Autonomic Nervous System Flashcards
what are the functions of parasympathetic system
day to day control of viscera
ex. breathing at rest, digestion, elimination of wastes
what are the functions of the sympathetic nervous system
active when the animal is stressed (fight or flight)
ex. increases in heart rate, respiration, blood flow to active muscles
what are the main control centres of the CNS
hypothalamus and midbrain
what are the functions of the hypothalamus and the midbrain
direct control of sympathetic & parasympathetic divisions
cerebral cortex can influence but not command the control centres (emotional status causes blushing)
where do the fibres of the CNS run
descending fibres to the brain stem and spinal cord
where is the outflow of parasympathetic innervation of the PNS
brain stem & sacral cord level
where is the sympathetic outflow of the PNS
thoracolumbar cord level
what is the two-neuron system in the PNS
- pre-synaptic fibre
- post-synaptic fibre
what are the neurotransmitters in the parasympathetic fibres
Ach
at pre and post
what are the neurotransmitters at the pre and post synaptic fibres in the sympathetic nervous system
pre = ach
post = ach or NE
where are the neural cell bodies located for sensory cell bodies, motor striated muscle, motorneuron cell bodies
dorsal horn for sensory cell bodies
ventral horn for motor striated muscle
intermediated/lateral horn for motorneuron cell bodies of ANS in thoracolumbar and sacral cord
how do parasympathetic fibres innervate viscera
cranial nerves from brain to head via CN III, VIII, IX
to cervical, thoracic and abdominal viscera via CN X and vagosympathetic trunk
segmental spinal nerves from sacral spinal cord S1, S2, S3 to pelvic viscera
what are the features of pre and post synaptic fibres and where do they synapse
pre-synaptic fibres: long
synapse: close to organ
post-synaptic fibres: short
how do sympathetic fibres innervate all viscera
thoracolumbar outflow from CNS –> C8/T1 to L4/5
thoracic cavity –> sympathetic chain of nerves and paravertebral ganglia
abdominal and pelvic cavitites –> fusion of fibres to form prevertebral ganglia –> celiac, cranial, and caudal mesenteric
head –> supplied by spinal nerves from C8-T7 via vagosympathetic trunk
what are the features of the pre and post synaptic fibres and where they synapse in the sympathetic system
pre-synaptic: short
synapse: remote from organ
post-synaptic: long
what is the white Rami communicans
carries presynaptic sympathetic fibres to the sympathetic trunk in spinal segments T1-L2
what is the grey rami communicantes
carries post-synaptic sympathetic fibres from the sympathetic trunk to all spinal nerves
where do the pre-ganglionic fibres from T1-5 (to T7) run in the sympathetic supply to the head and neck and where do they synapse
run cranially in vagosympathetic trunk
synapse: cranial cervical ganglion (located deep to tympmanic bulla)
where do the post-synaptic fibres of the sympathetic supply to head and neck run
some follow arteries of the head region (carotid artery)
some follow CN IX-XII, vagal nerve branches to larynx and pharynx
what are the functions of the post-synaptic fibres from the sympathetic
innervation of smooth muscle (vascular, ocular, orbital, erector pilae, glands (sweat, salivary, nasal))
what supplies the thorax in the sympathetic nervous system
sympathetic trun
vagus and sympathetic trunk company at chest entrance near middle cervical ganglion at first rib
fibres slpit to pass around the subclavian artery forming the ansa subclavia
large cervicothoracic ganglion followed by a regular chain of ganglia throughout thorax
what is the sympathetic supply to abdomen and pelvis
lumbar trunk steadily becomes more erratic –> branches of the sympathetic trunk
supply pre and post synaptic fibres to the abdominal and pelvic regions
whare the specific parasympathetic supplies to the body
- craniosacral system
- cranial origin: CN III, VII, IX, X
- sacral origin: S1-3 spinal cord segments
what is the nucleus of origin of the oculomotor nerve (CN III)
edinger-westphal (paras. nucleus of CN III) (midbrain)
what is the ganglion of the oculomotor nerve
ciliary (close to eye)
what is the target organs of the oculomotor nerve
ciliary muscles (regulate lens curvature)
muscles of iris (pupil constriction)
what is the nucleus of origin of facial nerve (CN VII)
rostral salivatory (paras. nucleus of CN VII) (brainstem)
what are the ganglions of the facial nerve
- pterygopalatine (sphenopalatine)
- sublingual and mandibular
what are the target organs of the pterygopalatine (sphenopalatine)
lacrimal, nasal & palatine glands (secretion, vasodilation)
what are the target organ of the sublingual and mandibular
sublingual and mandibular glands (secretion, vasodilation)
what is the nucleus of origin of the glossopharyngeal nerve (CN IX)
caudal salivary (paras. nucleus of CN IX) (brainstem)
what is the ganglion of glossopharyngeal nerve
otic
what is the target organ of the glossopharyngeal nerve
parotid and orbital salivary glands (secretion, vasodilation)
what are the nucleus of origin of the vagus nerve
dorsal efferent nucleus of CN X (paras. nucleus of CN X) (brainstem)
what is the ganglion of the vagus nerve
terminal (intramural)
what are the target organs of the vagus nerve
parasympathetic supply to neck, thorax, abdomen (majority of body viscera –> cervical, thoracic, abdominal)
what is the response of the vagus nerve
heart rate
peristalsis
sweating
larynx opening
many
where does the CN X travel down the neck
CN X travels down the neck in the vagosympathetic trunk
where are the cell bodies in the parasympathetic supply to the pelvic viscera
lateral horn of S1-3 spinal cord segments
what are the presynaptic and post synaptic fibres of the parasympathetic supply to the pelvic viscera
axons travel in pelvic nerves (located lateral wall of rectum)
synapse at terminal ganglion (near the bladder, rectum and sexual organs)
distribution to pelvic viscera, lower intestinal cavity and repro organs
what is the function of the sympathetic innervation of the eye
supplies smooth muscle of the orbit and the iris dilators
protrusion of eyeball
third eyelid retraction
dilation of pupils
widening of the palpebral fissure
how does the sympathetic nervous system innervate the eye
first order neuron goes down to spinal segments T1-T3
second order neuron (in vagosympathetic trunk)
third order neuron innervates the eye
what are the signs of Horner’s syndrome
- pupillary constriction (miosis)
- prolapse of third eyelid
- narrowing of the palpebral fissure
- enophthalmos
what are the causes of Horner’s syndrome
herniation (neck) or middle
ear infection (otitis) –> close to tympanic bulla
brachial plexus
lesion in spinal cord
what is the parasympathetic innervation of the eye
CN III is part of the pupillary light reflex
- retina –> optic nerve
- optic tract
- pretectal nucleus
- CN III parasympathetic nucleus
- ciliary ganglion
- eyeball (smooth muscle constrictor)
what does the oculomotor nerve innervate
primarily the smooth muscle constrictor of the pupil
what is the function of the oculomotor nerve
pupil constriction (miosis)
what are the signs of oculomotor nerve dysfunction
pupil dilation (mydriasis) unresponsive to light
a dog has anisocoria (right pupil smaller than left)
how will you determine which is the abnormal eye
put in the dark
should get dilation
left eye constricts when shine a light in eye
right eye already constricted
sympathetic
can’t dilate pupil in right eye
how does brain herniation lead to miosis
often miosis intially –> as midbrain swells –> compression of CN –> non-functioning parasympathetic nucleus of III –> mydriasis
progression from miotic to mydriatic pupils indiactes increasingly severe brain pathology
what is the sympathetic innervation of the urinary tract and its function
hypogastric nerve (L1-4 in dogs, L2-5 cats)
relaxes the detrusor muscle in the bladder
contraction of the smooth muscle of the bladder neck/internal urethral sphincter
what is the parasympathetic innervation to the bladder and its function
predominant in voiding phase
pelvic nerve (S1-3)
contraction of detrusor muscle of bladder wall
supplies urogenital organs, rectum, descending colon
what is the somatic innvervation of the bladder
pudendal nerve (S1-3)
contraction of the striated sphincter muscles for urinary retention
innervates anal sphincter (perineal reflex)
what is grass sickness
impaired activity of the gut due to ANS damage
cause still unknown
what are the 3 main presentations of grass sickness
- acute: severe and sudden onset with 100% mortality within 48hrs
- sub-acute: milder clinical signs but most usually die within 7 days
- chronic: slower onset presenting with rapid weight loss, some will survive
what are the clinical signs of AGS and SAGS grass sickness
depression
ileus
tachycardia
salivation
gastric reflux
fasciculations
ptosis
sweating
dysphagia
colic
impaction
what are the clinical signs of CGS
rapid and severe weight loss
rhinitis sicca
ptosis
tachycardia
fasciculation
patchy sweating
inappetance
dysphagia
what are thought to be the causes of grass sickness
clostridium botulinum type C
most cases between April and July
grazing increases risk factors, pasture disturbance, feed change, grazing previously affected pasture
what is feline dysautonomia
widespread dysfunction of the ANS
all breeds and ages susceptible but commonly seen in younger cats
what are the clinical signs of feline dysautonomia
depression
anorexia
bilateral pupil dilation non-responsive to light
third eyelid protrusion and ptosis
decreased tear and saliva production
megaesophagus
bradycardia
fecal and urinary incontinence
what does definitive diagnosis of feline dysautonomia
histopathology
radiographs, schirmer tear test and pharmacological testing
how is feline dysautonomia treated
purely supportive
where do the recurrent laryngeal nerves arise from and what do they supply
vagus at the middle cervical ganglion and run back up the neck
supply the trachea and cervical esophagus
