Medical Neurosciences: Olfactory And Visual Pathways

Front 1

Name 2 Disnosmias

Back 1

-Anosmia: No Smell
-Hyposmia: Decreased function

Front 2

What is Cacosmia

Back 2

-Hallucinations of unpleasant smells
-"uncinate fit"

Front 3

What makes up the olfactory epithelium

Back 3

-is within the nasal cavity and is covered with a thick mucosa secreted by Bowman's Glands
-Odorants must dissolve in the mucosa to be detected

Front 4

Where are Olfactory Receptors found

Back 4

-On the dendrites of neurons that extend into the mucosa
-Are highly sensitive metabotropic chemoreceptors
-Activation of these receptors depolarizes the first order neuron in the olfactory pathway

Front 5

Discuss the first order neurons in olfaction

Back 5

-bipolar neurons
-Axons leaving the olfactory epithelium collect into bundles of about 20 axons and travel through cribiform plate to the olfactory bulb, where the first synapse occurs

Front 6

Where do the first order and second order olfactory neurons synapse

Back 6

-In the olfactory bulb the fist order neurons synapse with the second order neurons, the mitral cells

Front 7

What are the 2nd order olfactory neurons called?

Back 7

-Mitral Cells

Front 8

Are there more first or second order neurons in the olfactory pathway?

Back 8

-There are many more first order neurins in this pathway, so there is lots of convergence of information

Front 9

Where do the second order olfactory neurons project to?

Back 9

-The axons travel through the olfactory tract

Front 10

What does the olfactory tract divide into?

Back 10

-The olfactory tract splits into lateral and medial olfactory stria

Front 11

Where does the lateral olfatory stria project to?

Back 11

-to the pyriform and entorhinal regions of the cerebral cortex, and the amygdala

Front 12

Where does the medial olfactory stria project to?

Back 12

-to the contralateral olfactory bulb via the anterior commissure

Front 13

What are the three main layers of the back of the eye from inner to outer?

Back 13

-Retina
-Choroid
-Sclera

Front 14

How is the retina divided

Back 14

-retina is divided into 10 different layers, and contain 5 types of neurons

Front 15

What are the 5 types of neurons found in the retina?

Back 15

-Receptor
-Bipolar
-Ganglion
-horizantal
-amacrine neurons

Front 16

What are the 2 types of receptor neurons?

Back 16

-Rods
-Cones

Front 17

What do the rods do?

Back 17

-respond to low intensities of illumination and subserve twilight and night vision
-With only rods, can't see any color
-contain more visual pigment than cones and are more sensitive, so can be activated with less light
-if all rods are destroyed, no night vision

Front 18

What do cones do?

Back 18

-have higher threshold of excitability and are stimulated bylight of a relatively high intensity
-responsible for sharp vision and color discrimination in adequate illumination
-There are three types, each of which is responsible for a different part of the visual spectrum

Front 19

Where do ganglion neurons project to?

Back 19

-project axons that become the optic nerve

Front 20

What is the function of bipolar neurons?

Back 20

-neuronal link between the receptor neurons and the ganglion neurons

Front 21

What do the amacrine and horizantal neurons do?

Back 21

-are interneurons in the retina that make synapses on other neurons
-involved with visual processing

Front 22

What type of receptor is found in the fovea

Back 22

-only cones

Front 23

List the pathways that visual information travels along, and their functions

Back 23

-central visual pathway - produces vision
-pupillary pathways - 1. to iris, constricts pupil, and 2. to ciliary body, lens accomodation
-visual association pathway - via superior colliculus
-reticular pathway - produces alertness
-hypothalamic pathway - circadian rhythm

Front 24

Give the pathway for vision

Back 24

-photoreceptor neurons project to the bipolar neurons which project to the ganglion neurons
-Axons of the ganglion neurons become the optic nerve

Front 25

What are the 1st order neurons in vision

Back 25

-bipolar neurons

Front 26

What are the second order neurons in the optic pathway

Back 26

-ganglion neurons

Front 27

Where do the ganglion cells have a myelin sheath?

Back 27

-As the ganglion cells exit at the back of the retina they aquire myelin sheaths and form the optic nerve

Front 28

What is the path of the optic nerve?

Back 28

-Enters the cranial cavity through the optic foarmina
-the two sides unite anterior to the infundibulum to form the optic chiasm
-At the optic chiasm there is a decussation of optic fibers - 1/2 the axons of each fiber will cross the midline

Front 29

Where do the optic tracts begin?

Back 29

-beyond the optic chiasm, the optic fibers continue as optic tracts

Front 30

Where are the fibers in each optic tract originating from?

Back 30

-All fibers in the optic tracts are from the contralateral visual field
-Each optic tract carries information from the lateral ipsilateral retina and the medial contralateral retina

Front 31

IS organization maintained throughout the visual pathway

Back 31

-Yes, retinotopic organization is maintained throughout the visual pathway

Front 32

Where does the central visual pathway convey information to and from?

Back 32

-conveys info to the cerebral cortex to produce visual perception
-1st order neuron - bipolar neuron
-2nd order neuron - ganglion neuron (which forms optic nerve)

Front 33

Where do the fibers of the optic tract synapse?

Back 33

-80% of the fibers synapse in the lateral geniculate body

Front 34

What information does the lateral geniculate body recieve?

Back 34

-recieves info from both eyes, but from the contralateral visual field
-is divided in to 6 fields, 3 of which recieve contralateral axons (layers 1,4,6), and 3 of which recieve ipsilateral axons (layers 2,3,5)

Front 35

Where are the third order neurons of the visual pathway located?

Back 35

-In the lateal geniculate body

Front 36

Where do the 3rd order neurons of the visual pathway project to?

Back 36

-project from thelateral geniculate body to the primary visual cortex in the occipital lobe

Front 37

What divides the occipital lobe horizantally?

Back 37

-The calcarine fissure on the medial surface of the brain

Front 38

What is the cortical area directly around the calcarine fissure known as?

Back 38

-The primary visual cortex

Front 39

What do the axonal projection sfrom the lateral geniculate body form

Back 39

The optic radiations, or geniculocalcarine tract

Front 40

How is the visual information organized in the optic pathway?

Back 40

-retinotopic organization is preserved in the pathway
-The left visual field projects to teh right occipital lobe
-The right visual field projects to the left occipital lobe

Front 41

Where does information from the fovea project to?

Back 41

The occipital pole

Front 42

Where does the visual information from the inferior and superior visual fields project to?

Back 42

-Information from the superior half of the visual field projects to the area inferior to the calcarine fissure
-Information from the inferior visual field projects to the area superior to the calcarine fissure

Front 43

What do the optic radiations form as they travel through the temporal lobe?

Back 43

--The optic radiations conveying information to the inferior occipital lobe sweep into the temporal lobe as they are projecting
-these sweeping fibers form the Meyer's loop

Front 44

What are some common effects of lesions in the visual field?

Back 44

-Agnosia - inability to recognize objects
-Prosopagnosia - inability to recognize faces (problem with grandmother cells in right occipitoparietal cortex)