Primary afferent neurons of the gut (消化道初级感觉神经元) Function: Monitoring and control of the digestive system, including generating appropriate reflex response to the gut lumen contents Participates in reflexes between organs s Convey signals from digestive organs to the CNS Trigger reflex Co-ordination with other body system Relate to sensation including discomfort, nausea, pain and satiety
1 Primary afferent neurons of the gut （消化道初级感觉神经元） Function: Monitoring and control of the digestive system, including: ❖ Generating appropriate reflex response to the gut lumen contents ❖ Participates in reflexes between organs ❖ Convey signals from digestive organs to the CNS – ➢ Trigger reflex ➢ Co-ordination with other body system ➢ Relate to sensation including discomfort, nausea, pain and satiety
Primary afferent neuronS: Extrinsic primary afferent intrinsic and extrinsic neurons, including 内源性和外源性 Vagal primary afferent neuron Stem Have cell bodies in(nodose and gular) ganglia神经节 vagal Primary AFferent Neuron nal com >Spinal primary afferent neuron Immune and Tissue Defence Sanas Intestnofuga Neuron Local and Systemie spinal Primary v have cell bodies in dorsal root Afferent Neuron Endocine Hormones Local and Circulating ganglia ☆ Intestinofugal neuron肠离心神 Intrinsic Pfimary Ameren Neurons Parts of the afferent limbs of Luminal stimulants Buk artoens nutrents entero-enteric reflex pathways talants emmert secretions Have cell bodies in en
2 intrinsic and extrinsic 内源性和外源性 Primary afferent neurons：❖Extrinsic primary afferent neurons, including: ➢Vagal primary afferent neuron ✓have cell bodies in (nodose and jugular) ganglia 神经节 ➢Spinal primary afferent neuron ✓ have cell bodies in dorsal root ganglia ❖Intestinofugal neuron 肠离心神 经元 ➢Parts of the afferent limbs of entero-enteric reflex pathways ➢Have cell bodies in ENS
Intrinsic primary afferent neurons IPANs, within ENS Spinal Cord > Myenteric肌间PANs: respond V Distortion of their processes in the external muscle layers Intrinsic Prmary Afferent Neurons AMeren Neurons v changes in luminal chemistry, via MP processes in the mucosa, Mucosal Chemical Intestinouga Mechano- sCeNE senstve cM> submucosal粘膜下 PANS Neuro detect SM Mechanical distortion of the mucosa Luminal chemistry LM, longitudinal muscle; CM, circular muscle; MP, myenteric plexus; SM submucosa; Muc, mucosa. Nerve endings in the mucosa can be activated by hormones released from entero-endocrine cells(arrows)
3 ❖Intrinsic primary afferent neurons, IPANs, within ENS ➢Myenteric 肌间 IPANs: respond to ✓Distortion of their processes in the external muscle layers ✓changes in luminal chemistry, via processes in the mucosa, ➢submucosal 粘膜下 IPANs detect: ✓Mechanical distortion of the mucosa ✓Luminal chemistry. LM, longitudinal muscle; CM, circular muscle; MP, myenteric plexus; SM, submucosa; Muc, mucosa. Nerve endings in the mucosa can be activated by hormones released from entero-endocrine cells (arrows)
I Intrinsic Primary Afferent Neurons and Nerve circuits within the intestine Reference Furness JB, Jones C,, Nurgali K, Clerc N. Intrinsic primary neurons and nerve circuits within the intestine Progressin Neurobiology 2004, 72: 143-164
4 I Intrinsic Primary Afferent Neurons and Nerve Circuits within the Intestine Reference: Furness JB, Jones C., Nurgali K., Clerc N. Intrinsic primary neurons and nerve circuits within the intestine. Progress in Neurobiology 2004, 72: 143 - 164
1. Types of neurons that form enteric nerve circuits According to the ☆ functions, ☆ key transmitters 9 projections to targets
5 1. Types of neurons that form enteric nerve circuits According to the ❖ functions, ❖ key transmitters ❖ projections to targets
NAL Myenteric neurons 4o 9 10 (1) Ascending interneurons( 5%) (2) Myenteric intrinsic primary fferent neurons(26%) Arte M Gland () Intestinofugal neurons(<1%) (4)Excitatory longitudinal muscle LM: longitudinal muscle: MP: myenteric motor neurons(25%) plexus; CM: circular muscle; SM submucosal plexus: Muc: mucosa 5)Inhibitory longitudinal muscle motor neurons(2% (8)Descending interneurons local reflex(5%) (6) Excitatory circular muscle motor neurons(12%) (9)Descending interneurons(2%) secretomotor reflex (7 Inhibitory circular muscle motor neurons(16%) (10) Descending MMC interneurons(4%)
6 LM: longitudinal muscle; MP: myenteric plexus; CM: circular muscle; SM: submucosal plexus; Muc: mucosa. Myenteric Neurons (1) Ascending interneurons( 5%) (2) Myenteric intrinsic primary afferent neurons (26%) (3) Intestinofugal neurons (<1%) (4) Excitatory longitudinal muscle motor neurons (25%) (5) Inhibitory longitudinal muscle motor neurons (2%) (6) Excitatory circular muscle motor neurons (12%) (7) Inhibitory circular muscle motor neurons (16%) (8) Descending interneurons local reflex (5%) (9) Descending interneurons (2%): secretomotor reflex (10) Descending MMC interneurons (4%)
NAL Submucosal neurons 4o 9 10 (II) Submucosal intrinsic primary cH afferent neurons(11%) sM(12) Non-cholinergic Arte M secretomotor/vasodilator neurons Gland (45%) (13 )Cholinergic LM: longitudinal muscle: MP secretomotor/vasodilator neurons myenteric plexus; CM: circular muscle SM: submucosal plexus: Muc: mucosa (15%) 14) Cholinergic secretomotor (non-vasodilator) neurons(29%)
7 LM: longitudinal muscle; MP: myenteric plexus; CM: circular muscle; SM: submucosal plexus; Muc: mucosa Submucosal Neurons (11) Submucosal intrinsic primary afferent neurons (11%) (12) Non-cholinergic secretomotor/vasodilator neurons (45%) (13) Cholinergic secretomotor/vasodilator neurons (15%) (14) Cholinergic secretomotor (non-vasodilator) neurons (29%)
2. Characteristics of intrinsic primary afferent neurons (IPANs) ☆ Shape: round or oval Synaptic Modulation 么-☆ Processes: multi- axonal or Axon Refe pseudounipolar(假单极) Transmisson to Transcellular oter neurons Conduction s☆ gnal Conduction >traverse the cell bodies M (transcellular conduction) >can be conducted to output synapses via an axon reflex(axon reflex onduction) transcellular conduction can be modified by the ynaptic inputs that it receives
8 2. Characteristics of intrinsic primary afferent neurons (IPANs) ❖Shape: round or oval ❖Processes: multi-axonal or pseudounipolar(假单极) ❖Signal Conduction: ➢traverse the cell bodies (transcellular conduction) ➢can be conducted to output synapses via an axon reflex (axon reflex conduction). ➢ transcellular conduction can be modified by the synaptic inputs that it receives
2. Characteristics of IPANs-Conti Communication 10 >with other neurons in the @书 myenteric and submucosal Arteriole Mud ganglia Gland 2 Myenteric intrinsic primary afferent neurons(26%)
9 2. Characteristics of IPANs- Conti ❖Communication: ➢with other neurons in the myenteric and submucosal ganglia. 2 Myenteric intrinsic primary afferent neurons (26%)
2. Characteristics of intrinsic afferent neurons - Conti Ca hump (N-type channel gNa. (TTX. Early AHP Na、( non TTx gca ADP Late AHP gCAN g(K, Na (IK channels (Caesium ☆ Electrophysiology K。,BK AHP current) IH current delayed rectifier Broad action potential carried by both sodium and calcium current >Followed by early and late(slow )afterhyperpolarizing potential AHP
10 2. Characteristics of intrinsic afferent neurons- Conti ❖Electrophysiology ➢Broad action potential carried by both sodium and calcium current ➢Followed by early and late (slow) afterhyperpolarizing potential (AHP)