Week 9 content - taste sensation and vision

Question 1

what are the neural structures associated with taste

Answer 1

 Receptor cells in the papillae (bumps on tongue). Papillae have taste cells and microvilli (taste hairs)

 Cranial nerves VII (facial), IX (glossopharyngeal), X (Vagus) synapse in the solitary nucleus in the brainstem.
o Facial – transmits from anterior 2/3 tongue.
o Glossopharyngeal – posterior 1/3 of tongue.
o Vagus – transmits into from epiglottis area.

ventral posteriomedial thalamus
gustatory cortex

Question 2

what is the process of tasting

Answer 2

when taste cells (papillae) are depolarized they release neurotransmitters that stimulate sensory neurons of the IV, X, XII, these neurons terminate in medulla, taste information is then sent to the ventral posteromedial thalamus, then to gustatory cortex (region of the cortex found between the anterior insula and frontal opercula) where information is consciously discriminate different taste stimuli as sweet, salty, bitter, and savory.

the specific flavor of food is create by the combination of taste and smell.

Question 3

function of taste

Answer 3

taste system functions with the olfactory system and trigeminal chemoreceptor system determines if the food is safe to eat.

olfactory - chemical sense of stimuli, used with sense of taste to perceive taste.

Question 4

causes of loss of taste

Answer 4

ageing
head trauma
upper respiratory and sinus infections
covid 19
radiation therapy in the area.

Question 5

changes to function associated with impairment of taste

Answer 5

taste, smell, appearance of food influence our food choices.
sensory stimuli act as triggers to initiate and modulate digestion.
complete or partial loss of taste or smell may result in loss of appetite.

Question 6

assessment of taste

Answer 6

tests - drops placed on tongue to identify taste, taste tablets, taste strips.

function - MRI

Question 7

role of vision in function

Answer 7

arm function such as reading, grasping and manipulating objects, walking and mobility.

analysis of environment and guiding movement - obstacle negotiation, road crossing, driving.

maintaining balance

depth perception
face and object recognition
reading

Question 8

what are the major accessory structures of the eye

Answer 8

eyelids
eyelashes
lacrimal apparatus (for production, secretion and removal of tears).

Question 9

major structures of the eye - internal

Answer 9

fibrous layer: sclera and cornea.

vascular tunic layer:
- choroid layer - vascular layer.
- ciliary body - muscles, process, suspensory ligaments that alter lens shape, iris (pupillary dilator muscle and pupillary constrictor muscle).

neural layer:
- retina - is the light sensitive nerve layer that lines the back of the eye) - contains rods (low light and no color) and cones (high light, colour).

• fovea - center of the macula, highest concentration of cones, site of sharpest vision - the fovea is not apart of the layers

Question 10

process of light going through eye

Answer 10

light travels through the cornea (clear domed shaped surface) though the pupil and the iris which controls how much light passes through the pupil.

then light hits the lens (clear structure inside of eye that focuses light rays onto the retina).
- to help maintain round shape and protection.
- then light hits the retina.

when light hits the retina, the image is inverted. photo receptors turn the light into electrical signals which are transmitted via the optic nerve to the brain.

retina is divided into the temporal hemi-retina (closest to temporal lobe) and nasal hemi-retina (closer to nose).

Question 11

what is the innervation of the extra ocular eye muscles

Answer 11

(SO4 LR6)3

muscles of the eye: 4 rectus and two oblique muscles.
- superior rectus (oculomotor III)
- inferior rectus (III)
- medial rectus (III)
- lateral rectus (abducens VI)

• superior oblique (trochlear IV)
• inferior oblique (III)

Question 12

what is the visual pathway

Answer 12

pupil, optic nerve, optic chiasm, optic tract, lateral geniculate.

the nasal hemi retina decassates at the optic chiasm.

left visual field ends up on right visual cortex.
right visual fields ends up on left visual cortex.

Question 13

damage to optic nerve

Answer 13

contralateral blindness

Question 14

damage to optic chiasm

Answer 14

bitemporal hemianopia (both outer halves blind)

Question 15

damage to optic tract

Answer 15

homonymous hemianopia (same half blind on each side - one nasal and one temporal half).

Question 16

visual fields

Answer 16

the central visual field is captured by both the right and left temporal hemi retina

the peripheral visual field - is captured by the left and right nasal hemi retina.

Question 17

smooth eye movements

Answer 17

smooth eye movements are used to follow a moving object whilst keeping it in the focus of the fovea - e.g., when someone is walking past.

the command to produce smooth pursuit movements are originates in the visual cortex and activates nerves III and VI for horizontal movement and oculomotor for vertical movements.

Question 18

smooth eye movements

Answer 18

smooth eye movements are used to follow a moving object whilst keeping it in the focus of the fovea - e.g., when someone is walking past.

the command to produce smooth pursuit movements are originates in the visual cortex and activates nerves III and VI for horizontal movement and oculomotor for vertical movements.

Question 19

what is gaze evoked nystagmus

Answer 19

involtunary beating of the eye when a person looks to the side which may cause a slow drift of the eye in one direction followed by a fast return in the opposite direction. - named for the direction of the quick beat.

Question 20

what are saccadic eye movements

Answer 20

Saccades are rapid movements that abruptly changes the point of fixation. They range in amplitude – a patient may overshoot or undershoot a target. This causes patient to then make a correct eye movement to find the target.

o Abnormal findings:
 Hypometric – eyes undershot when looking towards target and had to move more laterally to correctly focus on the target.
 Hypermetric – eyes overshot when looking towards target and had to move more medially to correctly focus on the target.
 Dysmetric – some combination of the two above with no discernible pattern.