Divisions of NS Flashcards
What does the central nervous consist of?
What does the peripheral nervous system consist of?
CNS = Brain and spinal cord
PNS = Somatic NS + Autonomic NS (para and sympathetic)
What controls the ANS?
Is it conscious?
Brain stem
No, unconscious
Parasympathetic vs. Sympathetic
- How targeted?
- Function
- Location in spine
- Ganglia location
- Length of neurones
- PSNS is so specific organs can receive signals, SNS is so one signal can go to multiple organs quickly
Which controls daily relaxed bodily functions and which if the flight or fight response out of sympathetic and parasympathetic?
Parasympathetic = relaxed day to day work
Sympathetic = flight or fight
How does the parasympathetic supply affect the following organs:
Eyes
Salivary glands
Bronchioles
Heart
Blood vessels
GI tract
Bladder
Eyes - constrict pupils, accommodates lens focus for close up
Salivary glands - stimulates secretion
Bronchioles - bronchoconstriction
Heart - decrease HR
Blood vessels - vasodilation in SOME
GI tract - increase activity, stimulate secretion
Bladder - urination
What signals does the PSNS respond to?
Where are the two locations of outflow and what do these nerves supply?
CNS
Exits brain - cranial nerves which supply organs
Exits sacral region - pelvic nerves that supply pelvic organs
Define the following:
neuron
synapse
ganglia
neuron - nerve cell
synapse - junction between two neurons
ganglia - cluster of cell bodies outside CNS that hold synapses
Organise the following pathway that the ANS follows:
Target organ
Synapse
CNS
Post-ganglionic neuron
Synapse
Synapse within ganglia
Pre-ganglionic neurons
CNS
Synapse
Pre-ganglionic neuron
Synapse within ganglia
Post-ganglionic neuron
Synapse
Target organ
How many neurons are required to work for CNS functions?
How many neurons are required to work for sensory/motor functions?
CNS - 2 neurons
Sensory/motor - 1 neuron
What are the main cranial nerves involved with the PSNS?
What are the main pelvic nerves?
Oculomoter (III)
Facial (VII)
Glossopharyngeal (IX)
Vagus (X) [sm. in airways, GI, HR]
Pelvic and splachinic nerves
How does the sympathetic supply affect the following organs:
Eyes
Bronchioles
Heart
Blood vessels
Adrenal glands
GI tract
Bladder
Eyes - pupil dilation
Bronchioles - bronchodilation
Heart - increase HR, increase contraction
Blood vessels - vasoconstriction
Adrenal glands - secretion of adrenaline* + noradrenaline
GI tract - decrease activity
Bladder - urine retention
*same as epinephrine
What signals does the SNS respond to?
Where do there nerves exit/outflow?
Signals from the CNS
Thoraco-lumbar region
In the SNS once exiting the spinal cord, what do the neurons enter?
What ganglia can the nerons then travel to to reach…
the head?
the neck?
the thorax?
the abdomen?
the pelvis?
Sympathetic trunk
Head - cranial cervical ganglion
Neck - cervicothoracic ganglion
Thorax - middle cervical + cervicothoracic ganglia
Abdomen - coeliac, cranial mesenteric, caudal mesenteric ganglia (splanchnic nerve)
Pelvis - caudal mesenteric abdomen ganglion (splanchnic nerve)
What is the origin of the vagus nerve?
Where does it exit from the cranial cavity?
Where do a couple of the vagus nerve fibres also go?
Exits from the medulla oblongata as a series of rootlets
Jugular foramen
In the recurrent laryngeal nerve
What are the vagus nerve fibres?
Mixed 80/20 (sensory/motor)
[motor is PSNS]
Describe the distribution of the vagus nerve in the head and neck:
Gives off the pharyngeal branch going to the pharynx (m+s)
Gives off the cranial laryngeal nerve going to the larynx (m+s)
Then,
Joins sympathetic trunk at cranial cervical ganglion forming the = vagosympathetic trunk
What structures can be found in the vagosympathetic trunk?
Sympathetic fibres running cranially (to head + neck)
Parasympathetic fibres running cranially (from receptors + viscera)
Parasympathetic fibres running caudally (to heart and viscera)
Fibres that for the recurrent laryngeal nerve (to laryngeal muscle)
Describe the distribution of the vagus nerve in the thorax:
VN enters thoracic inlet separating from sympathetic trunk at middle cervical ganglion (doesn’t synapse here)
It gives off:
- recurrent laryngeal nerve
- cardiac branches (cardiac plexus)
- bronchial branches (pulmonary plexus)
Divides into two branches caudal to the heart (dorsal + ventral branch)
Dorsal unite at oesophagus forming single dorsal vagal trunk
Ventral unite forming single ventral vagal trunk
Both pass through oesophageal hiatus of diaphragm
Describe the pathway of the recurrent laryngeal nerve (RLN):
Fibres leave vagal trunk in thorax
Right RLN hooks around right subclavian artery and travels back up
Left RLN hooks around aortic arch and travels back up (longer route than right)
Describe the distribution of the vagus nerve in the abdomen:
Dorsal and Ventral vagal trunks
- supply pre-ganglionic PSNS to abdominal plexus and the gut
- receive post-ganglionic sympathetics
Dorsal vagal trunk
- fibres to coeliac and cranial mesenteric plexuses
Ventral vagal trunk
- fibres to gastric and hepatic plexuses
Describe the distribution of the vagus nerve in the ruminant abdomen:
Dorsal vagal trunk
- rumen
Ventral vagal trunk
- reticulum, omasum, abomasum
- Gastric plexus, branches to duodenum, pancreas, liver, hepatic plexus
Give examples of diseases which involve the nerves within the vagosympathetic trunk:
Idiopathic Laryngeal Hemiplegia – RLN Problem = unilateral laryngeal paralysis (usually left side)
Horners syndrome - damage to sympathetic trunk in the vagosympathetic trunk causing loss of supply to smooth muscle in the eye (usually 1 sided). Clinical signs = enopthalmos (globe tracts) and mitosis (pupil constriction)
Vagal indigestion in cattle and ruminants. Clinical signs = acute bloat, chronic paralysis, poor motility
Fill in the missing blanks:
Using the diagram, identify each of the following stages of the nerve pathway:
1. Pre-ganglionic cell body in grey matter of spinal cord
2. Short pre-ganglionic nerve fibres
3. Point of synapse (with many post-ganglionic fibres)
4. In a number of ganglia (on either side of the spinal cord)