week 11 digestion

Question 1

Q1: What is the difference between the alimentary canal and accessory digestive organs ?

Answer 1

The alimentary canal is the continuous tube through which food passes while accessory organs (e.g. liver pancreas) assist digestion but food does not pass through them

Question 2

Q2: List the major organs of the digestive tract and their primary function

Answer 2

Mouth esophagus (ingestion/transport); stomach (breakdown); small intestine (digestion/absorption); large intestine (water absorption/feces); anus (elimination)

Question 3

Q3: Define peristalsis and segmentation

Answer 3

Peristalsis propels contents while segmentation mixes contents and enhances absorption

Question 4

Q4: Describe the main processes involved in digestion

Answer 4

Ingestion propulsion mechanical breakdown chemical digestion absorption defecation

Question 5

Q5: How does mechanical breakdown aid in digestion ?

Answer 5

It increases surface area for enzymes to work more efficiently

Question 6

Q6: What are the three main control systems of digestion and what does each regulate ?

Answer 6

Neural (ENS and ANS) controls motility and secretion hormonal control regulates secretion and myogenic control regulates muscle rhythm and contraction

Question 7

Q7: Explain how neural control regulates GI function

Answer 7

ENS controls local reflexes while ANS modifies ENS activity via parasympathetic (stimulatory) and sympathetic (inhibitory) signals

Question 8

Q8: Define myogenic control

Answer 8

It refers to the intrinsic rhythmic contraction of GI smooth muscle driven by interstitial cells of Cajal (ICCs)

Question 9

Q9: Which hormones are involved in hormonal control of digestion ?

Answer 9

Gastrin stimulates acid secretin stimulates bicarbonate and CCK stimulates bile and pancreatic enzymes

Question 10

Q10: How are internal stimuli like stretch or pH changes detected ?

Answer 10

They are detected by ENS sensory neurons (IPANs) that trigger reflexes to adjust motility and secretion

Question 11

Q11: Compare ENS and ANS roles

Answer 11

ENS independently manages digestion locally while ANS modulates ENS via inhibitory sympathetic and excitatory parasympathetic input

Question 12

Q12: Name the two ENS plexuses and their locations

Answer 12

Submucosal plexus lies beneath the mucosa and the myenteric plexus lies between muscle layers

Question 13

Q13: Functions of myenteric and submucosal plexuses ?

Answer 13

Myenteric controls motility while submucosal regulates secretion and blood flow

Question 14

Q14: Role of IPANs ?

Answer 14

They detect stretch and chemical cues and initiate local enteric reflexes

Question 15

Q15: How do interneurons and motor neurons support function ?

Answer 15

Interneurons relay ENS signals and motor neurons activate glands and muscle for GI responses

Question 16

Q16: What signals do ENS sensory neurons detect ?

Answer 16

They detect stretch pH levels and nutrients in the gut lumen

Question 17

Q17: Role of ICCs ?

Answer 17

They are gut pacemakers that generate rhythmic slow waves to coordinate motility

Question 18

Q18: Common ENS neurotransmitters/peptides ?

Answer 18

Excitatory signals include ACh and Substance P; inhibitory ones include VIP NO somatostatin and serotonin

Question 19

Q19: ICCs interact with ENS and muscle how ?

Answer 19

They receive input from ENS motor neurons and propagate slow waves to smooth muscle via gap junctions

Question 20

Q20: Smooth muscle structure and function ?

Answer 20

GI smooth muscle is organized in circular and longitudinal layers that contract in a coordinated manner due to gap junctions

Question 21

Q21: Parasympathetic effect on digestion ?

Answer 21

It stimulates smooth muscle contraction glandular secretion and overall GI activity

Question 22

Q22: Vagus and pelvic nerves: origins and targets ?

Answer 22

Vagus originates from the brainstem and targets upper GI; pelvic nerves arise from sacral spinal cord and target the distal colon and rectum

Question 23

Q23: Sympathetic effect on digestion ?

Answer 23

It inhibits motility reduces secretion and decreases GI blood flow

Question 24

Q24: Difference in fiber targets ?

Answer 24

Parasympathetic nerves usually act through ENS while sympathetic nerves can directly target GI effectors

Question 25

Q25: Significance of afferents in parasympathetic control ?

Answer 25

They provide sensory feedback to the brain about gut status like stretch and nutrient levels

Question 26

Q26: Short vs long reflexes ?

Answer 26

Short reflexes involve only the ENS while long reflexes involve the CNS and ANS

Question 27

Q27: Which reflex uses CNS ?

Answer 27

Long reflexes use CNS for integrated responses like the cephalic phase

Question 28

Q28: Example of cephalic phase reflex ?

Answer 28

Seeing or smelling food stimulates gastric secretion via the vagus nerve

Question 29

Q29: How do emotions affect digestion ?

Answer 29

Stress suppresses digestion while pleasant emotions enhance GI activity

Question 30

Q30: Importance of brain-gut communication ?

Answer 30

It allows integration of behavioral emotional and physiological control over digestion

Question 31

Q31: Hypothalamic role in appetite ?

Answer 31

The hypothalamus integrates hormonal and nutrient signals to regulate hunger and satiety

Question 32

Q32: Centers involved ?

Answer 32

The arcuate nucleus integrates signals VMN promotes satiety and LHA promotes hunger

Question 33

Q33: Short-term appetite regulators ?

Answer 33

Stretch receptors nutrients and gut hormones signal satiety to the brain

Question 34

Q34: Long-term regulators ?

Answer 34

Leptin and insulin signal long-term energy stores and suppress appetite via hypothalamic pathways

Question 35

Q35: How do ARC neurons affect appetite ?

Answer 35

NPY/AgRP neurons stimulate hunger while POMC/CART neurons promote satiety