Download THE CONTROL OF DIGESTIVE SECRETIONS

THE CONTROL OF DIGESTIVE
SECRETIONS
By NALAN IZZIGIL
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.
THE CONTROL OF DIGESTIVE
SECRETIONS
 WHICH TWO SYSTEMS ARE INVOLVED IN THE
CONTROL OF DIGESTION?
1) The Nervous system
2) The Hormonal system
1) THE NERVES WHICH CONTROL THE
DIGESTIVE SYSTEM
a) Extrinsic nerves
b) Intrinsic nerves
These two types of nerves do different
jobs in the digestive system
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.
b) INTRINSIC NERVES
 DEFINITION:
Intrinsic: internal/on
the inside.
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.
2) THE HORMONES WHICH CONTROL
THE DIGESTIVE SYSTEM
 WHICH ARE THE THREE HORMONES THAT ARE
SECRETED WHICH CONTROL DIGESTION?
a) Gastrin
b) Secretin
c) Cholecystokinenin-pancreozymin (CCKPZ)
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.
b) SECRETIN
 Released when
chyme reaches the
duodenum.
 Stimulates the
pancreas to release
HCO3- ions.
 Stimulates bile
production in the liver.
c) CHOLECYSTOKINENINPANCREOZYMIN
 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.
THE HORMONES SECRETED IN THE
CONTROL OF DIGESTION
Gastrin, Secretin and Cholecystokineninpancreozymin 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.
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.
TYPES OF REFLEX
1) SIMPLE REFLEXES
Cannot be controlled or learnt
Happen subconsciously
Controlled by parasympathetic nervous
system
2) CONDITIONED REFLEXES
Learnt through association
A SIMPLE REFLEX
 Occurs on the inside
of the body whilst
eating, without the
person knowing.
A CONDITIONED REFLEX
REFERENCES
www.tow.com/.../thumbs/2003-0712_1939-01.jpg
www1.istockphoto.com/file_thumbview_ap
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