12 ANS and pelvic viscera Flashcards
what does the autonomic nervous system consist of?
visceral efferent motor fibres
visceral afferent pain fibres
where is the ANS distrubuted?
CNS and PNS
what are the differences in the two divisions of ANS?
sympathetic and payasympathetic nervous system
- anatomical
- neurotransmitters
- physiological effects
function of sympathetic nervous system
prepare body for an emergency
- increase heart rate
- redistribution of blood- arterioles of skin and intestines constricted. arteriole of Skm dilated
- increased in BP
sympathetic nervous system
thoracolumbar outflow
- efferent outflow from spinal cord, sympathetic trunk, branches, plexuses and ganglia
- Lateral horn (preganglionic cell bodies location) positioned from T1-L3
- Axons of preganglionic neurones leave lateral horn and enter into paravertebral ganglia of the sympathetic trunk
SNS: Once pre-ganglionic fibres enter sympathetic trunk they can…
- synapse at entry level
- ascend and synapse- travel cranially
- descend and synapse- travel caudally
- no synpase with ganglia assocaited with sympathetic trunk- form splanchnic nerves
(synapse at ganglia some distance away)
what type of fibres are splanchnic nerves?
pre-ganglionic sympathetic fibres
what is the sympathetic chain/ paravertebral column?
two ganglionic nerve trunks that extend the whole length of vertebral column
- Superior cervical ganglion of each sympathetic trunk lies at base of cranium
- Ganglion impar forms inferiorly where two trunks unite at level of coccyx
- Associated with spinal cord
how many sympathetic ganglia are associated with:
neck
thorax
abdomen
pelvis
3
11/12
4/5
4/5
lower thoracic splanchnic nerve vertebrae
origin
greater- T5-T9 (T10)
lesser T10-11
Least T12
thoracic sympathetic trunk
2
6
yellow arrows
12
13
azygous vein
SVC
sympathetic chain
lesser splanchnic nerves
greater splanchnic nerves
which plexuses do the thoracic splanchnic nerves form
greater- pierces crura of diaphragm to synapse with coeliac plexus
lesser- pierces crura of diaphragm, descends with greater splanchnic nerves to join lower part of coeliac plexus
least- preganglionic fibres of excitatory neurones in ganglia of renal plexus
function of parasympathetic nervous system
cranio-sacral outflow
Function to conserve and restore energy
- Decrease heart rate
- Peristalsis and glandular activity increased
- Sphincters are opened
- Bladder wall is contracted
- Pupils are constricted
locations of nerve cells of PNS
CNIII oculomotor
CNVII facial
CNIX glossopharyngeal
CNX vagus
sacral segments of spinal cord- grey matter
S2-S4 anterior roots of spinal nerves
Efferent fibres of cranio-sacral outflow are pre-ganglionic and synapse in peripheral ganglia located close to viscera they innervate
waht type of nervous system are pelvic splanchnic nerves
parasymapathetic S2-S4
hypogastric nerve plexuses
superior hypogastric nerve plexus-> sympathetic
splits into R and L hypogastric nerves-> inferior hypogastric plexus -> mixed
7
34
7 inf mesenteric artery
34 internal iliac artery
enteric nervous system:
what plexuses does it consist of
Two important plexuses of nerve cells and fibres extend along/around the GI tract
Meisser plexus (submucosal plexus)
auerbach plexus (myenteric plexus)
- Capable autonomous (coordination of reflexes)
- Operate independently of brain and spinal cord
- Does receive autonomic nervous innervation
ENS: function of Meissner’s plexus and location
- Controls glandular secretion of mucosa
- Located between submucosa and circular muscle layer
- Also involved in local movement of muscle
ENS: function and locaiton of Auerbach’s plexus
- Controls peristalsis
- Movement of gut wall
- Between circular and longitudinal muscle layers
myenteric
stimulation
inhibition
- Myenteric: longitudinal chains of neurones
- Stimulated Plexus increases tone of gut and velocity and intensity of contractions
- Motility through gut
- Inhibition: relax sphincters, controls flow of digestive food/ waste
- Submucosal:
- Local conditions and controls local secretions and local muscle movements
- Mucosa and epithelial tissue have sensory nerve endings that feed signals to both layers of enteric plexus
- Tissues send info back to sympathetic prevertebral ganglia-> spinal cord-> brain stem
role of sensory nerves in ENS
monitor tension and gut wall and conditions in lumen
feedback to assc nerves
functions of ENS
Estimated more neurones associated with it than spinal cord
- Second brain
- Contains a variety of functional types of neurones and a plethora of neurotransmitters
- Controls motility and secretory functions
- Complete reflex circuit
- Afferent sensory neurones, interneurons and efferent secretomotor neurones
- Functions autonomously, but modified by sympathetic and parasympathetic nervous systems
pathology of ENS
Hirschsprung’s disease
- Congenital birth defect (1:5000)
- Enteric neurones absent from variable lengths of the distal gut
- Failure of neural crest cells to colonise region of gut (vs nerves not surviving)
- Intestinal obstruction or severe constipation
Descending colon: lacking enteric neurones (aganglionic)
- Contracted and devoid of content
- Region proximal to aganglionic zone is distended (megacolon) due to accumulation of fecal content
Mutations in identified genes 50% of causes
dorsal primary ramus
part of spinal nerve (contains motor, sensory and autonomic) innervating back.
ventral primary ramus
part of spinal nerve innervating everything in front of spinal cord – hence larger than dorsal primary ramus.
white ramus
preganglionic sympathetic fibres connecting ventral primary ramus with sympathetic chain. Myelinated nerves only found T1 – L2
grey ramus
post ganglionic sympathetic fibres connecting sympathetic chain to dorsal and ventral primary ramus of spinal nerve. Unmyelinated nerves
