GI Nervous System

ANS

Definition of ANS

The autonomic nervous system (ANS) is a system of motor neurons that innervate ? , ? and ?

ANS

The autonomic nervous system (ANS) is a system of motor neurons that innervate Cardiac muscle , smooth muscle and glands

SNS and PNSParasympathetic NS Sympathetic NS

Craniocaudal outflow Thoracolumbar outflow

Location on vertebra:a) CN III, VII, IX, Xb) Sacral spinal cord S2-4

Location on vertebra:a) T1- L2

Important Example:Vague NervePelvic Splanchnic Nerve

Important Example:Thoracic Splanchnic nerveLumbar Splanchnic Nerve

Long Preganglionic myelinatedShort Postganglionic unmyelinated

Short Preganglionic myelinatedLong Postganglionic unmyelinated

SNS and PNS• Somatic NS : 1 neuron

( from spinal cord to effector organ)

• ANS: 2 neurons ( from spinal cord to effector organ)– Parasympathetic : long

preganglionic, short post ganglionic

– Sympathetic: Short preganglionic, long postganglionic

All preganglionic axon myelinatedAll postganglionic axon demyelinated

NN: nicotinic cholinergic receptor M: muscarinic cholinergic receptor Alpha beta adrenergic receptors

SNS and PNSWhich is which?

Acetylcholine receptors: muscarinic and nicotinic

Muscarinic receptor Nicotinic receptor

All G protein coupledG proteins are activated

The response is either excitatory or inhibitory

All ligand gated ion channelNa+ ion channels open, which results in depolarization.The response is always excitatory

Slower response Faster response

Do not affect skeletal muscles Affect skeletal muscles

Adrenergic receptors:Alpha, Beta

• Epinephrine and Norepinephrine bind to adrenergic receptors

• When norepinephrine binds to adrenergic receptors, G proteins are activated.

• Response is either excitatory or inhibitory depending on target organ– ie α-receptors, which are mainly excitatory to

smooth muscles and gland cells but cause relaxation of intestinal smooth muscles

Splanchnic Nerves

Types Chemical Synapses

ANS Origin Target

Cardiopulmo Postsynap Symp Cervical and upper thoracic ganglia

Thoracic cavity ( ABOVE diaphragm)

Thoracica) Greaterb) Lesserc) Least

Presynapa) T5-T9b) T10-T11c) T12

Foregut, adrenal medullaMidgutKidney

Lumbar L1-L2 Hindgut: Distal 1/3 colon to rectum

Sacral Sacral part of sympathetic chain

Pelvic viscera (urogenital organs)

Pelvic Parasym S2-4 Hindgut: Distal 1/3 colon to rectum, Pelvic viscera

Pelvic Splanchnic Nerve

• This is parasympathetic nerve– Innervate distal 1/3 of the transverse colon, and

through the sigmoid and rectum, and pelvic viscera, sensation of pain.

• The proximal 2/3 of the transverse colon and the rest of the proximal GI tract is supplied by the vagus nerve

Summary of Foregut, Midgut and Hindgut

Foregut Midgut Hindgut

Sympathetic:Thoracic Greater Splanchnic Nerve

Sympathetic:Thoracic Lesser Splanchnic Nerve

Sympathetic:Lumbar Splanchnic Nerve

Parasympathetic:VAGUS Nerve

Parasympathetic:VAGUS Nerve

Parasympathetic:PELVIC SPLANCHNIC Nerve

Artery:Coeliac Artery

Artery:SMA

Artery:IMA

Referred Pain:Epigastrium

Referred Pain:Umbilicus

Referred Pain:Hypogastrium

Sacral Splanchnic Nerve?Sympathetic innervation for pelvic viscera

Visceral pain vs Parietal painVisceral Pain Parietal Pain

No somatic innervation Somatic Innervation

Poorly localized to the median plane (ie referred to the embryologic origin)

Well localized to the dermatome overlying the organ

Dull , colicky, cramping sharp pain

Visceral painEmbryological Origin

Anatomicals structures Arterial Supply Referred pain location

Foregut Esophagus until proximal duodenum

Coeliac artery Epigastric

Midgut Distal half duodenum until distal 2/3rd of transverse colon or splenic flexure of colon

SMA Umbilicus

Hindgut Distal 1/3rd transverse colon or splenic flexure of colon till proximal rectum.

IMA Hypogastric

Referred Pain

Explain why the pain from appendicitis appears to move?

• Site• Characteristic of pain• Pathology

Explain why the pain from appendicitis appears to move?

• Appendicitis begins as dull aching cramping periumblical pain

• Once the appendiceal inflammation becomes transmural, the parietal peritoneum becomes inflammed resulting in sharp pain localized in the area directly over the appendix at RIF

What are the 2 types of pain you just described about the moving pain in appendicitis?

• ?

What are the 2 types of pain you just described about the moving pain in appendicitis?

• Visceral pain• Parietal pain

What is the reason that could explain why parietal peritoneum pain is localized but poorly

localized in visceral peritoneum?

What is the reason that could explain why parietal peritoneum pain is localized but poorly

localized in visceral peritoneum?

• Parietal peritoneum shares somatic innervation with the abdominal wall

• Visceral peritoneum has no somatic nerve supple and so pain is poorly localized

What is the point with sharp localized pain directly above the appendix called?

• ?

Is the point right or left side of the abdomen?

How would you clinically determine this point?

• ?

• ?

What is the point with sharp localized pain directly above the appendix called?

• McBurney point

Is the point right or left side of the abdomen?

How would you clinically determine this point?

• Right

• 1/3 distance form ASIS to umbilicus

Stimulation of the greater splanchnic nerve produces:

a) Increased motility of the stomach & upper half of the small intestine. b) Inhibition of micturition. c) Increased blood levels of both glucose & catecholamines. d) V.C. of the blood vessels in the erectile tissue of both males & females. e) Increased secretion by both the stomach & pancreas.

Stimulation of the greater splanchnic nerve produces:

a) Increased motility of the stomach & upper half of the small intestine. b) Inhibition of micturition. c) Increased blood levels of both glucose & catecholamines. d) V.C. of the blood vessels in the erectile tissue of both males & females. e) Increased secretion by both the stomach & pancreas.

In the ANS, the preganglionic neurons synapse with postganglionic neurons in the

A)autonomic ganglia.B)brain stem.C)spinal cord.D)dorsal root ganglia.E)skeletal muscle cells.

In the ANS, the preganglionic neurons synapse with postganglionic neurons in the

A)autonomic ganglia.B)brain stem.C)spinal cord.D)dorsal root ganglia.E)skeletal muscle cells.

The effector organs for the somatic motor nervous system are

A)cardiac muscle.B)smooth muscle.C)glands.D)skeletal muscle.E)all of these

The effector organs for the somatic motor nervous system are

A)cardiac muscle.B)smooth muscle.C)glands.D)skeletal muscle.E)all of these

Which of the following characteristics apply to the ANS? 1. sometimes consciously controlled2. two neurons between the CNS and effector organs3. all neurons myelinated4. neurotransmitters can be acetylcholine or norepinephrineA)1,2B)1,3C)1,4D)2,3E)2,4

Which of the following characteristics apply to the ANS? 1. sometimes consciously controlled2. two neurons between the CNS and effector organs3. all neurons myelinated4. neurotransmitters can be acetylcholine or norepinephrineA)1,2B)1,3C)1,4D)2,3E)2,4

• The membranes of effector cells that respond to acetylcholine released from postganglionic neurons have

A)adrenergic receptorsB)muscarinic receptors.C)nicotinic receptor

• The membranes of effector cells that respond to acetylcholine released from postganglionic neurons have

A)adrenergic receptorsB)muscarinic receptors.C)nicotinic receptor

• When acetylcholine binds to nicotinic receptors, initially

A)Na+ ion channels open.B)G proteins are activated.C)K+ channels open.D)Cl- channels open.

• When acetylcholine binds to nicotinic receptors, initially

A)Na+ ion channels open.B)G proteins are activated.C)K+ channels open.D)Cl- channels open.

• When acetylcholine binds to muscarinic receptors,

A)Na+ ion channels openB)G proteins are activated.C)K+ channels open.D)Cl- channels open

• When acetylcholine binds to muscarinic receptors,

A)Na+ ion channels openB)G proteins are activated.C)K+ channels open.D)Cl- channels open

• When acetylcholine binds to nicotinic receptors, the response is

A)always excitatory.B)always inhibitory.C)either excitatory or inhibitory.

• When acetylcholine binds to nicotinic receptors, the response is

A)always excitatory.B)always inhibitory.C)either excitatory or inhibitory.

• When acetylcholine binds to muscarinic receptors, the response is

A)always excitatory.B)always inhibitory.C)either excitatory or inhibitory.

• When acetylcholine binds to muscarinic receptors, the response is

A)always excitatory.B)always inhibitory.C)either excitatory or inhibitory.

• When norepinephrine binds to adrenergic receptors, the response is

A)always excitatory.B)always inhibitory.C)either excitatory or inhibitory.

• When norepinephrine binds to adrenergic receptors, the response is

A)always excitatory.B)always inhibitory.C)either excitatory or inhibitory.

• Which of these structures is innervated almost entirely by the sympathetic division?

A)heartB)gastrointestinal tractC)urinary bladderD)blood vesselsE)reproductive organs

• Which of these structures is innervated almost entirely by the sympathetic division?

A)heartB)gastrointestinal tractC)urinary bladderD)blood vesselsE)reproductive organs