ANS and ENS

• What is the central nervous system composed of?

  The central nervous system is composed of the brain and spinal cord.
• What are the components of the reflex arc in the central nervous system?

  • Receptor
  • Afferent neurone
  • Efferent neurone (can be autonomic or somatic)
  • Muscle
• What is the function of somatic nervous system neurones?

  • Somatic neurones control movement and positioning of the skeleton
  • They run out from skeletal muscle
• Where is the cell body of somatic neurones located?

  The cell body of somatic neurones sits in the CNS, and the fibres run out to the end organ.
• What neurotransmitter is released at the motor end plate in skeletal muscle?

  Acetylcholine (Ach) is released and binds to nicotinic cholinergic receptors at skeletal muscle.
• What does ANS stand for?

  ANS stands for autonomic nervous system.
• What is the role of the autonomic nervous system (ANS)?

  • Part of the efferent division
  • Controls involuntary activities such as:
  • GI tract
  • Endocrine secretion
  • Cardiovascular responses
• From where does the ANS receive information?

  The ANS receives information from the spinal cord, brain stem, and hypothalamus.
• What role does the limbic cortex play in the ANS?

  The limbic cortex feeds information into the conserved areas of the brain that regulate the ANS.
• What types of efferent neurones are present in the ANS?

  Efferent neurones in the ANS can be sympathetic or parasympathetic.
• How does the ANS gather information from the periphery?

  The ANS picks up information from the periphery through receptors via afferent pathways fed into the CNS.
• How is the efferent pathway structured in the ANS?

  The efferent pathway in the ANS is made up of two neurones: pre-ganglionic and post-ganglionic neurones.
• What is a ganglion?

  A ganglion is a group of cell bodies that are not located in the CNS.
• What is the role of the pre-ganglionic neurone in the ANS?

  The pre-ganglionic neurone runs to a group of cell bodies in the periphery.
• What does the post-ganglionic neurone do in the ANS?

  The post-ganglionic neurone runs from the peripheral group of neuronal cells to the end organ.
• What is the structure of the efferent pathway in the ANS?

  • Made up of two neurones: pre-ganglionic and post-ganglionic
  • Contrasts with the somatic nervous system, which has only one neurone running out of the CNS
• What types of ganglia are found in the periphery of the ANS?

  • Para vertebral ganglia: sit close to the spinal cord
  • Prevertebral ganglia: located in the distal areas of the abdomen
• Where does the pre-ganglionic neurone sit in relation to the ganglia?

  The pre-ganglionic neurone sits within the CNS and makes contact with a second cell in the chain of ganglia.
• What type of fibres are myelinated in the ANS?

  Short fibres are myelinated (pre-ganglionic) and leave through the central region of the spinal cord.
• What type of fibres run from the end organ in the ANS?

  Long myelinated fibres (post-ganglionic) run out from the end organ.
• What is the significance of the chain of ganglia in the ANS?

  The chain of ganglia allows contact with multiple post-ganglionic fibres, resulting in a widespread response.
• From which regions does the sympathetic nervous system originate?

  The sympathetic nervous system comes from the thoracic and lumbar regions.
• What are the primary functions of the sympathetic nervous system (SNS)?

  • 4 F's: Fight, Flight, Freeze, and Faint
  • Mydriasis (dilation of the pupil)
  • Positive chronotropic effect (increase in heart rate)
  • Positive inotropic effect (increase force of contraction)
  • Positive dromotropic effect (increase speed of conduction)
  • Vasoconstriction to GI tract and vasodilation to legs
  • Bronchodilation
  • Decreased gastric motility
  • Increased sphincter tone
  • Glycogenolysis (breaking down glycogen)
  • Gluconeogenesis (producing glucose)
  • Bladder wall distension and constriction of bladder neck
• What is the effect of the sympathetic nervous system on heart rate?

  The sympathetic nervous system has a positive chronotropic effect, increasing heart rate.
• What is the positive inotropic effect of the sympathetic nervous system?

  The positive inotropic effect increases the force of contraction of the heart.
• What does the positive dromotropic effect refer to?

  The positive dromotropic effect refers to an increase in the speed of conduction in the heart.
• How does the sympathetic nervous system affect blood flow to the GI tract?

  The sympathetic nervous system causes vasoconstriction to the GI tract and vasodilation to other areas like the legs.
• What is the effect of the sympathetic nervous system on bronchial passages?

  The sympathetic nervous system causes bronchodilation.
• How does the sympathetic nervous system affect gastric motility?

  The sympathetic nervous system decreases gastric motility.
• What happens to sphincter tone under sympathetic nervous system activation?

  The sympathetic nervous system increases sphincter tone.
• What is glycogenolysis?

  Glycogenolysis is the breakdown of glycogen to free up energy.
• What is gluconeogenesis?

  Gluconeogenesis is the production of glucose.
• How does the sympathetic nervous system affect the bladder?

  The sympathetic nervous system causes bladder wall distension and constriction of the bladder neck.
• What is the role of the parasympathetic nervous system (PNS)?

  • Cranial and sacral outflow
  • Pre-ganglionic neurones are all in the CNS
  • Fibres run out to the end organ before making contact with post-ganglionic neurones
  • Ganglion embedded in the end organ
  • Activates one fibre, resulting in a localized response
• Where are the ganglia located in the parasympathetic nervous system?

  The ganglia are embedded in the end organ.