Peripheral nervous system

• Peripheral Nervous System:

  • NS outside brain and spinal cord, carries sensory and motor information to and from the CNS.
• Somatic Nervous System:

  • Part of the PNS, responsible for voluntary control and carrying sensory and motor information to and from the CNS.
• Autonomic Nervous System:

  • Part of the PNS, responsible for brain’s involuntary activities and self-regulating. Divided into sympathetic and parasympathetic branches.
• The peripheral nervous system is made up of all the nerves outside the central nervous system. Its function is to relay nerve impulses from the CNS to the rest of the body and vice-versa.
• The somatic nervous system is made up of 12 pairs of cranial nerves - nerves which emerge directly from the underside of the brain.

  • In addition, it is also made up of 31 pairs of spinal nerves - nerves that emerge from the spinal cord.
  • Cranial and spinal nerves contain both sensory and motor neurons. Sensory neurons relay messages to the central nervous system, and motor neurons relay information from the CNS to other areas of the body.
  • The somatic nervous system also includes reflex actions, which don’t involve the brain, allowing the reflex to occur quickly
• The autonomic nervous system:

  • Some actions, such as walking or clenching your fist, are voluntary - you are conscious of what you are doing.
  • Other actions are carried out by your body without conscious awareness, such as your heart beating and your intestines being able to digest food. These involuntary actions are regulated by the autonomic nervous system.
• ANS:

  • The autonomic nervous system has two parts - the sympathetic nervous system and the parasympathetic nervous system. These divisions regulate the same organs but have opposite effects due to the neurotransmitters used in each.
  • The sympathetic nervous system uses noradrenaline, which has stimulating effects, whereas the parasympathetic nervous system uses acetylcholine, which has inhibiting effects.
• The sympathetic nervous system:

  • The sympathetic nervous system helps us to respond in emergencies, for example, by increasing our heart rate and blood pressure.
  • When the sympathetic nervous system is triggered, nerve impulses from the sympathetic nervous system travel to almost every organ and gland in the body, preparing them for rapid action necessary for when an individual is under threat.
  • It causes the body to release stored energy, and slow bodily processes that are less useful in emergency situations, such as digestion and urination
• The parasympathetic nervous system:

  • the parasympathetic nervous system relaxes an individual once a threat has passed. Whereas the sympathetic nervous system causes the heart to beat faster, for example, the parasympathetic nervous system will slow it down
  • Additionally, functions that had been slowed down under threat are able to resume again, such as digestion. Because the parasympathetic nervous system is involved in energy conservation and digestion, it is sometimes known as the ‘rest and digest’ system.
• Effects of parasympathetic nerves

  • Constrict pupils
  • Stimulate saliva
  • Constrict airways
  • Slow heartbeat
  • Stimulate stomach activity
• Effects of parasympathetic nerves:

  • Inhibit release of glucose, stimulate gallbladder
  • Stimulate activity in intestines
  • Contract bladder
  • Promote erection of genitals
• Effects of sympathetic nerves:

  • Dilate pupils
  • Inhibit salivation
  • Relax airways
  • Increase heartbeat
  • Inhibit stomach activity
• Effects of sympathetic nerves:

  • Stimulate release of glucose, inhibit gallbladder
  • inhibit intestine activity
  • Secrete epinephrine and norepinephrine
  • Relax bladder
  • Promote ejaculation and vaginla contraction
• CENTRAL NERVOUS SYSTEM (brain & spinal cord):

  Similarities

  • The brain stem and spinal cord both control involuntary processes (e.g. the brain stem controls breathing and the spinal cord controls involuntary reflexes).
• CENTRAL NERVOUS SYSTEM (brain & spinal cord):

  Differences (Spine and brain)

  • The brain provides conscious awareness and allows for higher-order thinking, while the spinal cord allows for simple reflex responses.
  • The brain consists of multiple regions responsible for different functions, whereas the spinal cord has one main function
• PERIPHERAL NERVOUS SYSTEM (somatic/ autonomic & sympathetic / parasympathetic):

  Similarities

  • The sympathetic nervous system (part of the autonomic nervous system) and the somatic nervous system respond to external stimuli.
  • The sympathetic nervous system responds to external stimuli by preparing the body for fight or flight and the somatic nervous system responds to external stimuli (by carrying information from sensory receptors to the spinal cord and brain).
• PERIPHERAL NERVOUS SYSTEM (somatic/ autonomic & sympathetic / parasympathetic):

  Differences

  • The autonomic nervous system consists of two sub-components, whereas the somatic nervous system has none.
  • The autonomic nervous system controls internal organs and glands, while the somatic nervous system controls muscles and movement.
• PNS:

  • The nerves outside the CNS. Relays nerve impulses from the CNS to the body, and from the body back to the CNS
• ANS:

  • governs the brain's involuntary activity. Made up of sympathetic NS (fight or flight) and parasympathetic (rest and digest)
• Somatic NS:

  • the part of the PNS responsible for carrying sensory and motor info to and from the CNS