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Flashcards in ANS, visual, hearing pathways Deck (30):

outer layer of eye

cornea - transparent, a-vascular, refraction
sclera - white opaque area, muscles insert for eye movement


middle, vascular layer of eye

choroid- vascular, nourishes cornea, retina
iris- pigmented, vascular, muscles which change diamater of pupil
ciliary body- controls shape of lens via suspensory ligaments
lens- biconvex, A-vascular


inner layer of eye

retina (extension of diencephalon)


features of non-neuronal layer of retina

pigmented epithelium, sitting against choroid of eye.

absorbs light

maintains the metabolic activity of photoreceptors

provides cap. to the photoreceptors


features of neuronal layer of retina


1st order bipolar neurones

2nd order ganglion nuerones

optic disk --> point where axons of ganglion neurones leave the retina to become the optic nerve

interneurones: horizontal and amacrine interneurones

photochemical reactions occur here


features of rods

20 x more common, sensitive to light, vision in dim-light, high level of convergence
found everywhere


features of cones

colour vision, high visual acuity, lower levels of convergence , at macula= one cone for every ganglion cell
found in macula/ fovea/ not in periphery


the visual pathway is a 3 neurone chain. the optic nerves will combine to cross at ...

the optic chiasm: hemi-decusation (nasal fibres will cross, temporal will not)


location of the visual cortex

above and below the calcarine sulcus, extending to the occipital pole


our eyes are binocular. what does this mean

both of our eyes see the same thing


what is fixation point

point of visual acuity corresponding to the fovea. it where all quadrants of visual field meet


define scotoma

localised patch of blindness


define anopia and give examples of 2 types

the loss of one or more quadrants of the visual field

e.g. hemianopia= one HALF of the visual field is lost (both of upper and lower on that half are lost)

e.g. quadrantanopia= one QUADRANT of the visual field is lost only


define homonymous

visual field losses are on same side for both eyes


define heteronymous

visual field losses are on different sides for both eyes


3 examples of visual defects

monocular blindness (completely blind in ONE eye)

bi-temporal hemianopia (outer half BOTH right and left visual field is missing)

homonymous hemianopia (visual field loss on same side of both eyes)


which region of the external ear is bony/cartilaginous

lateral 1/3= cartilaginous

medial 2/3= bony


tympanic membrane may be called the eardrum. what is its function

to separate the external and middle ear.
--> it is part of middle ear


middle ear is high risk space why?

1. eustachian tube connects it to naso-pharynx= prone to infection

2. connected to mastoid air cells= infection spread to middle cranial fossa

3. inferior is the IJV= risk of thrombosis

4. anterior is the internal carotid artery= risk of pulsatile tinnitus

5. transversed by facial nerve and canal= infection spread to facial muscles


3 features of the auditory pathway

polysynpatic (many neurones/ synpases)

tonotopically organised

bilateral (recieve sound from both ears)


auditory centres in brainstem are...

cochlear nuclei
SUPERIOR olivary nuclei
inferior colliculus
MEDIAL geniculate nucleus


cell bodies of the cochlear nerve (CN8) are in the

spiral ganglion. will travel into the dorsal/ventral cochlear nuclei


where are low and high frequency sound recieved in cochlear and projected in the heschl's gyrus

base= high

low= antero-lateral part of heschl's gyrus
high= postero-medial part of heschl's gyrus


secondary auditory areas

brocas- anterior of frontal, motor production of speech

wernickes - posterior of temporal, understanding of speech


define anxiety

a FEELING of worry, nervousness, unease --> typically about an imminent even or something with an uncertain outcome BUT it has physical effects (racing heart, heaving breathing, sweating, dry mouth)


function of autonomic NS

to monitor the VISCERAL ACTIVITY to maintain homeostasis


distinct feature of somatic and autonomic MOTOR efferent fibres

in ANS, the visceral motor efferent fibres leave the spinal cord via the LATERAL GREY HORN which is present only within the segmental spinal nerves T1-L2 and S2-4


in the ANS there is a 2 neurone chain- not seen in somatic. what are the names of neurones and where are they located

pre-ganglionic neurone- somewhere in CNS

post-ganglionic nuerone going to target organ- somewhere in the PNS

NB. synapse at the 'autonomic ganglion'


outflow of symp and para are..

sympathetic= thoracolumbar outflow, T1-L2

para= cranio-sacral outflow, S2-S4 (occulomotor, facial, glossopharyngeal, vagus)


which neurotransmitter is released by symp/para fibres

para=acetylcholine released by BOTH neurones. localised effects (1:1 of pre and post neurones)

symp= acetylcholine by pre and then noradrenaline by post-ganglion neurone BUT sweat glands post-ganglionic neurones release a different neurotransmitter