Pathophysiology/Physiology

Cards (46)

  • What would an issue with the ventral pathway for vision lead to?
    Object recognition difficulties
  • What do ganglion cells act as?
    Output cells
    -> their axons form the optic nerve
  • What is a receptor potential?
    Electrical signals generated in response to a stimulus by a sensory receptor
    -> when activated, produces receptor potential that causes a change in cell membrane potential
  • What do amacrine & horizontal cells do?
    Enhance contrast & adjust to different levels of light
  • What is location coding?
    Encoded by the spinal pattern of neural activity -> allows brain to determine the location of stimulus
  • What do bipolar cells do?
    Acts as a 'middle man'
    -> passes info from the PR cell to the ganglion cell
  • What is type coding?
    Different types of sensory stimuli are detected by different types of sensory receptor cells
  • What is intensity coding?
    Frequency & amplitude of neural activity -> higher intensity stimuli = more frequent & stronger neural responses 
  • What would an issue with the dorsal pathway for vision lead to?
    Spatial awareness deficits
  • What is duration coding?
    Length of time that neural activity persists
  • What is the tectospinal tract for?
    Mediating movements in response to visual stimuli
  • What protein is found in cones?
    Opsin
  • What protein is found in rods?
    Rhodopsin
  • Where are rods & cones found?
    In photoreceptor cells
  • What is the cornea?
    Clear, transparent, avascular structure
    Provides 78% of focusing power of the eye
  • What are the 5 layers of the cornea?
    Epithelium
    Bowman's layer
    Stroma
    Descemet's membrane
    Endothelium
  • What are the endothelial cells of the cornea responsible for?
    Maintaining clarity of cornea by continuously pumping fluid out of the tissue
  • What is the sclera?
    Opaque white structure
    Covers 4/5 of the globe, continuous with cornea
    Extraocular muscles are attached to sclera
    Optic nerve perforates sclera posteriorly
  • What is the conjunctiva?
    Richly vascularized & innervated mucous membrane
    Covers anterior surface of sclera
  • What is the anterior chamber?
    Space between cornea & lens
    Filled with aqueous humour → produced by ciliary body, provides nutrients & O2 to avascular cornea
    Any factor that impedes aqueous humourraises intra-ocular pressure
  • What is the uveal tract?
    Iris
    Ciliary body
    Choroid
  • What is the iris?
    Coloured part of eye
    Under transparent cornea
    Muscles of iris regulate size of pupil
  • What is the ciliary body?
    Muscles control the accommodation of the lens
    Secretory epithelium produces aqueous humour
  • What is the choroid?
    Highly vascular
    Inner aspect of sclera
  • What is the lens?
    Responsible for 22% of refractive power of eye
    Changes shape of lens → alters refractive power → allows to focus on nearby objects
    By 40s, ability to change shape of lens declines
  • What is the vitreous humour?
    Clear gel-like substance in the eye
    Fills cavity between retina & lens
  • What is the retina?
    The retina is the light-sensitive layer of tissue at the back of the eye that contains photoreceptor cells
    Macula -> centre (where cones are most concentrated)
  • What is the blood supply to the eye?
    Ophthalmic artery
    Central retinal artery -> supplies inner retitnal layers
  • What is the venous drainage of the eye?
    Central retinal & ophthalmic veins
  • What is the lympathic drainage of the eye?
    Pre-auricular & submental nodes
  • What provides sensory innervation to the eye?
    Trigeminal
  • What provides motor innervation to the eye?
    Oculomotor nerve
    Trochlear nerve
    Abducens nerve
  • Pupuil dilation
    Sympathetic NS -> stimulates contraction of radial muscles (dilator pupillae) Begins in hypothalamus & descends through midbrain -> synapses in spinal cord (C8-T2) -> preganglionic sympathetic neuron exits spinal cord (through ventral roots) -> projects to superior cervical ganglion & synapses -> long ciliary nerve projects to dilator pupillae (radial muscle) -> pupil dilation
  • Pupil constriction
    Parasympathetic NS -> stimulates contraction of circular muscles (sphincter pupillae) Light enters eye -> stimulates retina -> signals travel via optic nerve & synapse with the pre-tectal nucleus -> synapses with Edinger-Westphal (oculomotor) nucleus -> gives rise to bilateral oculomotor outputs to ciliary ganglion -> short ciliary nerve innervates the sphincter pupillae (circular muscle) -> pupil constriction
  • Accommodation reflex - what is it? what does it involve?
    Visual response to focusing on nearby objects
    Involves;
    • contraction of medial recti muscles -> convergence
    • constriction of pupils (parasympathetic NS)
    • contractions of ciliary body -> broadens lens & increases refractive power
  • What is the role of the optic nerve?
    Carries afferent fibres from retina to visual cortices of the brain -> transmits visual image
    Surrounded by cranial meninges
  • Where does the optic nerve leave the skull?
    Optic canal
  • What is the function of oculomotor nerve?
    Movement of most extraocular muscles (except LR & SO) + levator palpebrae superiosis
    Parasympathetic division responsible for pupillary constriction -> pupillary reflex
  • Where does the oculomotor nerve exit the skull?
    Superior orbital fissure
  • What is the function of the trochlear nerve?
    Innervates superior oblique -> assists in depressing & abducting eye