T3.5 peripheral nervous system

• Peripheral nervous system


  Comprised of all nervous tissue outside the CNS
• Components of the peripheral nervous system

  • Cranial nerves arising from the brain (12 pairs)
  • Spinal nerves arising from the spinal cord (31 pairs)
  • Ganglia - the clusters of neuron cell bodies located along the nerves
• Function of cranial nerves, spinal nerves and ganglia

  • Transmit sensory info from receptors to CNS and transmit motor info from CNS to muscles, organ and glands
• Somatic nervous system

  Nerves transmitting information to skeletal muscle (voluntary and conscious)
• Autonomic nervous system

  Nerves transmitting information to cardiac muscle, organs and glands to maintain homeostasis (involuntary and unconscious)
• Divisions of the autonomic nervous system

  • Sympathetic
  • Parasympathetic
• Sympathetic division

  Maintains homeostasis during time of stress or periods of exercise, concerned with release of nutrients from stores to fuel activity, often called fight or flight
• Parasympathetic division

  Maintains homeostasis when body is at rest, primarily concerned with energy conservation and nutrient replenishment, often called rest and digest division
• Stimulus

  Detectable change in internal or external environment that acts on appropriate receptor or receptor to produce nerve impulse
• Sensation

  Registration of stimuli, generation of sensory info and its transmission to the CNS for processing and possible response
• Sensory pathways

  1. Sensory neurons in the periphery

  2. Sensory tracts in the spinal cord

  3. Specific regions in the brainstem and brain
• Major sensory pathways from the periphery to the brain

  • Fine touch, proprioception, and two-point discrimination (also known as the dorsal column medial lemniscus pathway)
  • Temperature and pain (also known as the spinothalamic pathway)
• Descending pathways


  1. Motor signals originate in frontal lobe, specifically primary motor cortex

  2. Signals travel down upper and lower motor neurons

  3. Trigger response in effector structure
• Reflex

  Sending sensory signal into spinal cord, synapsing with lower motor neuron, and sending reflexive motor signal out
• Cranial nerves


  • I Oh- olfactory some smell
  • II Oh- optic say vision
  • III Oh- oculomotor marry eye movement
  • IV To- trochlear money eye movement
  • V Touch- trigeminal but face sensation, jaw movement
  • VI An- abducens my eye movement
  • VII Feel- facial brother taste anterior 2/3 of tongue, face movement
  • VIII Very- vestibulocochlear says hearing and balance
  • IX Good- glossopharyngeal big taste posterior 1/3 of tongue, swallow
  • X Velvet- vagus brains heart, lungs, gastro intestinal tract
  • XI Ah- accessory matter spinal, shrug shoulders
  • XII Heaven- hypoglossal most tongue movement
• Spinal nerves


  • 8 pairs of cervical nerves (C1-C8)
  • 12 pairs of thoracic nerves (T1-T12)
  • 5 pairs lumber nerves (L1-L5)
  • 5 pairs sacral nerves (S1-S5)
  • 1 coccygeal nerve (Co1)
• Spinal nerves


  Mixed nerves, capable of transmitting both sensory information to CNS and motor info from CNS
• Autonomic nervous system

  Operates under level of consciousness (not consciously controlled), responsible for maintaining homeostasis, regulates physiological processes necessary
• Regulation by the autonomic nervous system

  • Heart rate, blood pressure, body temperature, digestion and sweating
• Autonomic nervous system pathway

  Employs 2 neuron pathway to connect with peripheral effectors, neurons synapsing in peripheral autonomic ganglion
• CNS structures regulating the autonomic nervous system


  • Hypothalamus
  • Brainstem
  • Spinal cord