopharyngeal nerve innervation
CN IX: throat
Spinal nerve C2
Part of pinna, cranial neck
Spinal nerve C3 innervation
Caudal neck
Branches of the trigeminal nerve
Ophthalmic
Maxillary
Mandibular
Sensory modalities of the trigeminal nerve
Touch, pain, temp, jaw position, muscle stretch
Trigeminal ganglion
In trigeminal canal of temporal bone
Contain neuron cell bodies from first order sensory neurons
Trigeminal sensory nuclei
3 sensory nuclei in the brainstem
Spinal - pain & temp
Pontine - light touch & proprioception
Mesencephalic - input from muscle spindles
First order neuron for trigeminal pathways
Processes in branches of CN V
Cell bodies in trigeminal ganglion
Synapse in trigeminal sensory nuclei in brainstem
Second order neurons in trigeminal pathways
Crosses midline
Ascends in the trigeminothalmic tract
Synapses in thalamus
Third Order neuron trigeminal pathways
Cell bodies in thalamus
Projects to primary sensory cortex
Somatosensory parts of VII and IX
First order neurons
cell bodies in separate ganglia associate w the cranial nerves
Second and third order neurons of VII and IX
Same as trigeminal
Visceral sensation
Sensory information from viscera (internal organs, heart, lungs stomach)
- can’t sense itch or temperature
Can sense stretch
Receptors of visceral sensation
Mechanoreceptors - stretch & distention
Chemoreceptors- pH, oxygen levels, CO2
Nociception - tissue damage, inflammation, ischemia
Visceral pain
Dull, aching pain
Poorly localized
- colic, pancreatitis, urinary obstruction, bowel obstruction
Visceral pain receptors
Free nerve endings w specialized ion channels
Opening channels cause depolarization (transient receptor potential)
If depolarization reaches threshold, action potential fires
Visceral pain pathways
Dual innervation of viscera
Somatic - spinal nerves
Autonomic - sympathetic: splenic nerves
Parasympathetic: vagus & sacral nerves
How signal is transmitted in visceral pain pathways
Signal ascends to the brain via the Spinothalamic and dorsal somatosensory pathways
Nociceptive or physiologic pain
Visceral or somatic pain
Caused by damage or potential damage to tissue
Neuropathic pain
Pain due to disease of nervous system
Burning, prickling, tingling
Can be central or peripheral
Causes of neuropathic pain
Trauma
Metabolic disease
Neurotoxic chemical
Infection
Tumor invasion
Mechanisms of neuropathic pain
Abnormal generation of action potentials by nociceptors
Decreased threshold for action potentials in first order neurons
Recognizing neuropathic pain
Constant chewing, biting, scratching at same spot
Spontaneous vocalization
Defensive to touch
Hypersensitivity - hyperalgesia, allodynia
Sensitivities for neuropathic pain
Loss of inhibitory interconnections in the spinal cord or brain
Activation or attack of the nervous system by immune cells
CNS sensitization to pain signals
Abnormal neural pathways
