Exam 2: Neurophysiology Part 4 - Hearing and the Visual System

Question 1

What are sound waves

Answer 1

Longitudinal vibrations of gas particles in an external medium (air)

Phases of compression and rarefaction alternate

Question 2

Intensity, frequency, and wavelength

Answer 2

Intensity - base of wave to top of wave (amplitude)

Frequency - distance from one wave to the next (peak to peak or valley to valley)

Wavelength - length of whole wave; one whole peak and one whole valley; distance between two areas of maximal pressure

Question 3

Outer ear parts and what is does

Answer 3

Ear pinna and ear canal

Funnels sound to the tympanic membrane

Question 4

Middle ear parts and what is does

Answer 4

Contains 3 ossicles (bones) - malleus, incus, stapes (AKA hammer, anvil, stirrup)

Air filled cavity connected to nasopharynx by eustachian tube

Question 5

skeletal muscles in ear

Answer 5

2 small skeletal muscles attached to malleus and stapes

Stapedius muscle and tensor tympani muscle

Question 6

what do stapedius and tensor tympani muscles do

Answer 6

work together in order to regulate vibration

react when there is sound

can control how much structures in ear move to act as a bit of a buffer

Question 7

Chambers of the ear and what they contain

Answer 7

Scala vestibule (dorsal) - contains perilymph

Scala tympani (ventral) - contains perilymph

Scala media - contains endolymph

Question 8

endolymph vs perilymph

Answer 8

endolymph - intercellular fluid; high in potassium

perilymph - extracellular fluid; high in sodium

Question 9

organ of corti and tectorial membrane and basilar membrane

Answer 9

Organ of corti - functional unit

Tectorial membrane - on top of organ of corti; gelatinous texture; hair cells are sustained here (this lies on top of hair cells)

Basilar membrane - contains hair cells; structure that moves as a wave

Question 10

hearing sequence of events (4)

Answer 10

1. Sound waves are collected by the outer ear and produce vibrations on the tympanic membrane (eardrum)
2. Movements of the ossicles in the middle ear
3. Vibrations on the oval window are transferred to the basilar membrane (through perilymph and endolymph) causing it to move up and down
4. Hair cells cilia shear along the tectorial membrane causing changes in transmitter release

Question 11

difference between low and high frequency vibrations

Answer 11

Low frequency causes vibrations of almost all cells and travels far in cochlea

High frequency causes vibrations in few cells and does not travel far in cochlea

Question 12

is glutamate excitatory or inhibitory in regards to hearing

Answer 12

Excitatory

Question 13

Components of the auditory pathway

Answer 13

Hair cell
Spiral ganglion (in periphery)
cranial nerve VII
Cochlear nuclei (in medulla)
trapezoid body
Superior olivary complex (in medulla-pons)
lateral lemniscus
Inferior colliculus (in mesencephalon)
brachium of the inferior colliculus
Medial geniculate nucleus (in diencephalon)
auditory radiations
Auditory complex (in telencephalon)

Question 14

where are receptor cells located in eye

Answer 14

retina

Question 15

parts of the retina

Answer 15

Temporal - closer to temporal region of brain, lateral

Nasal - closer to nasal area, incudes where optic nerve is, medial

Question 16

Chambers of the eye

Answer 16

Anterior chamber
Posterior chamber
Vitreous chamber

Question 17

What is aqueous humor and where is it

Answer 17

Nutrients for cornea and lens

located in anterior and posterior chambers

Question 18

what is vitreous humor and where is it

Answer 18

composed by gelatinous fluid and phagocytic cells

located in vitreous chamber

Question 19

Lens ligaments and muscles

Answer 19

Lens is suspended by ligaments (zonular fibers) that are attached to the ciliary body (muscles)

Question 20

Tears:
What do they do (4)
What immunoglobulin do they contain

Answer 20

Contains Immunoglobulin A (IgA)

Lubricates eye
Prevents frost damage of cornea
Moistens nasal cavity
Helps combat bacteria

Question 21

tapetum

Answer 21

Reflective patch for nocturnal seeing

Question 22

how does eye change for near and far vision

Answer 22

Ciliary muscles change tension on suspensor ligaments thereby altering the shape of the lens

Question 23

Shape of lens in near vs far vision

Answer 23

Near vision - ciliary muscles contract –> decreased tension of suspensory ligaments –> lens round

Far vision - ciliary muscles relaxed –> increased tension of suspensory ligaments –> lens flattened

Question 24

Cells of the retina and functions (6)

Answer 24

Retinal pigmented cells - nourishment and protection of photoreceptors –> 1st layer

Photoreceptors - rods and cones –> 2nd layer

Horizontal cells - lateral interactions among photoreceptors and bipolar cells

Bipolar cells - connect photoreceptors with ganglion cells –> 3rd layer

Amacrine cells - lateral interactions among bipolar cells and ganglion cells

Ganglion cells - axons from the optic nerve –> 4th layer

Question 25

Rods characteristics (5)

Answer 25

Most sensitive to light
Night vision (low light)
Low acuity
Achromatic
Peripheral retina

Question 26

Cones characteristics (5)

Answer 26

Less sensitive to light
Day vision (normal indoor and daylight)
High acuity 
Color vision
Central retina (fovea)

Question 27

Define acuity

Answer 27

Good at discerning image detail

Question 28

Parts of the rod/cone

Answer 28

Outer segment - plasma membrane; discs; cytoplasmic space; cilium

Inner segment - mitochondria and nucleus

Synaptic terminal - releases transmitters

Question 29

What do discs of outer segments contain

Answer 29

Visual photopigment:
Opsin - a GPCR
Retinal - an aldehyde of Vitamin A (retinol)

Question 30

Depolarization and hyperpolarization in photoreceptors

Answer 30

Depolarize when not stimulated by light

Hyperpolarize when stimulated by light –> cell becomes more negative

Question 31

Mechanism in darkness (2 steps) and in light (4 steps)

Answer 31

Darkness:

1. 11-cis-retinol and opsin bound together
2. cGMP produced

Light:

1. 11-cis-retinol configuration changed to all-trans which is split away from opsin
2. Opsin binds to and activates a G-protein (transducin)
3. Transducin activates phosphodiesterase that hydrolyzes cGMP
4. Decreased cGMP levels cause a closure of Na+ channels –> hyperpolarization –> less glutamate release (glutamate is the activating transmitter)

Question 32

types of cones

Answer 32

Cones differentiate colors

Blue cones - sensitive to smaller wavelength light
Green cones - sensitive to medium wavelength light
Red cones - sensitive to larger wavelength light

Question 33

Differences between species - number of cones/colors they can see

Answer 33

Birds, insects - different types of cones; good color vision

Humans, apes, old world monkeys - 3 cones (blue, green-yellow, orange-red) –> trichromatic vision

Dogs, cats, cattle - 2 cones –> dichromic vision

Dogs see mostly in blue and yellow

Question 34

carnivore vs herbivore field of vision

Answer 34

Carnivore - eyes are frontal, restricted monocular lateral vision, large central binocular field

Herbivore - eyes lateral, wide monocular lateral vision, narrow central binocular field

Question 35

Reticulo-geniculo-striate pathway

Answer 35

pathway to cerebral cortex

crosses at optic chiasm

lateral geniculate nucleus is located in thalamus

primary visual cortex is located in occipital lobe

Question 36

Reticulo-geniculo-striate pathway direction of travel

Answer 36

Right visual field projects to left (nasal) retina and axons travel to the left lateral geniculate nucleus and to the left primary visual cortex
- axons from right vision goes to left side of brain

Left visual field projects to the right (temporal) retina and axons travel to the right lateral geniculate nucleus and to the right primary visual cortex
- axons from left vision goes to right side of brain

Question 37

Where do axons from nasal and temporal retinas go

Answer 37

Axons from nasal retina of both eyes goes to contralateral part of brain
- left nasal goes to right side of brain and right nasal goes to left side of brain

Axons from temporal retina of both eyes stay on same side of brain
- left temporal goes to left side of brain and right temporal goes to right side of brain

Question 38

Pupillary light reflex and consensual response - circular vs radial muscle

Answer 38

Circular muscle –> constrictor –> parasympathetic innervation

Radial muscle –> dilation –> sympathetic innervation

Question 39

Which part of the brain is the olfactory brain

Answer 39

Rhinecephalon

Question 40

Why is olfaction important

Answer 40

Sense of smell important for seeking food; orientation; marking territory; choosing mate; recognition of danger

Question 41

Differences in passage of air through nasal cavity: sniffing vs breathing

Answer 41

Sniffing: air passes above heat exchanger reaching olfactory epithelium directly
Dogs sniff quickly to push air to olfactory

Breathing: air passes through the heat exchanger

Question 42

Olfactory cells discription

Answer 42

Primary receptor cells

Dendrite extending towards surface of epithelium

Mucus layer keeps epithelium moist and clean

Mucus layer contains cilia

Question 43

Olfactory cell cilia

Answer 43

Embedded in mucus layer of epithelium

Contain odor receptors

Question 44

Glomerulus of olfactory cell

Answer 44

Group of synapses between olfactory cell terminals and mitral cell terminals

Several unmyelinated axons of olfactory cells synapse with a mitral cell in the glomerulus (olfactory bulb) –> signal amplification

Question 45

Odor molecules and odorant receptors

Answer 45

Odor molecules dissolved in gas or water (aerosols)

Odorant receptors (OR) are GPCRs

Olfactory cells are extremely sensitive - single odor molecule can open several thousand ion channels

Question 46

Olfactory pathway to cerebral cortex

Answer 46

Olfactory epithelium
- olfactory nerve

Olfactory bulb

Olfactory cortex
anterior olfactory nucleus
piriform cortex
amygdala
entorhinal cortex

Thalamus or Hippocampus

From thalamus to frontal cortex or caudate nucleus

Question 47

Parts of the olfactory cortex and what they do and where the signal goes after

Answer 47

Anterior olfactory nucleus:
Create and store olfactory gestalts
Goes to thalamus

Piriform cortex:
Behavioral, cognitive, and contextual info
Goes to thalamus

Amygdala:
Emotional processing of olfactory info
Goes to thalamus

Entorhinal cortex:
Working memory
Goes to Hippocampus

Question 48

Vomeronasal organ location

Answer 48

Paired, cylindrical organ located ventrally and medially in anterior portion of nasal septum

Connected to oral cavity

Question 49

Vomeronasal organ function

Answer 49

Sexual behavior

Recognition of odor molecules dissolved in fluids such as urine and vaginal secretions

Flehmen response

Question 50

What is the Flehmen response

Answer 50

“to curl upper lip”

Observed in males (ungulates and felidae)

Direct the fluids in the vomeronasal organ

Question 51

Species differences in distribution of taste buds

Ruminants
Dogs
Birds

Answer 51

Ruminants - mostly in basis of tongue

Dogs - mostly in tip

Birds - poorly developed

Question 52

What kind of receptors (primary or secondary) are taste receptor cells

Answer 52

Secondary receptor cells

Question 53

How flavor particles get to receptors

Answer 53

1. Mastication
2. Flavor particles suspended in fluid
3. Fluid with flavor particles enter into the pores and bind to their receptors

Question 54

Differences in intensity of recognition of different gustatory stimuli based on location of tongue

Answer 54

Tip - more salty

Sides - more bitter and sour

Back - more bitter and sweet

Question 55

Different gustatory stimuli (5)

Answer 55

Sweet - glucose, saccharose

Sour - citric acid, H+

Salty - NaCl, Na+

Bitter - caffeine, nicotine

Umami - from Japanese “umai” = delicious and tasty –> tomatoes, meat, cheese, soja sauce, flavor enhancers

Question 56

Ionotropic gustation receptors

Answer 56

Salty, sour

1. Na channels at apical membrane of cell
2. When Na or H approaches it goes through Na channel
3. Leads to membrane potential
4. Depolarization of cell, Ca influx
5. Synaptic vesicles fuse with basal membrane then release transmitters
6. Activates neuron and info travels to CNS

Question 57

Metabotropic gustation receptors

Answer 57

Sweet, bitter, Umami

1. Glucose, glutamic acid, caffeine etc. bind to GPCR at apical membrane of cell
2. Signal goes farther with 2nd messenger DAG and IP3
3. Ca release from ER
4. Opens channels, like Na channels
5. Induces release of atypical transmitter (ATP)
6. Info travels to CNS

Question 58

What activates heat sensitive channels in the oral cavity

Answer 58

Capsaicin - in spicy foods

Capsaicin binds to heat sensitive channels

Question 59

What is a use of Capsaicin

Answer 59

Medicinal use in cremes for muscle pain and strains

Question 60

Central pathway for gustation

Answer 60

Afferent fibers in cranial nerves VII (facial) of nucleus of solitary tract that reach the thalamus and project to the cerebral cortex