Peripheral Nervous System

• the peripheral nervous system receives messages from receptors to the central nervous system and from the central nervous system to the muscles and glands
• the peripheral nervous system is composed of a group of cell bodies called ganglia
• types of nerves in the peripheral nervous system:

  • cranial nerves
  • spinal nerves
• cranial nerves


  part of the peripheral nervous system consisting of 12 pairs of nerves, mostly mixed nerves (both sensory and motor)

  includes optic (sensory), auditory (sensory), vagus (mixed), spinal accessory nerve (motor - controls muscle movement in the head, neck and shoulders)
• spinal nerves


  part of the peripheral nervous system consisting of 31 pairs of mixed nerves that arise from the spinal cord

  each nerve is joined to the spinal cord by two roots - dorsal (sensory neuron - entry) and ventral (motor neuron - exit) roots
• dorsal root


  contains axons of sensory neurons that have their cell bodies in a small swelling on the dorsal root known as the dorsal root ganglion
• ventral root


  contains axons of motor neurons that have their cell bodies in the grey matter of the spinal cord
• Peripheral nervous system


  Part of the nervous system that connects the central nervous system (CNS) to the rest of the body
• Efferent divisionof PNS


  Transports impulses away from the CNS
• Autonomic division of efferent PNS


  Transports impulses from CNS to cardiac muscle and involuntary muscles and glands

  structure - 2 pathways - 1st unmyelinated, 2nd myelinated, ganglion

  chemical - acetylcholine, adrenaline, noradrenaline

  effector - heart muscle, involuntary, muscles or glands
• Parasympathetic divisionod Autonomic division of efferent PNS


  Maintains the body during quiet conditions
• Sympathetic divisionof autonomic division of efferent PNS


  Transports impulses during strenuous physical activity
• Somatic division of efferent PNS


  Transports impulses from CNS to skeletal muscles

  structure - continuous and myelinated

  chemical - acetylcholine

  effector - skeletal muscles
• Afferent divisionof PNS


  Transports (sensory) impulses to CNS
• Visceral sensory neurons division of afferent PNS


  Sensory nerve cells that transport impulses from internal organs to CNS
• Somatic sensory neurons division of afferent PNS


  Transports impulses into CNS by sensory nerve cells from receptor in skin to muscles in joints
• divisions of the PNS

  • efferent
  • autonomic
  • parasympathetic
  • sympathetic
  • somatic
  • afferent
  • visceral sensory neurons
  • somatic sensory neurons
• efferent division of the PNS


  works without conscious control - regulated by medulla oblongata, hypothalamus and cerebral cortex

  involuntary movements/reflexes, and in control of homeostasis

  makes up spinal nerves and part of cranial nerves

  impulses are carried towards the heart, muscles and organs
• autonomic nervous system


  effectors:

  • heart muscle
  • involuntary muscle
  • glands

  function:

  • adjustment of internal environment

  efferent pathways:

  • 2 nerve fibres from CNS to the effector with a synapse in a ganglion

  neurotransmitter:

  • acetylcholine
  • noradrenaline
  • usually involuntary

  nerves to target organ:

  • 2 sets - sympathetic and parasympathetic

  effect on target organ:

  • excitation or inhibition
• somatic nervous system


  effectors:

  • skeletal (voluntary) muscle

  function:

  • response to external environment

  efferent pathways:

  • 1 nerve fibre from CNS to effector; no synapse, no ganglion

  neurotransmitter:

  • acetylcholine
  • usually voluntary

  nerves to target organ:

  • one set

  effect on target organ:

  • always excitation
• effect of sympathetic stimulation

  heart - increase rate and strength of contraction

  lungs - dilate bronchioles

  stomach and intestines - decrease movement

  liver - increase breakdown of glycogen

  iris of eye - dilates pupil

  sweat glands - increase sweat secretion

  salivary glands - decrease saliva secretion

  blood vessels of:

  • skin - constrict vessels
  • skeletal muscles - dilate vessels
  • internal organs (not heart and lungs) - constrict vessels

  urinary bladder - relax muscles of the wall

  adrenal medulla - stimulate hormone secretion
• effect of parasympathetic stimulation


  heart - decrease rate and strength of contraction

  lungs - increase movement

  stomach and intestines - increase movement

  liver - increase uptake of glucose and synthesis of glycogen

  iris of eye - constricts pupils

  salivary glands - increase saliva secretion

  blood vessels of:

  • skin - little effect
  • skeletal muscles - no effect
  • internal organs (not heart and lungs) - little effect

  urinary bladder - constricts muscles of wall
• sympathetic division of the ANS

  • fight or flight response
  • in case of emergencies which causes stress or requires us to euse fight or flight
  • originates in the spinal cord - thoracic and lumbar region
  • body needs to react or respond quickly
  • uses energy
  • increase blood pressure and heart rate
  • decrease digestion
  • neurotransmitter is noradrenaline
• parasympathetic division of the ANS

  • non-emergencies
  • originates in the brain and spinal cord
  • relaxes and saves energy
  • decrease blood pressure
  • increase digestion