Exam 3 neuro study guide

What are the main types of cells in the retina?

Photoreceptors (rods & cones), bipolar cells, horizontal & amacrine cells, and ganglion cells.

What do rods and cones detect?

Rods detect brightness and shape; cones detect color and fine detail.

What causes the natural blind spot?

The area where ganglion cell axons exit the eye as the optic nerve—no photoreceptors there.

How is visual information organized?

Contralaterally—each visual field projects to the opposite occipital lobe (based on visual fields, not eyes).

Which retinal fibers cross at the optic chiasm?

Nasal retinal fibers cross; temporal retinal fibers stay on the same side.

What is the pathway of vision from the retina to the brain?

Retina → Optic nerve → Optic chiasm → Optic tract → Lateral geniculate nucleus (thalamus) → Optic radiations → Primary visual cortex (V1, occipital lobe).

What happens with damage to the optic nerve?

Monocular blindness (loss of vision in that eye).

Damage to the center of the optic chiasm causes what?

Bitemporal (heteronymous) hemianopsia – loss of both temporal visual fields.

Damage to the optic tract causes what?

Homonymous hemianopsia (loss of contralateral visual field in both eyes).

What is macular sparing and where does it occur?

Central vision is preserved after occipital lobe damage—due to dual blood supply.

What is the dorsal visual pathway responsible for?

The “where” pathway—location and motion (parietal lobe).

What is the ventral visual pathway responsible for?

The “what” pathway—object and face recognition, color, size (temporal lobe).

What is visual agnosia?

Inability to recognize objects visually despite normal vision.

What is prosopagnosia?

Inability to recognize faces.

What is achromatopsia?

Loss of color perception (not color blindness).

What is akinetopsia?

Inability to perceive motion.

What is alexia without agraphia?

Can write but can’t read.

Relationship between bony and membranous labyrinths?

Membranous labyrinth lies within the bony labyrinth and holds endolymph.

What are the cochlear sections?What separates these sections?

Scala vestibuli, scala media, scala tympani.

Reissner’s membrane (vestibuli/media) and basilar membrane (media/tympani).

What fluids are in each section?

Endolymph (scala media, high K+), perilymph (vestibuli & tympani, high Na+).

What’s in the organ of Corti?

Inner & outer hair cells, tectorial membrane on basilar membrane.

What happens when the basilar membrane moves?

Stereocilia bend → K+ channels open → depolarization → Ca²⁺ enters → neurotransmitter release → AP in cochlear nerve.

What are tip-links?

Connections between stereocilia that open K+ channels when stretched.

Role of outer hair cell microtubules?

Let outer hair cells lengthen/shorten to amplify soft sounds; loss reduces hearing sensitivity.

Outline the auditory pathway.

Cochlear nerve → Cochlear nuclei → Superior olivary complex → Lateral lemniscus → Inferior colliculus → Medial geniculate nucleus → Heschel’s gyrus.

What does bilateral processing at the superior olivary complex do?

Allows sound localization (compare timing & intensity between ears).

Where are auditory & visual reflexes integrated?

Superior colliculus (midbrain).

What is tonotopic organization?

Neurons arranged by frequency sensitivity.

Where is Wernicke’s area?

Left superior temporal gyrus; for language comprehension.

What happens if Wernicke’s area is damaged?

Wernicke’s (fluent) aphasia—difficulty understanding language.

What does the temporoparietal junction do?

LH: language comprehension; RH: prosody (emotional tone).

What is aprosodia?

Flat, emotionless speech or difficulty understanding tone—damage to RH temporoparietal junction.

What is pure word deafness?

Can’t recognize speech sounds; damage isolating auditory cortex from language areas.

How are auditory and vestibular systems similar?

Both use hair cells and CN VIII; both convert mechanical movement to neural signals.

What do semicircular canals detect?

Rotational (angular) head movement.

What happens when you move your head?

Endolymph moves, pushing the cupula and bending hair cells in the crista.

What are the otolithic organs?

Utricle (horizontal) and saccule (vertical); detect linear acceleration.

What is the macula?

Region containing hair cells in otolithic organs.

What is the otolithic membrane and otoconia?

Gelatinous layer with calcium carbonate crystals that move with gravity.

How are vestibular action potentials generated?

Cilia move → K+ enters → depolarization → Ca²⁺ enters → neurotransmitter release.

What areas receive vestibular input?

Cerebellum (balance), spinal cord (posture), eye movement centers (superior colliculus), reticular formation (autonomic), thalamus & cortex.

What cerebellar region connects to vestibular nuclei?

Flocculonodular lobe (vestibulocerebellum).

What do vestibulospinal tracts control?

Head/neck posture and leg extension to maintain balance.

What kind of receptors are olfactory and gustatory?

Chemoreceptors (detect chemicals).

Where is the olfactory epithelium?

Roof of nasal cavity.

What do supporting cells do?

Secrete mucus; replaced every ~10 minutes.

What do odorants bind to?

Cilia on olfactory receptor neurons

Outline the olfactory pathway.

Olfactory neurons → Cribriform plate → Olfactory bulb → Olfactory cortex (piriform & entorhinal) → Orbitofrontal cortex, hypothalamus, amygdala, hippocampus, thalamus.

What is the function of the orbitofrontal cortex in smell?

Odor discrimination & conscious perception.

What is the hypothalamus’ role in smell?

Appetite and feeding behaviors.

What is the limbic system’s role in smell?

Emotional and motivational responses.

What are types of olfactory impairments?

Anosmia (loss), hyposmia (reduced), parosmia (distorted), phantosmia (hallucination), cacosmia (foul smell perception).

What’s conductive vs sensorineural anosmia?

Conductive = blockage (cold/allergies); Sensorineural = neuron or CNS damage (TBI, aging, Parkinson’s, Alzheimer’s).