Week 1 - Control of Digestive Tract
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Name the main cranial nerve involved in regulating the digestive system
Vagus Nerve (X) ((10))
What does Vagus Nerve X stimulate and supply?
Supplies parasympathetic fibers to most of the GI tract. It stimulates digestive secretions & motility
State the autonomic system that stimulates the digestive system
Parasympathetic nervous system
Name the two main reflexes that affect motility in the intestines
• Gastroileal reflex - Gastrocolic reflex
State the stimulus for the Gastroileal reflex
• Initiated when the stomach is distended (presence of food in the stomach)
State the stimulus for the Gastrocolic reflex
Initiated when the stomach is distended. It stimulates mass peristalsis in the colon to move faeces into the rectum
State the effect of the Gastroileal reflex
It intensifies peristalsis in the small intestine so chyme is moved into the caecum.
State the effect of the Gastrocolic reflex
Occurs during or after a meal & drives faeces into the rectum.
State the location of the Gastroileal reflex
In the stomach, and the junction of the small and large intestines (Caecum)
State the location of the Gastrocolic reflex
In the stomach and the colon
Describe the defecation reflex using the components of the reflex arc (STIMULUS)
As faeces moves into the rectum it causes distension of rectum, this stimulates stretch receptors in the rectal wall
Describe the defecation reflex using the components of the reflex arc (CONTROL CENTRE)
Reflex located in the sacral spinal cord
Describe the defecation reflex using the components of the reflex arc (EFFECTORS)
• Lower colon & rectal wall contracts • Internal anal sphincter relaxes • External anal sphincter is under voluntary control
State 2 situations that impact on the functioning of the defecation reflex
• If there is insufficient bulk or lack of faeces • Elimination of faeces cannot occur if there is damage to the neurons involved in the reflex arc or nerves that control the external anal sphincter
What are the 5 effects of ageing on the digestive system
• Decreased gustation & olfaction impact on the pleasure associated with food • Altered dental function resulting in decreased biting & chewing • Decreased secretion of digestive enzymes limits digestive functions • Decreased motility & loss of smooth muscle tone • Decreased neural & hormonal control
Describe ‘Decreased gustation & olfaction impact on the pleasure associated with food’ in ageing of the digestive system
Many older persons have reduced appetite & require smaller portions due to decreased activity
Describe ‘Altered dental function resulting in decreased biting & chewing’ in ageing of the digestive system
• Increased risk of gum disease if unable to attend to oral hygiene • Poorly fitting dentures
Describe ‘Decreased secretion of digestive enzymes limits digestive functions’ in ageing of the digestive system
Inadequately digested food results in decreased nutrition
Describe ‘Decreased motility & loss of smooth muscle tone’ in ageing of the digestive system
• May result in delayed passage of chyme & faeces • Increased risk of constipation (also associated with decreased intake of food & fluids & activity levels) • May have altered voluntary control of external anal sphincter resulting in faecal incontinence
Absorption of nutrients occurs primarily where?
Small intestine
Where does digestion begin?
Mouth
Where does most carbohydrate digestion take place?
Small intestine
Where is the cystic duct attached too?
Gallbladder
Where do the ducts of the pancreas and liver connect to the digestive tract?
Duodenum