8. Brain to Gut and Gut to Brain Signalling Flashcards
name for the GUT’S OWN NERVOUS SYSTEM
ENTERIC NERVOUS SYSTEM (ENS)
has 100 million neurones (same as spinal cord)
by which NERVOUS PATHWAYS do the CNS and ENS COMMUNICATE
VAGUS NERVOUS PATHWAY
&
SPLANCHNIC NERVOUS PATHWAY
AFFERENT and EFFERENT NEURONES carry Signals between…
Afferent : GUT TO BRAIN
Efferent: BRAIN TO GUT
AFFERENT NEURONES from GUT TO BRAIN are:
VAGAL AFFERENTS and SPINAL AFFERENTS
EFFERENT NEURONES from GUT TO BRAIN are:
VAGAL EFFERENTS and SYMPATHETIC EFFERENTS
the SENSATION of FULLNESS is CARRIED in which NERVES
VAGUS NERVES
(proposed by Sir Arthur Hurst 1911)
PAINFUL SENSATIONS in the STOMACH are conveyed by which NERVE FIBRES
SYMPATHETIC
(NOT vagal)
(proposed by Sir Arthur Hurst 1911)
GI is CONTROLLED by which NERVOUS SYSTEM
AUTONOMIC NERVOUS SYSTEM
- Parasympathetic and Sympathetic nerves
what do VAGAL (PARASYMPATHETIC) EFFERENTS act VIA
ENTERIC NEURONS
what do SYMPATHETIC EFFERENTS act on
BLOOD VESSELS and ENTERIC NEURONS
PARASYMPATHETIC NERVES …. DIGESTION
STIMULATE
(rest and digest)
SYMPATHETIC NERVES … DIGESTION
INHIBIT
(flight or fight)
which GI NERVES are PARASYMPATHETIC
VAGUS and PELVIC
EXTRINSIC NERVES (OUTSIDE GUT) have what effect on the Digestive System
Speed up or Slow down
what are the 2 NERVE PLEXUSES in the GUT WALL
MYENTERIC PLEXUS (Auerbach’s)
SUBMUCOSAL PLEXUS (Meissner’s)
what do the MYENTERIC and SUBMUCOSAL PLEXUSES do
- SENSE LUMINAL CONTENTS
- CONTROL MUSCLES and GLANDS
where is the MYENTERIC PLEXUS in the GUT WALL
BETWEEN LONGITUDINAL and CIRCULAr LAYERS
where is the SUBMUCOSAL PLEXUS in the GUT WALL
BETWEEN the CIRCULAR and MUCOSA LAYERS
ENTERIC NEURONS CONTROL:
- MOTILITY
- SECRETION
- BLOOD FLOW
- potentially MUCOSAL GROWTH
how does the ENS WORK
AUTONOMOUSLY - without input from CNS
in communication with SYMPATHETIC and PARASYMPATHETIC NERVES
GASTRIC DISTENSION (stomach stretching) is DETECTED BY
MECHANORECEPTORS
INTESTINAL CELLS DETECT NUTRIENTS as food enters/passes through and DRIVE PRODUCTION of:
- HORMONES
- PARACRINE MEDIATORS
what causes the VAGAL AFFERENTS to send SIGNALS TO the BRAIN
GASTRIC DISTENSTION and INTESTINAL NUTRIENTS
- MECHANORECEPTORS and PARACRINE MEDIATORS
what is the RESPONSE of the BRAIN that is sent via VAGUS EFFERENTS
- REDUCE FOOD INTAKE (sense of fullness)
- DECREASED GASTRIC EMPTYING
- INCREASED PANCREATIC and GASTRIC SECRETIONS
- INCREASED GUT IMMUNE RESPONSES
how do GUT IMMUNE RESPONSES change from BRAIN RESPONSE to GASTRIC DISTENSION and INTESTINAL NUTRIENTS
INCREASE
what NERVES cause DECREASED FOOD INTAKE
VAGAL EFFERENTS (from brain)
in the INTERDIGESTIVE PERIOD what HORMONE RELEASE is stimulated and what does this CAUSE
GHRELIN release
- INHIBITS RESPONSE from VAGAL AFFERENT NEURONES
hence informs brain to EAT
GHRELIN INHIBITS..
VAGAL AFFERENTS RESPONSE to BRAIN (to decrease food intake)
-> INCREASE FOOD INTAKE (HUNGER)
What are the 3 PHASES of GASTRIC ACID SECRETIONS
- CEPHALIC
- GASTRIC
- INTESTINAL
what happens in the CEPHALIC PHASE of GASTRIC ACID SECRETION
SIGHT,SMELL, THOUGHT of FOOD TRIGGERS GASTRIC SECRETION
- INSTIGATED by VAGAL FIBRES
-> RELEASE of ACETYLCHOLINE (ACH) and GASTRIN RELEASING PEPTIDE to start acid secretion
in CEPHALIC PHASE what is RELEASED in order to START GASTRIC ACID SECRETION
ACH and GASTRIN RELEASING PEPTIDE
CEPHALIC PHASE INSTIGATED by which NERVE FIBRES
VAGAL FIBRES
what happens in the GASTRIC PHASE of GASTRIC ACID SECRETIONS
food entering STOMACH STRETCHES IT
- TRIGGERS SECRETION VIA LONG (VAGAL) and SHORT (MYENTRIC) REFLEXES
- RELEASE of GASTRIN
GASTRIN SECRETION in GASTRIC PHASE is triggered VIA which REFLEXES
LONG (VAGAL) and SHORT (MYENTERIC)
what happens in the INTESTINAL PHASE of GASTRIC ACID SECRETION
FOOD in INTESTINES INDUCES the RELEASE of HORMONES
- which ALTERS GASTRIC SECRETION-FEEDBACK
-> RELEASE of INHIBITORY FACTORS so GASTRIC ACID SECRETIONS FALL
which GASTRIC ACID PHASE has the HIGHEST OUTPUT
1ST, CEPHALIC
what causes INHIBITION in INTESTINAL PHASE
RELEASE or HORMONES and INHIBITORY FACTORS as food enters intestines
PAIN in the GUT is DERIVED from which NEURONS
SPLANCHNIC AFFERENT NEURONS
SPLANCHNIC NERVES are … nerves
PAIRED VISCERAL NERVES
VISCERAL EFFERENT (carry fibres of ANS)
VISCERAL AFFERENT (SENSORY fibres from Organs)`
ALL SPLANCHNIC NERVES carry SYMPATHETIC Fibres EXCEPT…
PELVIC SPLANCHNIC Nerves
- PARASYMPATHETIC FIBRES
GREATER SPLANCHNIC NERVES
ORIGIN:
GANGLION:
VISCERA:
REGION of referred PAIN:
ORIGIN: T5-T9
GANGLION: CELIAC
VISCERA: FOREGUT
REGION of referred PAIN: EPIGASTRIC
LESSER SPLANCHNIC NERVES
ORIGIN:
GANGLION:
VISCERA:
REGION of referred PAIN:
ORIGIN: T10/T11
GANGLION: SUPERIOR MESENTERIC
VISCERA: MIDGUT
REGION of referred PAIN: PERIUMBILICAL
LEAST SPLANCHNIC NERVES
ORIGIN:
GANGLION:
VISCERA:
REGION of referred PAIN:
ORIGIN: T12
GANGLION: AORTICO-RENAL
VISCERA: KIDNEYS
REGION of referred PAIN: LOWER THORACIC
LUMBAR SPLANCHNIC NERVES
ORIGIN:
GANGLION:
VISCERA:
REGION of referred PAIN:
ORIGIN: L1, L2
GANGLION: INFERIOR MESENTERIC
VISCERA: HINDGUT
REGION of referred PAIN: HYPOGASTRIC
GUT-DERIVED PAIN
NOCICEPTION EXAMPLES:
- HYPERALGESIA : INCREASED RESPONSE to PAINFUL STIMULI
- ALLODYNIA: PAINFUL RESPONSE to a NORMALLY INNOCUOUS (harmless) STIMULI
GUT-DERIVED PAIN
ACID-PEPTIDE RELATED EXAMPLES:
- HEARTBURN: REFUF of ACID into OESOPHAGUS
- PEPTIC ULCER in STOMACH, OESOPHAGUS, DUODENUM
GUT-DERIVED PAIN
DISTENSION EXAMPLE:
MECHANORECEPTOR RESPONSE to stretch is ABOVE THRESHOLD
(may feel bloated)
GUT-DERIVED PAIN
INFLAMMATORY BOWEL DISEASE
examples and what it includes
- CROHN’S
- ULCERATIVE COLITIS
INFLAMMATION SENSITISES SPINAL AFFERENT NEURONS
GUT-DERIVED PAIN
IRRITABLE BOWEL SYNDROME includes..
FEELINGS of distension, BLOATING, SWELLING, DISCOMFORT
- CONSTIPATION or DIARRHOEA
what is SATIATION
Prompts the TERMINATION OF EATING
- feel full
what is SATIETY
FULLNESS that PERSISTS AFTER EATING
what does SATIATION DETERMINE
the AMOUNT CONSUMED at ONE SITTING
what does SATIETY DETERMINE
the LENGTH of TIME UNTIL NEXT EATING OCCASION
what are the CELLS in the INTESTINE that RESPOND to LUMINAL NUTRIENTS
ENTEROENDOCRINE CELLS (EECs)
- approx 12 Cell types
- largest Endocrine Organ
How do the ENTEROENDOCRINE CELLS (EECs) STIMULATE SECRETIONS from the INTESTINES
cause INCREASE in INTRACELLULAR Ca2+
-> EXOCYTOSIS of SECRETORY VESICLES
what is SECRETED from INTESTINES in response to the ENTEROENDOCRINE CELLS (EECs) causing INCREASED CALCIUM
LIPID MEDIATORS and GUT HORMONES (REGULATORY PEPTIDES)
GUT HORMONE RECEPTORS are on what part of VAGAL AFFERENT NEURONS
NODOSE GANGLION
receptors transported from cell soma to peripheral
what does CCK HORMONE from GUT STIMULATE
PANCREATIC ENZYME SECRETIONS
& GALLBLADDER CONTRACTIONS
- PROMOTES SMALL INTESTINE DIGESTION
GANGLION on VAGAL AFFERENT NEURON that has RECEPTORS for GUT HORMONES
NODOSE GANGLION
what does CKK HORMONE INHIBIT
FOOD INTAKE and GASTRIC EMPTYING
VIA VAGAL AFFERENT NEURONS
FOOD INTAKE and GASTRIC EMPTRYING is INHIBITED VIA which NEURON
VAGAL AFFERENTS
what does GLP-1 (GLUCAGON-LIKE PEPTIDE) GUT HORMONE STIMULATE
INSULIN RELEASE post meal
- to DECREASE blood GLUCOSE
what does GLP-1 INHIBIT
FOOD INTAKE and GASTRIC EMPTYING
VIA VAGAL AFFERENT
in OBESITY, VAGAL AFFERENT NEURONS are INSENSITIVE to…
CCK
GLP-1 BASED THERAPY includes…
(type 2 diabetes)
DPP-IV Inhibitors which DELAY GLP-1 BREAKDOWN
(GLP-1 persists in blood for longer)
GLP-1 ANALOGUES which MIMIC the EFFECT of GLP-1
how does GLP-1 LEVELS CHANGE after BARIATRIC SURGERY
INCREASE
GLP-1 DECREASE what levels
BLOOD GLUCOSE
- by stimulating INSULIN
what does GHRELIN GUT HORMONE STIMULATE
FOOD INTAKE and GASTRIC EMPTYING
when is GHRELIN SECRETION HIGHEST
BEFORE a MEAL
(hunger)
where are GHRELIN RECEPTORS EXPRESSED
on VAGAL AFFERENT (NODOSE GANGLION) and HYPOTHALAMIC NEURONS
What does GHRELIN INHIBIT
ACTIONS of CKK on VAGAL AFFERENT NEURONS (which would normally inhibit food intake and gastric emptying)
which GUT HORMONES INHIBIT FOOD INTAKE
CCK and GLP-1
which GUT HORMONE acts on PANCREAS and GALLBLADDER
CCK
- pancreatic ENZYME secretions
- gallbladder CONTRACTS
which GUT HORMONE PROMOTES SMALL INTESTINE DIGESTION
CCK
which GUT HORMONE action (on vagal afferent) is INHIBITED by GHRELIN
CCK
how does GHRELIN INHIBIT CCK actions on VAGAL AFFERENT
RECEPTORS for ghrelin and CCK are on the SAME PLACE of NODOSE GANGLION (overlap)
