Eye Flashcards
Autonomic Innervation of the Eye
pupillary response to light involves both sympathetic and parasympathetic divisions of the autonomic nervous system. Pupil dilatation in response to low light illumination is predominantly accomplished by an increase in sympathetic activity. Constriction of pupils in response to high light levels results predominantly from an increase in parasympathetic activity.
Sympathetic eye will what
Dilate
Parasympathetic eye will what
Constrict
Sympathetic nerves control the ____ causing the pupil to dilate.
iris dilator muscle
Sympathetic nerves innervate vascular muscle causing ___ to constrict.
blood vessels
[Symp] Preganglionic nerves arise in the ___ and travel upwards in the sympathetic chain synapsing in the superior cervical ganglion
upper thoracic spinal cord
[Symp] Preganglionic nerves arise in the upper thoracic spinal cord and travel upwards in the sympathetic chain synapsing in the ____
superior cervical ganglion
___ is the
neurotransmitter released by pre-ganglionic nerves for both.
Acetylcholine
[Symp] Postganglionic nerves originate at the ___and travel through the internal carotid plexus to the dilator muscle of the iris.
superior cervical ganglion
[Symp] Postganglionic nerves originate at the superior cervical ganglion and travel through the ___ to the dilator muscle of the iris.
internal carotid plexus
______ is the neurotransmitter released by postganglionic nerves
Noradrenaline
[Symp] Noradrenaline is the neurotransmitter released by postganglionic nerves and activates ____ causing the dilator muscle to contract and the pupil to dilate and increasing the amount of light entering the eye.
alpha1-adrenoceptors
[Symp] Noradrenaline is the neurotransmitter released by postganglionic nerves and activates alpha1-adrenoceptors causing the dilator muscle to_____ and the pupil to dilate and____ the amount of light entering the eye.
contract
increasing
[Paras] Parasympathetic nerves control the muscle cells of the iris sphincter muscle – the ____
sphincter pupillae.
[Paras] sphincter pupillae is shape muscle cells which cause pupil constriction when they contract.
circular
[Paras] _____ is circular muscle cells which cause pupil constriction when they contract.
sphincter pupillae
[Paras] _____(also known as the oculomotor nerve) conveys preganglionic nerves to the ciliary ganglion.
Cranial nerve III
[Paras] Cranial nerve III (also known as the oculomotor nerve) conveys preganglionic nerves to the ___
ciliary ganglion.
[Paras] Postganglionic nerves travel with the short ciliary nerves and innervate the _____muscle which causes a narrowing of the aperture of the iris and a reduction in the amount of light entering the eye.
sphincter pupillae
[Paras] Postganglionic nerves travel with the short ciliary nerves and innervate the sphincter pupillae muscle which causes a narrowing of the-____ of the iris and a reduction in the amount of light entering the eye.
aperture
[Paras] Postganglionic nerves travel with the short ciliary nerves and innervate the sphincter pupillae muscle which causes a____ of the-____ of the iris and a reduction in the amount of light entering the eye.
narrowing
aperture
[Paras] Acetylcholine is the neurotransmitter released by both pre-ganglionic (acts on___
receptors) and postganglionic (acts on____receptors) nerves.
nicotinic
muscarinic M3
Atropine
competitive muscarinic receptor antagonist
Edrophonium
short acting acetylcholinesterase inhibitor
Combine reversibly with acetylcholinesterase
minutes
diagnose myasthenia gravis
Increase ACh -> contraction
Pilocarpine
muscarinic receptor agonist
Apraclonidine
alpha-2-adrenoceptor agonist and weak alpha-1-adrenoceptor agonist
Phenylephrine
alpha-1-adrenoceptor agonist
Cocaine
inhibits the noradrenaline transporter (NET)
Hydroxyamphetamine
releases noradrenaline from sympathetic nerves
Olopatadine
histamine H1 receptor antagonist (antihistamine)
Physostigmine (longer acting) and neostigamine
Cholinesterase inhibitor
hydrolyses in min-hrs
Will form ACh -> acetylated intermediate and is destroyed in reaction.
So it takes long for acetylcholinesterase to metabolise this so more duration of action of acetylcholine.
Cholinesterase inhibitor
Inhibit ACh metabolism and increase ACh levels and neurtransmission.
ANS
innervates all tissues but not skeletal muscle
Cholinesterase
catalyze the hydrolysis of the neurotransmitter acetylcholine into choline and acetic acid
Acetylcholinesterase
terminates ACh action at nerve terminals
Acetylcholinesterase cold
cold temperatures can temporarily reduce the activity of acetylcholinesterase. When acetylcholinesterase is less active, it breaks down acetylcholine more slowly.
Edrophonium combines reversibly with ACh-esterase
Myasthenia gravis
eye droop put cold pack and droop resolve ACh-esterase + cold inhibit ACh breakdown
Drugs that dilate pupil
Cocaine
Atropine
Phenylephrine
Hydroxyamphetamine (in presence of endogenous NA)
Drugs that constrict pupil
Pilocarpine
Edrophonium
[Symp Impair]
Disruption of the sympathetic innervation to the iris dilator muscle allows the parasympathetically innervated iris sphincter to have the predominant action on the iris, thus causing the pupil to__.
constrict
[Symp Impair]
Disruption of the sympathetic innervation to the iris dilator muscle allows the____ innervated iris____ to have the predominant action on the iris, thus causing the pupil to constrict.
parasympathetically
sphincter
[Symp Impair]
Stimulation of sympathetic nerves that innervate____ muscle assists in the elevation of the upper eyelid. Interruption of this sympathetic innervation results in the upper eyelid dropping over the eye to some extent.
Mueller’s
[Symp Impair]
Stimulation of sympathetic nerves that innervate Mueller’s muscle assists in the____ of the upper eyelid. Interruption of this sympathetic innervation results in the upper eyelid____ over the eye to some extent.
elevation
dropping
[Symp Impair]
Dilation lag occurs when a pupil fails to re-dilate quickly to its original size when a bright light is____. This can be easily evaluated by comparing the speed with which the pupil in each eye dilates and size of the pupil in__ light. Dilation lag is useful in the diagnosis of sympathetic impairment.
extinguished
low
[Symp Impair]
Dilation lag occurs when a pupil fails to re-dilate quickly to its original size when a bright light is extinguished. This can be easily evaluated by comparing the___ with which the pupil in each eye dilates and ___ of the pupil in low light. Dilation lag is useful in the diagnosis of sympathetic impairment.
speed
size
[Symp Impair]
Dilation lag occurs when a pupil fails to re-dilate quickly to its original size when a bright light is extinguished. This can be easily evaluated by comparing the speed with which the pupil in each eye dilates and size of the pupil in low light. Dilation lag is useful in the diagnosis of___ impairment.
sympathetic
Since_____ nerve stimulation causes blood vessels to constrict, redness of the eye suggests _____ impairment may be involved. same blank
sympathetic
cocaine dilates the pupil by preventing the reuptake of____ that has already been released into the synaptic junctions of the iris___ muscle in response to a nerve impulse. If the sympathetic innervation to the eye is impaired at either the____ or ___ level, cocaine will fail to dilate the pupil as the flow of nerve impulses has been impeded and endogenous___ is not released. While cocaine may be used to confirm sympathetic impairment, the site of the impairment (i.e., preganglionic or postganglionic) cannot be localised.
noradrenaline
dilator
preganglionic or post
noradrenaline
Hydroxyamphetamine, an indirect acting ___ agonist, releases_____ from sympathetic nerves. Thus, hydroxyamphetamine will only dilate the pupil in the presence of endogenous__same___. Where the ___ganglionic sympathetic pathway is impaired, hydroxyamphetamine will fail to dilate the pupil. Where the preganglionic sympathetic pathway is impaired, the postganglionic pathway is undamaged and__same__ in presynaptic vesicles may be released by hydroxyamphetamine.
alpha-adrenoceptor
noradrenaline
postgang
[Paras Impair]
A fixed and dilated pupil may be caused by either parasympathetic impairment or a muscarinic____.
antagonist
Pre and post for sympathetic
Nico and alpha-adreno
Pre and post for parasympathetic
Nico and muscarinic (M3)
Parasympathetic impairment is associated with a dilated pupil that reacts very___ to light.
poorly
Impairment of nerves that innervates the iris sphincter pupillae muscle has been shown to cause _____ or denervation hypersensitivity. In these cases, the iris is much more sensitive to cholinergic____. A low concentration of muscarinic agonist will not constrict a healthy pupil but will constrict a pupil with_____ impairment and cholinergic or denervation hypersensitivity.
cholinergic
agonists
parasympathetic
[Paras Impair]
Accidental inoculation into the eye of a muscarinic____ in the form of a drug or other substance will cause pupil dilation. If the muscarinic receptors on the affected iris sphincter pupillae muscle are occupied by a muscarinic antagonist, even high concentrations of a muscarinic agonist will be___ to activate these receptors and constrict the pupil.
antagonist
unable
Parasympathetic Pathway:
Pathway: Preganglionic nerves travel via cranial nerve III (oculomotor nerve) to the ciliary ganglion. Postganglionic nerves then proceed via the short ciliary nerves to the sphincter pupillae muscle of the iris.
Parasympathetic Pathway: NT
Neurotransmitter: Acetylcholine is released from both preganglionic and postganglionic nerves, acting on nicotinic receptors at the ganglion and muscarinic M3 receptors on the iris sphincter muscle, causing pupil constriction.
Sympathetic Pathway:
Pathway: Preganglionic nerves originate from the upper thoracic spinal cord and ascend in the sympathetic chain to synapse in the superior cervical ganglion.
Sympathetic Pathway:
NT
Neurotransmitter: Noradrenaline (norepinephrine) is released from postganglionic nerves, activating alpha1-adrenoceptors on the iris dilator muscle, causing pupil dilation.
Low Light Conditions for. eye:
The sympathetic nervous system is activated, increasing noradrenaline release. This stimulates alpha1-adrenoceptors on the iris dilator muscle, causing the pupil to dilate and allow more light into the eye.
High Light Conditions:for eye
The parasympathetic nervous system is activated, increasing acetylcholine release. This stimulates muscarinic M3 receptors on the sphincter pupillae muscle, causing the pupil to constrict, reducing the amount of light entering the eye.
Sympathomimetics
These drugs mimic the action of sympathetic neurotransmitters, causing pupil dilation by stimulating adrenergic receptors.
phenylephrine, hydroxyamphetamine
Parasympathomimetics
These drugs mimic the action of parasympathetic neurotransmitters, causing pupil constriction by stimulating muscarinic receptors.
Pilcarprine
Parasympatholytics
These drugs block the action of acetylcholine on muscarinic receptors, leading to pupil dilation.
atropine
Atropine and ACh
Bind to Muscarinic rec and prevent ACh from bind so mora ACh
Alpha dreno
nora>adrena>isoprenaline
