Lesson 4
What do sensory systems do?
-receive information from the environment (ex: protection, movement)
- exact attributes of stimuli (ex: conscious and subconscious)
- have a common organization
- receptor: transducer energy into electrical stimulation (action potential)
- chain of neurons
- importance of the thalamus
- sensory regions of the cortex
- topographic organization
What is the function of the visual system?
- eye movement control
- CN 3,4,6,
- extraocular muscles
- sight
- information used in postural and limb movement control (enervates with vestibular system)
What are the two objectives to eye movements?
What are the eye movements?
- keep eyes stable during head movements
- direct gaze at visual target
Eye Movements:
- conjugate movements
- vergence movements (toward midline or away from midline)
What is fast saccadic?
Direction of gaze
- fast eye movement to switch gaze from one object to another (high speed, move objects into focus, eyes work together)
What is smooth pursuits?
Direction of gaze
- eye movements that follow a moving target (slower movements, conjugate)
What is Vergence movements?
Direction of gaze
- moves the eyes toward or away from midline (adjusting for different distances
What is VOR?
gaze stabilization
- vestibule-ocular reflex: adjusts eye position during fast head movements (walking, dancing, jumping)
What is optokinetic nystagmus?
Gaze stabilization
- adjusts eye position during slow head movements (or when objects move relative to the head)
(misunderstanding: you're stopped in your car at a red light, a bus goes by and you press on your brakes harder because you think you are moving)
What are neural peripheral structures?
-converts (transduces) light into electrical signals (AP) via photoreceptors (located in the retina)
- retina: a thin sheet of which lines the red wall of the eyeball
- macula: concave area
- fovea: center part of concave area
- nasal hemiretina: portion of retina that lies medial to fovea
- temporal hemiretina: portion of retina that lies lateral to the fovea
Wha does the retina consist of?
-photoreceptors: transduce light into electrical signals
-rods:detect dim light
- cones: acuity and detect color
- bipolar cells: link photoreceptors to ganglion cells
- ganglion cells: output neurons
-optic nerve: axons join together to exit the retina
- optic disk: area of no photoreceptors (blind spot)
What is the visual field?
- the amount of world that can be seen at a point of time, without head or eye movements (inverted representation)
- Monocular zone
- R monocular zone: ipsilateral nasal hemiretina
- L monocular zone: ipsilateral nasal hemiretina
- Binocular zone
- R visual field= R nasal hemiretina, L temporal hemiretina
- L visual field= L nasal hemiretina, R temporal hemiretina
Summary= monocular zone: ipsilateral nasal hemiretina, Binocular zone: ipsilateral nasal and contralateral temporal hemiretinas
What is the central visual pathway?
-optic nerve: carries info from both visual fields
- optic chasm: where optic nerves (One from each eye) come together and cross
- optic tract: conveys visual information from the chiasm to lateral geniculate nucleus (LGN) of the thalamus (relay station)
-optic radiations: emerge from LGN and project to the primary visual cortex (V1)
What is the visual cortex?
-primary visual cortex (V1)
- discriminates shape, size, texture of objects
- visual association cortices
- analyzes for colors and motion
- sent to other areas of cerebral cortex
- adjusts moements, visually identifies objects
What is age related macular degeneration?
- etiology: age related
- pathology: photoreceptor loss in macula
- symptoms: central vision impaired, blurriness, object distortion
- prognosis: progressive
Draw a lesion to the optic nerve
- total loss of vision in ipsilateral eye (blindness in one eye)
- loss of monocular
Draw lesion to the optic chiasm
- Bitemporal hemianopia
- interrupts fibers from both nasal hemiretinas
- loss of both monocular zones
(tunnel vision)
Draw lesion after optic chiasm:
-Optic tract, LGN, optic radiation
- loss of contralateral visual field
-contralateral homonymous hemianopia
Draw lesion to the primary visual cortex
- contralateral homonymous hemianopsia with possible macular sparing
Draw visual field with labels
-monocular zones
- binocular zones
- temporal and nasal zones
- optic nerve
- optic chiasm
- optic tract
- superior colliculus of midbrain
- LGN of thalamus
- optic radiations
- primary visual cortex (V1)
What does LGN stand for?
Lateral Geniculate Nucleus (LGN)
What is the primary role OT's have in management of macular degeneration?
- Patient education
(problem solving)
What does ipsilateral mean?
- same side of the body
We got this
I want to cry
I am feeling confident
Just kidding I am lying
Yes- let's move on
No- lets go over it again