case 10 Flashcards
long reflex in CNS
classix reflex begins with stimulus transmitted along a sensory neuron to CNS, where the stimulus is integrated + acted on.
disgestive reflexes integrated into CNS are long reflexes.
cephalic reflexes
outside of digestive system (emotional, reflexes –> sight, smell)
originate in the brain
short reflexes in enteric nervous system
enteric nerve plexus in gut act as little brain. reflexes begin and integrate and end completely in GI tract.
reflexes that originate in enteric system and integrated without outside input are short reflexes.
ENS can work in isolation, also coordinates with ANS bringing signals from CNS.
processes: motility, secretion, growth.
ENS integrates sensory information obtained by submucosal plexus in lumen of gut, and initiates responses through submucosal neurons that control secretion by GI epithelial cells. ENS works through neurons in myenteric plexus to influence motility.
reflexes with GI peptides
peptides may act as hormones/paracrine signals. secreted into blood and act on GI tract/brain.
paracrine molecules in ECF act locally.
peptides excite/ inhibit motility + secretion.
enteric nervous system
main divisions of ANS and consists of mesh-like system of neurons that governs function of GI tract. ENS functions autonomously, independent of efferent signals from CNS. shares many features with CNS
- intrinsic neurons
- neurotransmitters + neuromodulators
- glial support cells
- diffusion barrier
- integrating center
intrinsic neurons
of the two nerve plexuses of GI tract are those that lie within the wall of the gut. interneurons are completely contained within CNS. 3 types: sensory, inter + motor
extrinsic neurons
autonomic neurons that bring singals from CNS to digestive system
neurotransmitters + neuromodulators
ENS neurons release these. somtimes called: nonadrenergic, noncholinergic to distinguish them from norepinephrine and acetylcholine
glial support cells
glial cells of neurons within ENS are similar to astroglia than Schwann cells
diffusion barrier
capillaries that surround ganglia in ENS not very permeable and create diffusion barrier similar to blood-brain barrier of cerebral blood vessels
integrating center
reflexes that originate in GI tract can be integrated and acted on without neural signals leaving ENS. neuron network of ENS is its own integrating center
ENS plexuses
- submucosal nerve plexus: ascending + descending connected to mucosa + circular muscle. sense and secretes
- myenteric nerve plexus: ascending + descending connected to cirular + longitudinal smooth muscle, controls motility of intestines.
noradrenergic
parts of body that produce/are effected by norepinephrine. function is to mobilize the brain and body for action. inhibits voiding of bladder and gastrointestinal motility.
cholinergic
abbreviated term of referring to acetylcholine. parasympathetic nervous system, which uses ACh almost exclusively to send its messages, is said to be almost entirely cholinergic.
Auerbach/myenteric plexus
located between inner circular and outer longitudinal smooth muscle layer. regulate peristaltic waves that move digestive products. control local muscular contractions that are responsible for stationary mixing + churning.
Meissner/submucosal plexus
innermost group of neurons. regulates configuration of luminal surface, controls glandular secretions, alters electrolyte and water transport + regulates local blood flow
sympathetic nervous system
inhibits digestion activity, originates in spinal cord, fibers pass from lateral of spinal cord and separate into ganglia + postganglionic neurons, mainly secretes norepinephrine.
parasympathetic stimulation
increases activity of ENS. divided into:
- cranial
- sacral divisions
- post-ganglionic neurons
cranial
almost entirely in vagus nerves. provide extensive innervation to esophagus, stomach + pancreas and less to intestines
sacral divisions
originate in 2, 3 + 4 sacral segments of spine and pass through pelvic nerves to distal halve of large intestine to anus. sigmoidal, rectal and anal regions better supplied with parasympathetic fibers than other areas.
