Chapter 7 Flashcards
CN autonomous
Which Muscles Do The Sympathetic fibers of the eye innervate?
Orbitalis muscle- smooth muscle of periorbita and eyelids, incl. third eyelid, smooth ciliary muscle smooth dilator muscle of the pupil in iris.
The sympathetic innervation of the eye pathway within the internal carotid nerve.
Cranial cervical ganglion-tympanooccipital fissure-carotid canal- foramen lacerum-opthalmic nerve. This pathway follows the internal carotid artery.
Which structures (except eye) do the other sympathetic fibers innervate?
Smooth muscle of blood vessels, sweat glands of the skin of the head and cranial cervical area.
Whic fibers does the orbitalis muscle have?
Circular-makes eye protrude
Ventral sheet of longitudinal fibers- inferior eyelid ansr third eyelid.
Medial sheet of longitudinal fibers - superior eyelid and third eyelid.
Whic fibers does the orbitalis muscle have?
Circular-makes eye protrude
Ventral sheet of longitudinal fibers- inferior edel ansr third eywlid
Medial sheet of longitudinal fibers - Ich eye
Is sweating increased in horses with sympathetic innervation problem? What about other animals?
Yes. No, in other animals it’s decreased (planum nasolabiale in ox).
What is the sign of Horner Syndrom in goats?
Reduced palpebral fissure and warm ear.
Where will the horse sweat with lesion in the lateral funicular lesion in the cervical spine?
In the entire ipsilateral half of his body.
What supplies sympathetic ganglionic axons to the cervical spinal nerves from C2 through C6?
Vertebral nerve (branch of cervicothoracic ganglion). It follows vertebral artery into transverse foramen of C6 and continues cranially until C1.
Explain anatomic pathway of parasympathetic inervation of the eye.
Draw a picture please.
Explain anatomic pathway of sympathetic inervation of the eye.
Draw a picture please.
The course of the parasympathetic fibers innervating the detrusor muscle.
S1-S3 spinal segments-pelvic nerve-pelvic ganglion (synapse)-bladder wall.
Pathway of sympathetic innervation of the bladder.
Lateral grey column(cell bodies) of L1-4 (5) - ventral roots-spinal nerves-communicating ramus-longitudinal sympathetic trunk - TWO PATHS- 1. Lumbar splanchnik nerves-caudal mesenteric ganglion (synapse) -hypogastric nerve-pelvic plexus (some terminate here - synapse through alfa-2 receptors to parasympathetic ganglion neurons to inhibit them) - other sympathetic neurons go to the bladder neck (alfa-1) and detrusor muscle (beta).
Pathway of striated muscle innervation of the urethra.
Ventral grey horn sacral segments (cell bodies)-spinal nerves ventral branches-sacral plexus-pudendal nerve- bladder neck.
GVA neurons innervating the bladder.
Dendritic zones of GVA located in the wall of bladder and urethra (A-delta mechanoreceptors responding to stretch and distension) - pelvic nerve-dorsal roots-sacral segments-dorsal grey column.
Some may travel with hypogastric nerve
Pontine Micturition centers
Receives GVA signals
Pontine centers- reticulospinal tracts - grey matter where GSE and GVE LMNs are located.
Facilitate or inhibit them.
Pathways of parasymapthetic N. facialis neurons
Parasympathetic nucleus of the facial nerve in medulla oblongata (most cranial one from all parasympathetic nuclei) - GVE neurons travel with GSE neurons to enter internal acoustic meatus, then in the facial canal of the petrous portion of temporal bone branch off to form the major petrosal nerve, which is joined by deep petrosal nerve, a nerve of pterygoid canal is formed from those two and exits pterygoid bone and make synapses in the pterygopalatine ganglion. From here it joins the trigeminal nerve and innervates the tear glands, glands of third eyelid, palatine, lateral and mucosal nasal glands.
Other GVE preganglionic neurons in the facial canal branch off and join chorda tympani, goes through tympanic cavity and emerges rostral to oval foramen and joins the lingual nerve which synapses in the sublingual and mandibular ganglions and innervate the salivary glands.
Causes of protruded third eyelid in a dog and a cat.
Any time the eyeball is actively retracted by contractions of the retractor bulbi muscle (VI) or the rectus muscles (III, VI).
Constant partial protrusion of the third eyelid occurs in
Horner syndrome because of the loss of the GVE sympathetic innervation of the orbitalis smooth muscle
Brief, rapid, passive protrusions (flashing of the third eyelid) occur in the disease tetanus because of
the effect of the tetanus toxin on the neurons that innervate the extraocular muscles.
Cerebellar medullary lesions that affect the cerebellar nuclei may occasionally cause a protruded third eyelid, but the clinical signs of cerebellar ataxia predominate.
Cats with severe systemic disease and depression often have bilateral persistent protrusion of the
third eyelids. This may result from severe dehydration and depression or from a generalized decrease in sympathetic tone.
Bilateral protrusion may occur in animals
with severe cachexia because of the loss of orbital fat.
Bilateral protrusion may also be seen as one of the many clinical signs observed in cats and dogs with dysautonomia, which is a presumptive toxicoinfectious neuronopathy.
Severe atrophy of the muscles of mastication, resulting from trigeminal nerve denervation, chronic myositis, or excessive glucocorticoid therapy leading to atrophy, indirectly causes passive enophthalmos and therefore passive protrusion of the third eyelid.
Causes of anisocoria.
Causes for midriasis and miosis.
MYDRIATIC PUPIL
1. A unilateral general visceral efferent (GVE) oculomotor neuron lesion with ipsilateral mydriasis that is unresponsive to light directed into either eye.
2. Severe unilateral retinal or optic nerve lesions may result in a slight ipsilateral mydriasis that responds only to light directed into the normal eye. If the normal eye is covered, the pupil in the affected eye fully dilates.
3. Age-related iris atrophy is a degenerative disorder, especially in old dogs. Response to light is variable, but often the response is poor to absent.
4. A mydriatic drug administered for a fundic examination.
5. Ingestion of a species of belladonna plant that contains atropine.
6. Glaucoma that is an increase in intraocular pressure caused by defcient absorption of aqueous with an ipsilateral mydriasis unresponsive to light.
7. Unilateral cerebellar lesions, especially those that affect the cerebellar medullary nuclei, may result in a mydriatic pupil on the same side or the opposite side from the lesion, depending on the nucleus involved.
MIOTIC PUPIL
1. A unilateral GVE sympathetic neuron lesion with ipsilateral miosis. The affected pupil constricts more in bright light and dilates slightly in reduced light. The anisocoria may be more pronounced when examined in the dark.
2. Unilateral iritis with swelling in the iris.
3. Unilateral ocular disorders such as keratitis that cause discomfort may activate ophthalmic nerve sensory neurons, resulting in an oculopupillary reflex (V-III) that causes ipsilateral miosis.
Micturition phase, explain it
Bladder wall extends and the GVA stretch receptors reach the threshold, stimulation travels throught pelvic nerve to the sacral SC through dorsal nerve roots - pontine micturition center and thalamic nucleus-cerebral cortex. Micturition center is stimulated directly and indirectly. The cerebellum also is informed.
Reticulospinal tracts - inhibit sympathetic LMN in lumbar spine and somatic LMN in sacral spine and facilitate parasympathetic neurons.
May function without cerbral input.
Explain the reflex micturition.
GVA stretch receptors are stimulated-travels through pelvic nerves to sacral CS segments-activates parasymapthetic and inhibits GSE-LMN innervation. Results is partial bladder empying. Unconcious reflex.
Control of defecation
The sacral spinal cord segment parasympathetic preganglionic neurons provide facilitatory LMN innervation to the descending colon and
rectum via the pelvic nerve and ganglionic neurons within the wall of these portions of the digestive tract. The L1 to L4 or L5 lumbar spinal cord segment sympathetic preganglionic neurons provide LMN innervation to the descending colon, rectum, and internal anal sphincter via the ganglionic neurons in the caudal mesenteric ganglion, caudal mesenteric plexus, hypogastric nerves, and pelvic plexus.
The sympathetic innervation to the descending colon and rectum is inhibitory, whereas it is facilitatory to the internal anal sphincter. The sacral spinal cord segment GSE-LMN innervates the striated external
anal sphincter muscle via the sacral plexus and the caudal rectal branch of the pudendal nerve. Cranially projecting sensory spinal cord tracts to a poorly localized brainstem center exist for defecation, and tracts to thalamic nuclei exist for relay to the sensory cerebral cortex. UMN pathways involve the motor cortex and reticulospinal tracts.
Parasympathetic neuron pathway of glossopharyngeal nerve.
Parasympathetic nucleus is caudal to the facial parasympathetic nucleus.
GVE leave medulla with GSE and enter jugular formamen and before exiting GVE branch off to form as tympanic nerve, traverses the tympanic cavity in tympanic lexus. From this plexus is continued as minor petrosal nerve and joins the otic ganglion ventral to oval foramen. Synapses. Joins the mandibular nerve. Innervates the zygomatic and parotid salivary glands.
Parasympathetic neuron pathway of vagus nerve.
Parasympathetic nucleus of vagus nerve is caudal one and a large one.
The axons of these parasympathetic preganglionic neuronal cell bodies join the GSE axons from the nucleus ambiguus to form the motor component of the vagus nerve, which enters the jugular foramen and emerges from the tympano-occipital fissure.
The GVE parasympathetic preganglionic axons course caudally in this nerve, where it is associated with the cervical sympathetic trunk in the carotid sheath. They continue through the mediastinum, where they follow branches of the vagus to the heart muscle, lungs, and esophagus. Within these organs, the preganglionic axons synapse with the cell bodies of the ganglionic axons that innervate the cardiac muscle or the smooth muscle and glands in the lungs and esophagus. The remaining preganglionic axons continue into the abdomen in the dorsal and ventral vagal trunks, where they primarily follow the blood vessels to the
abdominal organs. They synapse on the cell bodies of the parasympathetic ganglionic axons within the wall of
the organ innervated. Within the wall of the digestive tract, this innervation becomes part of the enteric nervous system, which is an extremely complex and autonomous system.
The gastrointestinal system can carry out its major functions without this extrinsic innervation. Smooth muscle contractions occur using the intrinsic reflex activity of the enteric neurons. This extrinsic parasympathetic innervation provides what control the CNS has over the enteric nervous system. In a sense, this is an LMN acting as a UMN for regulation of gastrointestinal function.
How is dysautonomia syndrome called in horses?
Grass sickness
Horses may die acutely of gastrointestinal stasis and gastric reflux or have a chronic course with intermittent colic.
What is a Key-Gaskell syndrome?
It is a dysautonomie syndrome in cats.
Degenerative lesions are widely distributed in GVE ganglia, including the enteric components, but they also occur in spinal ganglia and in selected neuronal populations in the CNS. Clinical signs reflect the diffuse involvement of both the parasympathetic and sympathetic components of the GVE system. Dogs and cats exhibit dilated pupils that are unresponsive to light, protrusion of the third eyelid, dry oral and nasal mucosae, dysphagia, megaesophagus, vomiting, diarrhea or constipation, fecal or urinary incontinence,
and bradycardia. Pharmacologic testing may help to support the diagnosis. No specifc therapy exists, and spontaneous recovery is uncommon.
What is a complex regional pain syndrome?
Clinical syndrome that involves dysfunction of the cutaneous distribution of sympathetic nerves.
Syndrome consists of chronic pain with localized hyperalgesia, which is increased responsiveness to noxious stimuli and allodynia.
Signs: hyperthermia or hypothermia, hyperhydrosis or hypohydrosis, and edema.
Trauma of some sort is usually a precipitating event.. This syndrome has been reported in the horse and the dog.
