Anatomy: Autonomic Pathways and Eye Reflexes Flashcards
Organs in the head and neck with autonomic innervation
Skin
Eyes
Lacrimal Glands
Saliva Glands
Skin Autonomic Innervation
Sympathetic innervation of arteriole, sweat glands and arrestor muscles
Eyes autonomic innervation
Smooth muscle of iris (pupil diameter)
Smooth muscle of the ciliary body associated with the lens (focussing)
Lacrimal Glands Autonomic Innervation
Lacrimal fluid production
Saliva Glands autonomic innervation
Saliva production
Sympathetic innervation: route
originates from autonomic centres in the brain.
passes down spinal cord
Exits spinal cord with T1-L2 region (thoracolumbar outflow)
Travel to sympathetic chains running length of vertebral column
Pass into all spinal nerves (anterior and posterior rami)
Pass into splanchnic nerves to eventually supply organs
Presynaptic sympathetic axons from CNS
Exit spinal cord in T1 spinal nerve
Ascend within sympathetic chain
Synapse in superior cervical sympathetic ganglion
Post-synaptic sympathetic axons
Enter internal and external carotid arteries.
Carried to the organs of the head on the surface of the branches of these arteries
ophthalmic artery carries sympathetic axons into the orbit.
Parasympathetic Axons exit CNS
Leave the CNS via cranial nerves III, VII, IX and X and sacral spinal nerves
Craniosacral outflow
Parasympathetic Supply
Internal organs, not body wall
In head
- eye, lacrimal gland and salivary glands
Vagus nerve
Supples organs of the neck, chest, abdomen as far as the midgut
Sacral spinal nerves
Carry parasympathetic axons to the handout, pelvis and perineums
Ciliary ganglion
parasympathetic ganglion
Located in bony orbit
Fibres from CN III
Cranial nerve III
Oculomotor
Connects with CNS at junction of midbrain and pons
passes through cavernous sinus
Exits via superior orbital issues
Somatic motor to majority of extra ocular muscles
presynaptic parasympathetic axons to the ciliary ganglion
Sensory innervation: face
CN V1 (ophthalmic nerve) CN V2 (maxillary nerve) CN V3 (mandibular nerve)
CN V1 innervates
Upper eyelid
Cornea
Conjunctiva
CN V2 innervates
Skin of lower eyelid
Skin over the maxilla
CN V3 innervates
Skin over mandible and TMJ (except angle of mandible)
Corneal Reflex
Blink
Corneal Reflex Afferent Limb
Sensory (afferent) limb
Action potentials conducted from cornea via CN V1 branches to trigeminal ganglion.
Then along CN V to pons
Corneal Reflex Efferent Limb
Motor (Efferent) limb
Action potentials conducted via CN VII to eyelid part of orbiculares oculi
Autonomic Reflexes of Eye (5)
Wide eye opening of fight or flight Pupillary light reflex Accommodation Reflex Vestibula-ocular reflex Oculocardiac Reflex
Vestibule-ocular reflex
Turns the eye in the opposite direction to a head movement
Stabilizes gaze on an object during head movement
Vestibule-ocular reflex Cranial nerves
CNS connections between CN VIII and CN III, IV and VI
Oculocardiac Reflex
Reflex bradycardia in response to tension on extra ocular muscles or pressure on eye
Oculocardiac Reflex cranial nerves
CNS connections between CN VI and CN X
Wide Eye Opening Reflex
Levator palpebrae superioris (controlled by CN III)
- Contains skeletal muscle plus smooth muscle
- Muellers muscle
Muellers Muscle
used during wide eye opening reflex to elevate the eyelid by a further 2cm under sympathetic innervation
Postsynaptic sympathetic fibres travel via… (4)
Superior cervical sympathetic ganglion
internal carotid nerve
internal carotid plexus
Axons carried on ophthalmic artery and on its branches to orbital structures
Pupillary Constriction
Parasympathetic constrict the pupil
- in bright light and ‘rest and digest’
Sphincter pupilae fibres encircle pupil around the internal circumference of iris
Miotic pupil
non-physiologically constricted pupil
e.g. components off Horner’s syndrome
Fixed ‘pin point’ pupil
Often a serious pathological sign
e.g. opiate drugs
Fixed ‘dilated’ pupil
also called a blown pupil
often a serious pathological sign
E.g. CN III pathology
Pupillary dilation
Sympathetic innervation dilates the pupil
Mydriatic pupil
Non-physiologically enlarged pupil
e.g. mydriatic drugs induce dilation of pupil
Dilator Papillar Fibres arrangment
Radially arranged
Originate around the external circumference of iris - fixed
insert around the internal circumference of iris -mobile
pupillary light reflex
Special sensory (afferent) limb of the reflex is the ipsilateral CN II (optic)
CNS connections occur in the midbrain
Motor (efferent) limb of the reflex is bilateral via CN III
Light reflex- bilateral
Direct light reflex occurs in the stimulated eye
Consensual light reflex occurs in the. non-stimulated eye
Pupillary Light Reflex Neurones
1st neurones 2nd Neurones (bilateral) 3rd neurones (bilateral) 4th neurones (bilateral
Lens Accommodation Reflex
Suspensory ligament of lens connects the circumferences of the lens and the ciliary body
Ciliary body
Muscular and vascular
Smooth muscle like a sphincter around circumference
Ciliary muscle- ‘far vision’
Relaxes
- no parasympathetics
Ligaments tighten and lens flattens to focus on an object in the distance
Ciliary muscle - ‘near vision’
Contracts
-parasynmpathetic
Ligament relaxes and lens become spherical to focus on near objects
Clinical assessing components of accommodation reflex (3)
Bilateral pupillary constriction
- parasympathetic constriction of sphincter pupillae
Bilateral convergence of both eyes towards midline
- medial rectus
Bilateral relaxation of lens
- lens becomes spherical due to contraction of ciliary muscles
Cranial nerve for lens accommodation. reflex
CN III (oculomotor)
Lacrimation (3)
basal tears
Reflex tears
Emotional tears
basal tears
Corneal health
Clean/nourish and hydrate vascular cornea
Contains lysozyme 9hydrolyses bacterial cell walls)
Reflex tears
Extra tears in response to mechanical or chemical stimulation
Afferent limb in Cn V1 from cornea/ conjunctiva
Efferent limb is psaarasympathetic axons originating from CN VII
Emotional tears
happy, sad or frightened
