The Visual Nervous System and Upper Cranial Nerves Flashcards
The somatic nervous system innervates what?
Musculoskeletal muscle and sense organs of the skin
The sympathetic nervous system has a what type of outflow?
Thoracolumbar
The parasympathetic nervous system has a what type of outflow?
Cervicosacral
Your lateral rectus eye muscle does what?
Abducts the eye
Label the following muscles of the eye.
What does the superior rectus do?
Ellevates, adduct and intort the eyeball
What does your inferior rectus do?
Depress, adduct and extort the eyeball
What does your superior oblique muscle do?
Abduct, depress and intort the eyeball.
What is the sclera of the eye?
The tough fibrous outer coating.
What does the cornea do?
Refracts the light entering the eye
What are the two layers of the choroid of the eye, what do they do?
Outer pigmented layer that absrobs light
Inner highly vascular layer
What does the ciliary body do?
The ciliary body produces the fluid in the eye called aqueous humor. It also contains the ciliary muscle.
What does the ciliary muscle do?
Changes the shape of the lens when your eyes focus on a near object.
What are the two layers of the retina?
Outer pigmented layer and inner nervous layer
What is the function of the pigmented layer of the eye?
To absorb light
What is the macula lutea?
An oval yellowish area surrounding the fovea near the centre of the retina in the eye, which is the region of keenest vision.
How do photoreceptor cells work?
Phototransuction:
Photoreceptor cells absorb photons triggering membrane potentials, converting light into biological messages.
Outline the rods of the eye.
- Rods are responsible for vision at low light levels.
- Do not mediate colour vision
- Low spatial acuity
Outline cone cells, their function and when they are used.
- Active at higher light levels (phototopic).
- Capable of colour vision.
- Responsible for high spatial acuity.
What are the three types of cone cells?
Short, middle and long-wavelength sensitive.
What is meant by rod cells are scotopic?
They are respoinsible for vision at low light levels.
What is the optic chiasm?
The optic chiasm is an X-shaped structure formed by the crossing of the optic nerves in the brain. The optic nerve connects the brain to the eye.
What is meant by right anopsia?
Being blind in your right eye
Explain what bitemporal hemianopsia is.
A situation where the nerves in the optic chiasm are damaged at where they cross it.
This means you lose your right field of vision in your left eye and your left field of vision in your right.
Where does the optic nerve decussate?
The optic chiasm
Where does the optic tract run?
The optic tract runs posteirorly from the optic chiasma to the lateral geniculate nucleus in the thalamus.
Identify the structures labelled.
Where do most optic fibres synapse?
The lateral geniculate nucleus
Where do the optic nerve fibres that don’t synapse go and what do they do?
The optic fibres pass to the superior colliculus found in the tectum of the midbrain.
Responsible for visual reflexes.
Where is the primary visual cortex of the brain?
Calcerine sulcus of the occipital lobe
What is the lateral geniculate nucleus.
The LGN is the relay centre in the thalamus for the visual pathway.
What are the layers of the LGN?
Magnocellular layers
(1st and 2nd inner layers)
Parvocellular layers
(3rd 4th 5th and 6th layers)
What does the magnocellular layer of the eye do?
Relays the sensory information from the rods.
What does the parvocellular layer of the LGN do?
Recieves sensory information from the cones of the eye - perception of colour and fine detail.
Explain the muscles of the iris.
- Sphincter pupillae - formed by circular muscle fibres that cause the pupil to become constricted.
- Dilator pupillae - formed by radial fibres, dilates the pupil in dim light.
What type of muscle fibres form the dilator pupillae?
Radial fibres
What type of muscle fibres form the sphincter pupillae?
Circular muscle fibres
What does the aqueous humour of the eyeball fill?
The anterior and posterior chambers of the eyeball.
Where does the aqueous humour drain?
The anterior chamber of the eye
What innervates the superior oblique muscle of the eye?
Trochlear nerve
What nerve innervates the superior rectus muscle of the eye?
Occulomotor nerve
What does the aqueous humour do?
- Supports the wall of the eyeball
- Exerts internal pressure maintaining the optical shape of eye.
- Nourishes the lens and cornea which are avascular and removes the metabolite products.
What is the virtuous body?
The virtuous body is a transparent gel that fills the eyeball behind the lens.
How is the lens attached to the eye?
The lens is attached to the ciliary body by suspensory ligaments
Identify the nerve labelled.
Trochlear nerve
What innervates the lateral rectus muscle of the eye?
The abducent nerve
What is the nerve labelled?
Superior and inferior occulomotor nerve
Abducent nerve
What is the blood supply to the eye, and what is the artery a branch of?
Optic artery a branch of the internal carotid.
What produces the aqueous humour of the eye?
Ciliary body
