Anatomy of the GI tract part 3

Question 1

central nervous system

Answer 1

composed of brain and spinal chord

Question 2

peripheral nervous system

Answer 2

connects CNS to limbs and organs

Question 3

autoonomic nervous system

Answer 3

division of PNS influencing function of organs

Question 4

enteric nervous system

Answer 4

intrinsic nervous system of the GI tract

Question 5

how is the CNS and ENS connected

Answer 5

• vagus nerve

Question 6

what is the significance of serotonin

Answer 6

• neurons are present in both brain and gut producing neurotransmitters like serotonin (5-HT)
• serotonin
  
  • mood control, depression, agression
  • found at higher levels in intestine, notbrain
• could be reason why antidepressant, which raise serotonin levels in brain, are sometime ineffective in treating depression, whereas proper dietary changes can help
  
  • also why side effects occur in gut and the drug is not selective

Question 7

where is the eneteric nervous system found

Answer 7

• wall of GI tract from oesophegus to anus

Question 8

Myenteric (Auerbach’s) Plexus

Answer 8

• largely motor in function
• influeces muscle activity

Question 9

submucosal (Meissner’s) Plexus

Answer 9

• largely sensory
• receiving signals from epithelium and stetch receptors influencing secretory activity

Question 10

How is the enteric nervous system regulated?

Answer 10

• subject to regulation via the (Peripheral) Autonomic Nervous System (PNS and SNS)
• since fibres from both synapse with neuronones in the enteric nervous system (cross talk)
• thus CNA can influence GI tract activity

Question 11

afferent neurons

Answer 11

• sensory receptor neurons
• carry nerve impulses away from receptors or sense organs towards the CNS

Question 12

efferent nerves

Answer 12

• motor or effector neurons
• carry nerve impulses away from the CNS to effectors such as muscles or glands

Question 13

What activates nerve plexuses linked to CNS via afferent fibres?

Answer 13

• stretch
• chemical stimulation

Question 14

How does the GI tract receive efferent innervation from the ANS

Answer 14

• parasympathetic input
  
  • rest and digest
  • stimulates gut motility and secretory actiity
• sympathetic nerves
  
  • fight and flight
  • cause presynaptic inhibition of parasympathetic-induced contraction

Question 15