Download L12: Regulation of digestion

Coordination & Control in Nutrition
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• Endocrine
System
• Nervous System
Regulation of Digestion
Lecture 12
Winter 2014
Fig. 40.6
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Endocrine System
Major Human Endocrine Glands
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Hormone
• Secreted into extracellular fluid
• Circulates in the blood or
hemolymph
• Communicates regulatory
messages throughout the body
Endocrine system
• Internal system of communication,
includes:
– Hormones
– Endocrine glands
• secrete hormones directly into surrounding
fluid
– Molecular receptors of hormones
Nervous System
Fig. 45.4
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• Reflexes
– Body’s automatic
responses to certain
stimuli
– Spinal cord acting
independently from
brain
– Involuntary response
Fig. 49.4
Peripheral Nervous System
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Autonomic nervous system
• Regulation of smooth &
cardiac muscles
• Mostly involuntary
• Sympathetic division
– “flight or fight”
• Parasympathetic division
– “rest & digest’
• Enteric division
– Digestive tract, pancreas,
gallbladder
– Secretion, peristalsis
See Fig. 49.7
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Sympathetic & Parasympathetic Divisions
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Control of Gastrointestinal Tract
• Endocrine & nervous systems
• Chewing
• Antagonistic
– Voluntary & reflexive
• Saliva secretion
– Nervous: chemoreceptors & pressure receptors
– Sight, smell, taste & chewing
• Swallowing
– Nervous: pressure receptors
• Peristalsis & relaxation/contraction of sphincters
Fig. 49.8
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Hormonal Control
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Hormonal Control
Gastrin
• Stimulus that inhibits release
Gastrin
• Secreted by stomach
• Stimulus for release
– Acid in stomach
– Amino acids, peptides
in stomach
– Parasympathetic
nerves (stomach
stretch)
• Stimulates
– Production of gastric
juices in stomach
Fig. 41.19
Fig. 41.12
Hormonal Control
Secretin
• Secreted by small
intestine (duodenum)
• Stimulus for release
– Acids in chyme
• Stimulates
– Release bicarbonate
from pancreas
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Hormonal Control
Cholecystokinin (CCK)
• Secreted by small
intestine
• Stimulus for release
– Amino acids, fatty
acids in small intestine
• Stimulates
– Release of enzymes
from pancreas
– Contraction of
gallbladder (release of
bile)
Fig. 41.19
Fig. 41.19
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Hormonal Control
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Hormonal Control
Cholecystokinin (CCK)
& Secretin
• Inhibits
– Acid secretion in
stomach
Fig. 41.19
Fig. 41.19
Storing Excess Calories
Fig. 45.11
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Control of Food Intake
• “satiety” signals
– Hormones
– Stretch and
chemoreceptors in
stomach & duodenum
• Smell, taste, texture
• Stress
Fig. 41.21
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Fig. 41.21
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Control of Food Intake
Control of Food Intake
• Leptin
• Secreted by adipose tissue
• Inhibitor
– High leptin levels =
suppressed appetite
– Low leptin levels =
increased appetite
• Acts on hypothalamus
– Increases metabolic rate
• Read Fig 41.22 What are
the roles of ob and db gene
in appetite regulation
Gherelin
• Secreted by stomach
– Increases prior to meal
– Decreases after meal
• Stimulates appetite
PYY (peptide YY)
• Secreted by small intestine
– Secreted after meals
• Suppresses appetite
Fig. 41.21
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Control of Food Intake
Regulation of Blood Glucose Levels
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• movie
Insulin
• Secreted by pancreas
– Islets of Langerhans
• Stimulus for release
– Rise in blood sugar levels
• Suppresses appetite
• Works with glucogon to
regulate blood glucose
levels
Fig. 45.12, see
Fig 41.20
Fig. 41.21
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Regulation of Blood Glucose Levels
Regulation of Blood Glucose Levels
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• Glucose and
insulin
Fig. 45.12, see
Fig 41.20
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Regulation of Blood Glucose Levels
Diabetes mellitus
• Type 1 (insulin dependent diabetes)
– Immune system destroys beta cells
– No production of insulin
• Type 2 (non-insulin dependent)
– Target cells fail to respond normally to insulin
– Increase weight and lack of exercise increase
risk of Type 2
Mutualistic Adaptations
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• Animals do not produce enzyme for
digesting cellulose
• House microorganisms (bacteria, protists)
that can break down cellulose
– Mutualistic symbiosis
• Benefits both parties
• Location varies
– Cecum, crop, large intestine
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Mutualistic Adaptations
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Fig. 41.18
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