Anatomy- Reflexes Flashcards
what supplies the sensory innervation of the face
trigeminal nerve CN V (ophthalmic, maxillary, mandibular)
what does the ophthalamic nerve supply
forehead, upper eyelid, cornea, conjunctiva, skin of the root/bridge/ tip of the nose
what does the maxillary nerve supply
skin of the lower eyelid and maxilla, skin of the ala of the nose, skin/mucosa of the upper lip
what does the mandibular nerve supply
skin over the mandible, and TMJ
what supplies the sensory innervation of the angle of the mandible
C2,3 spinal nerves
what is the sensory (afferent) limb of the blink/corneal reflex
action potentials conducted from cornea via CN V1 (ophthamlic) branches to trigeminal ganglion then along CN V to pons
connections there to CN VII (facial nerve)
what is the motor (efferent limb) of the blink/corneal reflex
action potentials conducted via CN VII to eyelid part of orbicularis oculi
where do sympathetic axons leave the spinal chord
between T1 and L2 - thoracocolumbar outflow
how do sympathetic axons reach organs
via splanchnic nerves
how do sympathetic axons reach the sympathetic chains
spinal nerves
how do sympathetic axons reach the eyes
pre synaptic:
exit at T1 spinal nerve
ascend sympathetic trunk
synapse in superior cervical sympathetic ganglion
post synaptic:
enter internal and external carotid nerves
pass onto surface of the internal and external carotid arteries (form a plexus)
carried to organs and into the orbit
where do all parasympathetic axons leave the spinal chord
via cranial nerves III, VII, IX, and X
and
via sacral spinal nerves
craniosacral outflow
what supplies the parasympathetics to the organs of the neck, chest and abdomen as far as the mid-gut
vagus
where to parasympathetics in the sacral spinal nerves go
to the hindgut, pelvis and perineum
what ganglion do parasympathetic axons go through to get to the eye and ciliary muscles
ciliary ganglion
what ganglion do parasympathetic axons go through to get to the lacrimal gland, nasal, palatine and pharyngeal gland
pterygopalatine ganglion
where does the CNIII (oculomotor) nerve join with the CNS
at junction between midline and pons
what sinus does the oculomotor nerve go through
cavernous sinus
where does the oculomotor nerve exit the cranial cavity
via superior orbital fissue (where it enters the orbit)
what does the oculomotor supply somatic motor innervation to
superior, medial and inferior rectus
inferior oblique
levator palpebrae superioris
ciliary glanglion (sphincter papillae and cilliary muscles)
what does the superior division of oculomotor nerve supply
superior rectus and LPS
what does the inferior division of oculomotor nerve supply
MR, IR, IO, and cilairy ganglion
what do the ciliary nerves supply
automonic axons to control diameter of iris and refractive shape of the lens
what types of fibres are in the long ciliary nerves
sympathetic and somatic sensory
what types of fibres are in the short ciliary nerves
sympathetic, parasympathetic, somatic sensory fibres
what nerves form the first part of the blink reflex
the long ciliary nerves
what are the autonomic reflexes of the eye
maximal eyelid elevation in fight or flight
pupillary dilation/ constriction to adjust to light
focussing lens far and near vision: accommodation reflex
lacrimation reflex tear production
vestibulo-ocular reflex
oculocardiac reflex
what is the vestibulo ocular reflex
turns the eyes in the opposite direction to the head to stabilise gaze
CNS connections between CN VIII and CN III,IV and VI
what is the oculocardiac reflex
reflex bradycardia in response to tension on extraocular muscles or pressure on eye
CNS connection between CN V1 (ophthalamic) and CN X
what are the sympathetic functions of the eye
opens eyes wider
gets more light into eyes
focus on far objects
emotional lacrimation
what are the parasympathetic functions of the eye
gets less light into eyes
focus on near objects
reflex lacrimation
(allow obricularis oculi to work - more somator motor)
what types of muscle in levator palpebrae superioris
skeletal and smooth (F or F) muscle
how do postsynaptic sympathetic fibres reach levator palpebrae superioris
superior cervical sympathetic ganglion
internal carotid nerve
internal carotid plexus
axons carried on the ophthalmic artery…
and on its branches to the orbital structures
how does sympathetics affect the pupil
dilate it- in dim light and in fight or flight/ the sick patient
what is a mydriatic pupil
non physiologically enlarged pupil
what do mydriatic drugs do
induce dilation of the pupil
what dilates the pupil
dilator pupillae muscle fibres
describe the arrangement of dilator pupillae fibres
radially arranged
originate around the external circumference of iris (fixed)
insert around the internal circumference of iris (mobile)
how does parasympathetics affect the pupil
constrict the pupil
in bright light and rest an digest
what is a miotic pupil
non physiologically constricted pupil (seen in horners syndrome)
what is a fixed pin point pupil a sign of
serious- e.g. opiate drugs
what is a fixed dilated pupil a sign of
serious- e.g. CN III pathology
what constricts the pupil
sphuncter pupillae fibres encircle pupil
where are sphincter pupillae fibres
around the internal circumference of the eye
what is the sensory afferent limb of the pupillary light reflex
ipsilateral CN II - optic nerve
CNS connection occurs in midbrain
what is the motor efferent limb of the pupillary light reflex
bilateral CN III- oculomotor nerves
why in the pupillary light reflex is the afferent on one side and efferent on both sides
so a torch shone in one eye will cause a consensual light reflex in the non stimulated eye
what are the 4 neurones chains in the pupillary light reflex
1st- retinal ganglion- optic nerve- optic chiasm- synapse in pretectal nucleus in midbrain
2nd- (bilateral) midbrain- pretetcal nucleus- synapse again in Edinger westphal nucleus
3rd- (bilateral) EW nucleus- CN III- CN III inferior division- synapse in ciliary ganglion
4th- (bilateral) short ciliary nerves- sphincter pupillae muscles
what is significant about the Edinger Westphal nucleus
location of the cell bodies of the parasympathetic axons of CN III
what does the suspensory ligament of the lens do
connects the circumference of the lens and the ciliary body
describe the ciliary body
muscular and vascular, sphincter around a circumference
in what vision does the ciliary muscle relax
far - makes ligament tighten to focus on an object in the distance
when does the ciliary body contract
in near vision- relaxes the ligament which makes the lens become spherical to focus on near objects
what innervation controls the constriction of the ciliary muscle
parasympathetic
what innervation controls the relaxation of the ciliary muscle
happens when there is no parasympathetic actions
what are the 3 aspects of the accommodation reflex
bilateral pupillary constriction (CN III)
bilateral convergence (medial rotation of both eyes CN III)
bilateral relaxation of the lens (CN III)
in the accommodation reflex what is the purpose of bilateral pupillary constriction
to prevent diverging light rays from hitting the periphery of the retina and resulting in a blurred image.
Reduces amount of light that get into eye, only focused ray of light get in
in the accommodation reflex what is the purpose of bilateral convergence
simultaneous movement of both eyes in opposite directions to obtain or maintain single binocular vision
(Cross eyes)
in the accommodation reflex what happens in bilateral relaxation of the lens
lens become spherical due to the contraction of the ciliary muscles
what is the role of basal tears
important in cornea (avascular) health- clean, nourish and hydrate
contain lysozyme (hydrolyses bacterial cell walls)
what is the role of reflex tears
extra tears in response to mechanical or chemical stimulation
what are the afferent and efferent limbs of the reflex tears reflex
afferent limb is CN V1 from cornea/conjunctiva
efferent limb is parasympathetic axons originating from CN VII
what nerves carries parasympathetic axons for the lacrimal gland
CN VII
then branches of V2 then V1
what nerves does facial expression
CN VII somatic
what are the symptoms of horners syndrome (ipsilateral)
miosis
ptosis
reduced sweating (annhydrosis)
increased warmth and redness
what causes horners syndrome
Impaired sympathetic innervation to head and neck-
compression of the cervical parts of the sympathetic trunk:
- root of neck trauma
- carotid dissection
- internal jugular vein engorgement
- deep cervical node metastases
- pancoast tumour (lung apex)
