the control of digestive secretions by nalan izzigil
TRANSCRIPT
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THE CONTROL OF DIGESTIVE SECRETIONS
By NALAN IZZIGIL
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PRESENTATION PLAN
The nervous and hormonal systems.Nerves which control the digestive system
(Extrinsic & Intrinsic nerves).Hormones which control the digestive
system (Gastrin, Secretin, CCK-PZ).Differences between nervous & hormonal
control.Simple & conditioned reflexes.
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THE CONTROL OF DIGESTIVE SECRETIONS
WHICH TWO SYSTEMS ARE INVOLVED IN THE CONTROL OF DIGESTION?
1) The Nervous system2) The Hormonal system
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1) THE NERVES WHICH CONTROL THE DIGESTIVE SYSTEM
a) Extrinsic nervesb) Intrinsic nerves
These two types of nerves do different jobs in the digestive system
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a) EXTRINSIC NERVES
DEFINITION: Extrinsic: external/on the outside
Come to the digestive organs from the subconscious part of the brain and the spinal cord.
Chemical transmitters of the hormones acetylcholine and adrenaline.
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b) INTRINSIC NERVES
DEFINITION: Intrinsic: internal/on the inside.
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b) INTRINSIC NERVES
Act when the walls of the digestive system are stretched by food.
Trigger the release of hormones and of digestive juices.
Make up a very dense network.
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2) THE HORMONES WHICH CONTROL THE DIGESTIVE SYSTEM
WHICH ARE THE THREE HORMONES THAT ARE SECRETED WHICH CONTROL DIGESTION?
a) Gastrinb) Secretinc) Cholecystokinenin-pancreozymin (CCK-
PZ)
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a) GASTRIN
Stimulated by food expanding the stomach wall. It is the primary regulator of digestion.
Gastrin brings about the secretion of Hydrochloric acid (HCl) and of pepsinogen.
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b) SECRETIN
Released when chyme reaches the duodenum.
Stimulates the pancreas to release HCO3- ions.
Stimulates bile production in the liver.
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c) CHOLECYSTOKINENIN-PANCREOZYMIN
Released by the presence of fatty foods in the small intestine.
Stimulates bile to be produced.
Increases the amount of digestive enzymes that the pancreas release.
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THE HORMONES SECRETED IN THE CONTROL OF DIGESTION
Gastrin, Secretin and Cholecystokinenin-pancreozymin are only secreted when food is present in the digestive system.
Released by the cells in the mucosa of the stomach and the small intestine.
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DIFFERENCES BETWEEN NERVOUS & HORMONAL CONTROL
HORMONAL CONTROL NERVOUS CONTROL
RELEASES Hormones/Chemicals Nevous/electrical impulses
CARRIED BY Glands Chemical transmitters
AMOUNT OF TIME NEEDED TO WORK
Long time Quick-acting
HOW LONG THE EFFECTS LAST
Long time Short-lived
RESPONSE Can bring about several responses
Acts specifically
EXAMPLE A single hormone can bring about several different responses
Very specific - some act on single muscle
fibres
ONE OF THE MAIN ROLES OF THE NERVOUS SYSTEM IN DIGESTION IS TO STIMULATE THE RELEASE OF HORMONES.
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TYPES OF REFLEX
1) SIMPLE REFLEXESCannot be controlled or learntHappen subconsciouslyControlled by parasympathetic nervous
system
2) CONDITIONED REFLEXESLearnt through association
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A SIMPLE REFLEX
Occurs on the inside of the body whilst eating, without the person knowing.
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A CONDITIONED REFLEX
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REFERENCES
www.tow.com/.../thumbs/2003-07-12_1939-01.jpg
www1.istockphoto.com/file_thumbview_approve/1