Lecture 3 Flashcards
What are the three types of control of the gut?
Neural, endocrine, local
What are the two types of reflex in neural control?
Long and short
What do long reflexes use?
The central nervous system (brain and spinal cord).
What are short reflexes controlled by?
The enteric nervous system
Describe the short reflex arc
A local stimulus activates receptors and afferent neurones which activate interneurons which activate efferent neurones of the myenteric or submucosal plexus which cause contraction or relaxation of muscles
Give some examples of hormones used in hormonal control
Secretin, CCk-Pz, gastrin, GIP
What is a secretagogue?
A substance that stimulates the secretion of a hormone
Give some examples of hormones released locally in the gut
Histamine, somatostatin, prostaglandins
What are the three time phases of GI tract control?
Cephalic, gastric, intestinal
What kind of reflex is in the cephalic stage?
Only long reflexes
What are the two types of head receptors?
Intraoral (mechanoreceptors and taste receptors in the mouth) and extraoral (nose, ears, sight)
What is the higher centre of the cephalic long reflex?
The medulla and integrating centre
What are the post-ganglionic fibres of the sympathetic system like?
Long
Which parasympathetic cranial nerves go to the salivary glands?
XII and IX: facial and glossopharyngeal
Which nerve goes to the stomach, gall bladder and pancreas?
Vagus nerve (X).
What is the long reflex stimulated during the gastric and intestinal phase?
Vago-vagal reflex.
What is the short reflex in the gastric and intestinal phase?
The entero-gastric reflex.
Where is gastrin released from?
G cells in the antrum. Target cell in parietal cells in the body.
Where is secretin released from?
S cells in the duodenum. Target organ is the pancreas to release bicarbonate secretion.
Where is CCk-Pz released from?
I cells in the duodenum. Target organ is gall bladder and pancreas to increase secretion
Where is GIP released from?
K cells in the duodenum and upper jejunum. Target is stomach and pancreas to decrease secretions.
